SPACE STUDIES INSTITUTE
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[[librarian note: This address is here, as it was in the original printed newsletter, for historical reasons. It is no longer the physical address of SSI. For contributions, please see this page]]
THE HIGH FRONTIER® NEWSLETTER
VOLUME XIII ISSUE 2
VICE PRESIDENT’S COLUMN
The next few months include a number of opportunities for SSI members to get together and learn more about the work that we share. As you know, in May of this year SSI and Princeton University will hold the eighth of our series of conferences on Space Resources and Space Manufacturing. As a supporter of SSI’s research, you are invited to participate in this event.
These conferences are “where the action is” in the field of Nonterrestrial Materials Research. The people who are shaping the future of space development present their work here and there is a resulting excitement that’s hard to describe. Because we are limited to about 200 participants it’s a good idea to make your plans early. Drop us a note if you would like a registration packet.
It has been three years since the SSI Expedition to Cape Canaveral and the Epcot Center. One of the highlights of the trip was a seminar on the basic principles of spaceflight. On March 27, 1987 Captain Edward Daley and I will present a more detailed one-day seminar on basic spaceflight as a part of the Sixth Space Development Conference in Pittsburgh. SSI is a co-sponsor of this conference which is an annual production of the L5 Society (soon to merge with the National Space Institute). Dr. O’Neill is scheduled to give the keynote address at this event. The theme of the conference is Return to the Vision. If you would like further information on this conference or spaceflight course, please contact us.
SSI Bulletin Board Experiment
The Institute now has an experimental computer bulletin board set up at our Princeton offices. The board contains information about SSI research and other activities. The phone number of the board, which operates evenings, nights and weekends, is xxx-xxx-xxxx. The System Operator is Mr. Derek Fields of Princeton. This board supports several “conferences” or special message areas such as External Tanks Research, Lunar Development and Support Teams. We look forward to your experimenting with this new communications tool!
Dr. James French, former Senior Technical Manager at the Jet Propulsion Laboratory, is currently Vice President of Engineering for the American Rocket Company of Menlo Park, California.
Continued from Jan/Feb issue of UPDATE
LOW-COST LUNAR POLAR MISSIONS by J. R. French
In searching for deeper subsurface volatiles, as discussed in the previous issue, a radar sounder would be required. A relatively low frequency (e.g. L-band/VHF or HF) is required to penetrate rock or regolith. A radar operating in L-band, carried by the Space Shuttle, was able to distinguish ancient river beds and other geological features buried beneath the sands of the Sahara desert. The radar flown on the Apollo mission operated in three frequencies in the VHF and HF bands (Ref. 6).
A radar for probing beneath the Lunar surface would be much less sophisticated than the Shuttle-borne system, lacking imaging capability. A system more like the Apollo system would be able to provide depth profiles of reflective layers which might represent liquid water. The preferred survey orbit for missions of this type is polar (90 degrees inclination to the equator). While an orbit of this inclination is mandatory for a survey of the poles in any case, it has the additional advantage of providing a complete survey of the Moon since the orbit plane is essentially fixed in space while the Moon rotates beneath it as it proceeds in its orbit about Earth. Thus at the end of one lunar period (approximately 28 days) the orbit will be passing over the same features as it was at the beginning of the period having moved over the entire Moon (as viewed from the Moon) during the intervening period.
Since the gamma-ray spectrometer accepts radiation from whatever is in its line of sight, its resolution of areas on the Moon is a function of orbital altitude. The lower the orbit, the better the resolution. This is limited however by practical considerations. Even though the Moon has no atmosphere to cause orbital decay, low orbits tend to be unstable because of the Moon’s slightly irregular shape. This deviation from a perfect sphere will perturb the orbit significantly and will eventually lead to impact unless propulsion maneuvers are conducted to trim the orbit. How low an orbit is used depends upon how frequently the project management is willing to interrupt data taking for maneuvers, how much propellant is carried, and the accuracy with which the orbit can be monitored. All this is a suitable subject for study and tradeoff once a project is underway. As a strawman value however, an altitude of 50 km might be reasonable. This altitude yields a field of view of about 800 km in diameter which is essentially the horizon to horizon distance on the Moon from that altitude.
