The Venus-Mars Mission

Keith Cowing points out the political chicanery and fiscal absurdity of a 2021 attempt with SLS/Orion.

Also, note the technical issue. Orion was designed to come back from the moon, not from Mars. It can barely manage escape velocity on earth entry. Note page 17 of the Plymouth Rock paper:

Reentry velocities are 11.05 to 11.25 km/s for asteroid missions, vs 11.0 km/s for lunar return

TPS enhancement may be required depending on the ultimate capability of Orion lunar TPS

They’ll be coming in a lot hotter than that for Mars. And what will they use for habitat? There’s no way Orion itself is large enough for a mission of that duration.

Note: I do think that the mission is physically and fiscally possible, in that time frame. Just not with SLS/Orion.

[Update a while later]

28 thoughts on “The Venus-Mars Mission”

  1. Could they possibly bleed off some of that velocity by making multiple aerobraking passes through the upper atmosphere before final reentry? Or would that require additional propellant or other systems which would add too much mass?

    1. Actually, the Inspiration Mars proposal was to do a two-pass entry, so that is a possibility, but it increases mission risk significantly. If you don’t get the entry corridor right, you either come in too hot or bounce off into a new heliocentric orbit.

      1. Hmm, would it be possible to have an Earthbound craft meet up with some sort of tug in a friendly orbit that could then resupply, refuel, and/or use the tug’s propulsion to slow down the incoming craft enough for a re-entry with Orion or a Dragon Rider?

        1. @ Wodun

          The problem with a space tug idea is the meet-up itself. The Mars vehicle will be coming in at around 14 kilometers per second or more. Any tug would need to match velocity, not just location. To do so requires a massive delta/v capacity by the tug; it has to achieve earth escape velocity, then do a 14 kps burn back this way (It doesn’t matter whether it’s the propulsion system, or just delivering fuel; the delta/v needed for meet-up is the same). The amount of fuel needed would be enormous (a lot more than just going to Mars and back, which is less delta/v) . It’d take far less fuel to give the Mars vehicle the capacity to slow itself by the four or five KPS to get it into the range of a lunar return speed.

          1. massive delta/v + high thrust defines a space tug. It starts in a highly (ridiculously high, earth/moon together being one focus) elliptical orbit that comes up behind the returning vehicle. It then accellerates to matching velocity from there. But probably not workable without a nuke engine.

      2. Rand, could they do a close pass of the Moon on the return to use it’s gravity for a reverse-slingshot, give up some delta-vee to the moon in exchange for slinging it towards the earth?

        1. Of course, but it could extend the mission duration. It might require several passes even with perigee retro burns.

          Is that logical? Longer verses none?

  2. The biggest problem with SLS is that the block one is an incredibly inefficient launch vehicle. The exact same stack used for the Shuttle program got 250,000 lbs (125 short tons) into orbit. The SLS can only get 70 tons into orbit and the upper stage is so incredibly anemic that the payload to escape is not much more than twice that of a Delta IVH (For which it shares for the most part the DCSS upper stage).

    In 1962 the S-IV stage had 5 RL-10’s.
    In 1964 the S-IVB stage had a single J-2

    They could have just frigging copied the S-IV or S-IVB stages but opted for the DCSS as it cost less supposedly to develop, still $400 million frigging dollars just to stretch and existing stage!

    BoLockNor is coming to the logical end of the road in capabilities for spaceflight.

    1. Dennis,
      To be fair to the SLS guys, the iCPS was never meant to be the long-term upper stage, just a cheap stop-gap to enable them to do anything remotely useful with SLS before a real stage gets developed at some later date. They’ve always intended to do a real stage with multiple RL-10s or 1-2 J-2Xs. They just wanted to have the vehicle stamped “operational” sometime before the heat death of the universe, so they’re using a modified DCSS stage for the first few missions. Just like they’re reusing stock SSMEs instead of new expendable versions, etc. It’s all a ploy to make it look like it costs less to develop than it really does by declaring it operational as early as possible.


      1. Seems to me that was also the story on the Shuttle’s SRB. They were a stop gap until liquid fuel flyback boosters would be available. Of course they never were…

  3. After crunching some numbers, I think it’s possible to do a Mars flyby with SLSblockII/Orion, with the addition of a hab module. It would have to do aerocapture to return.

    Aside from the cost, there is one small problem; SLS blockII is scheduled to be flying by 2032 at the soonest, so using it to make the 2021 launch window (11 years before it can exist) would be – problematic. (Non-existent launch vehicles tend to be hard to use).

