• duheagle

    Yes, it’s always necessary to test theoretically-based calculations against rude reality in order to refine the math. SpaceX has done a lot of pioneering in flight envelopes not previously used by anyone else and has accumulated a lot of data in the process. But it seems they need still more.

  • Andrew Tubbiolo

    No arguments from me on that. Even from me an accused red communist (in your view). But they can’t move that fast, even when it’s all in shop. BFR is turning into a great experiment into the public sector vs private sector argument. The government is drawing down it’s investments into SX that carry over to BFR/BFS so we get to see how well they perform more or even totally out on their own.

  • duheagle

    Yes. This announcement was incomplete enough to open up quite a sizable sheaf of new possibilities and we have little solid basis – yet – for preferring any one of them to any other. I’m personally of the opinion that a Raptorized mini-BFR upper stage could be of maximum benefit to SpaceX both for what it would do to assist the BFR project itself, as well as for being a quickly available mechanism for initial deployments of Starlink birds while BFR is still in development and testing. But even an M-Vac-powered stage would be of non-trivial benefit in both those respects, just less so. A great deal will depend upon the size of the thing – something else we have no definite information about as yet. I hope SpaceX decides to more fully characterize its “Mini-BFR” effort fairly soon.

  • duheagle

    “Bare-bones engineering test object vs new operational vehicle,” is certainly one of the very significant bits of info we are currently missing – and likely the most important.

  • duheagle

    I don’t think you’re a commie, Andrew. You seem well to the right of center within the general rubric of academic leftism. That makes you pretty far to the left anent the general run of Americans, but, as campus lefties go, you’re pretty weak tea.

    Given the current climate on normative large university campuses, that puts you at significant risk of being denounced by one of the local Red Guards and haled into some Socialist Self-Criticism show trial for being a capitalist-roader before being sentenced to a long term in the Ag school (if UofA has an Ag school – I don’t remember) experimental fields “spreading night soil.”

    How fast SpaceX can move is definitely among the questions we should see increasingly definitive answers to starting, it now seems, in barely over six months. I think those answers will prove serially discomfiting to a great many people in legacy government and aerospace circles. I further expect the level of such discomfiture to continue ramping up significantly with every additional six months that passes. Jaws, prepare to meet floor.

  • Andrew Tubbiolo

    And what since 2011 causes you think that ‘jaws will be on the floor’? Unless they have a long lead on this thing, or unless it’s a kludged Falcon 2nd stage, what past performance on vehicle development do you base that assertion on? Additionally, how will you react in 9 months when it does not happen? Consider that you’re rooting for the most complex new vehicle option out there. New space frame, lifting body, Raptor engine, now the pads need to be outfitted to deal with LCH4, cargo bay/payload faring pinstripes, and chrome. That’s a lot of work for 9 months.

  • Michael Halpern

    I think it will just be a modified s2, that said not all D2 s are crew

  • Jeff2Space

    I am in agreement that it’s likely we’ll see BFR/BFS schedules slip some.
    SpaceX wouldn’t need this upper stage reentry/flight demonstrator if they were 100% confident they could jump straight to BFS testing in the same flight regimes. The fact that this new thing exists indicates that they have significant development risk that needs to be addressed a.s.a.p.

  • Jeff2Space

    This new upper stage is in direct support of BFS development. It’s essentially a subscale BFS demonstrator intended to test reentry and flight. One of the most critical aspects of reentry is the thermal protection system. Better to test that on a cheaper subscale demonstrator than on a full scale BFS if you’re not 100% sure it is going to work.

  • publiusr

    The mini-ship might be a good cubesat dispenser…

  • duheagle

    When SpaceX was still relatively tiny it went from Falcon 1 to Falcon 9 in two years. That included fitting out the plant that built F9 and building ground infrastructure at Canaveral. SpaceX is no longer tiny. The new 2nd stage just announced has certainly been in the works for at least awhile so I don’t find a target initial launch date of June 2019 “out there” at all. Nor do I find the prospect of initial hop tests of BFS before the end of 2019 incredible.

    As for CH4 plumbing at the Florida and/or Vandy pads, that would only be needed if this new upper stage is actually the Raptorized item from the USAF contract of two years ago. That seems uncertain just now. No Raptor engine, no need for new plumbing. But adding bulk CH4 handling to existing pad infrastructure doesn’t seem like too much of a stretch. SpaceX did a lot more pad work than that in Florida getting LC-39A ready for FH and rebuilding SLC-40 after the Amos-6 mishap and all that only took a year or so.

  • duheagle

    True, but the same problems apply. D2 will certainly be enabled to use the launch abort escape system to save cargo as well as crew.

  • Andrew Tubbiolo

    But that’s with NASA shoving a 1000 million dollars down their gullet. And they were able to hyper focus on Falcon 9 given their size. You make Falcon 9 sound like the result of a bunch of bare chested libertarians, when in reality they were on the dole and had one major task on hand which was to make an EELV for NASA that they could use commercially. Every time Space X goes libertarian, they get really slow. Falcon Heavy being a perfect example, or when government dollars slowed down, Dragon 2 slowed down. Again, I asked post 2011. And our reactions to the pad recovery time post Amos 6 is a similar data point leading to very different conclusions. So on the record, you can call me on this.

    What won’t happen in 2019.

    * SFS unless it’s a 2nd stage falcon kludged, or already built in 2018.

