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Everything posted by RCgothic
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Could the SuperHeavy booster be SSTO?
RCgothic replied to Exoscientist's topic in Science & Spaceflight
No. Double it and add 50t for propellant.- 156 replies
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More on that:
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And the whole engine's also about 50% bigger than Raptor anyway. Yeah, that pump is huge.
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“You got a bunch of guys down here about to turn blue, we're breathing again!”
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No successful landing callout...
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This is B4 from the closest angle I could find. Overall size is hard to tell. The cells on B7 are definitely closer packed.
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totm dec 2023 Artemis Discussion Thread
RCgothic replied to Nightside's topic in Science & Spaceflight
I've heard this might be fairly consistent with a solar panels not deployed issue, so comms were on battery until it died. If so the prospects for recovery are not good. -
Could the SuperHeavy booster be SSTO?
RCgothic replied to Exoscientist's topic in Science & Spaceflight
Making a recoverable SSTO Superheavy would require: Stretching it to accommodate more fuel. Adding a payload fairing and cargo door. The engines are less protected than on Starship so that's additional mass for a wider and more substantial base skirt. It'd also need fins like starship to prevent it orienting engines-first on re-entry, and they'd need to be a lot bigger than starship's. A full-length heat shield. And structural reinforcements to cope with the horizontal entry and fin loading. A normal Superheavy starts off at about 160-180t dry. All of the above could easily take it above 300t. The only positive is that there's no longer any need for grid fins.- 156 replies
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Presumably to allow access for weld inspections after test fire. I expect they'll be covered before launch.
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Could the SuperHeavy booster be SSTO?
RCgothic replied to Exoscientist's topic in Science & Spaceflight
Even if an upscaled EXPENDABLE SSTO SUPERHEAVY could put 150t pure payload in orbit, that: 1) DOES NOT match the 250t-300t of a similar expendable Starship/recovered Superheavy can manage whilst throwing away 24 or 27 fewer engines. 2) DOES NOT match the cheapness of a completely reusable Starship/Superheavy that throws nothing away. Generously, if the dry mass of an upscaled SSTO Superheavy would be around 80-90t, then that'd be 230-240t to orbit total. The dry mass of a RECOVERABLE SSTO SUPERHEAVY would be around 160-180t, and the fuel reserves for landing would be around 50t, so the payload would be maybe 10-30t for basically the same fuel expenditure as the TSTO. So the SSTO recoverable Superheavy (if it even works): 3) COSTS 5-15 X AS MUCH PER KG as a fully recoverable TSTO in terms of the only substantial consumable, propellant. Seriously, the TSTO performance and price is unassailable by an SSTO, even being generous. If recoverable SSTO Superheavy were preferable to TSTO Starship/Superheavy, that's what SpaceX would be building.- 156 replies
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Could the SuperHeavy booster be SSTO?
RCgothic replied to Exoscientist's topic in Science & Spaceflight
No, SSTO never matches TSTO. The reuse penalty is *already included* in the 150t to LEO. That's 100% reusable Starship, 100% reusable Superheavy. The Starship expendable payload is 250t to 300t. Superheavy is still recovered in this figure. The *fully expendable* Starship/Superheavy combo is somewhere between 420-500t . Superheavy SSTO can do maybe 50t payload expendably and does not have enough margin for recovery.- 156 replies
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Are we sure it's not just an illusion of size caused by the lack of engine bells in the picture?
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Could the SuperHeavy booster be SSTO?
RCgothic replied to Exoscientist's topic in Science & Spaceflight
Yes, the TSTO fully reusable payload of Starship Superheavy is ~150t. This is *already* with the reuse penalty applied. Total mass to orbit is ~265t (150t payload plus 30t landing propellant + 85t ship). Assuming a 40% mass to LEO penalty from booster reuse, the total mass to LEO expendably would be 475t. With an expendable 40t ship with no landing fuel, fins, heat shield etc, that's an expendable TSTO payload of 435t. That's your apple for comparison with the SSTO. And now we go back and see that even expendably an SSTO Superheavy would put up *maybe* 50t expendably. Then we note that making Starship reusable (an equivalent task to reusing Superheavy SSTO) more than doubles the structural weight, plus requires over 30t of reserved landing propellant and oh look we're all out of payload. Superheavy SSTO reusable doesn't close. SSTO *never* wins against TSTO- 156 replies
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If you have a drive capable of constant acceleration, don't worry about fuel efficiency when catching a target ahead of you in the orbit. You can brute-force it. Basically, you accelerate so you are going faster, so gravity is no longer enough to hold you at that radius and so your orbit would expand, but then you just thrust inwards to compensate. You'll catch the target much sooner than playing games with orbital mechanics. Also, most rendezvous dependent on orbital mechanics assumes a cooperative target. It can be very hard to next to impossible to catch an actively manoeuvring opponent if you're fuel-limited.
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Could the SuperHeavy booster be SSTO?
RCgothic replied to Exoscientist's topic in Science & Spaceflight
It will *never* make sense to throw away a 20+ engine booster to put 50t payload into orbit SSTO when you are aspiring to put 3x that into orbit TSTO completely reusable, or 5x that by only throwing away the 9-engine upper stage.- 156 replies
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Could the SuperHeavy booster be SSTO?
RCgothic replied to Exoscientist's topic in Science & Spaceflight
It's actually quite remarkable that the SSTO performance could even be as good as 1/3 the TSTO performance. Rockets are not remotely combat hardenable. It's akin to trying to land a very large and very delicate bomb near your own positions. Not remotely recommended anywhere even remotely unsecured. Add in that opponents are liable to view it as an incoming ICBM (and react to it as such) and this is probably not an idea that will reach widespread implementation.- 156 replies
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If it's there to help re-radiate heat from these edge boundaries then it might save the weight of an extra row of tiles or an extra thickness of steel. In those circumstances the paint could be mass negative.
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Pretty sure that's just shadow on the heat shield and reflection of the high bay door on the leeward side.
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totm dec 2023 Artemis Discussion Thread
RCgothic replied to Nightside's topic in Science & Spaceflight
Seems like the House is proposing full funding for Artemis: -
totm dec 2023 Artemis Discussion Thread
RCgothic replied to Nightside's topic in Science & Spaceflight
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Psyche slips to next year.
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totm dec 2023 Artemis Discussion Thread
RCgothic replied to Nightside's topic in Science & Spaceflight
(ノಠ益ಠ)ノ彡┻━┻ -
That's not insurmountable. Just include extra baffles or subdivide the main tanks to keep the remaining propellant stable. Recharge the header tanks from the mains once landed.
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What's the suborbital range for a full starship, reserving enough fuel for a return trip?