Draw Poisson lines
Draw Poisson lines, that is lines uniformly and isotropically
distributed in the plane.
---------
author : David Legland
INRA - TPV URPOI - BIA IMASTE
created the 24/06/2005
Contents
initializations
clear all;
close all;
lambdaRho = .5;
rhoMax = 150;
Nl = rhoMax*lambdaRho;
create lines
theta = 2*pi*rand(Nl, 1);
rho = rhoMax*rand(Nl, 1);
lines = createLine(rho, theta);
draw lines
clf;
axis([-100 100 -100 100]);
hold on;
drawLine(lines);
title(sprintf('poisson lines, with density %f', lambdaRho));
Also draw intersection points
pts = zeros(0, 2);
for i=1:size(lines, 1)-1
pts = [pts ; intersectLines(lines(i,:), lines(i+1:end, :))];
end
pts = pts(isfinite(pts(:,1)), :);
hold on;
drawPoint(pts, 'ro');


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Date : {{currentDate | date:'dd/MM/yyyy'}}
Subject: Car Loan sanction regarding
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We are glad to inform you, that your loan {{formLoan.loanAmount}} approved. This sanction letter for all the details regarding your loan, dated {{currentDate | date:'dd/MM/yyyy'}}.
Disbursment shall be made upon completion of required documents for the loan and the signature for agreement.
Regards,
Operational Manager


Loops are used in programming to automate repetitive tasks. This is one of the most basic tasks of programming. Ruby has some of the common loops that are used by other programming languages and a few very effecient loops of it's own. The syntax for Ruby loops is very easy to write and understand. With so many options available it is sometimes hard to decide which loop to use. Ever programmer feels comfortable using one loop over the other. I personally use the 'for' and '.each' loop the most in Ruby.
 Below I have listed some of the most commonly used Ruby Loops:
- While Loop:
A While loop is used when you want to perform a action until a certain condition is true. When the condition is false the While loop is exited. - Until loop:
An Until loop is the opposite of a While. A Until loop is executed till a condition is false. When the condtion is true the loop is exited - For loop:
A for loop executes the code for a given range of Numbers. E.g: If you want to execute a code 10 times, this can be achieved by using a For loop by giving the number range 1..10. You can also give a condition such as n < length - .times:
.times is similar to for loop with less restrictions. It is used to execute a given of code n times - .each:
.each is used to loop through all the elements of an array. - loop:
The Loop method is used to execute a given set of code infintely. It is crucial to have a break statement when you use 'loop' to prevent your code to run endlessly
Syntax:
while (condition = true)
code
end
Syntax:
Until (condition = false) do
code
end
Syntax:
for i in 1..n do
code
end
Syntax:
i.times
{code}
end
Syntax:
array.each do |x| {code}
end
Syntax:
loop
do
code
break if (condition)
end


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[23] The original impetus for Saturn envisioned a brawny booster to launch Department of Defense payloads. The von Braun team at the Army Ballistic Missile Agency (ABMA) received money from the Department of Defense's Advanced Research Projects Agency to demonstrate the concept. Furthermore, von Braun's group eventually became the nucleus of NASA's Marshall Space Flight Center (MSFC). These convolutions and the vague outlines of evolving Saturn vehicle technology constitute the themes of chapter 2.
The Saturn program eventually included three basic vehicles: Saturn I, Saturn IB, and Saturn V. Chapter 3 describes the events that led to these three separate rockets, whose configuration evolved out of the choice to go the moon by means of the lunar orbit rendezvous technique. MSFC began development of facilities to develop and test the mammoth boosters. Chapter 3 concludes with a discussion of the design and manufacture of lower-stage boosters for the Saturn I and Saturn IB.
[25] In November 1956, when the Air Force finally triumphed over the Army and Navy for leadership in long-range military rockets, planners at ABMA momentarily regrouped to plot a new direction, a strategy for large booster development geared instead to the exploration of space. Having lost round one to the Air Force, ABMA's stratagem was to leapfrog onward and upward to a quantum jump.1
In April 1957, ABMA began design studies on an advanced booster concept. With a total thrust of approximately 6 800 000 newtons (1.5 million pounds) in the first stage alone, the proposed vehicle was referred to as the Super-Jupiter. The impetus for the development of a Super-Jupiter class apparently evolved from Department of Defense plans for "certain advanced missions using space devices in communication," as well as space probes and weather satellites. However, such payloads, especially satellite programs, required a booster much larger than existing launch vehicles. The Department of Defense guidelines called for a launch vehicle capable of putting 9000 to 18 000 kilograms into Earth orbit or accelerating space probes of 2700 to 5400 kilograms to escape velocity. At that time, ABMA estimated that satellite carriers on order, such as Thor, Juno II, and Atlas, could be expected to put up to 1400 kilograms into orbit. This capability might be increased to 4500 kilograms with high-energy propellants in upper stages. However, these boosters, with conventional propellants, would not be available for at least two years. The high-energy versions would not be operational until 1961 or 1962. Given the urgency of Department of Defense requirements for large payloads, a new class of booster and associated equipment had to be developed in a very short time, while keeping costs within low DOD limitations.2
[26] Early design and cost studies at ABMA suggested the possibility of using a single engine of 4 450 000 newtons (1 million pounds) of thrust, for which Rocketdyne Division of North American had made a feasibility study for the Air Force. Although this was an "Air Force engine," no other large propulsion system existed. The F-1 engine seemed unlikely to reach the point of full-scale testing for at least two years-too late to meet the accelerated booster development program of the Department of Defense. In any case, a booster with 6 700 000 newtons (1.5 million pounds) of thrust was needed, so the ABMA planning staff gave up on the simplicity of one large engine and turned to a combination of four smaller ones.
Rocketdyne also had a project under way for a 1 600 000- to 1 690 000-newton (360 000- to 380 000-pound) thrust engine known as the E1. Proposals for the four-engine booster involved the use of what one ABMA official called "off-the-shelf tankage" (presumably a single large-diameter booster propellant tank from the existing stable of military missiles) with the four E-1 engines in a clutter underneath it. This version of Super-Jupiter was closely analyzed by ABMA and technical experts from North American, and a number of upper-stage configurations were suggested. With specific choices in terms of engines and tankage still open, ABMA was by now certain that the clustering of engines was the most feasible route to attain quickly the Department of Defense goal of a 6 700 000-newton (1.5-million-pound) first-stage booster. In December 1957, ABMA delivered its proposal to the Department of Defense: "A National Integrated Missile and Space Vehicle Development Program." The document affirmed the clustered engine mode as a shortcut method to achieve large payload capability in the least amount of time.3
Nevertheless, Super-Jupiter still remained a feasibility study, existing only on paper and within the fertile imaginations of von Braun and his group at Huntsville. The Department of Defense had its stated requirements for payloads of many tons, and ABMA had its proposals for possible booster configurations, but there was still no priority or money to get Super-Jupiter past the level of paperwork. The immediate catalyst came in the form of a new Department of Defense organization whose high-priority recommendations cut through layers of red tape and allocated dollars for converting studies into hardware-the Advanced Research Projects Agency (ARPA).
During the turbulent months of late 1957 and early 1958, the Eisenhower administration wrestled with the challenges posed by Sputnik I, the abortive launches of Vanguard, and the last ditch mission of Explorer I. A long-term, reasoned, and integrated space program called [27] for some informed and firm decisions. In February, President Eisenhower chartered a special committee under the guidance of Dr. J. R. Killian to study the issues and make recommendations for a national space program. As the Killian committee convened, the Department of Defense moved on its own to rationalize space research involving the armed services. On 7 February 1958, ARPA was formally established by Secretary of Defense Neil H. McElroy, and after part-time guidance through most of two months, Roy W. Johnson became the new agency's director on 1 April. Johnson, a graduate of the University of Michigan, had been executive vice-president at General Electric. There was no doubt that Johnson had extensive authority: he reported directly to the Secretary of Defense. The influence of ARPA became evident when William M. Holaday, Director of Guided Missiles in the Department of Defense, received orders to transfer some of his activities to the new agency. Johnson insisted on running ARPA as a mechanism for establishing goals and coordinating research efforts, as opposed to active R&D work and management of contracts. ARPA made top decisions and allocated the money, giving full rein to whatever organization was nominated to run a project. ARPA remained a small, tightly knit organization, numbering about 80 people "including the girls (in the office)," as Johnson put it, and drew the core of its technical staff from specialists in the Army, Navy, and Air Force.4
Through the spring of 1958, ARPA began to get its own organization in line while ABMA continued preliminary studies for the Super-Jupiter with E-1 engines. Then in July, ARPA began to show more specific interest in the huge 6 700 000-newton (1.5-million-pound) booster but argued for the use of available engine hardware, as opposed to the still untried E-1 propulsion systems. ARPA's line of reasoning was tied to its objective of developing the big booster in the shortest amount of time and doing the job within a framework of limited funds. The von Braun group in Huntsville possessed considerable experience with the engines for its own Jupiter series of rockets, and so a new cluster, with eight Jupiter engines instead of four E-1 types, began to evolve. Even though no formal agreements existed as yet between ARPA and ABMA, the close working relationship between the two organizations was evident in the name chosen for the new eight-engine booster. Known as Juno V, the designation followed ABMA's prior conceptual studies for advanced Juno III and Juno IV multistage rockets. By using off-the-shelf hardware, including the engines, it was estimated that Juno V, compared with the Super-Jupiter with E-1 engines, would save about $60 millon and as much as two years research and development time.5
With such preliminaries out of the way, ARPA issued more specific instructions to ABMA, granting authority and authorizing funds for the Juno V. ARPA Order Number 14-59, dated 15 August 1958, clarified the discussions of the previous weeks:
[28] Initiate a development program to provide a large space vehicle booster of approximately 1 500 000-lb. [6 700 000-newton] thrust based on a cluster of available rocket engines. The immediate goal of this program is to demonstrate a full-scale captive dynamic firing by the end of CY 1959.