Gamma-ray spectrometers have been flown in Lunar orbit on the Apollo missions. Those missions however were confined to low orbital inclinations and thus no high latitude or polar data was obtained. A polar orbiting mission was considered as part of an extended Apollo program but was not funded.
An interesting possibility is the addition of an X-ray detector to the instrument. The two detectors can share much of the same electronics and are complementary in detection capability.
For the mission, the instrument requires an accumulated observation time over a given point on the surface of about 10 hours in order to collect enough data to begin to resolve elements of interest. An accumulated observation time of 100 hours is more desirable. In order to achieve observing times in this range in the high latitudes, spacecraft operating time in its final observing orbit should be at least one month. Several months is preferred since this not only improves resolution in the immediate vicinity of the poles but extends the total area of the Moon over which at least minimal observation is obtained. One should not overlook the importance of obtaining data from the Apollo, Surveyor, and Luna sites since we have samples and/or in-situ composition measurements to provide “ground truth” calibration to the orbital measurements.
Based upon these considerations, the spacecraft must be designed to operate for at least six weeks to allow three days to reach the Moon and several days for calibration and checkout plus at least a month of observation. Since any spacecraft capable of operating for six weeks is quite likely to last for several months, the additional observation time can be obtained at no cost other than for tracking and ground operations. A full year of operation would provide at least minimal data for the entire Moon.
A radar survey mission could complete a survey of the Moon much more rapidly. Placed in a polar orbit, the spacecraft would complete a full survey of the Lunar surface within two weeks of beginning operations. (The time required for the Moon to complete a 180 deg. rotation under the inertially fixed orbit.) Somewhat longer term operation would probably be desirable to improve resolution and to get a second look at interesting locations.
The spacecraft for a single-instrument mission to look for water at the Lunar poles can be relatively simple and light in weight compared to the more elaborate scientific spacecraft commonly flown today. With one instrument there is no competition for field of view and data rates are modest. The instrument does impose some requirements or at least preferences, however. As noted earlier, because the spacecraft itself emits gamma rays, it is desirable to have the instrument mounted on boom which will place it a distance from the spacecraft approximating the major spacecraft dimension, farther is better. In addition, it is desirable that the instrument be extended toward the Moon and that orientation maintained. Since the instrument can detect radiation coming from any direction it can still obtain data even if the spacecraft is rotating it alternately toward and away from the Moon as a spin stabilized vehicle might. However the variation in bearing, shielding by the spacecraft bulk and other such factors can greatly complicate data analysis. Thus a nadir pointing configuration is desired.
The modest data rate and relatively short range back to Earth render a high gain antenna unnecessary. A mid-gain antenna for downlink (spacecraft to Earth) and an omni for command reception and downlink during maneuvers will probably fulfill all requirements for the mission.
In order to maintain a nadir pointing attitude, a Lunar horizon sensor will be required. On the day side of the Moon this presents no problem and an adaptation of an infrared based horizon sensor for Earth satellites will be quite satisfactory. The night side however presents a different problem. The lunar surface becomes so cold that it becomes very difficult (impossible for an ordinary sensor) to distinguish the Lunar surface from deep space. The ability to do this would require development of a highly sophisticated and expensive sensor. Fortunately, pointing accuracy requirements for the gamma-ray spectrometer are not especially tight. A drift of one or two degrees while the spacecraft is over the dark side would be acceptable. This can be met by a momentum bias system which uses a fly wheel to make the spacecraft rotate as it proceeds along its orbit at such a rate as to compensate for the motion and keep the spacecraft pointed toward the surface. Such systems require updates by horizon sensors to take out drift errors. In the case at hand, the horizon sensors keep the system updated while on the day side and the momentum bias system maintains control within adequate tolerance on the dark side.
