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In January, 2004, President Bush announced a new and grandiose goal for the US space program: NASA is to prepare to place a manned vehicle on Mars within the next 20-25 years. The cost of this program, with its open-ended and incredibly expensive followup to build and maintain a base on Mars (with a regular schedule of supplies sent there from Earth) will dwarf the Apollo effort that landed men on the moon in 1969, as it will dwarf the Space Shuttle program. The President's motivation for this budget-buster, in the middle of record-setting federal budget deficits, is unclear. One can hardly avoid thinking back on JFK's 1961 announcement that we would land a man on the moon "in this decade". And couldn't that just be Mr.Bush's point? JFK was hailed for his boldness. Why not GWB? What a way to be remembered!Abstract:
Yes, what a way to be remembered: The President plans to mortgage the nation to learn whether there has been life on the planet Mars, though no one can guarantee that the effort can answer that question. Now as a biologist I must say I have an above-average interest in such questions, but ... HAVE WE LOST OUR MINDS? Is the Congress seriously considering funding this monstrous boondoggle? With a hundred thousand Americans starving and on the street, with Social Security going bust, with an endless array of domestic problems, from education to crime to health care, that cry out for attention and funding that we can't afford, are we really going to spend hundreds of billions – perhaps a thousand billions – of dollars to find out if there has been life on Mars? Get a grip, Mr.President!
Pardon my energetic expression, but this is an issue that we should be energized about. It appears that one reason for Mr.Bush's plan is a fear that a non-American manned mission may get to Mars first. And that, to his thinking, would be a disaster. There are plans in varying stages of realization in China, in the European Union, and perhaps elsewhere, to send a manned mission to Mars. If they succeed, and we have not, that would apparently be – in the President's view – another "day of infamy" in our history. Not much needs to be said about that viewpoint: It is paranoid, chauvinistic, and egomaniacal. If we have arrived at the point as a "superpower" that we cannot tolerate success by other nations, it's truly time for a reexamination. If we are truly interested in the scientific questions that might be answered by a manned mission to Mars, we should be overjoyed that other countries are finally picking up the ball – and not least, picking up the bill – to help us move scientific inquiry forward. It's high time that tax payers in other countries watch their tax payments literally going up in smoke. Our view of this particular super-costly venture should be to welcome to the dance anyone who's willing to pay the entry fee, and be thankful for the chance to rest our dancing shoes while someone else cuts in for a while.
The likelihood is, however, that if the US pulls back from this unnecessary project, the other pretenders in the game will also see the folly of attempting such an undertaking. Not only is the project incredibly costly, it is technically extremely difficult, even for the US, not to mention for such entities as the EU or China, which have little or no experience even with Earth-orbital manned flight. And deep-space flight lasting a minimum of a year and a half is a whole other ballgame, with extreme risks to the crew. We've been witness to the many mishaps that have happened to the unmanned space probes sent out by NASA and ESA (the European Space Agency), several of which would have resulted in loss of a crew if the mission were manned. If a manned mission to Mars will ever be justified, it should only come when we're ready, i.e., when we are (1) caught up with our higher priority earthly expenditures, and (2) certainly only after NASA has demonstrated that its missions can be counted on to be successful. Neither of these conditions obtains today.
Mr.Bush's pie-in-the-sky Mars Madness deserves an immediate burial, before NASA spends another dollar on it. The MM would set back and postpone hundreds of other actually useful programs; it would worsen our budgetary deficit, add to our public debt, and destabilize our currency; it would achieve nothing necessary or meaningful for our country; and its chance of catastrophic and fatal failure is high. The Congress is skeptical at this time; they need to be shown that there are limits to the irresponsible adventures the American people will put up with. This cattle drive is headed for a cliff, whipped along by a nearsighted cowboy. So let's show him we're not his little dogies.
(The more detailed Appendix below suggests some of the difficulties and hazards of a manned mission to Mars. It's worth reading.)
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Appendix: Some notes on a manned Mars mission.
As the Mars mission is currently envisioned, over the next decade a series of conventionally powered unmanned missions to Mars would provide detailed maps, examine the soils for signs of water, minerals and organic chemicals, return soil samples to Earth, and test for the possibility of producing methane from the martian atmosphere for use as rocket fuel. These probes would also serve to test small-scale nuclear drive power on the surface of Mars, and provide the engineering experience to proceed with manned flight. In or about the year 2012, a nuclear powered spacecraft would take a probe ("JIMO") to Jupiter's moons, providing the first experience with a nuclear space engine, which would be needed for a manned mission.
