The Ph-D Project: Manned Expedition to the Moons of Mars
by S. Fred Singer

Abstract: The Ph-D (Phobos-Deimos) mission involves the transfer of six to eight men (and women), including two medical scientists, from Earth orbit to Deimos, the outer satellite of Mars. There follows a sequential program of unmanned exploration of the surface of Mars by means of some ten to twenty unmanned rover vehicles, each of which returns Mars samples to the Deimos laboratory. A two-man sortie descends to the surface of Mars to gain a direct geological perspective and develop priorities in selecting samples. At the same time, other astronauts conduct a coordinated program of exploration (including sample studies) of Phobos and Deimos. Bringing men close to Mars to control exploration is shown to have scientific and other advantages over either (i) (manned) control from the Earth, or (ii) manned operations from Mars surface. The mission is envisaged to take place after 2010, and to last about two years (including a three- to six-month stay at Deimos). Depending on then-available technology, take-off weight from Earth orbit is of the order of 300 tons. A preferred mission scheme may preposition propellants and equipment at Deimos by means of "slow freight," possibly using a "gravity boost" from Venus. It is then followed by a "manned express" that conveys the astronauts more rapidly to Deimos. Both chemical and electric propulsion are used in this mission, as appropriate. Electric power is derived from solar and nuclear sources. Assuming that certain development costs can be shared with space-station programs, the incremental cost of the project is estimated as less than $40 billion (in 1998 dollars), expended over a 15-year period. The potential scientific returns are both unique and important: (i) Establishing current or ancient existence of life-forms on Mars; (ii) Understanding the causes of climate change by comparing Earth and Mars; (iii) Martian planetary history; (iv) Nature and origin of the Martian moons. Beyond the Ph-D Project, many advanced programs beckon; discussed here are exploitation of Martian resources, Martian "agriculture", and the possibility of planetary engineering experiments that can benefit survival on the Earth.

INTRODUCTION

The last Moon walk took place a quarter-of-a century ago. Fewer than half of today's Americans saw the first Apollo landing in 1969. Skylab, a functioning space station, was allowed to die a fiery death as it entered the Earth's atmosphere in 1974. The dreams of visiting Mars died with Apollo and Skylab, at least as far as the government was concerned. Public interest, however, has never really waned. The "Mars Underground" came to life in 1981, together with the Planetary Society sparked by the charisma of Carl Sagan. Just in the past few years, the Mars Society, founded by Robert Zubrin, has gained popularity. But can this grassroots interest survive and be translated into action?

It may be taken for granted that Mars is the most interesting and worthwhile target for planetary exploration. However, it will take two concrete steps to bring men to Mars:

§ Step 1: Convince decision-makers, and also planetary and life scientists, that unmanned missions are not giving us the results we want. Manned Martian missions can solve the fundamental scientific issues of planetary evolution, climate change, and especially the origin of life within a reasonable time frame. And only manned missions can further international collaboration, enhance national prestige, and create the public interest and excitement that will produce the funding for Mars projects.

§ Step 2: Choose the first Manned Martian Mission with great care. If it is too ambitious, it will not be funded. A case in point is the Space Exploration Initiative (SEI) which NASA presented to then-President Bush. A package costing around $450 billion, it featured manned habitation of the Moon as a "stepping stone" to Mars, when in fact it is likely to be a detour. And it has provided grist for the mills of opponents of manned spaceflight. On the other hand, one should not automatically choose the simplest and least costly of the possible missions. A manned flyby of the planet has returns that are likely to be so small, it may well turn out to be the first and last Manned Martian Mission. Yet, with a small increase in cost, a Flyby can become a Mars Orbiter, with an orbit that matches that of Deimos, the outer Martian moon.

THE PH-D MISSION

In its simplest terms, the Ph-D mission is nothing more than the transfer of a manned habitat from near-Earth orbit to a circular Mars orbit at a distance of 6.9 Martian radii. After tying up to Deimos, a tiny body with negligible gravity, the astronauts start their program of exploration, beginning with Deimos. There is no need to set up a base; the habitat and laboratory of the space ship is the base. There follows a manned sortie to Phobos, the other small moon, to obtain samples, investigate its structure, and eventually figure out if the two moons are related and puzzle out their origin. Are they of uniform composition or are they mixtures of minerals? Are they similar - chemically and petrologically? Were they both captured after Mars formed? Or did they originate with Mars? Are they the remaining fragments of a much larger body? Or are they samples of the original planetesimals of the early solar system, left over when the planets formed? So many fundamental questions that can only be answered by direct exploration.

