THE HIGH FRONTIER NEWSLETTER VOLUME XIII ISSUE 1 JANUARY/FEBRUARY 1987 SPACE STUDIES INSTITUTE RO. BOX 82 PRINCETON, NEW JERSEY 08540 PRESIDENT’S COLUMN FORWARD TO THE MOON It is becoming apparent from a variety of sources that the work of the National Commission on Space, coupled with excellent work inside NASA and in European, Soviet and Japanese space agencies, has brought about a quantum change in experts’ perceptions of how we should enter the trans-terrestrial environment. Professionals now quite generally accept that we must make the fullest practical use of non-terrestrial materials to bootstrap our way outward. In that much-improved climate of expert opinion, SSI’s research programs take on an even more immediate value. The fundamental resources available in the trans-terrestrial environment are the rich, constant flow of energy from the Sun, and the materials on the trans-terrestrial bodies. As written by the Space Commission, the logical sequence of development for the new resources is to begin with those closest to Earth and progress later to those farther away. The closest by far are those of the Moon, our sister-planet, which remains fixed in the gravitational vice of our Earth, and is correspondingly accessible at all times. All other known resources, such as the moons of Mars, are about one thousand times farther away, and would take a correspondingly greater and much more time-consuming program to reach. We know already that materials vital for space propulsion and for construction are abundant on the Moon: lunar glasses for composites, oxygen for propellants, silicon, iron and aluminum for building factories and power satellites to serve the Earth from high orbit. What we don’t know about the Moon is exactly the point of one of SSI’s “Breakthrough Projects,” the design of a space probe to enter and remain circling in a low orbit over the poles of the Moon. That “Lunar Polar Probe” would be a simple spacecraft, designed to focus on a specific, vital question: are there frozen volatile materials, the life-giving elements carbon, nitrogen and hydrogen, trapped as kilotons of permafrost in the deep craters near the lunar poles, craters which have never seen the warmth of sunlight in millions or even billions of years? Theory, by leading space scientists working over a period of more than 20 years, says there should be. The Lunar Polar Probe would find the rich lodes of lifegiving elements if they are there. In keeping with SSI’s philosophy of focusing on specific vital questions rather than diffusing effort over many, the Lunar Polar Probe would carry only a small number of (continued on page 4) GUEST COLUMN 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. LOW-COST LUNAR POLAR MISSIONS by J. R. French PURPOSE OF THE STUDY The purpose of this study is to identify and characterize low-cost missions which could provide information concerning location and quantity of lunar resources. The particular focus of the study is the polar regions of the Moon because of the possible presence of water and because the polar regions offer particular advantages as a permanent base site. SIGNIFICANCE OF THE MISSION A permanent Lunar Base is potentially of great significance to humankind’s future activities in the solar system. Such a base is of undoubted scientific value. Its value as an operational support base however is in large degree dependent upon the availability of natural resources. We know from the results of previous Lunar exploration (Ref. 1) that most of the structurally important metals as well as useful materials such as silicon are available in the lunar regolith, mostly in oxide form. Various means of reducing the oxides have been identified. Thus a Lunar facility could be well supplied with structural and other raw materials and copious quantities of oxygen suitable for use as a propellant or for other purposes. The flaw in this rather rosy picture is the almost total lack of hydrogen on the Moon. Other than a very small amount deposited in the regolith as solar wind protons, no hydrogen has been found in the returned samples. There is no evidence that water, the most commonly found hydrogen compound on Earth, has ever existed in significant quantities on the surface of the Moon, at least in liquid form. As will be seen later, the presence of hydrogen, particularly in the form of water, will be of profound significance to Lunar operations. If there is no supply on the Moon, hydrogen can be imported from Earth or possibly from the moons of Mars or the asteroids. Clearly these options are less attractive than a local supply. Surprisingly, some theoretical work indicates the possibility that water ice in modest quantities could be permanently frozen in some polar regions of the Moon which never see sunlight. While this theory is somewhat controversial, its significance to future utilization of the Moon implies that a moderately priced mission to verify or disprove the theory should have a high priority in Lunar exploration. Fortunately, even if the results should turn out negative in regard to the presence of water, such a mission would be most useful in determining the distribution of other elements. This would be of substantial scientific interest as well as useful in selecting a base site. CONCLUSIONS OF THE STUDY The study described in this report concludes