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Mars Space Transportation

New Proposed Path for Manned Trips to Mars: Let Mars' Gravity Capture Spacecraft 105

Posted by timothy from the very-sun-tzu dept.
As illustrated in this article at io9.com, the conventional method considered for launching a manned craft to Mars might make less sense, even if it takes less time, than a more complicated but more efficient means akin to a method that's been already been successfully used to minimize the amount of fuel used in exploring both within and beyond the solar system. Known as the "Hohmann Transfer" method, this type of maneuver is known to be effective. But it is also quite expensive and relies very heavily on timing. Hence why a new idea is being proposed which would involve sending the spacecraft out ahead of Mars' orbital path and then waiting for Mars to come on by and scoop it up. This is what is known as "Ballistic Capture", a new technique proposed by Professor Francesco Topputo of the Polytechnic Institute of Milan and Edward Belbruno, a visiting associated researcher at Princeton University and former member of NASA's Jet Propulsion Laboratory. In their research paper, which was published in arXiv Astrophysics in late October, they outlined the benefits of this method versus traditional ones. In addition to cutting fuel costs, ballistic capture would also provide some flexibility when it comes to launch windows.
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New Proposed Path for Manned Trips to Mars: Let Mars' Gravity Capture Spacecraft More

New Proposed Path for Manned Trips to Mars: Let Mars' Gravity Capture Spacecraft

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  • I think its gonna be a long long time (Score:3, Funny)

    by rossdee ( 243626 ) on Sunday December 28, 2014 @04:06PM (#48685609)

    Mars aint the kind of place to raise your kids

    • Re:I think its gonna be a long long time (Score:5, Funny)

      by MightyMartian ( 840721 ) on Sunday December 28, 2014 @04:11PM (#48685619) Journal

      It's got to be better than New Jersey.

      • The first thing anybody who might even have the slightest possibly of going to Mars will have to do is sign a bundle of papers saying that everything they think, say or do is the property of a private corporation. Probably will also require they be spayed/neutered as well, because they can't legally require the person to sign over their children to the corporation, and the corporation will require all occupants of the planet to be completely indentured to the corporation.

    • Re:I think its gonna be a long long time (Score:5, Interesting)

      by rudy_wayne ( 414635 ) on Sunday December 28, 2014 @04:14PM (#48685639)

      It's an interesting idea, but getting *TO* Mars isn't the real problem. The biggest problem, that nobody is talking about (because they have no idea how to solve it), is *LANDING* on Mars.

      http://www.universetoday.com/7... [universetoday.com]

      The real problem is the combination of Mars’ atmosphere and the size of spacecraft needed for human missions. While the Apollo lunar lander weighed approximately 10 metric tons, a human mission to Mars will require three to six times that mass, given the restraints of staying on the planet for a year. Landing a payload that heavy on Mars is currently impossible, using our existing capabilities. "It’s this ugly, grey zone. There’s too much atmosphere on Mars to land heavy vehicles like we do on the moon, using propulsive technology, and there’s too little atmosphere to land like we do on Earth. Until we come up with a whole new system, landing humans on Mars will be an ugly and scary proposition."

      • Why should the Mars atmosphere be a problem for rocket engines like used when landing on the moon?

        • Re: (Score:2)

          by itzly ( 3699663 )
          Because the supersonic airflow into the nozzle makes it hard to control.
          • Uhhh, I think you could decelerate to subsonic velocities at the proper moment and then continue falling. If it works for the Falcon 9 first stage, under much worse conditions then in the Martian landing scenario (spacecraft mass and gravity), it should work on Mars, too. But I guess it would cost you even more fuel than purely propulsive landing on a Mars-sized body without atmosphere, which is bad enough already.

            • Re:I think its gonna be a long long time (Score:5, Informative)

              by Rei ( 128717 ) on Sunday December 28, 2014 @05:03PM (#48685851) Homepage

              Except that your terminal velocity on Mars is orders of magnitude higher than on Earth. Decelerate to subsonic then fall and you'll be back supersonic in no time.

              I'm sure this is possible to do, but it absolutely requires more research and testing.

