Musk Hints Details on Scaled Down Interplanetary Transport System

Musk is talking about the scaled down version of the Interplanetary Transport System that he plans to unveil in Adelaide, Australia at the end of September. For comparison purposes, the vehicle he unveiled last year had a 12 meter diameter. Falcon 9 has a diameter of 3.7 meters. The diameter of the Saturn V was 10.1 meters.


UPDATE:
The above graphic shows the engine layout for the ITS. It would seem they would lose 21 outside engines by shrinking the diameter to 9 meters. That would leave the ITS with 21 Raptor engines on the first stage.

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  • Tannia Ling

    You mean the original ITS was unrealistically big? No way!

  • opmyl

    I guess the real question then is, does a 9 meter vs. 12 meter diameter significantly alter total cost of development?

  • Dave Salt

    Getting suspiciously close to New Glenn proportions… I wonder what Bezos will say?

  • windbourne

    I wonder if this will be used for taking off/landing, while using a different craft for transportation?
    Perhaps a BA unit(s).
    To be honest, it makes no sense to have a craft for landing 100 ppl, also serve as the living quarters. They really should be separate.

  • Douglas Messier

    See above for an update. Looks like a narrower rocket would have 21 Raptor engines instead of 42.

  • Arthur Hamilton

    And they wouldn’t have to reinforce 39A.

  • That’s the REAL takeaway from this latest swirl! 🙂

  • Michael Vaicaitis

    More likely New Armstrong proportions. “small”-BFR will still be 2-3 times the lift of NG.

  • Michael Vaicaitis

    Makes absolute sense – Raptor is already built, so that wasn’t going to change, and so the diameter has to be measured in units of Raptor. 9m wide, along with some height shrinkage will put this at about 50% the original volume, so perhaps 30-40% of the original lift performance??. Guessing 100-150 tonnes to LEO fully reusable. Small enough to be usable for LEO/GEO/Lunar service and large enough to get early colonists to Mars 30-50 at a time. Development and manufacturing costs may not be reduced massively, but it’s an architecture that could viably replace F9/FH and help pay for itself.

  • Hypx

    Not really. You’re still larger than the SLS’s diameter (8.4m) and well beyond the market for any current satellites or ISS missions. SpaceX will have to pay everything themselves unless NASA decides to replace the SLS with this rocket.

  • Gerald R Everett

    Not unrealistically big, but unaffordably big for the time being. It is also not clear that the carbon composite tank is technically ready yet.

  • Gerald R Everett

    Replace the FH for sure. Don’t know that the F9 would be replaced. It seems to be a very sweet little rocket that is now approaching technical maturity and reliability. As it will be at least partially reusable so it should be around a while. They are still flying DC3s.

  • Michael Vaicaitis

    Do they throw away 20% of an DC3 after every flight and throw away the whole thing after 10 flights?. Wouldn’t it be better to keep the whole vehicle for a thousand flights?. Besides it’s going to be a good 5+ years and many years of overlap, so they’ll get plenty of value out of the F9 core design.

  • Gerald R Everett

    Yes. I am 70, I remember that there was originally to be three launch pads for the Saturn Vs. But the funding had been cut for the third. So the two remaining pads were sized to handle not only the Saturn V but the Nova. A 21 engine Raptor based rocket would have nearly the same sea level thrust as a Nova although it would be a bit smaller. Nova was to have been 12.2 meters at the base, with 8 F1A engines producing 13,920,000 lbs. Thrust. The 21 Raptors would produce 14,490,000 lbs. trust. So the 9 meter ITS is about as big a rocket as you could launch from 39A.

  • Gerald R Everett

    I think your major cost savings would be on the manufacturing and operational side. A 12 meter system would require a new pad. A 9 meter system could use Pad 39A/B. A 12 meter system would not fit into either Hawthorne (which would have to be re-purposed to BFR production only) and it would be to large a diameter for use of Michoud even after the tornado lifted the roof a bit;-> The 9 meter system could be assembled at Michoud where they already have a work force familiar with large aerospace grade composite construction.

  • Gerald R Everett

    I think that the push Elon is making to create awareness of the fixed price milestones based contracting is part of a larger agenda of letting the public an politicians know just how uneconomic the SLS is. Also the ideal two payload Geo orbit system would be a BFS with payload bay doors (ala shuttle bay doors). All of course completely reusable. Any large payload to cislunar space would require a large rocket.