    Using SLS block1… not viable; Orion weighs too darn much. SLS block1 just doesn’t have the Delta/v to do a TMI burn to send Orion, a hab, plus consumables and life support, to Mars, even for a reduced crew.

    Falcon Heavy, on the other hand, though it has a bit less LEO capacity than SLS block 1 (about 10 tons less) and a lower ISP upper stage for the TMI burn, could do it with dual launch. Launch 1, Dragon plus a hab, supplies, etc, to LEO. Launch 2 a few days later; no payload, which gives you an upper stage in LEO with enough fuel to do the TMI burn for the dragon/hab stack. This would be nowhere as easy as it sounds (For just one thing, docking the Dragon with the upper stage would be no walk in the park and would require hardware and capabilities that don’t currently exist) but less hard than the SLS route IMHO, and vastly, vastly cheaper. I know that FH doesn’t yet exist, but I’m willing to bet that it flies long before SLS.

    1. FH doesn’t exist as such, but all of its component parts do and have actually flown.

      SLS, despite being ostensibly made up of Shuttle derived components etc., can’t claim anything close to that level of readiness.

      1. Totally agreed, Rand, Dragon (or for that matter Orion) lack the internal volume to make the mission viable on their own.

        I should have elaborated instead of abbreviated; when I typed “dragon plus a hab” I meant Dragon plus a habitat module of some sort.

        @Ctrot, agreed, FH is a heck of a lot more complete than SLS. The F9 1.1 first stage form the three stacks with very little modification (there is some, such as the crossfeed on some at least some FH) but the structure is almost identical otherwise, and f9 1.1 certainly exists, and has flown.

        Okay, I’ve got a dumb question to ask; setting aside whether its needed or not, if NASA wants heavy lift, and wants it shuttle-based, why didn’t they simply use the existing shuttle stack, replacing the orbiter with a cargo module (the three engines, plus OMS, placed roughly as they are now, though at the end of the cargo module rather than a shuttle). Basically, I’m talking Shuttle-C here.

        It’s throw weight to LEO would, with unmodified ET and SRB’s, be (after subtracting the ‘boattail” mass) be at worst very close to SLS block II. SLS, on the other hand, is basically an all new system, due to the SRB’s and everything else being redesigned.

        Shuttle C has the issue of placing your cargo (or crewed vehicle) alongside the stack, which has risks (as seen with Colombia) but that’s for a fragile TPS. With a capsule, the heat shield would not be exposed, and for cargo, the damage risk is far less overall.

        I’m not saying Shuttle-C is a good idea (I think it’s cost too much), BUT, if it was decided to do heavy lift anyway, wouldn’t it have been a cheaper, faster, alternative to SLS? As things stand now, we wouldn’t even have SLS block II until 2032.

        But, I don’t recall seeing this option even discussed anywhere, so I’m guessing there’s a big glaring reason that I just haven’t noticed?

  4. The other, non-rocket part of this that’s missing is an ECLSS capable of reasonably reliable, autonomous 500+ day operation. I hope we hear some mention of that in today’s hearing.

  5. Have the “thing taking the trip” have -two- engines and a tether.

    You get the benefits of spinning.
    And you get to cut the tether at the optimum time.

    This change at the correct part of a slingshot should be an insane “ISP”.

    As an added bonus, you have a very fast deep space probe. Hopefully you didn’t leave anyone on that part.

  6. Woke up last night realizing that 1000 sq. km. is exaction one billion sq. meters. Which makes calcs easy.

    I figure $130m plus or minus 30 per mars colonist… So 16 cents per sq. m. pays for it all. So you commies can forget the sq. km. claims. Give ’em nothing. Ignore that the colony fails if the colonists fail. Make them pay for their own 40×50 (2000) m plots at $0.50 per sq. m. Meaning costs could go up as much as half a billion per colonists and they’d still make money.

    Offer to transport all Mars One colonists for free (they’re not going to make $6b but they could make 20% which would be enough to presupply a colony… they could refocus on training and presupply only.)

    We only need to presupply. No more supply required after the first landing. Subsequent colonists bring in the stuff they can’t manufacture on mars as their own personal property (includes $60,000/kg surcharge good for trade leverage.)

    Leverage the current high cost to make it possible. We can go now… Just don’t put govt. begging weenies like Tito in charge. Use a 13mt vehicle launched on and F9 and refueled by two FH to send a dozen. Land two at a time with half the payload the property of each.

  7. BTW, 13mt vehicle to orbit becomes 49mt with 12 crew and 3mt supply for each (2mt for 8 mo. then they land with one mt each.) Landers wait in orbit for them.

