MARS - NOW **** THE THEORY

STILL Under Construction for THEORY (9/3/05 Edit)

The basic calculations for this plan assume minimum energy transfer into a co-planar, "mean Mars" orbit, requiring 0.7 years. This transfer orbit normally requires 2,966 meters per second velocity AFTER LEAVING EARTH'S GRAVITY. However 393 meters per second added deep in Earth's gravity well, just after acceleration to escape velocity, adds all the energy needed for that transfer. I refer to the benefit of adding disproportionate energy by a "delta V" burn when the spacecraft already has high velocity, as "gravity well synergism". It occurs because a rocket "spends" fuel to obtain a fixed velocity change (Delta V), while the vehicle energy increases as V squared. From the standpoint of physics, energy is conserved by "dumping" the exhaust mass deep in a gravity well, rather than waiting to release it far from Earth.

The above calculation astonished me! I couldn’t believe that reaching Mars could be so easy! But it is. The 6020 Kg LEO payload promised for the Falcon 5 can carry 1800 Kg to the Martian surface! Aerobraking is of course a "done deal". It worked over and over again for Apollo, and it has worked for both Mars orbital capture and landing. This epiphany stimulated me to seriously address Mars mission needs. This round trip plan was one result. Another suggested that a one way trip would allow a small individual to start as part of the 670 Kg payload of a Falcon 1, and end up walking on Mars!

Given the elliptical Mars orbit, the actual need for a well timed transfer could be even less. However, there is no point in calculating this. The 1.8 degree Mars orbit inclination is a serious complication. A plane change burn at the start does not alter the celestial altitude at the 180 degree intercept point. The optimum plane change burn will be at the 90 degree point, far from Earth and offering no gravity well synergism. The maximum plane change delta V is less than 900 meters per second, but this is more than twice the optimized transfer delta V. This could burn nearly 30% of a vehicle's mass as storable fuel (with a similar problem for Earth return). (Note that this adjustment would be a very good use for solar powered ion propulsion or light sails). Much smaller acceleration is possible for some trip dates, but the minimum inclination adjustment does not occur for the closest approaches. Fast transfers (with one Earth year round trip time), when aided by the gravity well synergism, are not out of the question with chemical fuels, and could eliminate this large midcourse acceleration.

I am very interested in using a elliptical Mars orbit to preserve much of the energy needed for the Earth return trip. Anything over 608 meters per second of aerobraking deceleration close to Mars will capture a spacecraft into orbit. Restoring that small velocity later can set up the return transfer. However, the deep hyperbolic Mars encounter will nearly reverse the transfer velocity component, as desired to “slingshot” to outer planets rather than return to Earth. With a 1.2 Earth year delay, however, the geometry is closer to optimum, and a reduction in Earth return boost can be achieved. This concept is being developed.

A factor far more important for Lunar, Mars and Asteroid colonies is the perfection of appropriate hydroponics or aquiculture. Reported solar efficiency for Chlorella growth is so high that a 2 by 2 foot “Interplanetary Farm” could produce all the food needed by a standard astronaut and absorb all his wastes in the process! This assumes use in near Earth space, with continuous sunlight. The area doubles in Mars orbit, and more than triples for use on a planetary surface. However, these areas are still “ridiculously small”. But an effort to develop these processes will almost certainly have a large impact on space development economics!

The propulsion specifications are taken directly from the SpaceX Web site, adding my own achieved value (dry stage weight = 5% of fuel weight) for small liquid fuel stages. The published number for their pressure fed, upper stage is 327 seconds vacuum ISP. A third stage was assumed (with the same propellants) for acceleration to escape velocity with lower deadweight. Storable fuels have lower performance, but the assumed value of 300 seconds ISP appears to be achievable. The initial launch could actually be done with a number of different vehicles, Russian, American, French, etc. These options would raise the cost, but would not rule out this mission as a privately funded venture. A larger problem is the lack of any commitment to “man rate” any existing launch vehicle other than the Russian and Chinese designs.

One very significant reality is that lightweight Mars missions are very much “up for grabs” internationally. It is quite possible that a foreign national, and foreign financing, will be used for the first trip.

Note that no magic or exotic technology is assumed. While I have noted some more advanced technologies above, the proposed mission does not depend on these. Enough of the proposed life support system components are now in operation that the basic conclusions are not in doubt. The proposed mission does of course depend heavily on the same minimalist thinking which goes into a long backpacking trip, or mountaineering expedition. If you want to get up Mount Everest, you don’t take your RV. Jacques Cousteau invented the “Aqualung” and proved that you didn’t need Jules Verne’s “Nautilus” submarine to explore the oceans. In point of fact,living in space in not much different from living underwater!

to be continued