that a spacecraft and instruments capable of surveying the Lunar polar regions to determine the presence of hydrogen (water) and to give data concerning the presence and distribution of other elements can be built and flown for costs in the neighborhood of $40 million to $50 million dollars exclusive of launch costs. In order to achieve costs in this range, heavy reliance is placed upon adaptation of existing spacecraft designs and use of well developed instrument technology rather than extensive new development. DISCUSSION Theory of Lunar Water The presence of water on the Moon was first given credibility by Watson, Murray, and Brown in 1961 (Ref. 2). In this work it was postulated that certain regions in the vicinity (continued on page 2) Low cost Lunar Polar Probe searching for frozen volatiles. Copyright 1987 Space Studies Institute
GUEST COLUMN (continued from front page) of the Lunar poles which are never exposed to the sun may be at temperatures below 120 °K. Such areas might then function as cold traps, collecting and permanently freezing any volatiles which may be present which are solid at these temperatures. This would certainly include water and possibly carbon dioxide as well. Arnold (Ref. 3) estimates that the temperature might be as low as 40 °K. If this is the case, even methane and other low- temperature volatiles might be trapped. The permanently shadowed areas: the bottoms of deep craters, rilles, crevices, etc., are estimated to total as much as 2xl05 km in area. Such areas might be found as far from the poles as 60 ° latitude although the geometry of the situation obviously favors locations nearer the poles. Two sources are usually postulated for Lunar water. One is simply the primordial cloud from which the Moon originally condensed. The prevalence of water in the solar system gives clear evidence that water was a major constituent in the makeup of the planets. It would be remarkable indeed if the Moon had condensed without water. In the case of the rocky inner planets most of this original water was outgassed and a good deal was lost. In the case of Earth and Mars however some was retained. The Moon is small enough that it is probable that most of the primordial water was lost except perhaps at some depth in the interior. This water could occasionally be brought to the surface by vulcanism or major meteoroid strikes. Much of this water would be lost to space. However as it spread around the planet, some would be trapped in the shadowed regions. It is interesting to note that this may still be taking place to some extent. If the rather controversial Lunar Transient Events are indeed volcanic venting then the process is still at work. Another postulated source of water is cometary impact. Such bodies, composed of a high percentage of water and other volatiles would be vaporized by the impact. The vapors would migrate around the Moon (Ref.4) restrained by its gravity until they escaped due to random motion of the molecules heated by the sun, accelerated by decomposition of molecules such as water into its constituent elements by solar ultraviolet. During the time required for this to take place some fraction of the original molecules would be trapped in the shadowed regions. A critical question in regard to this theory is how long the Lunar poles have been where they are. Obviously most of the outgassing of the original water must have occurred early in the Moon’s history. Similarly most of the impact cratering was concentrated in the first one or two billion years. If the Lunar poles were in their present location 4.5 billion years ago and there has been no intervening migration then the cold traps have been in operation for essentially all of the Moon’s history including the Mare-forming events thus leading to the maximum possible accumulation of volatiles. It is generally considered improbable that this is the case. In Ref.3 Arnold postulates that the poles may have become fixed at the present sites some 3 billion years ago. This is well after the major outgassing phase and after the Mare-forming events. Based upon the 3 billion year number, an estimated outgassing rate, and the estimate of the percentage of migration of molecules and cold trapping from Ref. 4, Arnold estimates that the amount of ice accumulated might be about 1 meter in thickness over the shadowed area. This equates to 100 cubic km or about 10'' tons of water. It is clear that, even if these estimates are optimistic by two or three orders of magnitude, the amount of water which may be available dwarfs anything which we can even conceive of importing from Earth or from other space sources. One should not, incidentally, expect that analogs of the shining polar caps of Earth lie hidden in the dark regions of the Moon. The surface of the Moon is constantly being “gardened” by micrometeoroid impact. This stirring and overturning would tend to intermingle the dust and rock. The negative side of this is that each impact will vaporize some water of which some may be lost. On the positive side, a layer of dust would accumulate on the surface in this scenario, providing thermal insulation and protection from later impacts. In fairness, one must end this discussion of possible cold trapped water by pointing out that some scientists contend that there is no such water. Lanzerotti, for