This was an historic document, for it committed money and engaged the von Braun team at Huntsville in an effort they had long dreamed about. Juno V became the progenitor of a new family of launch vehicles that would be used in the nation's future space program. As von Braun himself put it, "Juno V was, in fact, an infant Saturn.6
Indeed, during this early period the Saturn designation was frequently used by von Braun and others inside ABMA. A new name seemed appropriate, because Saturn was seen as a distinct break from the Juno series-a new breed of launch vehicle that would see an active lifetime of a decade or more. "The SATURN," observed one ABMA report, "is considered to be the first real space vehicle as the Douglas DC-3 was the first real airliner and durable work-horse in aeronautics."7 In the autumn of 1958, however, the full development of the Saturn was only beginning. As two engineers from Huntsville commented, "The state of the art at this time classified the Saturn booster as almost impossibly complex."8
[29] The decision not to use the E-1 engine and to go to off-the-shelf hardware did not catch ABMA personnel flatfooted. Technicians and engineers at Huntsville were already working on propulsion systems related to the Jupiter to increase thrust, simplify operation, and improve overall mechanical and other systems. This work gave the engine development an important momentum early in the game and encouraged ABMA's optimism when ARPA requested a program for static firing a multiple engine cluster within 18 months, while operating on a shoestring budget. Still, "it was not easy," Willy Mrazek, one of the top ABMA planners, mused years later. One of the problems involved the engine manufacturer. When ABMA contacted Rocketdyne and laid out the program, company officials were intrigued by the big cluster idea but protested that the dollar allocation simply could not stretch far enough to finance the rebuilding and testing of engines and spares for the size of the program suggested by ABMA. By using all their persuasive power, and even a little "arm twisting," as Mrazek recalled, the von Braun group convinced Rocketdyne to take the plunge, including the authorization for the company to glean hardware from their stockrooms that was left over from prior manufacturing and development programs sponsored by the government. By 11 September 1958, Rocketdyne had signed a contract with ABMA to uprate the original Thor-Jupiter engine, known as the S-3D propulsion system, creating a unit suitably modified to operate in the cluster configuration. The new engine was called the H-1, and ABMA signed away half of its available funds to get it.9
With the money they had left, ABMA went to work in Huntsville to decide how to allocate their scarce dollars for oversized test stands and to define the configuration of the tankage. An early decision was made to modify an existing test stand "out in our backyard," as Mrazek phrased it, keeping in mind that, although it had been designed to take Army missiles like the Jupiter 2.67-meter-diameter tank and a thrust of 734 000 newtons (165 000 pounds) the test stand had to be reworked to take a "monster" that was 24 meters high, 6 meters in diameter, and built to put out a thrust of almost 6 700 000 newtons (1.5 million pounds). The lean budget also had to cover a miscellany of items such as tooling to fabricate the oversized tanks and development of a thrust structure to take the maximum force of eight engines firing together at full throttle. There was also the need for oversized assembly jigs for manufacturing and checkout of the big new booster and for the costs of getting all the materials and the manpower to put the thing together. Like Rocketdyne, ABMA found that short funds made a virtue of scrounging in the dark corners of warehouses and stockrooms and puts a premium on imaginative shortcuts.
Because ARPA Order Number 14-59 called only for a static demonstration in the test stand, not a flight-configured launch vehicle, the booster that began to take shape on the Redstone Arsenal drawing [30] boards and in the shops was definitely a bargain-basement and patchwork affair. The volume of the tankage posed a special problem. The fabrication and welding of a single 6-meter-diameter tank, with separate compartments for fuel and oxidizer, meant new techniques and working jigs. Consumption of time and money threatened to become exorbitant. A different approach to the problem evolved, and existing tanks were used instead. From its own earlier production runs, ABMA located partial rejects and incomplete 1.78-meter tanks from the Redstone and 2.67-meter tanks from the Jupiter missiles. Since the engines were going to be clustered, why not the tanks? "The dire need made us more inventive," Mrazek pointed out, "and we bundled the containers to be loaded with propellants." So the vaunted big booster emerged from the drawing boards as a weird compromise of eight separate 1.78-meter Redstone tanks surrounding a 2.67-meter Jupiter tank. It did not look exactly like a smooth, streamlined futuristic vehicle for the exploration of space, nor was it intended to be. Designed solely to see if a blockbuster of a rocket could run its eight engines in concert, ABMA was satisfied with its awkward-looking compromise.10
While the work in Huntsville progressed, representatives from ARPA kept a close watch on the proceedings and made frequent visits to Redstone Arsenal. They increasingly liked what they saw. So much so, in fact, that they decided to propose a series of test flights. On 23 September 1958, ARPA and the Army Ordnance Missile Command (AOMC) drew up an additional memorandum of agreement enlarging the scope of .....
[31] ....the booster program. Signed by Major General J.B. Medaris for AOMC and Roy Johnson for ARPA, the joint memorandum stated: "In addition to the captive dynamic firing..., it is hereby agreed that this program should now be extended to provide for a propulsion flight test of this booster by approximately September 1960." Further, the von Braun group was called on to produce three additional boosters, the last two of which would be "capable of placing limited payloads in orbit." Along with the new scheme came much needed funds. ABMA could now count on $13.4 million in FY 1959 and $20.3 million in FY 1960 for the captive firing test and first launch, in addition to $8.6 million in the same period for development of appropriate facilities. For the three additional flights by 1961, ABMA would receive as much as $25 million to $30 million.
The decision to make the Juno V into a flight vehicle added new dimensions to planning problems. First, a launch site had to be selected. Moreover, the size of the booster posed unique transportation problems. As long as the launch location remained undetermined (possibly a remote site in the Pacific), ABMA planned to dismantle the entire booster and airlift the components separately, a concept that would be possible because of the use of individual propellant tanks, engines, and associated structural modules. Still, the Juno V engineering team was never quite sure the dismantling and rebuilding scheme would work effectively. "Thank goodness," Mrazek admitted, "we never had to disassemble the first flight vehicle." In the end, it was agreed to launch from the Atlantic Missile Range at Cape Canaveral, and ABMA worked out a more feasible method of transporting its launch vehicles intact by relying on water routes.11
While ARPA proceeded to hammer out a program for booster development, a number of government committees were at work, attempting to clarify overall priorities for a national space program. On the heels of Sputnik, Senator Lyndon B. Johnson began probing the status of America's national security and the space program through hearings of the Senate Preparedness Investigation Subcommittee of the Senate Armed Forces Committee. As chairman of the subcommittee, Johnson kicked off the hearings on 25 November 1957. The National Advisory Committee for Aeronautics (NACA) was gearing up its own studies about the same time, and the White House also had a high-powered study in progress-the Killian committee, directed by President Eisenhower's recently appointed Special Assistant for Science and Technology, James R. Killian. The subcommittees of Killian's group reporting early in 1958 evidently had the most influence in shaping the Administration's approach. Even though the committee reports were shot through with overtones of [32] national security and the notion of a space race with the Russians, Administration officials generally agreed that proposals for a new space agency should result in an organization that was essentially nonmilitary. Because of its civil heritage, existing programs, and general programs, NACA was singled out as the most likely candidate to form the nucleus, though a new name was recommended. Strictly military programs would continue under the Department of Defense.12
During April 1958, Eisenhower delivered the formal executive message about the national space program to Congress and submitted the Administration's bill to create what was then called the "National Aeronautical and Space Agency." The hearings and committee work that followed inevitably entailed revisions and rewording, but the idea of a civilian space agency persisted, and the old NACA role of research alone began to change to a new context of large-scale development, management, and operations. Congress passed the National Aeronautics and Space Act of 1958 on 16 July, and Eisenhower signed the bill into law on the 29th. During August, the Senate speedily confirmed Eisenhower's nominations of T. Keith Glennan as Administrator and Hugh Dryden as Deputy Administrator. At the time of his appointment, Glennan was president of Case Institute of Technology and had been a member of the Atomic Energy Commission. Dryden, a career civil servant, had been Director of NACA but was passed over as the new chief of NASA. The subsequent days and months included some jockeying and horse trading to establish the principal directives of the new organization.
When the Space Act was signed, no mention was made as to the management of a program for manned space flight, and the Army, Navy, and Air Force continued to maneuver for position until late August, ....
[33] .....when Eisenhower specifically designated NASA as the agency to conduct manned space flight programs. In September, NASA's new Administrator, T. Keith Glennan, and Roy Johnson of ARPA agreed to cooperate in the development of a manned satellite. NASA's effective date of birth was l October 1958. The employees who left their NACA offices Tuesday evening, 30 September, returned to the same offices Wednesday morning as personnel of the National Aeronautics and Space Administration. With the passage of time, ARPA's entire big-booster program would find a niche in the new organization.13 These were bold plans, and neither the old NACA nor the new NASA possessed an existing capability for the job. Glennan wanted ABMA's von Braun team for its abilities in launch vehicles and the Jet Propulsion Laboratory (a major Army contractor) for its general expertise in astronautical engineering and payload development. NASA had to accept a compromise: the space agency got the Jet Propulsion Laboratory (officially transferred on 3 December 1958), but ABMA's missile team stayed in the Army. ABMA and its big booster were, however, already enmeshed in NASA planning, and it was only a matter of time before assimilation was complete.14
NACA, for its part, had already been speculating about its role in the space program, and several committees had been at work in late 1957 and early 1958 studying the various factors a space program entailed: vehicles; reentry; range, launch, and tracking; instrumentation; space surveillance; human factors; and training. Late in March 1958, a NACA group studying "Suggestions for a Space Program" included notations for a launch program in January 1959 to put satellites of 135 000 to 225 000 kilograms in orbit (reflecting the earlier Department of Defense plans), and development of a rocket of 4 450 000 newtons (1 million pounds) thrust, as well as "development of hydrogen fluorine and other special rockets for second and third stages."
