THE PH-D PROPOSAL:A MANNED MISSION TO PHOBOS AND DEIMOS
by S. Fred Singer
Presented at the Second Annual Convention of the Mars Society, August 12-15, 1999

The Ph-D mission involves the transfer of approximately eight men (and women),
six planetary plus 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,
four of the 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)
control from the Earth and (ii) a manned Mars landing. 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 will be
followed by a "manned express" that conveys the astronauts more rapidly to
Deimos. Both chemical and solar electric propulsion are used. Assuming that
certain development costs can be shared with other 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. The
outstanding achievements would be: (i) Existence of life on Mars; (ii)
Understanding the causes of climate change by comparing Earth and Mars; (iii)
Nature and origin of the Martian moons; (iv) A detailed radar look at the
surface of Venus. 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.

1 Based on a Study performed for the Marshall Space Flight Center, Huntsville,
AL. under Order No. H-27272B and H-343115B

2 University of Virginia, Charlottesville, VA 22903 and Science and
Environmental Policy Project, Fairfax, VA 22030

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A Personal Note

As a charter member of the “Mars Underground” 18 years ago, I presented the first public discussion of a manned mission to Phobos and Deimos, the moons of Mars.  It was right here in this building at the University of Colorado at the “Case for Mars” Conference. 

As I look at your young faces, most of you well under 30, I think I should tell you how I came to develop the Ph-D project.  After World War II, just out of the US Navy, I joined the high-altitude rocket research group at the Applied Physics Laboratory of Johns Hopkins University.  It was one of the earliest ventures in “space research.”  Using captured German V-2 rockets, and later US-developed Aerobee research rockets, we made the first measurements of primary cosmic rays (with James Van Allen), stratospheric and mesospheric ozone (with John Hopfield), and electrojet currents in the ionosphere.  Our rocket launchings, first from White Sands, NM, later ranged from the Equator to the Arctic.  These were hard work but exciting times; we thought of ourselves as pioneers on a new frontier.

Of course, all of these measurements used instruments.  The idea of sending humans beyond the Earth’s atmosphere seemed like science fiction to us, much too expensive and just useless.  Some of us even resented the idea, because it might make our research seem too fantastic to the “realists” who were funding our work.  Well, I went on from there to design, in 1952, an instrumented satellite, which we called the MOUSE (Minimum Orbital Unmanned Satellite of the Earth, with help from Arthur C. Clarke).  Ten years later, something like it became reality when I took over as the first director of the government’s weather satellite program.  It was only then that I realized that satellite instrumentation was becoming so complicated and expensive that it might pay to have a repairman in orbit, at least for short periods.

And so began my slow conversion to manned spaceflight.  It speeded up once I started to publish papers on the history and origin of planetary satellites.  I had formed a good theory about the capture of the Moon by the primitive Earth, but I was stumped by the puzzling orbits of the Martian moons.  While unmanned exploration would certainly give valuable results, such a program would likely have to stretch over decades.  A manned expedition could gain infinitely more information and would even be cost-effective.  In 1977, Dr. Jim Fletcher, NASA administrator gave me a small grant of $8000, so I could study the matter during a sabbatical at the University of Texas.  My two-volume report was delivered to the Marshall Spaceflight Center and to NASA Headquarters  and promptly disappeared.  If not for the Mars Underground, it may never have resurfaced in 1981.  It is a great disappointment to me that so little has been done to bring such a project to reality during all these years.  But thanks to the Mars Society, it is resurfacing again today.  I hope that the Ph-D project will fly.

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 in1974.  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 create the public interest and excitement, enhance national prestige and further international collaboration that can 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 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 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 could 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 minutes or 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 better 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 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 it 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.  Being on Mars 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.

Where does this leave us?  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.

One further point for those who are interested in 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 microgravity of the Martian moons.  It’s cheaper in terms of propulsion to transport material to Earth from Deimos than from the Moon.
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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.