    * 1st BFS hop flight.

  • Michael Halpern

    Not if it becomes the standard s2 with removable recovery hardware

  • gunsandrockets

    Since the standard Falcon 9 payload fairing is 5 meters diameter, I think an SFS could have a body of of the same diameter, which means a significant increase in size and propellant compared to the normal Falcon 9 upper stage.

    The sea level version of the Raptor has similar ISP to the vacuum version of the Merlin, so in theory the SFS could be use propulsive landing with sea level Raptor, without sacrificing Merlin performance. The smaller engine bell of a sea level Raptor would also ease shaping the SFS airframe.

    As for Falcon Heavy version of SFS, what about a manned version of the SFS? Could that serve as a fully reusable manned shuttle, able to fly to the NASA Lunar Gateway? Even if SFS only carried two crew to Gateway, because of full reusability it might be cheaper per seat than a Dragon 2 flight to ISS.

    Now that I think about it, launching SFS with Falcon Heavy seems inevitable. The BFS heat shield is supposed to cope with the high speed of Earth reentry when coming from Mars, right? So the SFS will need a more powerful first stage than Falcon 9 to test such high reentry speeds.

  • windbourne

    LOL.
    If you think that the average America is far right of ‘academic leftism’,
    then it is not surprising as to why your GOP just got crushed in this election.

  • duheagle

    Not a lot of point in continuing an argument about matters that will all be matters of record long before either of us would convince the other of anything a priori. We’ll both know soon enough.

  • duheagle

    If you think the average American is okay with mob violence against political opponents, open borders, censorship, abrogation of due process, legally mandatory use of wackadoodle invented “pronouns,” “toxic masculinity,” “toxic whiteness” or any of the other fever swamp stuff now normative in leftist academe, you are listening too much to the voices in your head.

    The GOP didn’t exactly get “crushed” in the recent mid-terms. It lost the U.S. House by a modest margin and had some minor reverses elsewhere. It also had some wins, despite ex post facto attempts by crooked local Democrat officials to steal back two Senate seats and a governorship.

    I predict the new House Democratic majority will quickly proceed to demonstrate why it should never have been elected in the first place. Having lied at the top of its collective lungs to get its marginal victory, it will now forget all about anything but attempted revenge for 2016. That will tee it up for another drubbing in 2020 and a second Trump term. It’s unfortunate that flagrant lying was even as effective as it was this year, but the results suggest the effectiveness of this venerable leftist tactic is diminishing. Another election cycle or two and perhaps its effectiveness will finally diminish to approximately zero.

  • duheagle

    Seems unlikely, but, given the current paucity of hard info, I can’t entirely rule that out.

  • duheagle

    Any or all of that could prove true – or not. If the new stage is really the Raptorized USAF item, then it will have to be at least 5M in dia. to accommodate the “fluffier” LNG fuel. Whether or not a larger version of an F9-optimized stage for FH makes sense depends, I think on how much lift capacity SpaceX figures to need for early Starlink deployment.

  • Michael Halpern

    It would be in line with what they did with the landing tests on the first stage

  • Michael Halpern

    both sides have been lying, what people want is to make sure that the two evils can balance each other out

  • duheagle

    Perhaps you would be so kind as to inform us all about what the Republicans have been “lying” about?

  • duheagle

    A strained comparison, I think. The Grasshopper stuff was all done starting and ending on the ground and at fairly low velocity. The intended flight regime for this “mini-BFS” would be pretty much the polar opposite of that. This isn’t something you can do by making a few quick mods to the current S2 – analogous to sticking over-heavy, fixed legs onto an F9 engineering test article 1st stage and flying it with a subset of engines.

    One of the things SpaceX says it want to test, for example, is the TPS. It’s far from obvious that a test TPS intended to shield a carbon fiber composite hull can be properly tested using an aluminum vehicle. Aluminum loses a lot of strength well below melting temperature, for example. Composites keep essentially all their strength right up until they begin to burn. The analogy would be to wooden, as opposed to metal, ceiling truss behavior in a fire. Aluminum also has a much higher thermal expansion coefficient than does carbon fiber composite. Expected expansion has non-trivial effects on the design of the attachment mechanism mating the TPS to the hull structure.

    Grafting experimental hypersonic control surfaces onto the current S2 would also be a non-trivial exercise. All sorts of structure and stress issues to work out. If that is going to be the case, it would make more sense to design something that is optimal from the start. It’s a lot easier to strategically “add beef” in particular areas using carbon fiber composite construction than it is using aluminum sheet.

    The TPS and experimental control surfaces will all add mass too. Compensating for this – even if only in part – by using an all-composite understructure, as BFR will have, just seems to make the most sense even for a test article.

    It’s also just what one would want to do if this new S2 is to later see actual service for launching real payloads. We don’t know yet if that is to be the case, but the possibility can hardly be rejected out of hand based on what little we know now.

  • gunsandrockets

    I don’t remember the source, but I read an analysis comparing Merlin vs Raptor propellent factors. The short version is: density of the propellants works out pretty equally (due to super-cooling, differing F/O ratios, etc.). So a 5 meter diameter upper stage would have a lot more propellant mass, even with the Raptor.

  • Robert G. Oler

    nothing unexpected here unless you are a fan boy. BFR is going to take a long time, they need to upgrade the F9/FH second stage…predicted this a year ago