The ABMA large booster program first entered NASA planning through the NACA Special Committee on Space Technology chaired by Guyford Stever. The Working Group on Vehicular Program included von Braun as chairman. Organized 12 January 1958, the Stever committee made its final report on 28 October, when NASA was already a month old.15 Von Braun's working group on vehicles had already made its preliminary report on 18 July. The language did not differ much from that of the final draft. The report began with harsh criticism of duplication of effort and lack of coordination among various organizations working on the nation's space programs. "The record shows emphatically," the report said, that the Soviet Union was definitely ahead of the United States in space travel and space warfare.
How was the United States to catch up? There were several existing vehicle systems to help the United States proceed on a logical and consistent space research program. At least two large booster types under [34] development or in the planning stages would place the Americans in a better position. The von Braun paper described five generations of boosters. First was the Vanguard class of launch vehicles, and second were the Juno and Thor IRBM vehicles. Third were the Titan and Atlas boosters from the ICBM inventory. Fourth came the clustered boosters, which would yield up to 6 700 000 newtons (1.5 million pounds) of thrust. Fifth, and last, was the possibility of using an advanced 6 700 000-newton (1.5-million-pound) thrust single-barrel engine in a cluster of two to four engines to give up to 25 000 000 newtons (6 million pounds) of thrust. How were they to be employed? The working group conjectured that the United States might put into operation a four-man space station in 1961 with the use of the ICBM boosters. By using clustered boosters, with first flights beginning in 1961, the committee estimated a manned lunar landing in 1965-1966. The clustered vehicles would also support the deployment of a 50-man space station in 1967, and the fifth generation of boosters would support sizable moon exploration expeditions in 1972, set up a permanent moon base in 1973-1974, and launch manned interplanetary trips in 1977. "The milestones listed... are considered feasible and obtainable as indicated by the supporting information presented in the body of the report," the working group concluded.16
The recommendations to achieve these goals included NASA's rapid development as the major director and coordinator of the vehicle program, working in partnership with ARPA. "The immediate initiation of a development program for a large booster, in the 1.5 million pound [6 700 000 newton] thrust class, is considered a key to the success of the proposed program," the report stated, and urged the development of such an engine. The program would cost about $17.21 billion to pay for 1823 launches, including the as-yet undeveloped ICBM and clustered boosters. There would be considerable savings, the group noted, if a comprehensive booster recovery scheme were incorporated.17
With von Braun representing ABMA on the Stever committee, his presence marked an early meshing of ABMA and NACA in the nation's space programs. Indeed, the Stever committee was intended to fill in the gaps in NACA space technology. NACA officials James Doolittle, Dryden, and Stever selected committee members with an eye to their future roles in the space programs as well as educating NACA personnel in space R&D. Large rocket boosters certainly constituted a big gap in NACA competence, so that the selection of von Braun was a key move, along with Sam Hoffman of Rocketdyne, Abe Hyatt of the Office of Naval Research, and Colonel Norman Appold, representing Air Force General Bernard Schriever, who spearheaded the development of big rockets in the Air Force.18
[35] The interwoven activities of a civilian space agency using a booster of military origins left the issue of payloads somewhat uncertain. ABMA had been operating its big booster program under the aegis of ARPA and considered the Juno V primarily a military vehicle with an imprecise potential for use in a civilian role. On 13 October 1958, ABMA listed its customers in order of importance. First was ARPA, as the Department of Defense representative of all military services, with the Juno V as a general carrier vehicle for research and development of "offensive and defensive space weapons." Certain specific tasks were forecast for each of the military services, including navigation satellites for the Navy; reconnaissance, communications, and meteorological satellites for the Army and Air Force; support for Air Force manned missions; and surface-to- surface supply for the Army at distances up to 6400 kilometers. For NASA, the ABMA planners considered the possibilities of the Juno V in support of satellites, space probes, and space stations, as well as a test bed for a 6 700 000-newton (1.5-million-pound) thrust engine and other propulsion systems. There was also conjecture about using the big clustered booster for international programs sponsored by the United Nations and for missions under contract to companies in the private sector.19
Because the mission plans were beginning to place more and more emphasis on putting payloads in orbit, there was an evident need for an upper stage to ensure orbital velocity of the payload. During the latter months of 1958, engineers at ABMA had already begun the search for a feasible upper stage for the Juno V, although the amended ARPA order in September called for lower flight stages only. Medaris urged upper-stage studies because he liked the idea of a unified and cohesive design effort; applying the "off-the-shelf" dictum, he sought to identify possible upper-stage candidates from projects already under way. One suggestion resulting from such brainstorming was to mount an X-15 research plane atop the Juno V, or perhaps incorporate an Air Force project known as Dyna-Soar. The X-15 idea did not last long, but Dyna-Soar persisted for several years. The Dyna-Soar (for dynamic soaring) dated from the autumn of 1957 and was envisioned as a manned, rocket-propelled glider in a delta-winged configuration, capable of reaching altitudes of up to 120 kilometers. More likely prospects for Juno V upper stages included Jupiter, Atlas, and Titan.20
The problems of selecting the Juno V configuration, upper stages, and payloads also bothered the people at NASA. Sitting in his office on the second day of the new year 1959, W. L. Hjornevik, Assistant to the Administrator, dashed off a memo to his boss, Glennan. Hjornevik's [36] message addressed itself to a basic issue in NASA's future: "Next Steps in the Development of a National Booster Program." The overtones in the memo suggested the uncertainties that still faced the young organization, not only in crystallizing specific goals but also in developing the capabilities for the tasks ahead. In spite of conversations with Dryden and others at NASA, Hjornevik wrote, he was still not sure of the proper route to take in developing a rational booster program. The payloads were still unsettled, and there was the problem of timing to bring boosters on line while the payload issue was still open. The question of a conventionally fueled second stage remained unanswered, even while "our position on the million-pound cluster" was unresolved.21
During 1959, NASA began to cope with these issues. A plethora of committees, long meetings, and voluminous reports provided the milieu in which NASA and Department of Defense personnel came to agreement on booster priorities, upper stages, and the issue of high-energy propellants. In the process of settling these problems, NASA acquired its own in-house capability for the production of the nation's first large launch vehicles, to be known as the Saturn rockets.
In a report prepared for President Eisenhower, dated 27 January 1959, NASA officially structured its own plan for a national space vehicle program. Attributed to NASA's propulsion staff, the document was prepared under the aegis of Abraham Hyatt, Chief of Launch Vehicles. The principal author was a NASA engineer, Milton Rosen. Preparation of the report included liaison with the Department of Defense, especially ARPA, the Air Force, and the Army to avoid duplication of effort and keep the Department of Defense informed of NASA's intentions regarding the use of military hardware. In its preamble, Rosen's report emphasized the lag in American rocket technology vis-a-vis the Russians and underscored the need for a new generation of large boosters. "The current group of booster vehicles, namely Vanguard, Jupiter C, Juno II, and Thor-Able, were all hurriedly assembled under pressure of meeting the threat of Russian Sputniks," the document declared, "and none of them possesses the design characteristics required by future needs of the National Space Program." A successful space program, in NASA's view, required three new classes of general-purpose launch vehicles.
The first type included two versions based on the Atlas, one as a single-stage booster, and the other as a two-stage booster using the liquid-hydrogen-fueled Centaur as the second stage. The Centaur proposal had special significance, because liquid hydrogen (LH2) technology was recommended for inclusion in later designs. In fact, if high-energy liquid hydrogen fuel failed to become an operable technology, then the Rosen report predicated disappointingly low payloads in the future.
The second group of boosters was keyed to the Juno V, the ABMA eight-engine cluster concept. NASA envisioned the Juno V as the first stage of a large multistage vehicle, requiring second and third stages to [37] make a complete booster, and the report proposed two different configurations. For the version known as Juno V-A, the NASA propulsion staff recommended adding the Titan I ICBM, itself a two-stage missile with conventional fuel, making a three-stage vehicle. For Juno V-B, the third (top) stage would be replaced with an LH2-fueled vehicle, probably the Centaur, to achieve higher escape velocities. Missions for the two Juno V variations included orbital research payloads, a five-man orbiting module, and unmanned lunar and other planetary missions using a fourth stage to gain escape velocity for larger payloads. The report further estimated that the Juno V configurations would be operational in 1963, with a useful lifetime of 5 to 10 years.
One of the most interesting items in the Rosen report pertained to a completely new class of launch vehicle-a super rocket of extraordinary size and payload capability known as Nova. Propulsion for the Nova class of vehicles would rely on the 6 700 000-newton (1.5-million-pound) thrust single-chamber engine that had been under development by the Air Force. With four engines clustered in the first stage, Nova would generate an unprecedented 25 000 000 newtons (6 million pounds) of thrust at liftoff. The second stage would use one of the same engines, and the third and fourth stages would incorporate liquid- hydrogen-fueled engines (developed in the Juno V program), with four of them in the third stage and one in the fourth stage. The amount of propellants needed for such a high-powered vehicle meant unusually large propellant tanks and a rocket that towered to a height of 79 meters. NASA, however, would also have a vehicle capable of fulfilling the dream of a manned lunar landing. "Despite its immense size," the Rosen report argued, "Nova is the first vehicle of the series that could attempt the mission of transporting a man to the surface of the moon and returning him safely to the earth."22
During the course of the year, NASA's attention was directed primarily toward Juno V and Nova, although some name changes occurred. In February, the Department of Defense announced that the Juno V development program would henceforth be known as Project Saturn, with work to be continued at Huntsville under the direction of ABMA. The change in big booster nomenclature was consistent with von Braun's earlier inclination to refer to the clustered rocket as Saturn and logically followed the Jupiter vehicle in terms of christening boosters after successive planets in the solar system. The Saturn also reflected a proclivity within ABMA to name some boosters after ancient gods,23 such as Juno and Jupiter.