    If you really want to cut the colonists throats (why make it easy. they fail the colony fails) You could cut costs by landing 3 or 4 at a time instead of 2 and give them all less supplies.

    The colonists are just an afterthought anyway. Why let them interfere with a good suicide plan?

    Yeah, not being able to take part in all that new solar system wealth is making me bitter. I got the old man part down already.

    [Do they get my humor? Do they understand the serious?]

  8. Of course the big question is what knowledge do you gain by a Mars/Venus flyby mission? Demonstration of a habitat that could keep the crew alive and well for 500+ days? You be going too fast for any real science on Mars or Venus. Seems you could do a demonstration in Earth Orbit for a lot less money and risk. Or if you need a PR stunt to justify the SLS than use a Earth-Moon L-2 halo orbit where you could actually do some useful science running rovers on the lunar far side.

  9. Ugh!!

    They apparently only mentioned the needed 500+ day life support issue in passing. (seeing as how it’s the greatest technical challenge of, and absolutely critical to, the mission, I guess it’s not important…)

    I noticed something very odd in the artwork. The vehicle stack inside the SLS shroud (8.3 meters) shows an Orion that’s less than half that, which is very interesting seeing as Orion has a 5 meter diameter. They do mention that it’s an Orion derived capsule with an upgraded heat shield, BUT… as I’ve mentioned before, back when Inspiration Mars showed their Orion concept, it’s apparently a scaled down version of Orion (the crew proposal is for a crew of four, so that fits).

    The problem is you might as well design and build a whole new capsule. You can’t just scale Orion down.

    My guess as to the reason they want to do this scaled-down Orion; a full Orion will mass at least 9000kg (without service modue). That, plus the hab, power, plus the life support and consumables, will mass at least 35000 kg, minimum. SLS block one payload to LEO will be 69000kg if they are lucky. So, they have a problem; they need to do a burn of about 4kps, and unless they shed some weight, they can’t.

    They could use multi-launch, but that negates the whole claimed idea of SLS. So, a smaller capsule is a must.

    And they sure as heck can’t use Dragon (which weighs less than half an Orion), not after spending billions on Orion. So, they’re thinking of a scaled-down Orion. Except it wouldn’t really be an Orion at all – it’d make as much sense (and save a ton of money) to slap an “Orion” label on a dragon and use that.

    Rand is right; if they were serous they’d scrap SLS/Orion and divert the funding to the hardware that could actually do the job.

    So, my guess; the chance of this mission actually happening with NASA/SLS are right around zero.
    That doesn’t mean they won’t spend a few billion on it though.

  10. Of course it will. When a new Administration comes into power in a few years they will send NASA in a new direction. SLS will be dumped and a new heavy lift system, with a new alphabet soup name, will replace for it a new mission.

    Really NASA has ceased to have any serious function in opening the high frontier. Its just a massive entitlement program for the Congressional Districts it has facilities. That is why it works so hard to assimilate any serious private space efforts like Bigelow Aerospace. It knows if the public ever finds out how much money and time NASA wasted NOT opening the high frontier its game over for their pork machine.

    The “nothing is impossible,” risk taking NASA of Apollo is ancient history. The new NASA probably couldn’t even do Project Mercury let alone go beyond Earth orbit.

  11. As an update to some points I raised regarding lift mass and life support;

    On the life support front, it’s even worse than I thought; the systems on ISS require a lot more maintenance and parts than I’d assumed, and those are the best currently in existence for long term space life support. They are also far too heavy for the Mars flyby mission.

    On the Orion front, I overlooked something big. Not only is a standard Orion too heavy for this mission and unable to handle the reentry speed, it’s not just a case of slapping on a better heat shield; Orion is already overweight for its parachute system, so adding more mass wouldn’t be helpful. I’m thinking that the above reasons are why the artwork is showing a far smaller Orion (which, of course, would not be an Orion at all, but a totally new capsule).

    On the SLS lift capability front, things aren’t as bad as I said. In reality, it looks as if SLS block II isn’t needed. The block 1A advanced SLS upper stage could do the job (assuming some magical low mass life support system and reentry capsule is created). And, unlike the 10 year gap (It’d first fly, at best, a decade after the launch window shuts) the advanced upper stage could be ready as soon as only five years after the launch window closes (if it’s rushed a bit and has no delays).

    However, stubborn soul that I am, I still believe that it would be a tad problematic to use a launch vehicle that, at time of launch, does not yet exist.

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