Have you ever randomly had a really good idea, only to realize someone else had already thought of it a few years ago? I had that experience recently when I was listening to a StarTalk radio show podcast hosted by Neil deGrasse Tyson in which they were discussing the logistical nightmares of planning a manned trip to Mars. The major tripping points seemed to be the amount of radiation that the astronauts would be subjected to, and also the amount of fuel necessary to complete a round trip. In discussing the latter of these problems, I was surprised to find that the Dutch firm Mars One has already received over 1,000 volunteer applications after announcing its plans for a one-way trip (suicide mission) to Mars in 2023 (1). For the rest of mankind that would rather not be martyred in the name of science, I felt that my idea would be the perfect solution: hitch a ride on an asteroid. Of course, a quick Google search revealed that I was not the first to think of this (2), but I still think it is a neat idea worth exploring. With that being said, now is probably a good time for a disclaimer: I am not an astrophysicist, astrobiologist, or astro anything for that matter. My expertise is in the field of cell biology so it’s probably a good idea to take my opinions of space travel with a grain of salt.
The problem of radiation exposure:
Current radiation shielding used for any type of aircraft needs to be lightweight in order to minimize fuel consumption and to also be conducive to flight. Unfortunately the only type of radiation shielding that would be effective for such an extended trip to Mars would be much too heavy to be used on a space shuttle given current technology. In fact, the lighter aluminum-based shielding that we currently use for space travel can actually result in secondary radiation when it is hit by cosmic rays, and this secondary radiation may be more dangerous than the cosmic rays themselves! Also, by “extended trip”, I do mean quite a long journey, as Dennis Tito’s recently announced plans for a Mars fly-by mission in which they won’t even land on Mars is estimated to take 501 days. When you also factor in landing on Mars, you would need to add at least another three months on top of those 501 days due to the fact that you would have to wait for proper Mars-Earth alignment before embarking on your return trip (3). How could these problems be addressed by riding an asteroid? By landing on an asteroid, the spacecraft could “duck down” into a crater that will shield the astronauts from radiation, and it would also be feasible to develop a tunneling technology in order to seek an even greater degree of radiation shielding. Any crater that is deep enough to provide a good cover of shade would also theoretically provide ample mass shielding from cosmic rays.
The problem of fuel consumption:
The paradox of fuel consumption in space travel is that the heavier you are, the more fuel you need; and the more fuel you are carrying, the heavier you are. Much like Marty McFly in Back to the Future grabbing on to car bumpers to propel his skateboard (AKA “skitching”), landing on an asteroid would allow the spacecraft to utilize the momentum of the already moving object, mitigating the need for fuel-consuming self propulsion. The fuel consumption concerns would then be the amount of energy required to move from planet to asteroid, asteroid to planet, planet to asteroid, asteroid to planet. Additional fuel consumption would be needed to maintain life support, but the total distance of self-propelled travel should be greatly reduced.
Why this may not be such a good idea:
The most glaring problem with what I think I will call “The Asteroid Skitching Strategy” is that we don’t really have any control over where the asteroid is specifically going, which seems to be a problem if you have a specific destination in mind. Sure, we can project where we think the asteroid will be, but a slight change in trajectory could doom all astronauts on board with too little fuel to abort the mission or change course. The reality of waiting for an asteroid that is the right size and is “going our way”, may turn out to be more than a minor detail when dealing with an otherwise highly controlled mission. Add in the fact that you may need to rely on a completely different asteroid for the return trip that also has all of the correct characteristics and trajectory, and the odds may not be in our favor. A hitchhiking strategy of jumping from asteroid to asteroid instead of waiting for the perfect trajectory could help, but adding in more takeoffs and landings will definitely affect the fuel consumption considerations.
It’s also (as far as I know) not all that easy to land safely and reliably on an asteroid. Landing on the moon seemed like a pretty big deal and there are still countries today that can’t do it successfully with today’s technology. I’m guessing that landing on an object that is moving much faster, is much smaller, and is much more morphologically dynamic would up the ante just a bit. All in all to a layperson it seems basically feasible to pool the resources of the asteroid mining groups and Mars exploration groups in order to develop more robust and realistic short term goals, however it seems like it’s going to be a very iterative process and I’m not holding my breath for a successful attempt within the next 20 years. In other words, I’m not volunteering to be on board for the first try.