Meanwhile, the von Braun team at Redstone Arsenal was becoming thoroughly enmeshed with the problem of selecting Saturn's upper stages. A "Saturn System Study," completed and submitted to ARPA on 13 March, contemplated the use of either Atlas or Titan upper stages. But dozens of potential upper-stage configurations were possible. This....
.....made NASA a bit anxious because realistic planning was difficult as long as no firm booster configuration was drawn up. T. Keith Glennan expressed his concern in a memo to Roy Johnson at ARPA within a week of the publication of the "Saturn System Study." An early decision on Saturn upper stages was needed, he said, and he urged Johnson toward an early resolution of the issue.24
ARPA's own plans for the Saturn booster remained tied to a combination with Centaur, to place "very heavy satellites in high orbits, especially for communications purposes." In testimony before Congress in late March, Johnson described the ARPA program for such satellites in equatorial orbits for global communications. More than that, he emphasized development of the Saturn cluster as a number one priority because it would serve a number of vehicle requirements for the next two years, not only for communications but also as an all-purpose space "truck" for a variety of missions, including launches of manned orbital satellites.25
The all-purpose Saturn suddenly ran into stiff opposition within the Department of Defense. Herbert York, Director of Department of Defense Research and Engineering, announced that he had decided to [39] terminate the Saturn program. In a memorandum to Johnson dated 9 June 1959, York rebuffed an ARPA request for additional funds. "In the Saturn case," York said, "I consider that there are other more urgent cases requiring support from the limited amount... which remains uncommitted." York's reasoning apparently stemmed from a position taken by other Eisenhower Administration advisors that the requirements of the Department of Defense for launching military communications satellites would be achieved more effectively by relying on existing ICBM boosters. Saturn had always been touted as the military's booster for such missions, so it did not seem to be needed any more. Saturn was a "costly operation being conducted at ABMA," York wrote, and advised Johnson, "I have decided to cancel the Saturn program on the grounds there is no military justification."26 York's bombshell came as a real blow to ABMA, especially since the first H-1 engines for the Saturn cluster had begun arriving in Huntsville some weeks before, in April.27
With NASA programs tied closely to the Saturn, as indicated in the earlier Rosen report, the launch vehicle staff in Washington immediately got to work to head off the York cancellation order as soon as they heard the news. Collaborating with Saturn supporters from within the Department of Defense, Rosen and Richard Canright from ARPA drafted a crucial memorandum in defense of the clustered booster program. They realized that Saturn as an Army project was in trouble apparently because the Army had no specific use for it. At that time, neither did NASA, although Rosen and Canright felt that the range of potential missions cited in the prior Rosen report offered, in the long run, enough justification to keep Saturn alive. Rosen and others in NASA were completely captivated by Saturn's promise. "We all had gut feelings that we had to have a good rocket," he said, emphasizing the appeal of Saturn's size. Rosen felt that he had "lived all his life with too small a launch vehicle."28
Thus, in a tense three-day meeting, 16-18 September 1959, York and Dryden co-chaired a special committee to review Saturn's future and discuss the roles of the Titan C boosters and the Nova. Committee members included representatives from the Army, Air Force, and NASA as well as Canright from ARPA. After hours of intensive presentations and discussion, the Saturn backers finally carried the debate, but not without some conditions. Under York's prodding, it was agreed to start discussions to transfer ABMA and the Saturn project to NASA. York also insisted that such a transfer could be accomplished only with the Administration's guarantee for supplemental funding in support of Saturn.29
Years later, reviewing the issue of Saturn's cancellation, York elaborated on his reasoning. For one thing, there seemed to be a strong feeling within the Department of Defense that Saturn tended to siphon off money, not only from important military projects in ABMA but from [40] the Air Force as well. The Secretary of Defense twice turned down requests for a DX (priority) rating for Saturn, once in December 1958 and again in May 1959. Moreover, York felt that Saturn was simply too big for any military mission, and that included men in space. Big boosters of the Saturn class should be NASA's responsibility, he reasoned, because there was no urgent military application and because of York's own reading of the Space Act of 1958 and his understanding of Eisenhower's views on the matter. In the meantime, York apparently agreed to continue adequate funding of Saturn through ARPA until the issue of ABMA's transfer to NASA was resolved. As for the von Braun team at Hunstville, York recalled that von Braun himself "made it very clear in a face-to-face discussion in the Pentagon that he would go along only if I allowed Saturn to continue."30
The near loss of the Saturn booster was a sobering experience. This close brush with disaster underscored NASA's problems in securing boosters developed and produced by other agencies; many in NASA now believed they had to have control of their own launch vehicles. In fact, York had already favored the transfer of ABMA, with responsibility for Saturn, to NASA. Late in 1958, when Glennan and Deputy Secretary of Defense Donald A. Quarles had proposed such a transfer, the Army and ARPA had strongly opposed the move.31 The ABMA transfer continued to beguile top NASA executives, and Hjornevik emphatically urged action on the matter. In a memo to Glennan late in January 1959, Hjornevik argued that the role of ABMA as consultant and supplier was operable as long as NASA was content merely to buy Redstone rockets in the Mercury program, but the rapid changes in an ambitious NASA launch program revealed a gap in the agency's capabilities, and Hjornevik left no doubt that NASA needed ABMA's competence. Hjornevik phrased his recommendations in no uncertain terms. "I for one believe we should move in on ABMA in the strongest possible way," he declared. "It is becoming increasingly clear that we will soon desperately need this or an equivalent competence." Hjornevik cited NASA's needs in managing the national booster program, especially the engines and "the big cluster," and the suggested joint funding as a means to "achieve a beachhead on the big cluster."32
Roy Johnson, speaking for ARPA, emphasized the need for keeping the von Braun team together, particularly if a transfer occurred. "At Huntsville we have one of the most capable groups of space technicians in the country," Johnson said during congressional testimony in March 1959. "I think that it is a unique group... a national resource of tremendous importance." Then he added, "ABMA team is the kind of group that, if somebody had planned 10 years ago to create it, could not have been done better." Although Johnson told the congressional committee that he could work with ABMA in or out of the Department of Defense, he personally preferred it in the Department of Defense.
[41] Among other things, he commented, he was not optimistic about lunar payloads taking precedence over the Saturn's role as a booster for military satellites.33
NASA's lively interest in Saturn and the Huntsville group continued to mount. In mid-April, Glennan called a meeting of Dryden, Hyatt, Hjornevik, and others, including Abe Silverstein, Director of Space Flight Development. The NASA executives got together one Friday to assess the events of the past week and, among other things, to consider the question of Saturn. In the course of the discussion, the participants reached a consensus that the highly competent ABMA group had the best qualifications to develop the total Saturn vehicle, and they should be encouraged to forge ahead. At the same time, NASA should keep a sharp eye on its own interests in regard to Saturn and build a "significant financial and management role." A distinct takeover move, previously pushed by Hjornevik, did not take place for several months, simply because, as Glennan himself observed, NASA lacked a specific mission for Saturn that would justify wrenching the booster away from ARPA.34
But the days of Saturn's ties to ARPA were numbered. After letting the issue simmer on a back burner most of the year, York raised the transfer issue again in the autumn of 1959, and this time got the support of both the Secretary of Defense and President Eisenhower.35 Given the inclinations of the NASA hierarchy, ABMA's transfer from ARPA became inevitable. NASA's own requirements for a booster the size of the Saturn had been made more explicit as a result of the Research Steering Committee on Manned Space Flight, chaired by Harry J. Goett of NASA's Ames Research Center. The Goett committee, formed in the spring, had considered NASA goals beyond the Mercury program, and during the summer a circumlunar mission emerged as the principal item in NASA's long-range planning. A manned lunar landing required a much larger booster-Saturn. With potential mission and booster requirements finally outlined, satisfying Glennan's criteria to have a specific mission for the launch vehicle, total NASA responsibility for Saturn was obviously needed.36
The transfer of ABMA, Saturn, and the von Braun team was phased over a period of nearly six months. NASA's technical direction of Saturn dated from a memorandum signed by Glennan on 21 October 1959 and by the acting Secretary of Defense, Thomas Gates, on 30 October, and approved by Eisenhower on 2 November. The document affirmed continuing joint efforts of NASA and the Department of Defense in the development and utilization of ICBM and IRBM missiles as space vehicles. Pointing out that there was "no clear military requirement for super boosters," the memorandum stated that "there is a definite need for super boosters for civilian space exploration purposes, both manned and unmanned. Accordingly, it is agreed that the responsibility for the super booster program should be vested in NASA."