To the author’s knowledge, no studies have been conducted on a dedicated Lunar radar mission. One might hazard a guess that the spacecraft design would be somewhat more demanding since deployment of multiple antennas would probably be required. The data rate back to Earth would probably be higher than for a gamma-ray spectrometer mission. Pointing accuracy requirements are not clear. If very tight, it may be that good data can only be taken on the day side which would then imply that a month is required for complete mapping.
The potential for a combined mission carrying both a gamma-ray spectrometer and a radar sounder is obvious. There is no obvious reason why the requirements for the two payloads would be in conflict to such a degree as to preclude flying them on the same spacecraft. Configuration and field-of-view constraints should present no more difficulty than many such spacecraft already flown. The greater complexity and higher data rate would make the project more costly than a singleinstrument concept but certainly less than flying two independent spacecraft.
As will be discussed below under “Costs,” the concept of modifying existing design Earth orbit spacecraft for the Lunar mission appears to offer considerable saving over new design. An in-house study at JPL (Ref. 8) identified an adaptation of the RCA Atmospheric Explorer/Dynamics Explorer series of spacecraft as quite viable for the gamma-ray spectrometer mission. The TIROS/OMSP weather satellite series is also a candidate but represents considerable “overkill” in terms of capability for a single instrument mission. Other potential candidates include the Boeing MESA low-cost spacecraft and possibly other similar concepts. This does not constitute a recommendation of any particular spacecraft but rather serves to define the class of vehicle which might be modified for the task.
Spacecraft in this general size category can be placed on a Lunar transfer trajectory by a variety of launch vehicles including Delta, Ariane, and Shuttle with a suitable upper stage. Among the latter the PAM-D and PAM-DII seem to be the most logical choices. To allow for the propulsion required to enter Lunar orbit one may conservatively assume that 50% of the mass on the transfer trajectory can be delivered into Lunar orbit as useful spacecraft mass over and above propulsion inerts, maneuvering fuel, etc. Based upon these approximations, it appears that PAM-D could place a 300 to 350 kg spacecraft in Lunar orbit while PAM-DII could deliver a spacecraft mass of about 500 kg.
Reference 8 states that a Lunar spacecraft based upon the AE/DE as discussed above would have a mass of about 280 kg while a new design optimized spacecraft might be as low as 180 kg. Either of these is clearly within the capability of PAM-D. Going to the PAM-DII would have the salutary effect of effectively eliminating concerns about mass, a circumstance invariably conducive to staying on schedule and within cost. Should use of a larger spacecraft become desirable for programmatic or other reasons (e.g. ready availability) then PAM-DII definitely becomes the choice. However, a combined gamma ray and radar mission might demand a larger vehicle.
The study of a single instrument spacecraft reported in Ref.8 indicated that a reasonable duration for such a project from start to launch would be two and one-half to three years. The development of the instrument to flight status is quite compatible with this sort of schedule since the technology is reasonably mature.
For a project start date at the beginning of fiscal year 1988 (for example), the launch could take place during fiscal year 1990. This is a reasonable schedule based upon technology and program requirements. There are however a variety of regulatory and bureaucratic impediments which could delay the project beyond what might reasonably be expected.
The study reported in Ref. 8 quoted a cost for the spacecraft alone of $88 million for a new development spacecraft or $27 million for an AE/DE derivative. The total program costs for the two approaches was $97 million and $36 million respectively. These were fiscal year 1982 dollars and thus would be somewhat higher today. These costs include mission operations costs for the minimum mission but do not include launch vehicle costs.
A recent study by Orbital Sciences Corporation of a low cost Lunar orbiter came up with a spacecraft cost of $20 million in fiscal year 1985 dollars and a total program cost of $30 million (Ref. 10). Given the accuracy of preliminary cost estimation, this is not substantially different from the costs quoted above. The OSC estimates can be considered to corroborate the JPL estimate.
