A New Way to Reach Mars Safely, Anytime and on the Cheap
scientificamerican.com
scientificamerican.com
I wrote my MSc thesis on weak capture trajectories and the concept of the Weak Stability Boundary [2] that was introduced by Ed Belbruno. It's a fantastic aspect of the gravitational 3-body problem and has been probed from a number of different perspectives over the last two decades, including tying in the phenomenon of weak/ballistic capture into our understanding of the structure of invariant manifolds and the periodic orbits about the Lagrange libration points.
Disclaimer: Francesco is my boss but I haven't spoken to him yet about the paper.
TL;DR: Ballistic Capture aka "Low-energy transfer" is being rekindled by NASA, Boeing, Belbruno, Topputo and colleagues. Fly the spacecraft ahead of Mars in formation of the planets orbit relative to the sun allowing gravity to gradually slow the spacecraft down. This saves on fuel/weight for entering orbit at high velocity.
Another thing to notice is these trajectories are no good for manned travel as they can take years or decades extra, they are even slower than the more traditional multi-planet slingshot maneuvers.
The second is harder: We need to go to Mars at least three times and bring back the men and women successfully. Once is not enough. Three proves we've mastered the engineering, financial, physical, and physiological aspects.
[1] http://www.pbs.org/wgbh/nova/space/aldrin-mars-au.html
[2] http://www.guardian.co.uk/science/2010/jun/03/mock-mission-m...
First we'd need to find a way to bring back pretty much anything else successfully, no?
The first is an easy problem to solve, compared to pretty much every other issue. More space (or better space) is a non-linear issue.
Plenty of robots must be sent beforehand to build greenhouses, setup solar panel arrays, dig deep tunnels to provide shielding against cosmic radiation, etc.
Furthermore, if there are indigenous biologic agents there, I don't think we want them coming back. Like the Greek expedition to Asia Minor, Mars is a burn the ships mission.
> The principle behind all of its vehicles is total re-usability; every single system must be able to be serviced and pressed back into operation. This is to cut down on the already astronomical cost of space flight (pun intended), making it more affordable for private companies to conduct missions into the heavens. The company’s main goal is to eliminate the equipment cost for space travel, leaving fuel as the only financial burden.
http://www.extremetech.com/extreme/122923-spacex-ceo-claims-...
The problem with the return trip is Earth reentry. Coming in at interplanetary speeds (falling to the sun from a "height" of Mars' orbit to Earth's), it is impossible for humans to reenter the Earth's atmosphere safely. It's barely possible from the moon.
This means that there has to be about as much deceleration before reentry than there was there was acceleration on the way out. So now you have to carry double the fuel, and the fuel to carry that, etc. This vastly complicates the problem with a manned mission to mars.
The real problem with the return trip is getting off Mars. Specifically, putting enough propellant on the surface to get you back up. Sure, it's easier than Earth, but it's still a planet. If NASA were serious about Mars, they would be sending prototype ISRU plants every cycle, because having rocket fuel waiting for you on the surface is the real enabling technology for Mars exploration. Or Lunar or Venus for that matter.
The speed of light means no real time support from Houston. If ten people go out, then ten people have to get an interplanetary space program established on Mars. It ain't gonna be a matter of pushing the easy button.
One way of handling things if there's a long-term station is to build the ship to Mars in space (or at least refuel at the station). If you send the return fuel ahead (or find a way to make it while at Mars) you aren't required to carry a large amount of fuel.
Colonizers could probably live on packaged food from here 'til Judgment Day (or as long as Earth is willing to send always more supplies), but I would still add the maintenance of man-made ecosystems for food production to the list of big problems that we have not yet solved.
Bubbleheads can do that, current and ex.
>> We need to go to Mars at least three times and bring back the men and women successfully.
I don't know that the delicacy of the orbital entry described is going to be sufficient for long term operations. It sounds like an artistic dance combined with luck. I think the old wing it into space at high velocity then put on the brakes method is more deterministic. Whole transportation systems on Earth function this way.
It would certainly still be cramped by conventional standards, but conceivably much less so than the flight there.
Also excursions, though you need a space suit.
It seems that the bigger advantage of this is adding a few months but doing away with waiting for a launch window. Definitely great for equipment, though it would put two months' worth of extra stress on actual human travelers.
Yes, by the facts and speculation reported in the article kindly submitted here, the headline phrase "on the cheap" is plainly wrong, and "anytime" is an exaggeration, as the overall trip time will tend to be longer for most such missions. The article also notes, "The burn-free, capture altitude is also quite high—some 20,000 kilometers above Mars, far beyond where science satellites set up shop to scrutinize the planet up close. But taking along just a little extra fuel can then gently lower a ballistically captured spacecraft into scientifically valuable, standard orbits of around 100 to 200 kilometers like those achieved with Hohmann transfers—or even onward to the Martian surface for a landing." So one part of the article says that the mission will take less fuel (to leave the vicinity of earth), while another part of the article says that the mission will have to carry along extra fuel (in the Mars exploration modules) to arrive at a location where useful science can be done. The bottom line here is that these missions will still be about as expensive as current missions, and manned flight to Mars and back will be staggeringly expensive.
Less fuel means more payload, which means more science or less cost (because you don't have to build so exotically to save weight.) Either way is good. Only in a radically different launch cost regime will we cease to care about efficiency of transfer.
You aren't actually trying to match it; as I understand this kind of orbit is a slightly slower (so slightly closer, on average) orbit that the vessel achieves somewhat ahead of Mars, so that when Mars passes it, Mars' gravity is enough to capture the vessel. In essence, some of the energy to match the orbit comes from Mars itself (slowing down Mars, but for any realistic spacecraft this is completely negligible because of the enormous mass ratio between the planet and the craft.)
I'd guess the target orbit for a craft performing this maneuver would still have a periapsis in the neighborhood of Earth's orbit, meaning it'd still be very unlike Mars' orbit until the craft was captured by Martian gravity.
(googles a bit)
It looks like these exploit Lagrange points somehow[1]. Precision maneuvers and weird, long routes to the target body. I'm not quite following how this works with only two bodies (Sun and Mars), versus the Sun-Earth-Moon trio. Wikipedia claims the Mars Orbiter Mission used a low-energy transfer at some point, but I can't figure out whether that was for the insertion into Martian orbit or some earlier maneuver it performed.
[1] http://www.gg.caltech.edu/~mwl/publications/papers/lowEnergy...
[edit] Hoffman -> Hohmann, because I'm an idiot.
With nuclear pulse propulsion, we could send a craft to Mars in 2-3 weeks, safely, any time, and on the cheap.
The mass that can be transported is quite enormous, so we could piecemeal launch the components of a huge habitat and vast amounts of supplies into an outer orbit of Earth, robotically load them onto the pulse ship, and then shoot that baby to Mars.
Probably the slowest part of the plan would be launching the stuff into orbit. They scrubbed the idea of launching using nuclear pulse propulsion because of the dangers of radioactive fallout. Too bad, because that would have made things even simpler.