[42] Specifically, the core of ABMA's Development Operations Division would be shifted to NASA-Saturn personnel, facilities, equipment, and funds. Both sides agreed on the unique talent of the von Braun team and the need to keep it intact. "The Department of Defense, the Department of the Army, and NASA, recognizing the value of the nation's space program of maintaining at a high level the present competence of ABMA, will cooperate to preserve the continuity of the technical and administrative leadership of the group."37
The process of coordinating the administrative, technical, and physical transfer of the Saturn program progressed during the early months of 1960. To help provide guidelines and avoid as much chaos as possible, NASA called on McKinsey and Company, a private management consulting firm with offices in several major U.S. cities, including Washington. McKinsey and Company had helped NASA set up its own organization in 1958 and was thereby familiar with the agency's headquarters structure and personnel. By March 1960, the move was complete. On the 16th of the month, NASA assumed both administrative and technical direction of the Saturn program. The Goett committee, having wound up its work in December 1959, had pointed NASA in the direction of lunar-oriented missions as a goal. The transfer of the von Braun team, completed in the spring of 1960, gave NASA the expertise and a vehicle program to perform the task.38
In the process of shedding ABMA's initials, the von Braun team now acquired a new set. By a presidential executive order on 15 March 1960, the space complex within the boundaries of Redstone Arsenal became the George C. Marshall Space Flight Center (MSFC). On 1 July 1960, Major General August Schomburg, commander of the Army Ordnance Missile Command, formally transferred missions, personnel, and facilities to von Braun, as Director of MSFC. Official dedication took place on 8 September with Mrs. George C. Marshall and President Dwight D. Eisenhower heading the list of distinguished visitors. In his public remarks, President Eisenhower noted Marshall's military career, his distinguished service as the Secretary of State, and the award to Marshall of the Nobel Peace Prize, the only professional soldier to have received it. "He was a man of war, yet a builder of peace," proclaimed Eisenhower. These sentiments fittingly paralleled the evolution of MSFC, with its origins in the Army Ballistic Missile Agency. In a brief, but moving ceremony, Mrs. Marshall unveiled a red granite bust of her late husband. Then von Braun escorted Eisenhower on a tour of the site, including a close-up inspection of the Saturn booster under construction.39
During the months in which their relocation was being debated, ABMA personnel in Huntsville were still absorbed in the exercise of [43] trying to determine the configuration of upper stages for their multiengine booster. Design drawings of Saturn B and Saturn C studies during the first few months of 1959 showed clustered tank-and-engine first stages of 6.5 meters diameter and various combinations of upper stages of 6.5-meter and 3-meter diameters towering as high as 76 meters. The use of new hardware was apparently not contemplated; given ARPA's guidelines for economy in the program, a more realistic possibility was to add upper stages that used Titan or Atlas ICBM vehicles fitted directly to the clustered tankage and engines. By the spring of 1959, both ABMA and ARPA agreed on the feasibility of Titan and Atlas versions. ARPA advisors leaned more toward a decidedly hybrid concept in which a modified Titan second stage was used in combination with a modified Centaur third stage from the Atlas vehicle. Yet another twist in the evolution of Saturn upper stages came in July, when DOD's Director of Research and Engineering issued a new directive to both the Air Force and ARPA to consider the joint development of a second-stage vehicle keyed to the Air Force Dyna-Soar project, since the Saturn second stage and the Dyna-Soar booster appeared to be similar in design and concept. So ARPA ordered work on the Titan upper-stage studies to stop, pending further studies on this new DOD directive, although R&D work on the first-stage cluster forged ahead through the summer.40
The decision to halt work in mating existing military missiles to the Saturn came as something of a relief to ABMA. Using such off-the-shelf hardware definitely narrowed the flexibility of mission planning. As a second-stage booster, it turned out that Jupiter just did not have the muscle, and the Atlas and Titan, although adequate in thrust for their ground-launch ICBM role, lacked performance capabilities as upper-stage vehicles to be ignited at altitude. Moreover, their 3-meter diameters limited their growth potential in relation to the possibilities of the far bigger Saturn. "In comparison," Willy Mrazek said, "this was like....
[44] ....considering the purchase of a 5-ton truck for hauling a heavy load and finally deciding to merely load a wheelbarrow full of dirt."41 As a result of new evaluation studies that followed cancellation of work on the Titan as an upper stage, ARPA decided to forego requirements to employ existing hardware, and ABMA confidently embarked on a new series of design concepts for Saturn upper stages, utilizing large diameters that offered increased mission flexibility and payload capability. Undertaken in the fall of 1959, these new "Saturn System Studies," as they were called, were conducted with an eye to NASA requirements in particular.42
The last months of 1959 could be called a watershed period for NASA in many respects. The agency had acquired the von Braun team and sharpened the focus on upper stages for a multistage vehicle. In December, a critical judgment on the application of high-energy propellants for Saturn's upper stages was in debate. The issue of high-energy propellants centered on liquid hydrogen in combination with liquid oxygen-and the use of liquid hydrogen (LH2) did not have the wholehearted support of von Braun or his staff at Huntsville.
At NASA Headquarters, on the other hand, Abe Silverstein and several others were convinced that LH2 was the key to future Saturn success. Silverstein had joined NACA in 1929, and worked in wind tunnels at the Langley Laboratory. When the Lewis Propulsion Laboratory was formed in Cleveland, Ohio, in 1943, Silverstein joined the new organization and became its Associate Director in 1952. He had come to Washington in 1958 to become Director of Space Flight Development. For the next three years, Silverstein played an important role in policy decisions at NASA Headquarters before returning to Cleveland as Director of Lewis Research Center.
NASA had inherited an LH2 development program as a result of NACA work carried on at Lewis Research Center throughout the 1950s; the work culminated in the successful test of an 89 000-newton (20 000-pound) thrust LH2 engine and propellant injector in the late l950s. The Lewis LH2 group, led by Abe Silverstein, had been convinced of the practicality of LH2 by subsequent successful test runs. The research at Lewis-and its successful prototype engine design-encouraged Silverstein to push hard for LH2 engines in Saturn's upper stages.43 The first practical application of the LH2 engine was planned as a high-energy stage, named Centaur, for Atlas or Titan. The plan stemmed from an ARPA directive to the U.S. Air Force's Air Research and Development Command. During congressional testimony in March 1959, Roy Johnson noted early plans to incorporate an LH2-fueled stage (apparently the Centaur, or a close derivative) on the Saturn vehicle. Continuing research was solving problems of pumping LH2 in large quantities, he explained, and he expected a breakthrough in propulsion for use in a second or third stage. Johnson's enthusiasm for an LH2 vehicle was unbounded. "It is a miracle stage as I see it," he declared.44 By the summer of 1959, the LH2 rocket [45] also had support at NASA Headquarters, where Hyatt was corresponding with Silverstein about it.45
Just before the Christmas holidays, the stage was set for a high-level conference at Headquarters to determine the basic configuration of the multistage Saturn. On 17 November, Associate Administrator Richard Horner told the Director of Space Flight Development to organize a study group to make additional recommendations concerning the transfer of the von Braun team to NASA, "to prepare recommendations for guidance of the development of Saturn, and specifically, for selection of upper-stage configurations." A "Saturn Vehicle Team" was organized; it comprised representatives from NASA, the Air Force, ARPA, ABMA, and the Office of the Department of Defense Research and Engineering (ODDR&E). Chaired by Abe Silverstein, the seven-man group was known as the "Silverstein Committee." In addition to Silverstein, the NASA representatives included Hyatt and Eldon Hall, and the other members were Colonel N. Appold (USAF), T. C. Muse (ODDR&E), G. P. Sutton (ARPA), and Wernher von Braun (ABMA).46
When the Silverstein committee convened in December, not everyone was in favor of the untried LH2 technology because LH2 was widely thought to be too volatile and tricky to handle. Von Braun in particular expressed doubts about LH2 even though the Saturn-Atlas combination had the Centaur's LH2 system in the Atlas final stage, and he was definitely opposed to a new LH2 Saturn second stage. On the other hand, several influential committee members made a forceful case for LH2. Hyatt was already for it; Eldon Hall, not long before the committee had been organized, had analyzed the performance of launch vehicles using various combinations of propellants. Using his background in the work previously done at Lewis, Silverstein argued with all the persuasive powers at his command. It was just not logical, Silverstein emphasized, to develop a series of vehicles over a 10-year period and rely on the limited payload capability of conventionally fueled boosters with liquid oxygen and kerosene-based propellants. He was convinced that the use of LH2 in the upper Saturn stages was inherently sound, and his conviction was the major factor in swaying the whole committee, von Braun included, to accept LH2 boosters in the Saturn program. "Abe was on solid ground," von Braun acknowledged later, "when he succeeded in persuading his committee to swallow its scruples about the risks of the new fuel."47
Next, von Braun had to convince his colleagues back at Huntsville. Before the committee adjourned, von Braun telephoned the Redstone Arsenal to talk to Mrazek, one of the key team members who had come with him from Germany, and the two men brainstormed the possibilities.
As Mrazek recalled his phone conversation, von Braun made the following points: The Saturn could not use existing hardware for the upper stages-it needed an original design; the Saturn plan should stress the new hydrogen technology and the Centaur's engines; and the hydrogen upper stage would need six engines. This final aspect could have been controversial because some experts still harbored strong doubts about the use of eight conventional, though proven, rocket engines for the first-stage booster. There would be even more carping about a half dozen new and untried engines burning exotic liquid hydrogen. But von Braun said he was not overly concerned about the cluster of six hydrogen engines, since at least a dozen Centaur launches were scheduled before the first Saturn would have to go up. The ABMA group could profit from whatever trials and tribulations the Centaur engines developed, with plenty of time to iron out any problems before the first Saturn left the launch pad. In short, von Braun was confident of success with the new hydrogen technology, and Mrazek agreed; so the scenario was finally set.48 (See chapter 5 for further details of LH2 technology.)
[47] In the spring of 1960, as the word of NASA's decision to rely on the novel propellant combination for Saturn reached the public, Eldon Hall and Francis Schwenk, from the Office of Launch Vehicle Programs at NASA Headquarters, outlined the reasons for the choice. The higher vehicle performance required for advanced missions simply required higher energy propellants, they explained. The staging of several rockets using conventional propellants rapidly reached optimum design limits, because advanced missions and payloads required more thrust and more engines-which meant heavier rockets with bigger tanks and engines and proportionately less efficiency in design and capability. On the other hand, high-energy propellants promised the best results for advanced missions requiring high escape velocities. "The choice of high-energy upper stages for Saturn is based almost entirely on the fact that, with present knowledge of stage construction, at least one of the upper stages must use high-energy propellants if certain desirable missions are to be accomplished with this vehicle," Hall and Schwenk emphasized. So "the Saturn program was established for early incorporation of a high-energy second stage into the vehicle system."49
In the course of the deliberations of the Silverstein committee, three types of missions for the Saturn vehicle emerged. First priority was given to lunar and deep-space missions with an escape payload of about 4500 kilograms. Next in order of priority came satellite payloads of about 2250 kilograms in a 24-hour equatorial orbit. Finally, the committee considered the possibility of manned missions involving the Dyna-Soar program, in which a two-stage vehicle would be used to put 4500 kilograms into low orbit. On the basis of these assumptions, the committee stressed the evolutionary pattern of Saturn development and its potential for a variety of future roles. "Early capability with an advanced vehicle and possibilities for future growth were accepted as elements of greatest importance in the Saturn vehicle development."