Based upon these estimates it would appear reasonably safe to conclude that a simple Lunar polar orbiter could be built and flown for a total cost in the range of $40 million to $50 million exclusive of launch costs or costs of extended mission operations beyond the minimum mission.
1. A Primer in Lunar Geology, Ronald Greeley and Peter Schultz editors, NASA Ames Research Center, 1974
2. “On the Possible Presence of Ice on The Moon,” Kenneth Watson, Bruce C. Murray, and Harrison Brown, J. Geophysical Res. 66, p.1598, May 1961
3. “Water on the Moon,” James R. Arnold, Univ. of Calif. San Diego, presented at Seventh Annual Lunar Science Conference, 16 March 1976.
4. “The Behavior of Volatiles on the Lunar Surface,” Kenneth Watson, Bruce C. Murray, J. Geophysical Res. 66, p.3033, Sept. 1961
5. “Prospects for Finding the Most Valuable Potential Resource on the Moon: Water,” P. M. Muller, Jet Propulsion Laboratory, presented at Seventh Annual Lunar Science Conference, 16 March 1976
6. “Apollo Lunar Sounder Experiment,” R. J. Phillips et al, Apollo 17 Preliminary Science Report, NASA, 1972
7. “Commonality: A Multimission Gamma Ray Spectrometer,” Albert E. Metzger, Richard E. Parker, David A. Gilman, JPL Planetology Publication -326-80-57, 15 April 1980
8 “Lunar Volatiles Explorer,” J. R. French & A. E. Metzger, presented to Committee on Planetary and Lunar Exploration, 23 June 1981
9. PAM-D/PAM-DII User’s Requirements Documents, McDonnell Douglas Astronautics Co.
10. Personal communication, Orbital Sciences Corp.
THE 8th BEINNIAL SSI/PRINCETON CONFERENCE ON SPACE MANUFACTURING
May 6 – 9, 1987
The 8th Biennial SSI/Princeton Conference on Space Manufacturing, sponsored by Space Studies Institute and AIAA, is a forum for papers on all aspects of the use of non-terrestrial resources. The program includes papers both on technical aspects of space development and on the social sciences.
In order to accomodate a broad range of presentations, three different types of presentation will be encouraged: 1) the traditional presentation of papers in the auditorium at the Woodrow Wilson School, 2) a poster session and display, 3) an evening roundtable for interaction between participants.
The first three days of the Conference will be open only to registered participants. A summary session on Saturday, May 9 is free and open to all.
A registration fee of $290 includes lunches, coffee breaks, the Friday night banquet and a copy of the published proceedings. Registration through the Space Studies Institute is available.
Gregg Maryniak, Chairman
Gerard K. O’Neill
The Ramada Inn has been selected as our Conference Headquarters. It is located approximately three miles north of Princeton on Route 1. The Inn will provide bus service to and from the University’s Woodrow Wilson School as parking spaces in town and on campus are severely limited. Upon receipt of the Conference registration fee, a hotel reservation card will be mailed to you; or you may make reservations directly by phone.
Following is a listing of sessions, chairmen and a brief description of content matter. In some cases a partial list of participants is included.
Woodrow Wilson School, Princeton University
Wednesday, May 6
8:30 am Registration
8:45 am Welcoming Remarks:
Gerard K. O’Neill, President
Space Studies Institute
9:00 am Keynote Address
9:30 am Session I BIOMEDICAL CONSIDERATIONS
Chair: Stanley Mohler, M.D.
Wright State University
School of Medicine
This session will take the form of a panel discussion. Participants will be Dr. James Logan, Dr. Paul Buchanan, Dr. David Tipton and Peter Diamandis. Topics to be covered will include physiological aspects of health maintenance in long term space flight.
2:00 pm Session II SPACE TRANSPORTATION
Chair: Ed Bock General Dynamics
This session will cover recent developments in new and conventional types ofspace vehicles and transportation systems.
7:30 pm Informal Discussion – Recycling the E.T. and other ways to dramatically lower the cost of space projects.
