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My third assumption concerns the available technology for space
program development. Twenty years ago, the launch of Sputnik I led to a
great technical effort by the United States. That effort resulted in the launch of Explorer I on January 31st, 1958
twenty years ago next Tuesday. At that time, we were stretching the available technology to the limit, to put a small satellite into low earth orbit. Everyone here remembers the failures that preceded that success.
Today, the situation is very different. We have on hand all the technology that we need for projects in low earth orbit, and a good deal of what we need for geosynchronous orbits and for lunar and planetary exploration. The problem now is much more one of selection. There are many more candidate missions than we can afford to use.
Hence, the third assumption:
Assumption 3: Technology is no longer the main bottleneck for space exploration and utilization.
This assumption needs to be handled with care. It does not mean that there are no difficult engineering problems to be solved. There are many, and some of them are very hairy. It does mean, however, that we can now have the luxury of picking and choosing among a variety of projects in setting up a preferred development plan.
Technical feasibility does impose limits. Other witnesses to these hearings may suggest that the right way to structure our programs is through the use of off-Earth materials. They argue that it is highly inefficient to conduct operations in space if every ounce of payload has to be lifted up from the bottom of Earth's deep gravity well. It would be much better, and more satisfying, if we could use resources from somewhere else, such as the surface of the Moon.
The problem is, we happen to be here, like it or not. Although in the very long term we may be able to use off-Earth resources, I do not see this as feasible within the framework of my twenty-year plan. In the same way, although the chemical rocket is noisy, wasteful and unesthetic, I expect it to be the main tool for launch and for propulsion for the foreseeable future. I would very much like to be proven wrong, but meanwhile: Assumption 4: The U.S. Space Program will depend on the use of Earth-based materials, launched into orbit using chemical rockets.
This does not mean that there will be no use of ion propulsion or solar sailing. These can be very useful for maneuvers that involve orbit transfers. But they will not be the work-horses of the program, they will be used for long timescale, low-thrust missions.
The last assumption will be attacked by some groups as unimaginative. As I said, I would just love to be proved wrong. My main point, however, is that a very attractive twenty-year plan can be built, without moving outside the basic assumptions I have made. Anything else that came along, in the way of new inventions and capabilities, would be gravy. The plan
I propose is structured so that we can take advantage of new tools as they arrive, without wasting any of what we have already invested.
Let us first recognize where we stand at the moment. What systems do
we have, existing and planned?
During the first half of the 1980's the Space Shuttle will greatly increase our access to and uses of low earth orbits. With that vehicle we wil be able to launch, and will launch, a wide variety of unmanned satellites, for applications and for scientific experiment. We will also have a manned space station, Spacelab, in which we will continue to learn about
the effects of very low gravity on the human body. I regard these studies as enormously important, since I am not at all convined that humans can ever survive for very long periods in a weightless environment.
In addition to the near-Earth activities, we will have a variety of new unmanned satellites exploring the Solar System. The Jupiter-Orbiterwith-Probe should be launched in about four years, and will get to Jupiter about 1985. Notice that last point. It will be three years after launch before the satellite begins its real mission.
This is something that we have to get used to
the very long duration
of experiments that involve planetary probes. It means that we are approaching the point where a scientist may spend most of his productive career in conceiving, designing, executing and analyzing a single experiment.
Will he be willing to do this, if the U.S. Space Program is itself so fickle and variable in its funding and public support, that projects can be chopped, delayed and cancelled in an arbitrary manner? I think not, and if in what follows I seem to be short-changing the scientific experimenter, it is because I believe that his interests are best served if we can assure
a general, long-term national commitment to an active space program. That commitment will not be forthcoming unless the program can offer clear practical benefits (perhaps hard to quantify accurately in advance) as well as scientific experiments and dreams.
The Space Shuttle is a big step forward, but we also need a reuseable vehicle that can get substantial payloads to geosynchronous orbit and back: a Space Tug. Many applications are best conducted from platforms in geosynchronous orbit. Although there are big technical problems to be solved, I believe that we need a Space Tug as soon as we can get it, and I suggest
that an initiative be taken to have such a vehicle ready for use in ten years
Proposed: That a program be initiated to develop a reuseable Space Tug, with first launch scheduled for 1987.
What would this give us? First, it would greatly lessen the cost of
a renewed lunar exploration program. Before we can even dream rational dreams of using lunar materials for construction in space, we must get to know the Moon much better what it can offer as resources, what it would
be like as a place to work. Until we know that, we should defer any decision as to how large space structures should be created (i.e. using Earth-based or off-Earth material supplies). I believe that we need to revive the manned spaceflight program, with an emphasis on lunar exploration, before we can evaluate a variety of other projects.
Proposed: That a new manned lunar exploration program be initiated, with the first missions to take place in 1986.
Two points should be made here. First, such a program will be costly. NASA cannot accomplish it at present levels of budgeting, and it is not my suggestion that we undertake a new manned lunar exploration by eviscerating on-going programs. Thus we are talking of a new start, and an expensive one. The other point is that the new missions would begin before the Space Tug is ready. This may sound irrational, since the Tug will make such missions much less expensive. However, I believe the programs can be integrated in such a way that most missions will use the Tug, from 1989 onwards.
What about useful applications? As I already mentioned, a number of these are accomplished better at geosynchronous altitudes. Weather and communication satellites are already in use there. It would be logical to add an earth resources satellite at such an altitude, to permit frequent coverage of the United States. Currently, we get weather satellite images from the SMS/GOES satellite every half hour, but we get images from each Landsat only once every eighteen days. Landsat-D will not materially alter
this situation. However, a combination of the Large Space Telescope, already under development, with a Landsat type of sensor system could provide an image from geosynchronous altitudes as often as required. The ground resolution at the nadir point would approach ten meters, which is considerably better than that planned for Landsat-D. It would be quite feasible to obtain an image each hour of the whole United States. A combination of the Large Space Telescope and Landsat would be a very complex device and the probability of failure may seem high. That danger would decrease greatly were we able to offer service to such an assembly using a Space Tug carrying human technicians and maintenance engineers. From this point of view, there are advantages to setting up
a single, loosely-coupled set of application satellites at one geosynchronous location. Such a Combined Applications Platform (CAP) should include the working quarters for service and maintenance personnel. The latter will not live there. They will make service calls on a regular basis, to check instrument performance, replace parts, and vary the orbiting devices to reflect new technology or changed data needs.
The Combined Applications Platform, with human service, needs a Space Tug to make it an economical and practical reality.
Proposed: That a CAP project be initiated, with launch planned for 1993. I suggest that the CAP may include a pilot version of the solar power satellite. This would not be the large structure envisioned for provision of gigawatts of power. Rather, it would be a test version, scoped to confirm a basic design philosophy and establish system efficiency.
I believe that this approach is consistent with Resolution 451, introduced by Mr. Teague in December, 1977, and I believe that it has one very attractive feature: it does not put all our eggs in one basket. If there should be a breakthrough in clean fusion power in the next fifteen years,