Once more, the Saturn Vehicle Team reviewed the wide array of potential configurations, reduced the number of choices to six, and began to weed out the least promising. The A-1 version, with modified Titan and Centaur upper stages, would provide the earliest flight schedules and lowest costs with existing hardware. It was rejected because it could not meet lunar and satellite payload requirements and because the slender 3-meter-diameter upper stages were considered to have potential structural weaknesses. The A-2 type, with a cluster of Intermediate Range Ballistic Missiles (IRBMs) in the second stage, also saved money and promised early availability but did not have the capability for some of the planned missions. A proposed B-1 vehicle met all mission requirements but needed a totally new stage with conventional fuels. The B-1 type was expensive, would take a lot of time to develop, and had some shortcomings for advanced missions.
[48] Moreover, all first three candidates needed high-energy propellants in the top stage. So why restrict the promise of LH2 to the top stage alone? "If these propellants are to be accepted for the difficult top-stage applications," the committee concluded, "there seem to be no valid engineering reasons for not accepting the use of high-energy propellants for the less difficult application to intermediate stages." The Saturn family of rockets finally envisioned by the Silverstein committee included C-1, C-2, and C-3, all with LH2 in the upper stages. The three-stage C-1 met the mission requirements and used Centaur engines in the LH2 upper stages. The second stage had four uprated Centaur engines, designated the S-IV stage, and the S-V top stage was the Centaur itself, with two engines. The hop-scotch numbering occurred because of the "building block" concept, in which hardware was used as available, the concept, was tested, and then newer and advanced stages were incorporated in the next major configuration. During C-1 development and flight, for example, a new S-III stage for Saturn C-2 would be prepared with the use of a newer, more powerful generation of LH2 engines. As the development and flight test of Saturn C-2 proceeded, the S-II stage would be worked up with four of the newer LH2 engines. The final C-3 vehicle would stack all the various stages together as a five-stage booster. Further, the Saturn Vehicle Team suggested that the first stage of the C-3 model might even include an F-1 engine to replace four of the cluster of eight uprated H-1 engines.
In its final recommendations for the phased development of Saturn C-1 through C-3, the Silverstein committee emphasized the building block concept keyed to the Saturn first-stage cluster, along with hydrogen-oxygen propellants in all the upper stages. Proceeding from the Centaur technology under development at the time, the committee urged immediate development of a new LH2 engine and initiation of design studies for the S-II and S-III stages to use the more powerful engines.50
With in-house capability established, in the form of the ABMA transfer, and with immediate vehicle guidelines established as a result of the Silverstein committee, NASA now proceeded to refine its priorities and goals.
The ultimate goal was a lunar landing. The Director of Lunar Vehicles, Donald R. Ostrander, stated in a planning conference for NASA and industry in January 1960: "The principal mission which we have used as an objective in these planning studies has been that of a manned landing on the moon and return to earth."51 Looking ahead, NASA executives told Congress during hearings late in the same month that the agency planned a circumlunar flight by 1970 and a manned ....
[50] .....lunar landing soon after. The agency also estimated the cost at $13 to $15 billion over the coming decade, and Associate Administrator Horner explained the need to look so far ahead and plan a budget:
Virtually all of our key programs presume a scheduled progress in launch vehicle and spacecraft development. These major developmental tasks frequently require time periods of 5 to 6 years for completion and can be substantially longer under given circumstances of technological progress and research availability.
Thus, although the usefulness of highly tentative plans might be questioned, long-term objectives, on the order of 10 years in advance of today's program, are essential to keep our development activities properly focused.
The actions we initiate this year and next in the vehicle development program will have a determining influence our capabilities for meeting national objectives in the last half of this decade and even beyond. Accordingly, we have developed a 10-year plan, one which we expect to modify from year to year on the basis of realized experience, development progress, and resource availability. It is formulated around the requirement that its implementation must so utilize the resources of the United States that our national role as a leader in the aeronautical and space sciences and their technologies is preserved and steadily enhanced. We have also assumed that a steady growth in the scale and intensity of our efforts, especially for the next 5 years, is an essential basis for consistent and fruitful efforts in meeting this requirement.52
As NASA prepared to forge ahead on its 10-year program in 1960, the agency enjoyed increased support from Eisenhower, and Glennan won an important advantage for the Saturn program in terms of a high priority endorsement. "As we have agreed," the President wrote to Glennan on 14 January, "it is essential to push forward vigorously to increase our capability in high thrust space vehicles." In the same directive to Glennan, Eisenhower gave his authorization to prepare an additional funding request for the balance of fiscal 1960 and 1961, "to accelerate the super booster program," and to use overtime as needed, "consistent with my decision to assign a high priority to the Saturn development." Four days later, on 18 January, the rating for highest national priority (DX rating) became official, authorizing the use of overtime wages and giving Saturn precedence for materials and other program requirements.53
The configurations of the Saturn family were still in a state of flux, however, and the Nova was still a probability in the NASA scheme. Straightening out the lines of development and mission application became an issue that absorbed personnel in program studies and committee meetings for another two and a half years. Although the Saturn Vehicle Team did not mention Nova in their recommendations, the towering booster figured prominently in plans for manned lunar landings. During a meeting on advanced propulsion requirements at NASA Headquarters in early June 1960, the Huntsville group discussed Nova "for manned lunar landing and return," in a configuration that [51] would boost a 81 600-kilogram payload to escape velocity and return 6800 kilograms to Earth. The vehicle featured eight of the 6 700 O00-newton (1.5-million-pound) thrust engines in the first stage, four LH2 engines in the second stage, and one LH2 engine each in the third and fourth stages. Data for a C-2 launch with assisted boost from Minuteman missile solid-fuel strap-ons were also discussed, although "Marshall people were not enamored with the idea of any changes to the C-2."54 Therefore, the Saturn configurations remained keyed to liquid propulsion engines, especially the LH2 propulsion systems. NASA planners considered using the Saturn "C" series of vehicles for manned space stations, manned circumlunar missions, and unmanned lunar and planetary probes. Manned lunar excursions, Homer Stewart reminded NASA Administrator Glennan, would definitely require the application of the 6 700 000-newton (1.5-million-pound) thrust engine (known as the F-1) used in a cluster, probably in a Nova vehicle, and if the LH2 program developed any snags, he warned, the Saturn program would quickly find itself in dire trouble.55
Toward the end of 1960, NASA planners decided it was time to review the space program once again and make more specific recommendations for future development in the Saturn and Nova projects. Early in November, NASA laid out its milestone for the next 10 years. "A ten-year interval has no special significance," the report asserted, "yet it is considered to be an appropriate interval since past experience has shown that the time required to translate research knowledge into operationally effective systems in similar new fields of technology is generally of this order." This time span permitted opportunity to establish mission goals and plans and coordinate the development of spacecraft and appropriate booster hardware. Apparently there was already some confusion about terminology, since the "Proposed Long Range Plan," as drafted by the Headquarters Office of Program Planning & Evaluation, included some definitions. "Launching vehicle" meant a first-stage booster and upper stages to inject a spacecraft into proper trajectory. "Spacecraft" included the basic payload as well as guidance and its own propulsion systems for trajectory modifications following injection. The term "space vehicle" encompassed the entire system-launching vehicle plus spacecraft.56
With definitions thus established, the document discussed the major launch vehicles, or boosters, under NASA cognizance: C-1, C-2, and Nova. The C-1 and C-2 descriptions closely followed the analysis prepared by the Silverstein committee the previous year, the descriptions reaffirming the building block concept with the C-1 as a three-stage vehicle and the C-2 as a four-stage booster including a newly developed second stage with a cluster of four 890 000-newton (200 000-pound) thrust hydrogen engines. The R&D for the Centaur and the new hydrogen engines appeared to be the biggest gamble in the long-range plan. The decision to use LOX-LH2 engines in C-1 and C-2 upper stages "was based on a calculated risk," the report stated, that such engine technology [52] would come along smoothly enough to keep the building block sequence on schedule. By FY 1964-1967, according to the "Proposed Long Range Plan," the C-1 should be operational in support of preliminary Apollo orbital missions, as well as planetary probes and as a test bed for advanced technology electron engines and nuclear engines. The C-2 should be ready somewhat later to place twice the payload into orbit, as well as for launching deep-space probes.57
As for the Nova, "its primary mission is to accomplish manned lunar landings," the plan said. Nova was admittedly still in the conceptual stage, since its size and ultimate configuration depended on space environmental research, progress in advanced chemical engines such as the F-1, and potential development of nuclear engines. The Nova, with an F-1 cluster combination to total 53 million newtons (12 million pounds) of thrust in the first stage, seemed to be the most feasible, and the Nova booster could make a manned lunar landing mission by direct staging to the moon and return or by a series of launches to boost hardware into low orbit for a series of rendezvous operations, building up a space vehicle in low orbit for the final lunar mission.58
As a prelude to the ambitious moon missions, a lot of basic research had to be integrated into the plans for the launch vehicle development. Guidance and control was one area singled out for special attention, requiring advances in the state of the art in accelerometers; in cryogenic, electromagnetic, and electrostatic support systems for gyros and attitude control; inertia wheels; in long-life gyro spin axis bearings. The long-range plan noted research challenges in terms of heating and other aerodynamic problems, along with mechanical, hydraulic, electrical, electronic, and structural difficulties. The space environment created a wide range of potential trouble spots in metals, plastics, seals, and lubricants. The scaled-up size of Saturn and Nova suggested difficulties in devising adequate automatic test equipment and techniques for the fabrication and assembly of oversized components. The long-range plan provided the opportunity to look ahead and anticipate these problem areas, giving NASA designers and engineers the chance to start working on solutions to these and other problems that were sure to crop up in the course of launch vehicle development.