Chair: T. F. Rogers
External Tank Corporation
Thursday, May 7
9:00 am Session III NONTERRESTRIAL RFSOURCES
Chair: John Lewis
Lunar and Planetary Laboratory
Latest advancements in utilization, mining, extraction and application of extraterrestrial materials will be covered. Drs. T.D. Lin and Kyle Fairchild will be among the authors presenting papers on their research projects.
1:30 pm Session IV EXTERNAL TANKS AND SPACE HABITATS
Chair: Gregg Maryniak
Space Studies Institute
This session examines the most readily available form of non-terrestrial resource – the Shuttle’s large external tank. In addition, habitable space platforms will be discussed.
2:15 pm Session V INTERNATIONAL AND ECONOMIC CONSIDERATIONS
Chair: Irwin Pikus
National Science Foundation
This session will include discussion of economic factors and implications of space development, and international aspects of present, past, and future space activities.
7:30 pm Roundtable Discussion: Return to the Moon
Chair: Gregg Maryniak
Space Studies Institute
Friday, May 8
9:00 am Session VI SPACE MANUFACTURING AND SOLAR POWER SATELLITES
Chair: Peter Glaser
Arthur D. Little Company, Inc.
Research projects involving various aspects of space structures, solar power satellites and Space Station will be included in this Session. Dr. William C. Brown will present a paper entitled “A Microwave Powered Orbiting Industrial Park System” and Joel Sercel and Robert Frisbee will co-author a paper on beamed power for space propulsion.
1:30 pm Session VII ARTIFICIAL BIOSPHERES AND CLOSED-CYCLE LIFE SUPPORT
Chair: Carl Hodges
Environmental Research Laboratory
Among the topics covered in this session are air and water purification, plant production and other aspects of closed-cycle living systems. Exobiologist Clair Folsom ofthe University of Hawaii will present a paper on ecosystems.
3:45 pm Session VIII SOCIAL ASPECTS FOR SPACE FLIGHT
Chair: B.J. Bluth
Pioneering the space frontier involves an external social context and an internal social dimension both of which will be addressed in this session. Speakers will include Dr. Judith Quellar of the Space Station Office at the Johnson Space Center and Dr. Paul Rambaut of the National Institute of Health.
Chair: Morris Hornik
Space Studies Institute
Poster topics will cover a wide range of disciplines. These will be highlighted during breaks and at a special reception.
Ramada Hotel, Princeton, NJ
6:00 pm Reception
7:00 pm Banquet Guest Speaker: Professor Freeman Dyson Institute for Advanced Studies
Woodrow Wilson School, Princeton University
Saturday, May 9
9:00 am Summary Session
Each chairman will present a summary of the papers within that session.
Space Studies Institute, Rocky Hill, NJ
12:30 pm Box Lunch Picnic
Informal gathering of Conference participants and Senior Associates ofthe Institute. Tickets for this event may be purchased through the Institute or during the Conference at the Registration Table.
SSI Members Invited to Open House at JPL
A Tradition of Discovery will be the theme of a public open house at the Jet Propulsion Laboratory, Pasadena, California to be held June 13-14, 1987 from 9 am to 5 pm.
All JPL Offices and Divisions will participate with displays, exhibits, demonstrations, and presentations. Shuttle buses will run throughout Saturday and Sunday to move visitors to outlying sites with members of the Speakers’ Bureau on board buses to describe buildings and facilities along the route.
The public will see presentations and multi-image productions about past, present, and future JPL deep space missions. Such missions as Voyager flights to Jupiter, Saturn, and Uranus and Viking landings on Mars will be featured along with JPL’s future role in space. Souvenirs representing these space flights will be on sale. Cameras will be permitted.
We hope you will be able to attend this rare event. The last major JPL open house was held in 1980. Facilities not normally accessible to the public will be open and many presentations will be made during the two days. Programs will be geared for the technically inclined, for children, and for the general public.
For additional information about this open house program, please call the Public Education Office, JPL, 818-354-8594.
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