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RCgothic

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Posts posted by RCgothic

  1. Robert Zubrin was very critical of Dynetics:

     

     

    "3. While clearly better on a conceptual level than the National Team offering, the Dynetics design never really had a chance, because the team behind it was not credible enough to be given responsibility for something of such central importance to the space program. Rather, they were given a nice chunk of change in order to assure a wide base of support for Artemis."

     

     So a better idea, but not credibly going to acheive success due to the team (as was born out in NASA's selection document).

  2. 43 minutes ago, tater said:

    Wow, somehow I did not know that.

    vostok-1-orbit-path_590x379.jpg

    If his flight counts as orbital, so would the Starship flight (else the first man in orbit was actually Titov).

    In this case it's a test of orbital velocity reentry for SS, and a test of the booster, period.

    There's not really any useful testing of the booster except static fires (for the LV, and to test the pad/GSE/vibration), and an actual flight. Any hop seems like it needs a mass simulator, and the mass on top is ~1300t.

    Looks like Vostok did actually complete a full circle though (the ground track moves), and had to retrofire to get down.

  3. Well I reckon someone is going to have to come up with a way to do large scale carbon removal at some point. And I think whoever comes up with a way of doing so efficiently is going to make a lot of money in future getting paid to do so by governments.

    Personally I think extracting it from sea water might be the way to go, as it's easier to process large masses of water than air.

    If Musk wants to learn how to do it to produce rocket fuel I'm all for.

  4. 21 minutes ago, sevenperforce said:

    If reusing a stage costs $1M and saves them the ~$18M it costs to build a new stage, and they can reuse stages ten times each, then it would take 66 launches at full commercial price to recover the $1B it cost to develop Falcon 9 first-stage reuse. That's a long time.

    Instead they're reinvesting that capability by selling themselves Starlink launches.

    The difference between govt and a private company is that a govt must count the cost of every penny spent to taxpayers, but a private company never has to pay back its development capital as long as it can service the interest.

  5. 21 hours ago, tater said:

    What do people think the dry mass of SH is? 200t? Stripped as an expendable, maybe 180?

    Looks like a 180t SH with just 24 Raptors can put almost 56t into a 60x185km orbit. Yes, intentionally leaving the SH to go for a swim. That's as a single stage. Every ton saved on the SH is a ton to that orbit. If a LSS is ~85t, then a similarly built SH (~1.5X larger) should be ~130t—meaning as an SSTO, SHe can put ~96t into that orbit. So the payload/upper stage has to do the rest.

    With a 40t dry partial SS (half size) with 3 vac raptors, the expendable can throw 53t of additional payload to Earth escape (~TLI). Not sure what the TLI hit is for SH RTLS, if it's still 40%... that's >30t to TLI (<cough> Orion</cough>).

    SH is kind of remarkable—and it really is the easy part of the system. SHe with a expendable upper stage can pretty easily hit/exceed SLS Block 2 level payloads to TLI—and SpaceX could still make money selling those launches for 10X less than an SLS launch (1/10th of the very best case SLS cost by the usual SLS fan posters, way less than the actual cost of SLS).

     

     

    34 engines at <$1m each plus tanks so cheap SpaceX can afford to build them as GSE instead of COTS. For 300mt+ to LEO.

    And because private capital never has to be paid back, only the interest needs to be included in the launch price. This may be an unfair way of comparing SLS to SSSH, but taxpayers have different standards to private investors.

    And whereas STS required rapid reusability to be truly revolutionary, SSSH is already revolutionary even before considering the benefits of reusability.

  6. I would expect BN3 to be static fired without SN20, but flown with. If BN3 RUDs then the next test needs to wait for BN4 anyway, by which time SN21 will probably be ready. So it won't matter too much if SN20 was on top of BN3 or not. But if SN20 is up top, they get more data.

  7. They wouldn't be testing the same thing.

    Flight data is not as good as teardown data. Being able to teardown SN15 may have made SN16 and 17 unnecessary.

    Whereas they can learn new things from SN20/BN3's orbital flight. As testing and flying SN16 or SN17 will interrupt work at the launch site it may be better to not push ahead with 16 and 17.

  8. 14 hours ago, magnemoe said:

    Now SN15 used did an 4:30 minutes burn reaching 10 km, that is an average velocity of 133 km/h who is car speeds not even propeller planes, driving at 120 km/h you do 2 km / minute. 
    Why so slow?  MaxQ Structural? doubt it forces on forward fins coming down is pretty large and sideways, TWR? well Wikipedia list over 200 ton trust. 
    Safety?  I say doing an shorter burn is safer as the engines run for an shorter time so less time for something going wrong. 
    What is  I missing. 

    We think that in order to go from up to belly down in a controlled manner a kick from the raptors is required. Therefore they can't just coast to apogee, which means they have to keep the speed down so as not to exceed the altitude limit.

  9. Starship is intended to be a controlled vehicle. It'll be able to deorbit with Raptors, or RCS if necessary, or even orient for maximum drag. It'd take a major failure for it to be an uncontrolled object.

    And the initial orbit could indeed be low to decay within a few orbits 

    That's quite different from launching something to orbit with no control at all.

  10.  

    I think it's increasingly likely that BN2.1 isn't a thing. Just a prototype intertank bulkhead and nothing more.

    SN17 also seems decently close to completion. There's a real question mark over whether it will fly though. It'll probably depend on how the schedule works out. If 16 is delayed or 15 can be made ready for flight again, then the probability of a flight for 17 goes down.

    I'd expect we'll start seeing parts for SN21 shortly.

  11. 1 hour ago, SOXBLOX said:

    Aaaand so the environmental problems in the Gobi Desert, where there's breathable atmosphere and no dangerous radiation, are harder to deal with than the problems in space? Hah!

    If it comes to it that we're so short on space that we have to industrialise deserts, then that is a future from Blade Runner rather than Star Trek. If we want to preserve our planet in its current form then we cannot use up all the space.

    Arguably we have already used enough space that there will be unpleasant consequences once the initial inertia wears off.

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