The long-range plan also projected a series of key dates in the development of launch vehicles:
|
1961 |
first suborbital astronaut flight |
|
first launch Saturn 1st stage | |
|
1963 |
launch 2-stage C-1 |
|
launch 3-stage C-1 | |
|
1964 |
qualification of 200K LH2 engine |
|
1965 |
qualification of 1.5-million-pound engine |
|
launch 3-stage C-2 | |
|
1968-1970 |
Apollo manned orbiting lab and circumlunar flights |
|
Beyond 1970 |
manned lunar landing |
The long-range plan also estimated the costs.59 NASA's plans at this time found support from the President's Scientific Advisory Committee, which had formed a special ad hoc group to examine the space program to date and analyze its goals, missions, and costs. In its report, released on 14 November, the group advanced the rationale that "at present the most impelling reason for our effort has been the international political situation which demands that we demonstrate our technological capabilities if we are to maintain our position of leadership." The report considered the scientific motive of much less significance than prestige but commented that "it may be argued that much of the motivation and drive for the scientific exploration of space is derived from the dream of man's getting into space himself."60 The committee wondered if 25 test flights for the C-1 and 16 for the C-2 were enough to qualify the vehicles for manned launches but gave NASA good marks overall on their plans and schedules. Further, the committee endorsed the R&D plans for liquid hydrogen technology and encouraged development of larger post-Saturn launch vehicles like the Nova.61
But NASA was not entirely free from difficulties. NASA Administrator Glennan departed NASA at the end of the Eisenhower Administration and resumed his position as president of Case Institute. Several weeks passed before President John F. Kennedy's new Administration settled on a successor. Lyndon Johnson, the Vice-President, still played a strong hand in space program planning, and favored someone with strong administrative credentials. Other advisers contended that NASA needed a technical man at the helm. As the Kennedy Administration prepared to take over early in 1961, the space agency received some hard knocks from the President-elect's science advisor, Jerome B. Wiesner, of the Massachusetts Institute of Technology. Kennedy announced Wiesner's appointment on 11 January and released the "Wiesner Report" the next day.62 Officially titled "Report to the President-Elect of the Ad Hoc Committee on Space," the report gave due credit to the "dedication and talent" that had achieved notable advances in space exploration during the past few years but implied deficiencies in the booster program. "Our scientific accomplishments to date are impressive," the document observed, "but unfortunately, against the background of Soviet accomplishments with large boosters, they have not been impressive enough."
Among other recommendations, the Wiesner report urged technical competence in the positions of Administrator and Deputy Administrator, along with technical directors for propulsion and vehicles, scientific programs, nonmilitary space applications, and aeronautical programs.63
For several weeks, contact with the new Kennedy Administration was [54] haphazard. The Wiesner report aroused real concern among NASA personnel; there was a definite feeling that the report was neither fair nor carefully prepared. The issue of NASA leadership was resolved in February, when James E. Webb was nominated as Administrator. Vice President Johnson had found the managerial talent he wanted. A lawyer and ex-officer in Marine Corps aviation, Webb had headed the Bureau of the Budget and served as Undersecretary of State during the Truman Administration. At the time of his appointment, Webb was actively involved in the management of large corporations and was an active member of several professional administrative and policy organizations. Webb was sworn in by 14 February, with Dryden again as Deputy Administrator. Members of the Wiesner committee were subsequently given a deeper insight into the NASA program and organization that produced a much more positive feeling on their part. The organizational structure of the space agency was indeed firmed up, and a healthy rapport was established with the new Administration.
During the 1960 campaign, Kennedy had made an issue of the Eisenhower record in space, although the question was addressed more in terms of the so-called "missile gap" than in terms of space exploration. After the election, however, the Kennedy Administration evinced a growing interest in NASA's programs. In February, Webb was asked to conduct a thorough review and make recommendations; although a revised NASA budget request was trimmed, the space agency went to Congress in March with a program that amounted to over $125 million more than Eisenhower's original $1.1 billion for fiscal 1962. On 10 April, Kennedy submitted a specific request to amend the Space Act, in keeping with a campaign statement, to revive the dormant National Aeronautics and Space Council, and to appoint Vice-President Lyndon Johnson, a partisan of space exploration, as its head. In sum, the national space program under the new Kennedy Administration began moving with positive, if modest, momentum. Rapid acceleration occurred as a reaction to dramatic Russian progress.64
The successive achievements of Russian efforts in space exploration early in 1961 not only intensified NASA's plans in astronautics, but also influenced President Kennedy's commitment to a more active program by the United States. The day after Webb and Dryden were sworn in, the Soviet Union launched a probe to Venus from a space vehicle in a parking orbit; Kennedy remarked at a public press conference that the Russian lead in space boosters was "a matter of great concern."65 Then, on 12 April, while Congress was debating additional funds for NASA's budget in the coming year, a Russian booster put Yuri Gagarin into Earth orbit-the first human to orbit the Earth. On the evening of the following day, President Kennedy hosted a meeting at the White House, inviting Webb, Dryden, Wiesner, Theodore Sorensen, and several others, including [55] a reporter, Hugh Sidey, from Life magazine. The conversations revealed Kennedy's considerable concern about the Soviet Union's growing preeminence in space. The President speculated about the steps the United States could take to improve its own activities and about the costs involved in an accelerated program. Dryden observed that it might cost up to $40 billion to fund a program to land on the moon before the Russians, and even then, the Russians might make it before the Americans. But the President clearly wanted action. "There's nothing more important," he was remembered as saying.66 Not long afterward, in remarks to the Congress, Kennedy firmly asserted that it was "time for this nation to take a clearly leading role in space achievement, which in many ways may hold the key to our future on Earth."67 Shortly thereafter, Kennedy instructed Johnson and the Space Council to study space projects that would give the United States a visible lead in space exploration.
Congress also wanted more information from NASA about costs and the problems of landing on the moon ahead of the Russians. In mid-April, Webb repeated to Congress what Dryden had told the President. The cost would be anywhere from $20 to $40 billion. Some congressmen suggested the possibility that the Russians might attempt a lunar landing around 1967, in conjunction with the 50th anniversary of the Russian Revolution. With massive infusion of funds, the representatives asked, could the Americans beat a Russian landing? In his response, Associate Administrator Robert Seamans was wary. The target date of 1967 for the Russians was only an assumption, he said. Current NASA planning put an American lunar landing in 1969 or 1970 at the earliest. To reduce American intentions by three years was not necessarily an impossibility, Seamans stated, but would certainly be tremendously expensive in the short term.68
During April and May, the executive and legislative branches of government blossomed committees and working groups like flowers in a spring garden. Within NASA, planning groups funneled a series of honed and polished study papers to the White House for Kennedy's consideration, and the Department of Defense and the space agency refined mutual goals and individual efforts to ensure cooperation where necessary and to avoid needless redundancy. The nexus of all these streams of activity culminated in President Kennedy's State of the Union message on 25 May 1961. The manned space program would be the province of NASA, a civilian agency, not a military agency. He proposed to increase NASA's 1962 budget by more than $500 million. Kennedy left no doubt as to NASA's objective or its schedule for realization. "This nation should commit itself to achieving the goal, before this decade is out, of landing a man on the Moon, and returning him safely to the Earth."69
[56] Haltingly, a national space program coalesced around a new entity, the National Aeronautics and Space Administration. After turning to the Department of Defense for its large boosters, funded through ARPA and under development by ABMA, NASA realized the need to control its own booster program when the Saturn project was nearly canceled owing to budgetary cross-currents. The eventual transfer of the von Braun team and the Saturn booster was a significant step forward for NASA. During 1959-1960, important agreements on upper stages and the use of high-energy LH2 technology were also worked out, capped by President Kennedy's decision to achieve a manned lunar landing within the decade of the 1960s. The next moves required decisions on mission profiles and production facilities.


Buhari Re-appoints NIMC Boss, Aliyu Aziz
by Faderera FaladeThe re-appointment of Aliyu Aziz, Director-General, National Identity Management Commission, (NIMC) for a second term has been approved by President Muhammadu Buhari.
This was disclosed by Mr Abdulhamid Umar, General Manager, Operations and Corporate Communications of the organisation, in a statement he signed and made available to the News Agency of Nigeria (NAN) in Abuja today.
According to Umar, the re-appointment of Aziz was conveyed in a letter by the Secretary to the Government of the Federation (SGF), Mr Boss Mustapha.
“The President of the Federal Republic enjoins Engr. Aliyu Aziz to continue with the good work he is doing and take NIMC to the next level, in consonance with the Federal Government’s doctrine of integrity, transparency and accountability.’’
“This re-appointment is in pursuant to the NIMC ACT that provides two terms tenure for the Chief Executive Officer of the Commission,’’ he said.
He said the second tenure of Aziz, commences today, Nov. 22.


Big button: Used for Primary Call-To-Actions on the Page. For instance, "Go to dashboard", "Open Report", etc
Mid button: Used for Secondary Call-To-Actions on the Page. For instance, "Link to CaseStudy" CTA in Product Update email, etc
Small button: Used for multiple Call-To-Actions sharing common purpose on the Page. For instance, "Open Comment thread", etc
Paragraph: Used for multiple Call-To-Actions sharing common purpose on the Page. For instance, "Open Comment thread", etc
This is a brilliant paragraph being read by a brilliant person, in a brilliant setting possibly while eating a brilliant cheesecake. Replace this brilliant statement with yours.
Ordered list: Used for items with a specific order.
Unordered list: Used for items without any specific order.
Grid: Made up of Rows and Columns. Column follows 12 section grid.
Greeting: Name says it all.
Hello Timothy!