example, contends that sputtering by solar wind particles would remove the cold trapped water as rapidly as it is laid down. Another less prominent theory concerning lunar water offers that it could be widespread. Muller (Ref. 5) notes that the Lunar subsurface temperature is below 0 ° C at fairly shallow depths and that a 100 meter overburden of Lunar soil could preserve ice for geologic time. Thus if the Moon so developed that a percentage of the primordial water remained in the interior while the surface and top tens of meters was thoroughly outgassed and desiccated, large amounts of water could be available near the surface in many areas of the Moon. Near the surface, water could only exist as ice, at greater depth the temperature begins to rise again and liquid water could possibly exist at some depth beneath an overburden of dust, rock, and ice. While it would seem difficult to detect liquid water at such a depth without drilling, we have already flown an instrument in Lunar orbit capable of making such a detection. In fact it may have done so. The radar sounder flown on one of the later Apollo missions had the capability of penetrating to considerable depth through very dry rock. It would also penetrate through ice buried in the rock without detecting the difference since the dielectric coefficients are very similar (3 for ice, 4 for regolith). It would not penetrate through liquid water which has a high dielectric coefficient (about 80). In fact the sounder would see a very bright reflection off a water layer and would be unable to see beyond it. The sounder observed exactly this phenomenon in both Mare Crisium and Mare Serenitatis. The reflecting layer came up from deep beneath the mare to within 200 to 1000 m of the surface near the shore. The subsurface water explanation of the observed data is not accepted by the scientific establishment and it may well be that other, more prosaic explanations exist for these observations. However the existence of a liquid water layer is at least a possibility and worthy of further investigation. Significance of Lunar Water The apparent lack of Lunar hydrogen was discussed briefly in an earlier section. This lack has a profound significance in regard to long term utility of the Moon as a support base for space operations. Simply put, hydrogen is the basis for all high energy fuels for rocket engines. It may be used by itself or in various energetic chemical compounds such as methane (CH4) and other hydrocarbons, metal hydrides such as diborane (B2H6), etc. Hydrogen holds this unique position because of its very low atomic weight and highly exothermic reactions with most oxidizers. In fact very few practical fuels exist which do not contain hydrogen. One such is carbon monoxide (CO). Table 1 presents performance data for several propellant combinations for comparison. While the arguments presented in the preceding paragraph are not exhaustive, they clearly indicate that, if propellant manufacturing in large quantity is to take place on the Moon, the presence of hydrogen is most important. If only oxygen can be produced as a result of ore reduction, it will still be significant but clearly of less importance than ability to generate both oxidizer and fuel. The significance of water in the life support system of a Lunar Base is obvious at the simplistic level in that human and most other forms of Earth life depend upon the availability of water. However, in terms of basic life support, the amounts are relatively small on a per-person basis and closure of the water loop in a life support system is one of the easier aspects of life support system design. Thus for simple survival, availability of Lunar water may not be of great significance since it could be imported from Earth except perhaps in the case of very large nonulations. TABLE 1 Propellant Performance Liq. oxygen/carbon monoxide (CO) 275 sec Liq. oxygen/RP-1 (kerosene) 351 sec Liq. oxygen/hydrazine 367 sec Liq. oxygen/hydrogen 492 sec
Lunar Polar Probe showing boom for gamma-ray spectrometer. It can be argued however that the availability of generous quantities of water can greatly enhance the quality of life and ease of function within a large permanent base. People require recreation and relaxation and the ability to provide such apparently “frivolous” amenities as swimming pools, decorative ponds and fountains, plenty of water for baths and showers should not be overlooked as a morale factor. Similarly, generous amounts of water for washing, cleaning, sewage transport, portable radiation shielding, and other uses can greatly facilitate base operations. On Earth, water is a major component in many manufacturing processes. It can function as a cooling or heating agent or heat transfer medium and as a diluter, carrier, or reagent in a variety of chemical processes. The hydrogen and oxygen which can be obtained from water are equally useful as chemical reagents in various chemical operations. Examples include use of hydrogen in reducing ores and oxygen in the combustion of waste products into harmless oxides. While a variety of innovative techniques have been devised for carrying out industrial processes without water, the ready availability of water will make it much easier to apply well understood techniques now used on Earth to Lunar operations. Mission Concept The primary instrument