  • Gerald R Everett

    EM says they will try to return the second stage on some missions along with the fairings. The fact that you have DC3s doesn’t mean you don’t also haves Boeing 747s as well. I assume that when the F9’s stop being cost effective they will replace them, but their is a lot that goes into that.

  • Tom Billings

    I will enjoy seeing how these larger rockets interact economically with manufacturing in space. The width problems for payloads will disappear, which means it will be tonnage to altitude, whether by one launch or by 20 launches. The 9m rocket has better prospects than a 12 m rocket in that environment, I think.

  • MzUnGu

    That’s like comparing one imaginary number to another imaginary number… 😛 My guess, the difference is probably just few Unicorn Dollars. 😀

  • Mr Snarky Answer

    Consider 21 engines an upper bound not an exact number. Also we don’t know for sure if they will roll first mini BFR on existing Raptor thrust levels and then ramp into it or not.

  • Mr Snarky Answer

    You need to room for several month transit anyway.

  • Mr Snarky Answer

    Imagine how much less origami you need for a telescope (or same origami and more capability).

  • Mr Snarky Answer

    No they are in actual planning to develop the vehicle, location of manufacture (down to the building). They are in active development of the engines as well. It isn’t as Ethereal as you make it sound.

  • Mr Snarky Answer

    Assuming 21 Raptors at 600K pounds.

    Consider this:

    The development of ITS may be similar and different than F9 at the same time. SpaceX likes walking up a maturity curve, fly hardware early and improve/scale as you go rather than flying nothing and throwing it all together analytically and flying at the end. However, with F9 they had the luxury of feathering in booster landings as a side goal, not going to be the case with these monster 9 meter carbon fiber tanks…they are going to want them back from the beginning and 21 engines costs more than 12.

    So, what I would do is build a 9 meter ITS with depopulated (dozen or more engines) at the current 200K pounds of thrust as a mini ITS-DEV1 vehicle. This could be used for suborbital hops and to prove out the cradle landing system. Same sub-scale upper stage could be build to prove out landing and the rest. Then move to same 9 meter tank (perhaps with some iterative improvements or even the exact same tank) mini ITS-DEV2 which is fully populated doing missions. At some point when Raptor is ready you switch over to bigger Raptor variant (where-ever it lands on the thrust targets) to give you the full vehicle at around ~10 million pounds of thrust on 39a).

  • Mr Snarky Answer

    The water coolers at the MAF must be buzzing this week.

  • Andrew Tubbiolo

    Mini BFR makes sense. It should bottom out where Falcon H tops out. That way there are payloads to feed it, once it works.

  • Michael Vaicaitis

    Agreed, an upper stage with three configurations would be ideal to do everything Elon wants and needs: 1) Interplanetary Spaceship for passengers/cargo to land on Mars/Lunar, 2) Tanker for on orbit refuelling of config 1, 3) A payload doors variant for LEO/GEO.

  • Michael Vaicaitis

    Yes, this is the second part of the affordable use of space puzzle. Firstly, we need cheap launch services via fully reusable rockets. Secondly, we must make deeper inroads into the one-of-a-kind payload model. We need simpler, cheaper, and easier to launch payloads, and large reliable cheap launchers is what makes that possible.

  • Enrique Moreno

    Probably he is thinking about a 3 core first stage concept as the FH instead of a gigantic alone core.

  • Back-of-envelope, to keep thrust-to-GLOW at 1.4 and still provide 9.4 km/s of delta-v, I got about 150t expendable, which is probably 110-120t reusable.

    However, I strongly suspect that there’s an intermediate step here: Develop reliable (and crew-safe) rendezvous and docking for payloads and D2 (probably “D3” by the time you develop something that’s cis-lunar worthy), then launch a single-Raptor transfer stage on a separate FH. If you really want to do D3 crewed to some kind of lunar orbit (LLO, DRO, or NRHO), you probably also need a hypergolic stage for lunar insertion and TEI, because I doubt NASA will look very favorably on a long-dwell cryo stage to get people home.

    More back-of-envelope shows you could launch a 12t D3 on an F9 (man-rating an FH will be tough), then launch a 2-booster-recoverable FH with a short Raptor stage for TLI and an OMS-like stage for LOI and TEI (44t total). Or you can do a one-way 21t payload to LLO with a 51t Raptor upper stage (two FH launches, one fully reusable and one 2-stick reusable).