Brand Logo Used in the header. Can be plugged in anywhere.
Banner For hero images, used to record shout-outs via illustrations, patterns, type.
Credentials
Link: Used for redirection links, whether stand-alone or in paragraphs.
Image Link: Used for redirecting links that are bound on images used, primarily for icons.
Quote
Comment block
FB Engagaement Report / Widget Table
Jimmy
@Tim, check this report out. We are losing engagement. Can’t go like this.
Jessy
Hey, @Tim, Congratulations!


Literacy is crucial for individuals and countries as a whole.
This data dashboard displays graphs and charts related to youth (ages 15-24) literacy rates in different countries.
Data Source: World Bank Open Data
The first two graphs display information on youth literacy rates
aggregated by income group. You can learn more about the country income groups here:
WDI - The World by Income and Region
For reference, here is the population for each group.
The next two scatter plots relate youth literacy rate and income.
Income is measured as GNI converted to current U.S. dollars.
You can read more about GNI here:
What is the World Bank Atlas method?


by Mikael Hvidtfeldt Christensen ( @SyntopiaDK).
More...
Save attractor as image (PNG) (or press 'return')
Attribution Source code for this project on Github. Inspired by the wonderful renderings by Chaotic Atmosphere Formulas from Jürgen Meier: code / descriptions 3D graphics using three.js. GUI using dat.gui.
Version 1.0 - Jan 13, 2018.
Preparing image.
Image will automatically download when ready...


Right! We've done some HTML, jazzed it up with a little CSS and now we've got a website.
 It holds information, displays it and lets users navigate about. Job done, right?
Well kind of. See, our website exists and works but it's not much more than a collection of pages and items, it's not very dynamic, is it?
All we currently have is a bunch of HTML elements and a bit of CSS styling that could just as well be screenshots uploaded!
HTML and CSS are the same stuff though, aren't they?
No... Maybe we should have a refresher.
Most websites are made of HTML and CSS files, at their most basic.
They look very similar, and work very closely with each other but the difference is basically this:
HTML is a sort of framework, a list. It's a document containing all the differnt pieces of text, images, boxes, buttons and the likes that make up the webpage. It's no more than a text document, really, a list of different elements and a rough idea of which ones are inside the others.
That's why we we create some styles with our CSS document.
On its own, a CSS file is even less exciting than an HTML document, at least we HTML we get an ugly list of parts while with CSS, you wouldn't see anything at all!
CSS files exist to tell the HTML Elements how they should look, where they should sit on the page and where they should sit compared to each other
In short, HTML describes WHAT is in your page and CSS describes HOW that stuff should be shown!
Well, my sarcastic alter ego, that's a good question!
If you consider that HTML describes WHAT to build and CSS describes HOW it should look, JavaScript describes what to DO with your page!
HTML is what goes on your page when it loads, same with CSS. Once that little wheel stops spinning or the bar is filled, that's it. That page will never change, grow or do anything exciting.
Sure, you can make certain elements cange colour when you hover your cursor over them, mayba dropdown menu or two, but nothing genuinely dynamic - nothing that wasn't in your CSS or HTML to start with.
That is where JavaScript comes in. Instead of being a document your browser reads and sets up, it's a programming language that allows your browser to run real code, using the parts of your website in its programme.
Enough is never enough for you, is it?
Alright, fine. JavaScript is basically just a programming language, you set it up and runs through its Control Flow, repeats its loops, and acts just like any programme.
Yes! Those!
Don't worry, they're not as scary as you think. The Control Flow is just the order that code is executed (top to bottom).
If running your code just once, from start to finish, isn't enough for you - maybe you need to count, do something multiple times or check back on previous runs - the you can use loops.
Consider making a cup of tea. You might grab a mug object, throw in a teabag, fill the mug with water and once all those are done, stir that mug 12 times and remove the teabag.
That's a few steps that have to be performed in order, plus a few repated stirs of the spoon.
But instead of making our own cup of tea (boring), let's write some snazzy JavaScript that will make it for us! It'd look something like this:
Okay, let's walk through what all that means.
That first line creates a new mug with a couple properties. It's a smart mug, so it knows if it has a tea bag and some water in it, but it starts empty.
That next chunk is a set of instructions, called a function. Functions are handy because they're a set of instructions that all happen together, which we can trigger in lots of ways. We could just request some tea by typing in a command, or it could happen at a set time, or when a microphone hears us ask. The sky is the limit!
Inside our function is where the instructions are, so what do they do?
Well first, we tell the mug that it now has a teabag, then we tell it it has some water, remember the mug knows if it does or doesn't have those things, we're just changing that.
Now is where we play around, up until now we were letting the flow do its thing, one instruction after another down the page.
Now, we're creating a loop, we're creating a repeating piece of code that does whatever it contains until it's counted to the limit (in this case, 12).
That means our makeTea function will call a stirSpoon function 12 times, so we know it's properly stirred. After it's finished with the loop, our code goes back to its normal flow and works down the list.
It goes to the next command, where it removes the teabag. We've left this outside our loop because we don't want it trying to remove the bag 12 times, once every stir, because that'd be weird
The final curly brackets at the bottomm end our function and lets our code finish up.
So what did we do? We made some code, which will work through step by step in its normal flow, doing each task once, until we need it to repeat something a few times so we break that flow with a loop!
A function, dear friend, is basically a command that you can call on in other parts of your code.
That code up top was for a makeTea() function, which means we can have other pieces of code that can ask makeTea() to run, then carry on with what it was doing!
So what goes into a function?
Well, first we have the name, in this case that's "makeTea". Then we have a pair of brackets.
Inside those brackets we can make our function expect certain pieces of information, called arguments. With arguments, we can pass information over to our function that it can use when it does its thing.
Let's do an example. Imagine we want to make that cup of tea, but we want to be able to tell our function how many times it should stir the spoon.
We'll have to rewrite our function so that it can receive an argument and use that to decide how much to stir.
That would look like this:
See the difference? We've put "stirs" as an argument of MakeTea(). So instead of just calling makeTea() and it giving us the same cup every time, we now call the function and give it a number as its argument. So now we can call makeTea(12) and our tea maker will read our number of stirs, and use that as the number it'll count to! And yes, we did just ask it to stir the same number of times as it already did...
This might seem like a minor change, but the less we explicitly code in numbers, amounts, words and so on, the better. This means our code can change, work as needed and if we found we like our tea with more stirs, we don't have to go through and change the number every time.
Exactly! Repeating yourself in your code is messy and confusing, better to have lots of small functions than a few big ones
...Okay. I feel like you're asking these questions just to help a blog post flow.
But fine! Let's say we have five friends, each of whom like their tea stirred a different number of times.
We could just call our makeTea() function five times and give it a different stir argument every time, that would look like this:
There you go, we've asked our tea maker to do its thing 5 times over and given it different numbers each time
But that's pretty messy, and we're repeating ourselves so we should probably ask our tea maker to read the orders from a list.
There are a few ways we can try, but how about we use an array.
Kind of. Think of them more as a spreadsheet that we can hold information in.
Let's make an array of all those different tea orders, it would look like this:
There we are! We've declared stirOrders and by using those square brackets, we've made it into an array. For simplicity, we've thrown our list of orders straight into the array.
Now we have to read our order list. Again, there are a few ways to do it but we'll make a quick loop that'll make a cup of tea for every order in the list
Here goes:
Simple as that!
Our new loop uses the length of our order list as its maximum, so it will make orders one by one until it's worked through our array.
It's important to remember that JavaScript arrays are 0 indexed, the first entry is number 0 and so on, which is why we start our count at 0 and end it 1 before the full length.
Now that we're counting an array, we need to access the information inside it.
Since our counting variable "I" is the same number as our position in our array, we can use that to tell our tea maker which stir request it'll use.
To read data from an array we use arrayName[theEntryWeWant], and we've put that code as the argument of each makeTea call!
I did! How about instead of a list of orders, we make each person an object and give them a stir preference?
First, we'll make a person who only has two traits, their name and how they like their tea:
There we go, we've made a "person" object and decided they'll have a string for their name and a number for their preferred stirs.
Like before, let's make an array containing our five friends:
There you go, we've made an array of people containing our five friends.
Now we can loop through each person, just like the previous array, and access their stirs properties.
Just like last time, we're cycling through our array of 5 items, but this time those items are people instead of numbers.
For each person, we access their stirs property by using either object.property or object[property] (we've used dots so it's easier to read).
An array would work just fine if we only wanted a list of tea orders, but we're only making a list of orders, we're not making tea for a list of people
Objects, on the other hand, can have loads of properties! What if each person could decide the temperatur, type of tea, decide if they want a keep cup and decide their cup colour? Our array suddenly gets very big and very complicated, and we can still only ask for a person's order by knowing their place in our list
An object means we can just make tea for a certain person by using their name, make it just how they like it and do it whenever we like!
And that's the important part!
Our JavaScript can interact directly with out HTML and CSS code by looking at the DOM.
No, not a Don, the DOM. The DOM (or Document Object Model) is a representation of all the objects that make up a webpage.
All those Divs, Imgs, paragraphs and headings? They're all viewed as objects by the DOM, and the DOM is how our code sees our page.
Because of our DOM, our JavaScript can access elements on our page without having to read the HTML code and figure it all out.
Let's do an example, let's say we want to run a JavaScript function when our page loads. In fact, let's create a link that'll ask for a cup of tea when we click it!
There! We've made some JavaScript that'll access our DOM and once the whole DOM has loaded, it'll run our makeTea() function and brew us a lovely cup.
Our scripts can also access individual page elements, seeing each one as an object, make changes to them, make our content dynamic and so much more.
In short, the DOM is the model we use to describe our HTML and CSS in a way that can be viewed, accessed and changed by our code.
Anything we can do in JavaScript, we can do to our websites by access the DOM!
It certainly was! But now we're done, how about a cup of tea?