              • Well, at the point when atmosphere starts becoming a nuisance and you're forced to do a braking burn, isn't it safe to deploy some reasonably sized parachute afterwards? It's not like you're going to hit the ground with it, you just need to keep your velocity reasonably in check.

                • Re:I think its gonna be a long long time (Score:4, Interesting)

                  by Rei ( 128717 ) on Sunday December 28, 2014 @06:18PM (#48686141) Homepage

                  Yeah, but experience with gigantic hypersonic parachutes is also rather limited.

                  Again, it's really doubtful that there's any show stoppers here. But there's a lot that needs to be done before you can bet a whole mission on these sort of things. There's many thousands of little details that could kill the crew if they go wrong, so the odds of any one doing so must be kept to the tiniest fraction of a percent.

                  • it's really doubtful that there's any show stoppers here.

                    God I hate that phrase. So many failed NASA programs started because someone said "There's no show stoppers". I needs to be purged from NASA's vocabulary.

                  • Yeah, but experience with gigantic hypersonic parachutes is also rather limited.

                    Yes, but there is no reason it must stay that way. We have lots of upper atmosphere with even higher gravity with which to experiment.

            • Re:I think its gonna be a long long time (Score:4, Interesting)

              by FatLittleMonkey ( 1341387 ) on Sunday December 28, 2014 @07:57PM (#48686541)

              I think you could decelerate to subsonic velocities at the proper moment

              The "proper moment" is before you enter the atmosphere. So no. As soon as you enter the atmosphere, you can't do a retro-burn until you are subsonic, and you can't slow to subsonic without multiple hypersonic and supersonic parachutes. (Terminal velocity for a capsule on Mars is supersonic. You would hit the ground before you slowed enough to be able to fire retro-rockets.)

              The only alternative is to have enough fuel in Mars orbit to do a retro-burn that virtually zeros the orbital velocity before you enter the atmosphere. And, by definition, that takes as much fuel as it does to launch from the surface into orbit.

              Have a look at the entry sequence for MSL-Curiosity, hypersonic heat shield, supersonic drag-chutes, huge subsonic parachutes, and retrorockets, because the parachutes aren't enough to let you land on the surface. And every stage pushed the state of the art to the limits of current technology. All that just to land 900kg.

              Now imagine what you'd have to add to land a multi-ton human-scale capsule...

              Oh, did I say capsule? No. You have to get back home, so you need to land an entire launch vehicle on the surface of Mars. Plus all the infrastructure necessary to refuel and launch that vehicle.

              under much worse conditions then in the Martian landing scenario

              Earth reentry is much easier than Mars. A nice fat atmosphere to bleed off all your velocity, down to subsonic, before you even worry about parachutes or retro-rockets. Mars' atmosphere is just awful. Too thick to be ignored, too thin to be useful. Exactly, precisely wrong.

              • Re:I think its gonna be a long long time (Score:4, Interesting)

                by Cyberax ( 705495 ) on Sunday December 28, 2014 @08:23PM (#48686651)
                The best idea I've heard is to make use of aerodynamic lift for that, so instead of falling down on a purely ballistic trajectory you make large enough surfaces to actually _fly_.

                You won't be able land like airplanes (or Space Shuttles) do on Earth, but you'll be able to use the lift to cause a stall. If you are careful then you can make your vertical speed to be zero at that moment and your horizontal speed will just be subsonic (I remember reading calculations proving that) for a reasonably shaped airfoil. Then you can use retro rockets to bleed away the remaining speed.

                It's complicated, but we have some experience with Space Shuttles that we might be able to reuse.

                • That doesn't sound like a half-bad idea. :)

                  I want to see this simulated. Kerbal Space Program probably isn't accurate enough to real-world to pull it off natively, but maybe it could be modded to something fairly close. Or do something with Orbiter, or mod X-Plane, or build something from scratch. I want to see it done. :P

                  • You can try this in KSP with the Ferram Aerospace mod installed (it adds a much more realistic aerodynamic model). I've just given up on it after three attempts, but maybe it's doable... ... Actually, just have Scott Manley pilot the landing!