At the same time, the Mars manned spacecraft would be designed, built, and tested. The craft would be modular, and would be assembled in low Earth orbit, the various parts brought on station by the aging Atlas 5 or the brand new Delta 4 rockets, or perhaps even by the Apollo program's retired giant, Saturn V. The craft would fire up and launch from orbit, and would likely be initially propelled by conventional rocket fuels, then by a nuclear reactor (firing hydrogen as drive mass) after being well clear of the Earth.
By 2010 operational tests might begin of the new spacecraft; first as an unmanned version, later – perhaps by 2015 – as a series of flights to the Moon, building bases there to serve as a training ground for the Mars mission. By 2020 the Mars ship might be sent on longer missions in the inner solar system, lasting perhaps a couple of months. Then in 2025-2030 (all these dates have several years of flexibility) the first space ship to Mars would be on its way. The journey to Mars would last some 8 months, and after a one month stay the trip back to Earth could take some 9 months.
And that's all there is to it.
Are there drawbacks (other than the astronomical cost) of this plan? There are plenty, and they revolve around the hazards to the crew and the mission – the odds that the whole expensive undertaking will end as the most spectacular technical fiasco in the history of modern civilization.
Consider that NASA has lost two space shuttles with their full crews on near-Earth missions lasting a few days – missions that, while complex enough, are like child's play compared with a mission to Mars. Recall also the many times that orbital flights, "skylab" stations, and moon flights have developed problems that required emergency power-downs or early termination, or even a rescue flight or supply flight to bring parts and equipment up in orbit. (The International Space Station is in need of more parts as I write, and they'll be sent up.) Then consider that once the Mars mission launch rocket is fired, there's no abort, there's no turning back, there's no one to bring spare parts; the crew is committed to a self-supported flight of a year and a half where everything must go right. Even if we were not aware of the too-frequent mission failures by NASA (and by every other active space agency), we should be skeptical that a year-and-a-half long mission requiring near-flawless mechanical reliability can be carried out with a reasonable assurance of success and safety. Given NASA's blemished record, the chance of success of the planned mission is based on hope and prayer, not on facts. And that's just the main flight. Consider that all the preparatory flights must be successful for this program to survive. If a ship is lost on a training mission to the Moon, for example, the Mars mission would be politically dead. In fact, now that the planned unmanned probes to Mars are seen as a part of the manned mission program, a failure of any of them would suggest that NASA is not able to guarantee reasonable safety for the mission, and the program would likely be scrapped. We'll save ourselves a lot of expense by scrapping it now.
But mechanical reliability is perhaps not the most difficult problem or the most likely hazard on such a mission. The crew of about seven will live in intimate contact in tight quarters, with little to do, for nearly three-quarters of a year while the ship moves imperceptibly away from the Earth through monotonously unchanging space. The group dynamics underways and each crewman's personal psychological processing of his situation will be impossible to predict. True, the Apollo astronauts handled the similar tension of unknown physical danger well, but they were three, not seven, and their flights lasted a week or so, not eighteen months or more. The contrary was the case on the Russian Solyut 7 station, where after a few months cosmonauts Beresovoy and Lebedev sat facing in opposite directions, neither speaking nor cooperating with one another. Much can go wrong when you add tension, fear, boredom, discomfort, atrophy, loneliness, monotony, marginal hygiene, isolation, and throw in personal peccadillos and a few disagreements. And stir. A crewman losing his mental balance during such a long flight is not unlikely, and it could bring the entire mission down.
Yet the greatest hazards may be external to the ship. Space is full of fast fliers. Some are macroscopic meteoroids. They may be as small as a grain of sand, but a grain of sand going 30,000 MPH can pierce and disable vital functions on a space ship, or cause catastrophic leaks. We have had many cases of unmanned space probes suddenly ceasing to respond to signals from Earth. We usually don't know what has gone wrong in such cases, for the simple reason that the unit is not responding, but it is not unlikely that some such failures may have been caused by a meteoroid hit. We can do a simple calculation related to the likelihood of a hit: If a small space probe presents an effective surface area of, say, ten square meters, and if the probe's trip to Mars takes, say, 1000 days, then the chance of it being hit by space debris is the same as a surface of 10,000 square meters (roughly two football fields) exposed in space for one day. Now, the Mars manned spacecraft would be the largest space ship ever sent out from Earth, and would have an effective surface area of probably 200 times that of the small probe. It might, however, get to Mars in half the time, and would therefore have at least 100 times the chance of being hit by space debris. Let's visualize exposing 200 football fields in space for a day, and betting the lives of seven astronauts that there will be no hit by a meteoroid in that area over that time. That's what NASA is preparing to do.