which is usually considered for a mission of this type is the gamma-ray spectrometer. This instrument depends for its function on the detection of gamma rays which are emitted from all bodies in the solar system. The original source of the energy is cosmic rays which penetrate the mass and in decelerating deposit energy in the mass in the form of orbital electrons excited to a higher than normal energy state. When the electrons decay back to their normal state the energy is emitted as a gamma ray. The energy of the gamma ray is characteristic of the specific atom from which it is emitted. Therefore, if the gamma rays can be detected and sorted according to energy then it is possible to derive what atoms in what percentage make up the mass from which the rays are being emitted. Several problems arise inherently from the nature of the gamma-ray spectrometer. The number of gamma rays given off depend upon the intensity of the incident cosmic radiation. Since this is relatively low, the emitted gamma ray flux is also low. Since this is a characteristic of the universe, there is nothing which can be done about it except to accumulate data over a long period of time. Common materials can be detected reasonably quickly while less common ones require long integration times. Another problem is the lack of discrimination. Since all objects in the solar system are bombarded by cosmic rays, all objects give off gamma rays and therefore will be detected by the gamma-ray spectrometer. This means that the instrument is not only measuring the elemental composition of the astronomical body in question but also of the spacecraft which brought it and even of itself. In order to distinguish the signal from the target planet the instrument must be calibrated by reading this background signal while it is in deep space far from the planetary body. Even this does not completely solve the problem since the process of burning propellant to enter orbit will change the background because of the removal of the propellant mass. While all this complicates the issue, careful mission design and data analysis can still provide a useful result. Because of its sensitivity to background radiation from the spacecraft and because the more sensitive detectors must be maintained at a low temperature (as low as 90 °K) the gamma ray spectrometer will most probably be mounted on a boom which will place it some two meters from the spacecraft. This remote placement aids both problems since gamma ray intensity decreases with distance from the source. (For a point source the rate of decrease is as the square of distance however typically the spacecraft will be too large and too close to appear as a point source.) The thermal requirement is aided by the fact that the detector is isolated from the heat generated by electrical activity in the spacecraft. By careful thermal isolation from the spacecraft, prevention of energy from sunlight, earthlight or moonlight from reaching the detector, and design of a radiator to reject any internally generated heat to space it is probably possible to cool the detector to the desired temperature without active refrigeration. This is desirable from considerations of reliability and weight reduction. If necessary refrigeration of the detector can be provided by a variety of means. The most reliable is probably thermoelectric cooling since it requires no moving parts or consumable substances although fairly inefficient. Even given the complications discussed above, the gamma-ray spectrometer appears to be the instrument best suited to detection of water and other volatiles in the lunar polar regions. It is quite sensitive to hydrogen and many of the other lighter elements which would be expected to constitute deposits of volatiles. Because gamma rays are emitted from the bulk of the material, elemental abundances are sensed to some depth beneath the surface (limited by self shielding of the gammas by the material itself), usually about half a meter. Thus even if a layer of dust overlies the volatiles they will still be detected if within a half meter of the surface. This would seem probable for cold trapped materials. Given adequate observing time, the gamma-ray spectrometer can also provide an abundance map for a variety of other elements. Table 2 shows sensitivity of the instrument to the elements. TABLE 2 Minimum Detection Concentration Material Concentration Water 0.7% Hydrogen 0.08% Oxygen 0.5% Carbon 1.0% No other instrument capable of operating from orbital altitudes can provide elemental data equivalent to that available from the gamma-ray spectrometer. Because of the lack of atmosphere and the large area to be surveyed, orbital exploration is the only practical approach. Therefore, any mission dedicated to the discovery of cold trapped polar volatiles will include a gamma-ray spectrometer regardless of other instrumentation. The second half of this paper will appear in the March/April issue of the UPDATE. REFERENCES 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.3O33, 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