                • The best idea I've heard is to make use of aerodynamic lift for that, so instead of falling down on a purely ballistic trajectory you make large enough surfaces to actually _fly_.

                  I think the big issues is that the atmosphere of Mars isn't really enough to use like that. Keep in mind that even at ground level, the average atmospheric pressure of Mars would be considered a medium vacuum in a lab here on earth. the upper atmosphere would be even less.

              • Except that SpaceX has performed multiple supersonic retro burns, so your chain of reasoning breaks at the first step. Supersonic retro burns have been avoided previously due to uncertainty as to whether it'd work, not because of certainty that it wouldn't. They have now been flight proven.

              • The only alternative is to have enough fuel in Mars orbit to do a retro-burn that virtually zeros the orbital velocity before you enter the atmosphere. And, by definition, that takes as much fuel as it does to launch from the surface into orbit.

                No. There is no "definition" here, unless you ASSUME you are beginning from an orbit in the first place. But why should that be necessary?

                Tricky, I admit, to do it differently, but that doesn't violate any laws of physics.

                Plus all the infrastructure necessary to refuel and launch that vehicle.

                You are fixated on Earth gravity. It is vasly easier from Mars, and again there is no law that requires "refueling". Lower gravity gives enormous advantages. Look at the size of the engine of the old lunar lander vs. the size of the Saturn V, for example.

                Granted, doing it different w

                • Jane, before you try to lecture people about orbital mechanics, you should first make sure you understand more fundamental concepts like "conservation of energy".

                  But net radiative power out of a boundary around the source = "radiative power out" minus "radiative power in", so the equation Jane just described also says:

                  NO!!!!! As I have explained to you innumerable times now, you can also consider your heat source, by itself, that "sphere". The only NET radiative power out comes from the electrical power in.

                  • Jane, before you try to lecture people about orbital mechanics

                    First, you MISREPRESENTED my words again. While I admit that I did write this post very coherently -- mea culpa -- it was NOT about "orbital mechanics". It was about non-orbital mechanics.

                    Yet again, you fail to grasp my meaning. Although in this particular instance, I can't honestly say I blame you much. I was not very clear about what I meant.

                    As for the rest: you lost that argument a long time ago. I am not going to re-argue it with you. I will just repeat what I've told you already, innumerable time

              • The "proper moment" is before you enter the atmosphere. So no. As soon as you enter the atmosphere, you can't do a retro-burn until you are subsonic, and you can't slow to subsonic without multiple hypersonic and supersonic parachutes. (Terminal velocity for a capsule on Mars is supersonic. You would hit the ground before you slowed enough to be able to fire retro-rockets.)

                "You can't"? Except that you've already been proven wrong before you even wrote this. Already this year, such a supersonic (if not borderline hypersonic) retro burn has been performed on Earth, under atmospheric conditions similar to what you'd expect on Mars from 10 to 50 km, with the vehicle eventually surviving in a flight-worthy shape until it touched the ground. So now you claim that the laws of physics work differrently on Mars?

                Have a look at the entry sequence for MSL-Curiosity, hypersonic heat shield, supersonic drag-chutes, huge subsonic parachutes, and retrorockets, because the parachutes aren't enough to let you land on the surface. And every stage pushed the state of the art to the limits of current technology. All that just to land 900kg.

                Yes, to land 900 kg, with initial TMI payload mass of almost 4000 kg and a

            • This is precisely what SpaceX is working on doing with the Dragon series spacecraft [youtube.com], a combination of drag and propulsive landing, no parachutes, depending on the nature of the atmosphere and local gravity

              If the body has no atmosphere (i.e. the moon), it would do a purely propulsive retro-fire and landing.

              On a body with a thick atmosphere (i. e. Earth), drag on the heat shield would do most of the deceleration, with a final propulsive touchdown.

              Mars is a middle case, there is some atmosphere but not nearly

          • Re:I think its gonna be a long long time (Score:4, Interesting)

            by confused one ( 671304 ) on Sunday December 28, 2014 @05:32PM (#48685993)
            This has been standard NASA thinking for decades, that it was too hard to start an engine in the supersonic regime, hard to control flight, and therefor too risky to incorporate into any mission. However, SpaceX has shown that you can relight an engine pointed into a supersonic flow, and maintain control of the vehicle with the engine pointed into the supersonic flow. It's not without flaws, but it works. There are groups inside NASA that are beginning to rethink the old arguments and investigate this for use in future applications.