Since the likelihood of a meteoroid hit on the space craft is critical to the Mars mission, one might expect that NASA has studied the density of debris in outer space very deeply. Well, there have been studies (next paragraph), and NASA acknowledges it as a serious issue, but they don't like to dwell on it. In the end, NASA says only they'll do their best to provide a safe environment for the crew; they prefer to avoid talking about the likelihood of serious damage. But let's look at that likelihood:
One NASA-sponsored study indicated that the interplanetary density (flux, actually) of particles greater than 10 mg in mass – large enough to cause direct damage – is expected to average around 1 per 1012 square meters per second. If the Mars mission exposes a surface of about 200 m2 for a period of about 50 million (5x107) seconds (about 550 days), – which comes to an exposure of 1x1010 m2 sec – these data suggest a likelihood of approximately one in a hundred that the ship would be struck by one meteoroid, 10 mg or larger in size, during its round trip. It is perhaps this estimate that gives NASA confidence. However, the study's authors – Grun, et.al., their summary graph is reproduced below – report that the uncertainty of the meteoroid particle size estimate is greater than an order of magnitude, which could shift the flux estimate to as high as 1 per 1010 square meters per second. If this is a correct estimate of the flux, the odds of such a hit becomes a 50-50 chance during each Mars mission. One would have to be irresponsibly optimistic to accept such odds. And in addition to the few larger meteoroids, there is a dense flux of finer space dust which constantly impacts the spacecraft and abrades its surfaces. The ship must be (and would be) designed to withstand this constant abrasion; the problem is that NASA would again be guessing – they don't know the actual density of such dust, and are hoping to over-engineer sufficiently to give a safety factor. If they don't, the ship could fall apart in the last months of the return to Earth.
A final very serious problem on a flight to Mars would be the physical health of the crew. Their exposure to ionizing radiation during the voyage, even with the spacecraft's built-in radiation protection, would be expected to be in the range of 500-1000 mSv (milli-Sieverts). The normal annual exposure of people on Earth is in the range of 1-3 mSv, depending on latitude and altitude (somewhat higher for frequent airline passengers or crew). The astronauts' trip to Mars would be expected to increase their lifetime risk of cancer by as much as 20 percent from this increased exposure to radiation. The constant radiation can also lead to vision problems, as in the case of several Apollo astronauts after only a week or two in space. We can't know ahead of time which astronauts will be affected, or how bad it will get after more than a year of unremitting radiation. A particular danger comes from solar flares, which emit strong waves of particle radiation that can kill the astronauts in short order if they're not adequately protected. In 1972 this hazard was not well understood, and no provision against solar flares had been made in the Apollo program. The astronauts of Apollo 16 were fortunate when they returned to Earth a couple of months before a powerful solar storm occurred that could have killed them. Now NASA plans to provide a protected space on the ship, where the crew can retire during solar flares, which can last several days. For the eventuality of loss of radio contact with Earth, the ship would need onboard sensors to detect solar flare activity. But in any case, a solar flare-up would likely lead to a significant and hazardous increase in the crew's absorbed radiation.
Additional medical hazards have become well known as a result of our space station experiences, where some crew have spent time equivalent to the Mars mission's travel time. The problems that have afflicted these astronauts have varied, but some are predictable, such as muscle atrophy, body fluid shifts, sleep difficulties, and bone brittleness. Some astronauts have been carried off on a stretcher after their flights, others have spent much of their flight being sick. All have been exhausted. NASA is planning on the Mars astronauts jumping directly into an exhausting 30-day exploration of Mars soon after landing (this is after all the point), then starting off on another nine-month return flight to Earth. How the various crew members will respond to this regimen is very uncertain, but it can be said to amount to a brutal human experiment on NASA's part – or perhaps on Mr.Bush's part.
As I've suggested above, human exploration of Mars would be a fascinating adventure, and the search for past life there might succeed. I don't much doubt that we will some day make the journey. It may be a cooperative effort by many nations, after we've reached some social stability on Earth, after some decades of routine shorter space flights, and after we've learned to understand fully the problems and hazards of the flight and how to overcome them. That day may come; but that day is not now.
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Graph from Grun et.al:
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