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sun.

The earth is a natural, manned space ship in orbit around the
Planning, building, and operating artificial, manned,

space

ships is expected to give us many new insights into the management of the man-earth system. For one thing, we will be forced to develop information management equipment and techniques which are applicable to any complex operation, and, particularly, to the manThe earth system as a total, closed network of feedback loops. artificial space ships would simulate the natural space ship, with similarities and differences which can be deliberately varied to gain insights and test hypotheses about the natural operation and artificial management of either system.

What we know how to do is to plan a configuration based on existing engineering knowledge, including, but not limited to existing hardware. Existing engineering knowledge requires no critical research or development (invention) not already completed during past programs. Existing engineering knowledge can be defined as that body of insights and data which is sufficiently well established that a system designed by its use can be assembled from components fabricated under compartmentalized assignments, with the reasonable expectation that the components will fit and, function together. Using existing engineering knowledge, it is possible to juxtapose the insensitive regions of all important variables and unknowns. Conscientiously done, this is far more effective than experimental testing in eliminating "tricky" characteristics of the system, and thereby making the system predictable, and hence reliable. There was a time, of course, when the existing engineering knowledge was not adequate for the juxtaposition of the insensitive regions of all the important variables in a space rocket system, but that time is past.

Whether we can afford the space program described in this paper depends on its size relative to the national economy; on whether its benefits exceed its costs; on whether some alternative expenditure would yield a greater return; and, finally, on whether we want it. As long as the cost is less than half of 1% of the gross national product, or less than the cost of tobacco, or of alcoholic beverages, or less than 20% of the aerospace industry, there is little point

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to discussing whether the economy can support the program. support it if it wants to do so.

It can

Costs are not to be measured in dollars as such, but in how many dollars worth of effort are diverted from other sectors of the economy. There is reason to believe that the economy is operating at a small fraction of its potential. If this is true, it is entirely possible that the space effort is in addition to, and not in place of, some other activity which might be added to the economy. Certainly it is by no means clear that an army of former space workers looking for jobs in slum elimination, for example, would hasten the formulation of an effective slum elimination program. Indeed, the history of dying industries and dying regional economies is that former employees singly remain unemployed, while only their children migrate to new jobs. The NASA space program has in many ways amounted to an addition to the universities. It has provided a technical education to many people who otherwise would have remained in obsolete callings, and unemployed. There have been some benefits from the NASA space program, but the big benefits, both of the NASA program and of the proposed new space program, will appear in the future, if at all. What these benefits may be expected to be will be seen by reference to the check list of missions, Section 4.

An economic want is what people are willing and able to buy. The preceding paragraphs point out that people are able to buy a space program. Whether they want to buy it depends on what it will cost, and what benefits it will yield. Congress has very clearly stated, and correctly, that NASA will receive no more blank checks, but must first show an acceptable plan which can survive informed criticism. The plan must be workable, it must yield benefits greater than the cost, and it must be better than any alternative plan which is offered.

The problem is to determine what a space program is worth, since its benefits are as diverse as adventure, philosophy, technology, and commerce. There is the familiar and proven method of the competitive market place. Goods and services are worth no more then.

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they cost, no ratter how great the benefits. Air is very beneficial, but it is free. Food is also very beneficial, but it too is priced at what it costs. To ascertain what a space program is worth, it is only necessary to prepare a rational plan, and determine its cost. People will either buy it at its cost, or reject it. They will not buy it at a price above its cost, and they will not get it for less.

The remainder of this paper will detail the specifics of a plan.

2. REFERENCE ROCKET-SPACECRAFT COMBINATION

One purpose of this section is to describe a chart on which any launch rocket can be placed, and compared with any other launch rocket. The chart can also be used to gererate and evaluate new launch rocket designs.

A second purpose is to describe a space rocket-space ship combination to be carried into an Earth parking orbit by the launch rocket. The combination is designed such that a stendary production model will suffice for all colar system missions within the present state of engineering knowledge, es tabulated in the "Check List of Missions", Tables 4.2-a, b, and c.

2.1 THE LAUNCH ROCKET

It is convenient for both planning and operation to assume that the space rocket-space ship combination will first be placed in a parking orbit around the earth, and that it will either remain there or depart from there on some mission elsewhere. The basic function of the launch rocket is to place the space rocket on a properly chosen parking orbit.

For the most part, parking orbits fall into two distinct categories. Oe is a low-altitude circle, and the other a nearparabolic ellipse having a low-altitude perigec. The launch rocket will follow essentially identical, gravity-turn trajectories to reach either kind of parking orbit.

Either a one-stage or a two-stage launch rocket can be used. A three-stage rocket is more complicated and expensive than a twostage rocket, and has no apparent advantage. A one-stage rocket

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can be considered as a special case of a two-stage rocket in which the first stage is reduced to zero.

Each of the two stages may be independently recovered or expended. Recovery may be by aerodynamic means, such as by wings or lifting-body; or it may be by means of rocket retro-thrust. Aerodynamic return can be combined with retro-thrust for the final touch-down on a launch structure in a tail-sitting attitude. Provision for recovery increases the mass of the empty stage, and thereby the mass of the fully loaded stage.

It is possible to propose a bewildering array of combinations of propellants, structures, and operations. In such a situation, a well-chosen reference design is useful for comparison. Rather than propose a reference rocket, it is more useful to propose a reference family of two-stage combustion rockets. The first stage burns oxyger and propane, end is recovered from a gravity-turn trajectory to the launch site by retro-thrust. The second stage burns oxygen and hydrogen, and is expended.

Another set of specifications could have been been chosen for the reference family. However, the given specifications are simple and adequate, and conform most closely with the present state of engineering knowledge. Other designs, using wings, nuclear propulsion, recovery at down-range locations, etc, can all be evaluated by comparison with members of the reference family, and thereby also evaluated relative to one another.

Figure 2.1-a is a chart showing the masses of the two stages of the reference family of rockets. The mass is normalized with respect

to the mass of the detached space rocket to be placed on a nearparabolic ellipse around the earth. By analogy with JATO rockets on airplanes, the first stage may be called a JATO. The curves reflect assigned values of specific impulse, structure masses, etc, which are typical of the present state of engineering knowledge. All point on the curves were calculated for a single gravity-turn trajectory optimized for a single-stage-to-orbit, hydrogen-oxygen rocket.

Such trajectory is not ontimun for return of the first

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MASS NORMALIZED WITH RESPECT TO UNIT MASS OF SPACE SHIP ON PARABOLA

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HORIZONTAL COMPONENT OF SPEED AT DETACHMENT FROM JATO
IN THOUSANDS OF FEET PER SECOND

FIG. 2.1-a MASS OF ROCKET REQUIRED TO LAUNCH A UNIT MASS OF SPACE ROCKET INTO A NEAR-PARABOLIC ELLIPSE AROUND THE EARTH

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