The high point of the mission would be a manned sortie (of perhaps two astronauts) to the surface of Mars. Even if they only spend a couple of days on the surface, exploring the immediate vicinity of the landing site with a rover vehicle, selecting interesting samples and perhaps digging below the surface, it would be a great human adventure.

All the while, the remaining astronauts would launch robotic rovers to promising locations on Mars, as far as the ice caps, to take measurements and recover samples from the surface and subsurface. Deimos is close enough so that the vehicles can be operated in a telepresence mode in real time. Based on the data received from the initial rovers, others would follow up, leading to a system of "sequential experimentation", a most efficient way of getting important scientific results. A laboratory analysis of a sample sent back from the rover to Deimos could trigger a request to get more material from the same location, or to dig deeper.

All of this would be impossible to do if the rovers were to be controlled from Houston. The average time delay of about 40 minutes would make telepresence impractical. Autonomous rovers, if they existed, might help but could never fully take the place of human control. Sequential exploration that included sample examination would stretch over decades not hours. Moreover, the volume of data that would have to be transmitted to Earth is so large as to overload any reasonable communication system.

How to Carry out the Ph-D Project

There is one point to keep in mind: It can all be done with existing proven technology: chemical propulsion and solar electric power supplies. But it may be possible to reduce cost without undue delay by using improved rocket boosters to put the nominal 300-ton payload into low earth orbit (LEO); a nuclear reactor to supply electric power; and low-thrust but high-efficiency ion propulsion. Power reactors have already been tested in space and several schemes of ion propulsion have been successfully flown. Intriguing proposals abound for a cheaper "space truck" to provide the heavy lift. Such proposals include the use of the large Russian SS-18 missile booster and other surplus ICBMs, to schemes for a series of reusable rocket planes launched from large carrier aircraft flying at 40,000-ft altitude.

Such decisions can only be made in detailed engineering studies that try to optimize the mission. First and foremost, a decision must be made on whether to divide the mission into a "slow freight" (SF) that is prepositioned on Deimos, followed by a "manned express" (ME) that carries the astronauts in their habitat. By increasing chemical propellant weight, or with ion-propulsion during the coast phase, or with the use of both, the ME can cut the time for reaching Deimos, and reduce mission duration, weight of consumables (atmosphere, water, and food supply), and overall risk. The duration may become short enough to eliminate the need for an artificial-G environment.

Another decision concerns near-Mars operations. Should one use aerobraking in the Martian atmosphere and then boost the spacecraft into a Deimos orbit? Alternatively, is may be cheaper and/or safer to ease into the orbit directly by the use of propulsion? Much will depend on whether ion propulsion is available.

Electric power is a must for all spacecraft operations, for communications, and for ion propulsion. It may be advisable to consider both a solar photovoltaic and a nuclear supply. The nuclear unit could be carried with the SF, the solar with the ME. Nuclear power would overcome the inevitable shadow problem that turns solar into an intermittent supply source. The nuclear supply could be left behind on Deimos to continue resource recovery experiments and await the next mission, while the astronauts return to Earth with their solar supply.

Ph-D versus Surface Operations

It is necessary finally to compare the costs and benefits of a Ph-D project with a mission where the spacecraft lands on Mars, with perhaps a half-dozen astronauts who remain there for several months. What would they do; how effective would they be; and what kind of problems would they face?

First of all, operating on the planet, driving rover vehicles, involves risk and safety problems, especially if one is distant from the base. It is far safer and also more efficient to operate rovers by telepresence and radio control. The astronauts can then remain at the Mars base and conduct a virtual operation. However, with the difficult Martian topography, a satellite communication system would seem to be essential. Control from a base on Mars surface would thus have no advantage over human control of rovers from Deimos.

How would samples get from distant rovers, perhaps operating near the ice caps, back to the Mars base, near the equator? Rocket delivery would be the answer, allowing rapid transport, which would be especially important for volatile samples. Again, no special advantage over a Deimos base. But when if comes to scientific examination of the samples, Deimos has a real advantage: It furnishes a ready-made natural vacuum, while the Martian laboratory needs to provide a full-blown vacuum system to operate its mass spectrometers and scanning electron microscope.

And how to provide electric power? An obvious point: On Deimos, there are no dust storms that can cover up solar cells or even damage them. A solar supply on Mars would have a 24-hour day-night cycle, just like on Earth. It would require costly (in terms of weight) battery storage. A similar problem might occur on Deimos, whose orbit is nearly synchronous with Mars' rotation. However, one might circumvent the problem there by dividing the photovoltaic supply and disposing it around Deimos so as to always receive solar illumination (albeit reduced). (Using the same technique, it would be much easier to stay warm on Deimos.) By moving the habitat around Deimos, the astronauts can also protect against solar cosmic rays and against the impacts of meteor streams.

