"... In fact, not only do the cosmic ray alarmists lack foundation for their claims, we have direct contrary evidence. As a result of extensive stays onboard the International Space Station or Mir, about a dozen astronauts and cosmonauts have already experienced cosmic day doses comparable to a Mars journey, and there have been no radiological casualties. This is not surprising, since, on the basis of extensive radiation health knowledge, the radiation doses and dose rates involved pose no threat whatsoever of short-term effects, and at most about a 1 percent increase in statistical risk of contracting cancer at sometime later in life.
The authors are on somewhat firmer ground when they talk about the dangers of extended exposure to zero gravity, as there have in fact been harmful effects, including thinning of bones and weakening of muscles, observed. However, it must be noted that literally scores of astronauts and cosmonauts taking six-month tours (an equal duration to that required for flight from Earth to Mars using current propulsion) have survived such exposures. Moreover, a countermeasure -- artificial gravity produced by spinning the spacecraft -- that would eliminate all such effects is readily available.
Ignoring these facts, Wohlforth and Hendrix say that “space propulsion would need a giant technical leap to make a Mars roundtrip in a safe period of 150 days.” They then pile on further impossibilities by saying that the goal should really be not Mars at all, but Saturn’s moon Titan, which is not only ultra cold and ultra dark, but ten times further away than the Red Planet.
Engineering is the art of making the impossible possible. Those who seek to make the possible seem impossible are members of a very different profession. Americans should not allow their horizons to be constrained by such defeatists.
Mars – the new world of our time – is within reach. It holds the key to the truth about the potential prevalence and diversity of life in the universe. It is the bracing challenge that will draw millions of our youth into science and engineering, with vast benefits to our society as a result. But more than that, it is the first step into an open frontier, offering an unlimited future for humanity.
The effort to get there won’t be free of either risk or cost. But from a technical point of view, we are much closer today to being able to send humans to the Red Planet than we were to being able to send men to the Moon in 1961, and we were there eight years later. For us to accept claims that we can no longer do such things is to accept the idea that we have become less than the kind of people we used to be.
And that is the one thing that this country cannot afford."
An alternative scenario is offered by Fred Singer, emeritus Professor at the University of Virginia and director of the Science & Environmental Policy Project. Singer advocates setting up a base on Deimos, one of Mars' two moons, first. He has coined this approach the PH-D project, from the two moons' names, Phobos and Deimos. Phobos, which measures about 27 × 22 × 18 km, is closest to Mars, orbiting only 6,000 kilometers above the planet's surface. Deimos, at about 15 × 12.2 × 11 km, is the smallest of the two, is also far more irregular, and orbits at about 23,460 kilometers.
This is a scenario also championed by others, such as Buzz Aldrin, 2nd man on the Moon, or Lockheed Martin Space Systems:
"... The PH-D project is basically a manned transfer from Earth orbit to Mars orbit, taking about six months; there don’t seem to be any showstoppers at all. A rough calculation has convinced me that ordinary chemical propulsion is quite sufficient -- no need for any exotic schemes that require lengthy development. Any simple fuel, like kerosene, suffices, and any of the available oxidizers can do the job. No special rocket engine is needed; existing ones will do -–as explained below. And propulsion is surprisingly cheap -- only a few percent of the total project cost; more than 95% of the cost is engineering and design -- and the US has many well- qualified engineers.
Electric power -- again no problem. Of course, solar photo-voltaic becomes more difficult at Mars distance, where solar energy is less than half that at Earth orbit. But the Russians have space-tested nuclear reactors, and units are available for purchase. I estimate that 100 kilowatts should do nicely and would even provide an adequate reserve of power.
Other issues, relating to maintenance and life support of astronauts, present no problems either; they have been mostly solved in the International Space Station. As in the ISS, one would recycle liquid waste, but not solid waste. With cheap propulsion and essentially unlimited payload, one simply carries more food and water. The same argument applies to maintaining a healthy breathing atmosphere.
Radiation is usually cited as the major health risk; but propellants turn out to be the most effective shield, especially against heavily ionizing particles of the incident galactic cosmic radiation -- GCR. Once the astronauts set up their base on Deimos, the preferred destination, they can construct also a more permanent shelter against the omni-directional cosmic rays, the unidirectional meteor showers, and the occasional solar eruptions that can lead to penetrating particle radiation. Note that none of that protection is present in the ISS, but Deimos itself provides shielding against unidirectional radiation; it is only necessary to move to the opposite side.
Absence of gravity can lead to long-term health problems. The answer here, as in the ISS, is regular exercise, aided by artificial gravity from a centrifuge; such a scheme should be tested in the ISS.
Scenario of Deimos Base
Assemble propellants in low-earth orbit -- LEO; then send to Deimos as “slow freight” – including a nuclear reactor, spare habitat, spare rocket engine, penetrators and rover vehicles equipped for return of samples; release penetrators that will provide also seismic data, and some rovers while underway to Mars. Send one habitat, two rovers and some of the propellant to Phobos -- for use on the later sortie to Phobos and Mars surface.
Test the habitat-lab while in LEO with 5 astronauts aboard; then send them to Deimos on a “fast express” trajectory. Upon arrival, shield and activate the reactor; surround the habitat-lab with rocket propellants to provide additional shielding; set up a GPS system and weather satellites for Mars.
Start sample-return program, analyzing initial samples -- and call for follow-up samples from different Martian locations or different depths, based on the initial analyses– all the while consulting with experts on Earth.
Sortie to Phobos and Mars Surface
Two astronauts depart for Phobos and meet two rovers, collect samples of regolith and deeper, and send them back to Deimos base, then move on for a powered landing on a preselected Mars site, meet rover vehicle there, collect samples, set up an experimental equipment, and then take off for return to Phobos and thence to Deimos base. Note that take-off from Mars requires only our small rocket -- while a direct return to Earth would have required a special, high-thrust rocket, capable of lifting the large propellant load necessary for transit to Earth.
Deimos Base vs Mars Base
There is no question that a Deimos base is easier to set up, much cheaper, safer, and better in all respects than a base on Mars. Besides, it can be accomplished much sooner, perhaps within 10-15 years.
A Mars base does not confer mobility, does not provide a view of the rovers; from Deimos one can view the surface from pole to pole for up to 40 hours. [Deimos is in a near-synchronous orbit, with an orbital period of 30.3 hours, just a little longer than the spin period, 24.7 hours, of the planet.]
On Mars, because of its gravity field, meteor impacts are more frequent and also more energetic; there is interference from Mars’ atmosphere, from winds, and from dust storms—while on Deimos one gets a ‘free’ vacuum, essential for most lab instruments, such as mass spectrometers, electron microscopes, etc..."
Using the Mars moons as a stepping stone seems indeed to be an idea gaining importance. See also this highly interesting slide provided by Michael Gernhardt, NASA astronaut:
Lecture of all this material does seem to indicate that the radiation protection offered by these moons is a key advantage of this approach.
The mere fact that both approaches, Mars per direct or using Deimos and/or Phobos as stepping stones first, are still heavy contenders, is in itself an impediment to getting to work. So if the new administration is serious about its promise to put people on Mars, it better resolve this question first.
MFBB.
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