    This gives SpaceX three main development arcs (assuming that FH goes more-or-less as planned):

    1) Commercialize the Raptor Upper Stage from the Air Force contract to act as a medium-dwell transfer stage. This gets SpaceX a cis-lunar COTS-like capability.

    2) Evolve D2 to a cis-lunar version, along with a short RUS and some kind of hypergolic stage above that. This gets them cis-lunar CCtCap.

    3) Build a 9m-diameter first stage using Raptor, and some kind of Mars-capable thing to put on it. This will be roughly triple the payload of a single FH, but frankly this sounds like the project that will slip nearly to infinity.

    One other thing: heavy lift makes a lot more sense with really, really good ride-sharing capability. I keep wondering if SpaceX will eventually buy Spaceflight Industries. Getting the ride-sharing logistics built into a system that can send 3 10t satellites to GEO on a reusable FH seems like a pretty good business model for getting the market used to routine heavy lift. Beyond that, SpaceX is gonna have to wait a while until there’s enough business to cis-lunar before it’s worth building a bigger launcher than FH.

  • Vladislaw

    I believe some of what drives Musk’s direction was future congressional funding for NASA and where the sense of the congress was heading. Mars for Bush and continued by Obama. Now the sense of the congress is back to Luna and Musk has simply adjusted to the new reality?

  • He would have been extremely happy if he’d managed to stampede NASA all the way to buy SpaceX as the way to Mars. That didn’t happen, but:

    1) SLS is shakier than ever.

    2) This whole DSG/DST thing wouldn’t have happened if NASA and the SLS mafia hadn’t been shamed into needing to justify SLS/Orion’s existence. Since deploying stuff that can support both Mars and the Moon is a step in the right direction, that’s useful.

    3) Assuming they don’t screw the pooch in the near- to medium-term, SpaceX has positioned itself to be the contractor of choice for building launch vehicles once SLS has wound down (which is still at least 10 years away).

    All-in-all, that’s a pretty good return on a few thousand hours of design work and a pretty deck of slides.

  • The obvious next step is to prove out the Raptor as an FH upper stage. Beyond, that a 9m depopulated ITS-scale first stage would have a hard time getting a thrust-to-GLOW greater than 1.

    BTW, the testing for a cradle system is easy: Just land sufficiently accurately on the pad.

  • Mr Snarky Answer

    “The obvious next step is to prove out the Raptor as an FH upper stage. ”

    It isn’t obvious, it’s asinine. Limited capability given the tank size and huge disruption due to GSE/TEL changes for existing launch sites. FH is already big enough to cover the market until fully-reusable BFR/BFS comes on-line. All you end up testing is the engine. SpaceX has been clear F9/FH are mature and in sustaining at block V. Additional, Dragon v2 was de-scoped to no drag out qualifications as well. The idea is by the end of next year significant engineering resources will be moved to mini-BFR/BFS while the existing systems are earning not burning (hopefully). Musk is playing with S2 recovery, but I think that is on a lark at this point.

  • Tom Billings

    Well, once a manufacturing facility using SpiderFab or Archinaut technology is established for a given energy-level in the Earth/Moon Gravity Well, no origami is needed at all. At a place like EML-1 you bring up the structural materials, build the apertures needed, and string everything else out along the trusses that stabilize the larger apertures. Sometime in the 2025+ time frame you start getting kerogens and water from asteroid mining retrievals to make carbon composites. You add a facility to make carbon fiber and matrix materials from that, and the costs per kilo of spacecraft drop steeply yet again.

  • Kenneth_Brown

    The mass of 42 engines and support systems is insane. The F9 works due to having a bit of redundancy and cost savings through manufacturing more smaller engines than just a few large ones, but that concept doesn’t scale up indefinitely. The ITS isn’t going to benefit from the same cost savings of using more copies of a smaller engine. There just won’t be enough launches. Even a 21 engine rocket would require heaps of excess plumbing to make it work.

    For manned missions further than the moon, it seems a better approach to assemble a craft in orbit and launch towards the target from there. Getting travel times down will be a huge step forward for missions to Mars. Once at Mars, the main rocket could be refueled and sent on to the asteroid belt.

    Honestly, I don’t have any faith that Elon is going to be able to hold things together as a part time CEO to all of his ventures. Something is bound to break.