      • Exactly. The concept of the proposed article has been discussed to death for decades. It is often used as the rocket can be be launched and head towards mars, they can land, do SCIENCE!!!, and return all in the same (I think) 6 month window. Where the traditional launch and orbital transfer setup requires a multi year mission.

        I won't bother RFTA this is slashdot after all

        • Re: (Score:3)

          by Rei ( 128717 )

          How exactly would that happen? Isn't ballistic capture's main drawback that it's slower than a Hohmann transfer?

          Isn't leaving crews drifting in space longer increasing one of the main challenges of a mars mission - crew survival in transit?

      • I'm still sort of confused by that claim. I've performed some rudimentary energy calculations some time ago and I simply haven't found a way to make a purely propulsive landing NOT significantly heavier than what you need with using the atmosphere. Of course it sounds like an engineering challenge, but also like a significant payload win. We wouldn't have been able to send the MSL to Mars on anything smaller than a Delta IV Heavy if it weren't for the Martian atmosphere. To claim that we'd be better off wit
      • Oh, BTW...quoting from the article:

        "...and there's too little atmosphere to land like we do on Earth."

        I wonder if those people even considered the Red Dragon approach, i.e. whether "land like we do on Earth" even includes "like we'll do in fairly close future". (Of course, if they talk about the Apollo capsule approach, THAT is not going to work.)

      • Re:I think its gonna be a long long time (Score:5, Interesting)

        by Dan East ( 318230 ) on Sunday December 28, 2014 @04:41PM (#48685763) Journal

        That article is from 2007. Since then a Sky Crane was used to land the 1 ton Curiosity rover on Mars. I think it's pretty clear that we simply may not land an entire 100 ton payload as a single vessel, but would instead land the various supplies, habitats, and people as separate payloads. Perhaps they all come on a single ship (unlikely), but there's no reason with our current technology that we couldn't land the pieces separately. Worst case would be the humans don't land close enough to the supplies to be able to survive long-term, in which case Plan B is to explore similar to how the Apollo Lunar program did, and head back after several days. Then a later mission would bring another set of people to use the supplies already delivered.

        • That article is from 2007. Since then a Sky Crane was used to land the 1 ton Curiosity rover on Mars.

          Which means we've upped the current limit to around 6% of the fifteen ton weight of the Apollo LM. Which in turn means we're still far, far short of the weight of any plausible manned Mars landing vehicle.

          Worst case would be the humans don't land close enough to the supplies to be able to survive long-term, in which case Plan B is to explore similar to how the Apollo Lunar program did, and head back

          • Do you know why it was only one ton? Because Atlas V isn't Saturn V. It's as simple as that.

            • Which is completely fucking irrelevant to the question of soft landing a heavy object on Mars.

              • I think you missed my point. MSL landed a 0.9 ton object with a 3.8 ton TMI injection payload. That's 25% of delivered cargo as a fraction of initial payload. Perhaps it could be better still but it's already very good, definitely better than what you'd have with fully propulsive landing - and Atlas V couldn't deliver anything larger, which is why it's "only" 0.9 tons, the payload had to be developed so that it would be "launchable" in the first place! Apollo effectively (using a similar metrics) delivered

      • Re:I think its gonna be a long long time (Score:5, Interesting)

        by Nidi62 ( 1525137 ) on Sunday December 28, 2014 @04:42PM (#48685771)
        Why send/land everything at once anyway? Send living/experimentation modules and any needed non-perishable supplies or equipment such as vehicles on previous missions. Then send in a manned mission with perishable supplies/experiment subjects (seeds, plants, animals, whatever) afterwards. This allows for smaller payloads that can land easier, and has the added benefit of being easier to launch from Earth. It also gives you the chance to resend any critical supplies should one of the landings go wrong or land really off course.