The 8th Biennial SSI / Princeton Conference on Space Manufacturing May 6 - 9, 1987 GENERAL INFORMATION The 8th Biennial SSI/Princeton Conference on Space Manufacturing, sponsored by Space Studies Institute, is a forum for papers on all aspects of the use of nonterrestrial 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. CONFERENCE PROGRAM Following is a listing of sessions and session chairmen scheduled for this year’s Space Manufacturing Conference. Wednesday, May 6 □ Biomedical Considerations Stanley Mohler Wright State University, School of Medicine □ Space Transportation Ed Bock General Dynamics □ Nonterrestrial Resources John Lewis Lunar and Planetary Laboratory Thursday, May 7 □ International and Economic Considerations Irwin Pikus National Science Foundation Friday, May 8 □ Space Manufacturing and Solar Power Satellites Peter Glaser Arthur D. Little Company □ Artificial Biopheres and Closed-cycle Life Support Carl Hodges Environmental Research Laboratory □ Social Factors for Space Flight B. J. Bluth AC4SA Headquarters □ Poster Session Morris Hornik Space Studies Institute □ Roundtable “Return to the Moon” Gregg Maryhiak Space Studies Institute Gerard K. O'Neill CONFERENCE REGISTRATION A registration fee of $290 includes lunches, coffee breaks and the Friday night banquet. Registration through the Space Studies Institute is available. If you would like a registration package please send your name, address, and affiliation to: Ms. Barbara Faughnan, Conference Cordinator, SSI, P.O. Box 82, Princeton, NJ 08540. PRESIDENT (continued from front page) instruments. Concentrating in that way on one problem rather than many, it could be inexpensive: according to studies funded by SSI, only about $50 million, plus the cost of launch, instead of the billion dollars or more that a multi-function space platform, satisfying many desires, would cost. With cooperation from SSI, NASA and possibly the space agencies of other nations, by the very early 1990’s the Lunar Polar Probe could be in permanent circling orbit above the Moon, relaying back data in seconds to the Earth. It would be our “Prospector” for the now- hidden lunar resources. The National Commission on Space named a goal of high priority, to be met as soon as possible in NASA’s program: that is the Robotic Lunar Return vehicle (Figure 1, Page 15 of the Commission’s Executive Summary). That vehicle is targeted for operation in about 1998. Logically it fits beautifully with the Lunar Polar Probe. In the few years after the Probe first returns its findings to the Earth, entities such as SSI, entrepreneurial new companies, or divisions of major companies and agencies here and abroad can develop robotic, tele-operated mini-factories, to make use of the newly-found lunar resources to benefit the space programs of all nations. The Robotic Lunar Return vehicle will then come into operation, if on the Commission’s schedule, at just the right time to emplace those mini-factories on the Moon. Tele-operation, the direction of those factories by workers here on Earth, is practical for the Moon for two critical reasons: it takes only 2.6 seconds for a television signal to arrive here from a lunar factory and for a resulting command signal to return to the Moon directing action in response; and the Moon remains in gravitational lock, always presenting the same face to us, rather than rotating in a manner that cuts off communications. With these logical, simple, relatively inexpensive steps we can prove, much sooner than in any other way, the real economic value of the trans-terrestrial resources, and set the space programs of the world on a forward course from which there can be no faltering. Therefore I speak not of returning, but rather say “Forward to the Moon.” DIRECTORY Bibliographies: If you would like a copy of the SSI produced Space Bibliographies, send $2.00 with your request and address to SSI, P.O. Box 82, Princeton, NJ 08540. Conference: To receive registration information for the 8th SSI/Princeton Conference on Space Manufacturing please contact Ms. Barbara Faughnan, Conference Coordinator, SSI, P.O. Box 82, Princeton, NJ 08540. Corporate Membership: For information regarding Corporate or Organizational Membership please contact Gregg Maryniak or Bettie Greber at the SSI Princeton office: P.O. Box 82, Princeton, NJ 08540, or phone: 609-921-0377. Lectures: To book an SSI speaker contact the SSI office, 609-921-0377. Membership: To receive SSI Update bimonthly, send your name, address, and contribution to SSI, P.O. Box 82, Princeton, NJ 08540. All contributions are tax-deductible, but to receive Update a gift of $25.00 or more is necessary. National Commission on Space Report: Pioneering the Space Frontier Copies of the report are available to SSI members for $1 LOO each. Reprints of the six-page summary are available for 254 per copy, minimum 10 copies. Send your request, check, and address to SSI, P.O. Box 82, Princeton, NJ 08540. Senior Associate Information: Contact Connie Tevebaugh, Senior Associate Coordinator, SSI, P.O. Box 82, Princeton, NJ 08540 or call 609-921-0377 Slides: Slide Sets are available depicting Mass-Driver Research or Space Manufacturing. The cost of each set is $15.00 postpaid. Send name, address, set desired and check to SSI, P.O. Box 82, Princeton, NJ 08540 Special Report on High Frontier® Research: Reprints are available for 25 cents per copy, min. 10 copies. Send your request, check, and address to SSI, P.O. Box 82, Princeton, NJ 08540. Video productions by CSSS: for information write Larry Boyle, c/o SSI, P.O. Box 82, Princeton, NJ 08540.