  • Here’s why I think you’re wrong:

    First of all, SpaceX wouldn’t have cut the deal with the Air Force for the prototype Raptor stage if they didn’t plan on using it. They could have just as easily cut an engine-only deal, and the Air Force would have been just as happy.

    Second, if SpaceX is serious about the satellite constellation (and they appear to be), then the launch costs scale much better if they launch 35t of sats at a time on a reusable FH than if they launch 10t on a reusable F9. That requires a wider fairing–there’s just not room for enough 400 kg sats in a 5m fairing. So if they’re going to go to a 6-7m fairing, hammerheading a 5m second stage probably helps. And if they do that, at least the TEL system has to be modified anyway–and you get a higher-energy upper stage at the same time. Similarly, FH doesn’t make much sense without at least a 25t payload attach fitting. That’s probably a decent-sized structural change to the second stage all by itself.

    Yet another reason to go with a Raptor upper stage is for longer dwell capability and a larger number of restarts. FH can launch a lot more economically if it ride-shares better, which requires more orbit flexibility. I suppose you could build the long-dwell stuff into a Merlin, but why would you bother? It makes more sense to put the effort into a RUS.

    Finally, while it’s true that Block 5 is it for the F9, that can’t possibly be right for the FH. The center core is already different, so making the mods for the RUS fit well into its evolution. Yes, that absolutely requires different GSE. But so does any effort to use Raptor, unless they’re going to use a different pad for everything that has methalox. That… doesn’t sound very efficient, especially if it means that you dedicate a pad for the heaviest lift launchers you’ve got, which will almost certainly launch the least frequently.

  • Mr Snarky Answer

    “First of all, SpaceX wouldn’t have cut the deal with the Air Force for the prototype Raptor stage if they didn’t plan on using it. They could have just as easily cut an engine-only deal, and the Air Force would have been just as happy.”

    There is no such contract. This has been re-hashed ad nauseam. The contact was for a development engine (and milestones) with potential to be used for a future upper stage, Mars rocket or lawn ornament at SpaceX HQ. The mention of FH upper was justification for the engine dev contract (not required). Nothing more. There is no contractual obligation to build this stage or even request further phase B funding for such a system. SpaceX may do this if the USAF is going to just throw more money at them, but not without that, and it really is not needed. USAF also threw money at OA to look at EELV development program (which may or may not go forward). But the phase A in either case is not a requirement that a stage or LV be built.

    “Second, if SpaceX is serious about the satellite constellation (and they appear to be), then the launch costs scale much better if they launch 35t of sats at a time on a reusable FH than if they launch 10t on a reusable F9. That requires a wider fairing–there’s just not room for enough 400 kg sats in a 5m fairing. ”

    Yea, you know what has a wide fairing? A 9m mini-BFR that is targeted for commercial operations per Musks comments in last weeks interview. Dozens of medium sized satellites packeted into a huge fairing that is fully reusable is the plan for bootstrapping mini-BFRs commercial demand. So, you had the right idea, FH is the wrong rocket.

    “Yet another reason to go with a Raptor upper stage is for longer dwell capability and a larger number of restarts.”

    Already have the long duration mission kit demoed on NROL-76 with the first block IV upper stage (3 hour coast). They will further expand testing to the ~6 hours or so they need for direct to GEO insertion. This problem has already been solved (heater, batteries and avionics hardening) done.

    The total length of the vehicles are the same, fineness ratio, the same. Making the stack longer without wider is not really an option. Making the stack wider is not an option. Jacking with the GSE/TEL is expensive and invasive for a money money making stable system both NASA crew and the USAF want to be reliable and non-moving target. Mixing both uppers on the same launch pad requires TEL swapping or some other technique that would invariably slow down launch cadence.

    In other words, unneeded and dumb.

  • redneck

    You do not want Mars as a stopover for frequently visited asteroid missions. The launch opportunities are about half of those direct from Earth due to the longer year. For the occasional one offs, maybe.

  • Michael Vaicaitis

    I get the impression that most people see big launchers as useful only for lifting big payloads. I see big launchers as being just as useful for lifting many small payloads more economically than using many small launchers. Perhaps most important is that a big architecture can include enough margin to allow for a fully reusable second stage. I think one of the important features of the original ITS was that the upper stage allowed for a very large heatshield. A a wide body rocket brings many advantages to the economics of launch and space transportation. The fact that such a rocket is bigger than FH is not relevant – the important point is that it would be cheaper to operate.