        • Re:I think its gonna be a long long time (Score:5, Interesting)

          by K. S. Kyosuke ( 729550 ) on Sunday December 28, 2014 @04:53PM (#48685809)
          There's perhaps an even more compelling argument why the atmosphere is good for us if we intend to land on Mars AND launch again: ISRU and the Sabatier reaction could be a huge win. If you plan to spend a few months on the surface, you can generate a ton of methalox fuel using the local atmosphere and only half a ton of water. Even if you needed to bring the water with you (which would be the safe option, I guess), it would effectively double your engine's Isp! You could even produce fuel for the trans-Earth injection this way, further saving the total Martian payload you'd need to launch. Without the atmosphere, none of this would be possible.

          • Minor quibble - instead of water, you send hydrogen, only takes 1/8 of a tonne.

            • It may take less mass in hydrogen, but you also need insulation and cooling systems to keep it liquid, and tanks large enough to contain enough liquid hydrogen. The big winner is to use water, and to obtain that water from local sources on Mars.

            • hydrogen has nothing to react with right? still need the oxygen component.

          • There's perhaps an even more compelling argument why the atmosphere is good for us if we intend to land on Mars AND launch again: ISRU and the Sabatier reaction could be a huge win. If you plan to spend a few months on the surface, you can generate a ton of methalox fuel using the local atmosphere and only half a ton of water.

            If the process works that is... that is, the machinery to manufacture the fuel has never been tested beyond the crudest laboratory bench level. There's a whole host of known unknow

            • This is the same process that's currently a part of the oxygen generation loop on the International Space Station. So, technically, one such unit has already been trusted with human lives.

              • In other words, a unit that's completely unlike the one that will be required on Mars... It doesn't have to deal with abrasive dust... it doesn't have to compress and liquify the output gasses...

                etc... etc...

                • You said "If the process works that is." You said "we're only doing this in labs". And it turns out that the process works, and it works on the ISS. Of course the rest will have to be developed, but if I were you, I wouldn't worry about that and I'd leave it to all those smart people who get paid for thinking about these things. ;-) The cryo technology, for example, is something we'll have to develop whether we want to synthesize methane or not, so for this purpose, it's a complete non-issue. It will have t
      • The biggest problem is getting to Mars without the crew dying from cosmic radiation. Or, rather, finding a way to lift and transport a radiation shield. Oh, and landing the radiation shield on Mars too, assuming you want your adventurers to be able to function properly for more than a few months.

  • Wrong optimization (Score:5, Insightful)

    by Tough Love ( 215404 ) on Sunday December 28, 2014 @04:14PM (#48685635)

    For a manned mission it is necessary to minimize time, not fuel.

    • Re: (Score:3, Insightful)

      by Anonymous Coward

      Send the supplies ahead the slow way, just like cargo/freight ships.
      Then send people the fast way, like on airliners.

      • Re:Wrong optimization (Score:5, Insightful)

        by confused one ( 671304 ) on Sunday December 28, 2014 @05:38PM (#48686013)

        Send the supplies ahead the slow way, just like cargo/freight ships. Then send people the fast way, like on airliners.

        This. the described method could be used to litter Mars' orbit with supplies, which would be scooped up by the planet periodically.

        • Re: (Score:3)

          by dryeo ( 100693 )

          Wouldn't that result in the supplies spread out over the Martian surface? Mars is big and the supplies need to be deposited close to where the explorers are going to land.

          • You realize you could control flight leading up to re-entry and upon re-entry, right?

            • Re: (Score:2)

              by dryeo ( 100693 )

              How much when you're littering the orbit in front of Mars with landers? Every Martian day Mars will travel over 1/2 a degree of its orbit, close to a couple of million miles. If you're going to do that much maneuvering, perhaps over twice the distance between Earth and the Moon, why not just directly land.

              • There's no need to do that much maneuvering. I'm not talking about wholesale landing on the X (marks the spot). You only have to do minor course corrections to be sure you land in roughly the right region on the surface. Mars missions will need some kind of transportation (or what's the point). You only need to put the drop within a day or two transport distance.