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 609-921-7079. 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! Gregg Maryniak GUEST COLUMN 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. PART n 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 (continued on page 2) THE HIGH FRONTIER® NEWSLETTER VOLUME XIII ISSUE 2 MARCH/APRIL 1987 SPACE STUDIES INSTITUTE RO. BOX 82 PRINCETON, NEW JERSEY 08540 Low cost Lunar Polar Probe searching for frozen volatiles. Copyright 1987 Space Studies Institute
GUEST COLUMN (continued from front page) 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. Candidate Spacecraft As will be discussed below under “Costs,” the concept of modifying existing Lunar Polar Probe showing boom for gamma-ray spectrometer. 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/DMSP 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 (continued on page 4)
The 8th Biennial SSI / Princeton Conference on Space Manufacturing May 6 - 9, 1987 GENERAL INFORMATION 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. CONFERENCE REGISTRATION 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. ORGANIZING COMMITTEE Gregg Maryniak, Chairman Andrew Cutler David Odom Gerard K. O’Neill HOTEL ACCOMODATIONS 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 at 609-452-2400. CONFERENCE PROGRAM 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 of space 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 RESOURCES 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 nonterrestrial 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 of the University of Hawaii will present a paper on eco-systems. 3:45 pm Session VIII SOCIAL ASPECTS FOR SPACE FLIGHT Chair: B.J. Bluth NASA Headquarters 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. POSTER SESSION 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 of the Institute. Tickets for this event may be purchased through the Institute or during the Conference at the Registration Table.
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. REFERENCES 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.3O33, 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. DIRECTORY Bibliographies: If you would like a copy of the SSI produced Space Bibliographies, send $2.00 with your request and address to SSI, P.O. Box 82, Princeton, NJ 08540. Conference: To receive registration information for the 8th SSI/Princeton Conference on Space Manufacturing please contact Ms. Barbara Faugh- nan, Conference Coordinator, SSI, P.O. Box 82, Princeton, NJ 08540. Corporate Membership: For information regarding Corporate or Organizational Membership please contact Gregg Maryniak or Bettie Greber at the SSI Princeton office: P.O. Box 82, Princeton, NJ 08540, or phone: 609-921-0377. Lectures: To book an SSI speaker contact the SSI office, 609-921-0377. Membership: To receive SSI Update bimonthly, send your name, address, and contribution to SSI, P.O. Box 82, Princeton, NJ 08540. All contributions are tax-deductible, but to receive Update a gift of $25.00 or more is necessary. National Commission on Space Report: Pioneering the Space Frontier Copies of the report are available to SSI members for $11.00 each. Reprints of the six-page summary are available for 25c per copy, minimum 10 copies. Send your request, check, and address to SSI, P.O. Box 82, Princeton, NJ 08540. Senior Associate Information: Contact Connie Tevebaugh, Senior Associate Coordinator, SSI, P.O. Box 82, Princeton, NJ 08540 or call 609-921-0377 Slides: Slide Sets are available depicting Mass-Driver Research or Space Manufacturing. The cost of each set is $15.00 postpaid. Send name, address, set desired and check to SSI, P.O. Box 82, Princeton, NJ 08540 Special Report on High Frontier® Research: Reprints are available for 25 cents per copy, min. 10 copies. Send your request, check, and address to SSI, P.O. Box 82, Princeton, NJ 08540. Video productions by CSSS: for information write Larry Boyle, c/o SSI, P.O. Box 82, Princeton, NJ 08540. 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. LUNAR POLAR MISSIONS (continued from page 2) 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. Schedule 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. Costs The study reported in Ref. 8 quoted a cost for the spacecraft alone of $88 million
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