    For a sub-scale ITS the most important factor is still that Musk wants to go to Mars and so he will be looking to design an architecture that can do that job – 30-50 passengers per vessel would still be a good rate to start with. I don’t see Elon entertaining new designs for cis-lunar that do not simultaneously translate to Martian use, so the new BFS will be Dragon 3.
    I agree that a new F9/FH second stage seems to be the most obvious route to getting experience with Raptor, methalox and carbon fibre. Problem is, do SpaceX really want to tool up for such an intermediate step?.

  • “I see big launchers as being just as useful for lifting many small payloads more economically than using many small launchers.”

    Yes, but that puts several requirements on the upper stage, and on the logistics of managing the payloads:

    1) Medium-to-long dwell. Everything has to stayed powered up and warm for the duration of however long it takes to put all the payloads in all the right orbits.

    2) Large number of restarts. The odds of getting everything deployed from a single orbital inclination/ascending node go down as the number of payloads goes up.

    3) Lots of delta-v, both to change orbital planes and to get payloads on station quicker. This is a big reason why I think that we see a Raptor Upper Stage. Whether or not it’s the actual second stage, it’s almost certainly the transfer stage.

    4) Wide fairings. It’s unlikely that a heavy will be used for cubesats. Instead, your payloads are more likely to be in the 500-6000 kg class. Those take up a lot of volume, and you need to get 20-30t of them packed in to be economically viable.

    5) A clean, insurable pipeline of rides. The more things you fly at once, the more things you have to integrate, which means that underwriters can’t get squirrelly about the other payloads on the bird, and you have to have the ability to rapidly move payloads into and out of a particular launch slot. If everybody flies at the mercy of the satellite with the most unreliable schedule or the most risk, it’ll never work. Bumping the problem child and replacing it with something else has to be the work of days, not months.

    “Perhaps most important is that a big architecture can include enough margin to allow for a fully reusable second stage.”

    Before you can refuel, really need a heat shield for this, which I think pushes things into the ITS-class stages. I don’t think that SpaceX will have the luxury of waiting that long for a competitive heavy-lift solution. A market for fairly regular cis-lunar flights is going to start to open as soon as DSG/DST or whatever takes its place starts to firm up. If SpaceX wants to bid on that stuff, it’s going to need to have the technology needed to do it on FH, which at least implies the ability to launch transfer stages separate from their payloads and dock ’em in a parking orbit.

    Once you have transfer stage technology, it’s a much smaller step to refueling those transfer stages, and then your launch architecture looks much better. If you can refuel your second stages prior to reentry, the thermal and mechanical loads go way down, because you can kill a lot of speed prior to interface. There’s a good chance that that gets you into the realm where hypersonic retropropulsion will support most of the thermal protection.

    The 35t reusable FH with transfer stage and refueling technology path sounds a lot more profitable than going straight for a 120t reusable mini-ITS. There’s a lot to be said for having all of these capabilities 5-10 years earlier. Plus, you need the refueling tech for mini-ITS anyway. Might as well profit from it sooner rather than later.

    “I don’t see Elon entertaining new designs for cis-lunar that do not simultaneously translate to Martian use, so the new BFS will be Dragon 3.”

    I don’t see the mission profiles being similar enough to be handled with one vehicle. You can do cis-lunar with a fairly modest upgrade of a D2 and a transfer stage; that’s not even close to what you need for a Mars-bound BFS. And there’s too much money on the table for him to punt on the cis-lunar business.

    My guess:

    1) FH transfer stage tech.
    2) Cis-lunar “D3” (probably with a hypergolic stage for LOI and TEI).
    3) Refueling tech.
    4) Reusable second stage.
    5) Mars-capable BFS.
    6) ITS-class booster.

  • “Yea, you know what has a wide fairing? A 9m mini-BFR that is targeted for commercial operations…”

    If you could do a mini-BFR in the time frame needed to bid on the cis-lunar stuff that’s going to show up in the early 2020’s, I think I’d agree with you. But you can’t, and at the very least you need a separately-launched transfer stage to make FH capable of performing those missions. That’s a fine job for a Raptor.

    Same argument goes for the satellite constellation. If they’re looking at NET 2025 to begin deployment, they’re going to have their lunch eaten by OneWeb or some other yahoo that comes along. They need something to deploy at scale by 2020ish, or New Glenn (7m fairing) is going to get the lion’s share of the business.