MARS RESOURCES AND PLANETARY ENGINEERING

The Ph-D project is conceived as the initial mission to Mars, to be followed by more ambitious undertakings. The exploitation of mineral resources on the planet has been widely discussed. The Martian moons offer an even more exciting potential for economic returns. Phobos and Deimos have as of now an unknown resource potential. However, they do contain minerals of some sort and can provide the cheapest source of materials for solar system operations, far cheaper than the Moon. It's not distance that counts but the micro-gravity of the Martian moons. It's cheaper in terms of propulsion to transport material to Earth from Deimos than from the Moon.

It is generally agreed that the preconditions for some kind of life are present on the surface of Mars. Even if no evidence is found for living material, it might still be possible to implant organisms which can exploit the various ecological niches available in the different regions of Mars. It may be possible to use existing organisms from the Earth, such as algae, bacteria, or combinations such as lichens. It may even be possible to develop or engineer specific organisms which could prosper under Martian conditions. Once we can simulate the Martian environment on the Earth, we may be able to proceed more rapidly with the design of such organisms. If one succeeds in populating the surface of Mars with organisms that multiply rapidly, and if one can develop higher organisms which can efficiently harvest the lower forms, then we may have the basis for a renewable resource which takes advantage of the ecological opportunities of Mars. It would be fascinating to study this problem further, even up to the point of devising a self-sustaining system of Martian "agriculture" which could support eventual human settlements on the surface of Mars.

A different investigation might be along the line of biological evolution. Certain kinds of experiments may not be appropriately done on the Earth because of the danger of interaction with existing life forms. They could be done more easily on Mars, which might serve as an appropriate laboratory for such work. The Martian environment with its higher radiation levels (or by increasing radiation artificially) may speed up the process of evolution and allow us to study the evolution process under different environmental conditions.

From many points of view, climate studies are most fascinating and perhaps most useful. We have already discussed earlier the possibility of unraveling the history of climate change on Mars and comparing it with that of the Earth, thereby elucidating the different causes for climatic change. Here we can speculate about the future possibility of being able to modify the Martian atmosphere artificially and carry on other climate control experiments on Mars. These could be done without any danger to the climate on the Earth, but would provide important lessons that could be applied to the Earth. As we know, climate changes constantly on the Earth; but we are not certain about the causes nor about the magnitude of the effects. It is particularly worrisome that human activities may be influencing climate in ways which we do not fully understand.

The Martian atmosphere provides us with a laboratory where many scientific ideas about climate can be tested. The thinness of the Martian atmosphere may be of some advantage in these studies. It should be possible to modify the atmosphere either by adding trace gases which have important radiative properties or by releasing gases from the polar cap. One experiment, often suggested for the Earth's Arctic Ocean, is to sprinkle carbon black on the ice so as to speed up melting and evaporation. Another might be to promote volcanic eruptions which would put large quantities of dust as well as gases into the atmosphere. For obvious reasons, one may not wish to go ahead with such experiments on the Earth for fear of causing irreversible changes. Such fears may not be as worrisome when we consider the planet Mars; yet the information gained can be of tremendous importance to us on the Earth in understanding climate change and especially the human role in climate change.

CONCLUSION

The Ph-D project has a clear scientific and operational advantage over manned surface operations and a huge cost and safety advantage. We need to consider then whether having six people on Mars for 200 days is so much better for public interest than two men on the surface for two days. I think not.

REFERENCES

The Case For Mars (P.J. Boston, ed.) American Astronautical Society, Vol. 57, San Diego, CA, 1984

Strategies For Mars: A Guide to Human Exploration (R.C. Stoker and C. Emmart, ed.) American Astronautical Society, Vol. 86, San Jose, 1998

S. FRED SINGER is director of the Science & Environmental Policy Project in Fairfax, Virginia, and Distinguished Research Professor at George Mason University. A pioneer in space research, he developed instruments for remote sensing of stratospheric ozone and was the first director of the US Weather Satellite Service (now part of NOAA). He served as principal investigator on the LDEF interplanetary dust experiment, which discovered the existence of artificial debris clouds in Earth orbit. He devised the cosmic-ray method of dating meteorite ages [featured in Scientific American] and published early calculations on the orbit evolution and origin of the Martian moons.