    • It is basically impossible to make a return trip to Mars because of the fuel requirements, which is why there has not been any manned missions, and will likely not be any in the near future. It takes a lot of fuel to deliver a very small amount of fuel to Mars. There'd have to be a long series of fuel delivery flights before a manned mission. For those, fuel efficiency is of course priority one.

  • Misleading quote of TFA (Score:4, Informative)

    by CrimsonAvenger ( 580665 ) on Sunday December 28, 2014 @04:18PM (#48685663)

    So, we start with the quote about a Hohmann Transfer, in such a way as to suggest something completely different.

    I'm sure there was a good reason for that, though TFA itself manages to mangle a bit of orbital physics all on its own, in addition to whoever submitted/edited the /. suumary....

    • For one, a Hohmann Transfer is actually the least energy direct trajectory between two orbits. It was used for all interplanetary missions before Mariner 10, Pioneer 11, and the two Voyager spacecraft, when people got the idea and computing power made possible the calculation of gravity assist orbits [wikipedia.org] which could get you there for even less energy. This has culminated in the discovery of the Interplanetary Transport network [wikipedia.org].

      If you're willing to use more energy than a Hohmann Transfer (accelerating away

  • Expensive? (Score:1)

    by Anonymous Coward

    Which is it? Efficient or expensive?
    If it's more efficient, e.g. costs less fuel, it should be less expensive. We've been calculating orbits that could thread a comet past Jupiter's orbit for decades now. Complexity just costs a few microseconds of computer time.

  • The important unanswered question (Score:1)

    by Anonymous Coward

    How do I do this in Kerbal Space Program?

  • Didn't we already... (Score:3)

    by GNious ( 953874 ) on Sunday December 28, 2014 @05:07PM (#48685881)

    Wasn't this already addressed recently?

    1) This is horrible for manned craft, due to the much longer flight-time resulting in higher costs for maintaining the crew
    2) This is far from new, though so far only used for getting to the moon
    3) ... uhm, I'm sure there were more points

  • Why link to Gawker instead of the original article (Score:4, Informative)

    by TechnoGrl ( 322690 ) on Sunday December 28, 2014 @05:24PM (#48685963)
    Why is this linking to a Gawker site (IO9) instead of the actual original article at:
    http://www.universetoday.com/117615/making-the-trip-to-mars-cheaper-and-easier-the-case-for-ballistic-capture/

    The Gawker site merely copies/pastes what the original article states plus ad LOADS of additional advertising.
    How does this get past the Slashdot editors? Was this an intentional Promo or has Slashdot declined just this much these days :(

    • Gawker sites are always useless clickbait advertising traps. Thus they have so many sites linking to each other for more advertising clicks. What passes for journalism there is simply reposting other people's work. Buzzfeed actually manages to be worse (you know it is bad when Gawker calls someone out for plagarisim.)

  • KSP test anyone?? (Score:1)

    by Anonymous Coward

    I hope they tested [xkcd.com] in the proper program [kerbalspaceprogram.com] before the big announcement.

  • So obviously their definition of efficiency seems to be a little different from common definitions. Then they say it is effective but complicated. Looks they are shooting for a well diversified portfolio of adjectives,
  • Look out for transformers :P Not a place for your kids!
    http://popularbloggingtopics.c... [popularblo...topics.com]

  • If it works in Kerbal Space Program, what the hell, go for it :-)

  • "At the same time, sending a rocket into space, through the vast gulf that separates Earth's and Mars' orbit, and then firing thrusters in the opposite direction to slow down, requires a great deal of fuel."

    The Hohmann Transfer is, mathematically provably, the *most efficient* way of travelling between any two orbits. It may require a "great deal of fuel", but that's still a great deal less than any other trajectory, which is precisely why we're willing to wait for the launch windows.

    As to the rest, aerobra

  • A science fiction short story used it as a plot device decades ago. Might've been in an ACE or Tor printing, so that probably dates it to the late 1960s? The Bad Guys dropped into the planet's orbit, more or less matched speeds with the planet (remember, they need to move fast enough to avoid the well documented "Bug on the Windshield" Effect), and "simply" let the planet drive under them. They faced the same problem that NASA does, too. The story hinged on the difficulties of landing in the smallest numb

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