    It’s certainly possible that SpaceX will do a transfer-only RUS for the cis-lunar biz first, but that leaves them at a distinct disadvantage when people want to start rolling out these mega-constellations. They can hammerhead it as a 2nd stage a lot faster than they can build a BFR.

    “Already have the long duration mission kit demoed on NROL-76 with the first block IV upper stage (3 hour coast).”

    You need the restartability, too. I don’t think 25-35t of sats all deployed from one orbital plane will cut it. How many TEA/TEB cartridges can you stack onto an M1D? For that matter, how much energy can you pack into a single F9 stage 2?

    “Jacking with the GSE/TEL is expensive and invasive for a money making stable system both NASA crew and the USAF want to be reliable and non-moving target.”

    Those arguments apply just as much for a BFR, as well. Somebody’s going to be making mods on a launch complex, or building a new one. So the real question comes down to: Is GSE/TEL and a new RUS hammerhead cheaper/faster than the GSE/TEL for a mini-BFR? The answer to that question is almost certainly “yes”. The follow-on to that question is: Is there enough market to warrant the intermediate step for the RUS, before when we could start bidding mini-BFR for big/multiple payloads? That answer to that question is less certain, but still likely to be “yes”.

    We know that this is exactly the market that New Glenn is aimed at, and they’ll certainly get there before a mini-BFR can get there. I don’t see Elon ceding any market share to Bezos if he can avoid it.

  • Mr Snarky Answer

    “If you could do a mini-BFR in the time frame needed to bid on the
    cis-lunar stuff that’s going to show up in the early 2020’s, I think I’d
    agree with you”

    However, implausible it is to you, Musk has aggressive timeline for 9m BFR in the early 2020s.

    “You need the restartability, too. I don’t think 25-35t of sats all
    deployed from one orbital plane will cut it. How many TEA/TEB
    cartridges can you stack onto an M1D? For that matter, how much energy can you pack into a single F9 stage 2?”

    Already there. In case you haven’t noticed they can restart MVAC multiple times already (They often restart again off air to ditch the stage or put in graveyard orbit). Just increase the TEA/TEB reservoir if needed (who said they were in cartridge form anyway? That was F1 to spin up turbine, MVAC uses He). Why pursue long duration mission kit for MVAC based upper if you can’t do the restarts for direct to geo anyway? That would be dumb. They aren’t dumb. The most stressful mission is 6.4 mT to GSO EELV profile (FH can do this already with long duration kit). No more is needed for Commercial or Military launch. The only thing needed beyond this is a slightly enlarged fairing which may be developed per subsequent EELV funding along with the vertical integration. Neither of these require re-engine or changing propellants of the stage.

    “Those arguments apply just as much for a BFR, as well.”

    No, BFR would use a separate TEL/Launch Mount side by side that could be built between flights. This would not touch existing Flight or GSE hardware. Key is to not massively change the pad GSE after certified for crew.

    Below is an example of the arrangement
    https://www.nasaspaceflight.com/wp-content/uploads/2017/07/2017-07-24-202650-350×187.jpg

    Your sauce is getting weak. FH out of the gate cannot compete with fully operational NG, that is why they need to leap frog.

  • Michael Vaicaitis

    When you say “long dwell”, I don’t imagine you mean longer than the 150-200 days for the transfer to Mars, so that shouldn’t be a problem?.

    Lifting 100+ tonnes and deploying out of payload doors is more of a volume issue (payload bay of 8m x 20m??) and I don’t see any other than SEP being allowed on board – non-electric need not apply. Much of the established launch/sat paradigm will have to change – there’s little point in developing new/cheaper/better/easier ways of doing things just in order to keep doing things the same way they’ve been done since the 70’s. Payload share could be passengers and cargo to space stations, or, sats with closeish inclinations. If plane changes are too large for BFS, then the satellites own prop will need to be used or better still reusable SEP tugs.

    “If you can refuel your second stages prior to reentry, the thermal and mechanical loads go way down, because you can kill a lot of speed prior to interface. There’s a good chance that that gets you into the realm where hypersonic retropropulsion will support most of the thermal protection.”
    You talking Mars here , or Earth?. The biggest (that is most frequent for an architecture that pays for itself) problem is Earth re-entry is at orbital speeds – thermals and mechanical loads on a large surface area, high volume vehicle are much lower than something like Dragon. Mars could be made easier by aerobraking into orbit, but time in low g and fuel constraints are probably bigger issues.

    “I don’t see the mission profiles being similar enough to be handled with one vehicle.”
    A fully reusable, 100 mission lifetime BFR/BFS (mini or max) will be cheaper per misssion than F9 and have 5-10 times the payload at that lower cost. The vehicle is not the critical issue, cost is. Elon worked out a way to get lots of people to Mars. Now he has to find a compromise path to getting “quite a lot” of people to Mars with an architecture that is LEO and cis-lunar viable – can’t wait till September.

  • Long dwell for purposes of Earth and cis-lunar stuff is merely long enough to complete all the burns necessary to do the mission. That’s probably no longer than a few days, maybe weeks for cis-lunar. But that’s long enough that battery power isn’t good enough. It effectively means that you either need to deploy solar panels or run some kind of generator (which is what ACES plans to do with IVF). But it’s not something that an existing F9 stage 2 can do. (Of course, it doesn’t really matter, because the F9S2 doesn’t have enough delta-v to do the kind of burns we’re talking about here.)

    “Much of the established launch/sat paradigm will have to change – there’s little point in developing new/cheaper/better/easier ways of
    doing things just in order to keep doing things the same way they’ve
    been done since the 70’s.”

    Not sure what you’re driving at here. If you’re thinking that they’re gonna deploy bunches of satellites from something like the BFS, I guess that’s possible, but it’s a terrible platform for that, and it’ll take way too long to develop. The market opportunity for this starts in a very small number of years. That’s why I think they need to capitalize on it with an FH, not with a mini-BFR.

    “You talking Mars here, or Earth?. The biggest (that is most frequent for an architecture that pays for itself) problem is Earth re-entry is at orbital speeds – thermals and mechanical loads on a large surface area, high volume vehicle are much lower than something like Dragon.”

    Earth. And I don’t believe for a second that a stage 2 is going to survive a >7000 m/s reentry without massive structural reinforcement, some kind of heat shield, and some way of protecting the engines.

    However, there’s another way to do it: a fully-fueled F9 stage 2 with no payload can generate almost 12,000 m/s of delta-v. That’s more than enough to slow the stage to the 2000 m/s speed that the first stages come back at. You’d have to burn at a negative angle of attack and spend a couple of km/s in gravity drag, or you’ll drop to entry interface too quickly, but it’s only fuel. And you could obviously do the same sort of thing with a Raptor upper stage, too. But you need to refuel.

    “A fully reusable, 100 mission lifetime BFR/BFS (mini or max) will be cheaper per misssion than F9 and have 5-10 times the payload at that lower cost.”

    …And when SpaceX has that vehicle, with that kind of reusability and operational expense profile, 10-15 years from now, it’ll be great. But if they want to operate FH profitably in the mean time, they’re going to have to do something a lot simpler than implementing an architecture capable of getting to Mars. And all of this stuff is doable for the cost of implementing a RUS for the FH.

  • Michael Vaicaitis

    Well in order to refuel an upper stage for retropropulsive re-entry you’d need a tanker upper stage which would need to re-enter without being refuelled. So a big ass heatshield is the simpler and more likely route.

    Seems to me the competition for FH in the next 10-15 years is going to be New Glenn, Ariane 6, Long March ?, and perhaps Vulcan. In none of those cases do I see them beating or even matching what SpaceX can do on price with the help of first stage core recovery. So Elon’s only time pressure is a combination of his own impatience to get to Mars and the realities of developing and paying for mini-ITS.

    A new Raptor powered second stage looks like the simplest path forward, but there’s plenty of development and qualification issues. New inter-stage, new fairings, new aerodynamics, how to land with a single vac engine, etc.. Would SpaceX really want to be putting time and effort into this and delaying the mini-ITS that Elon really wants. I reckon mini-ITS is the way forward – they have Raptor and have started down the path of carbon tankage. All they need to make this commercially viable is to have a fully reusable orbital system that can operate cheaper than F9/FH. Niceties like optimising the way satellites are deployed en masse can be added over time. The big fleet companies and even the USAF are already showing an eagerness to adapt their satellite design strategy to take advantage of cheaper more regular launch services.

  • publiusr

    I was hoping for larger..but..this is more do-able.

    Hell–cluster the Falcons into a scaled up Saturn IB–that might be easier to control than just two strap-ons

  • publiusr

    No SLS mafia. The EELV depot hucksters–that’s another matter.