RCgothic
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Posts posted by RCgothic
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17 minutes ago, sevenperforce said:
I think the RVac can throttle just fine. But you're right, it can't gimbal.
I don't remember him saying six vacuum Raptors.
Found it:
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Probably just a pathfinder.
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6 hours ago, xebx said:
Starship only need 3 Raptor Vac and 3 Raptor SL (SL can be shut down at around 4500m/s) to deliver approximately :
120t (high DeltaV loss = SH come back to launch pad)
or 180t (low-med DeltaV loss = SH land on a boat)
or 240t (no recovery).
(SH : 69MN, 215t dry weight, 3400t fuel, SLT=1.35; Starship : 105t dry weight, 1170t fuel, Twr=0.98 at staging, once in orbit 3 Raptor Vac can do all the job even fully refueled; DeltaV Starship 8700 m/s+11t fuel for landing)
Btw, I'd expect a fully expendable starship to have a substantially lighter dry weight. No fins, no heatshield, no header tanks and disposable fairing.
At 5% dry mass, disposable starship would be ~62.5t. F9US is 3.9%. Expendable Starship could even be better because of the way square cube works.
Expendable Starship may be a fairly niche application for distant destinations once they get orbital refuelling worked out. They absolutely do not want to be expending these things.
But it kind of makes sense as an easily acheivable early milestone. Personally if I were Elon I'd like to do it just to smash the "double Saturn V to LEO" marker.
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Elon has previously agreed a pure tanker with stretched tanks and 9 raptors (6Vac, 3SL) might make sense.
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1 hour ago, Mikenike said:
Still, you are correct, how in the heck would you hide something that is 1000 sq ft in LEO, or even HEO.
If it had to be in LEO I probably wouldn't bother with solar, I'd go straight to bomb-pumped. Much smaller, much cheaper. One-shot, but you could have multiple.
If it absolutely had to be solar-powered, I'd put the solar collector somewhere separate from the weapon and beam the power with a microwave laser or similar.
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It'll probably be a dual ASDS landing for the side cores with centre core expended.
15t is comfortably within FH's GTO expendable capability of 26.7t, but enough more than the 8t reusable threshold that being on a sub-GTO trajectory probably won't make enough of a difference.
I wonder if using an extended fairing comes with much of a performance penalty?
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What happens to the light that comes from this angle?
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I'm not sure I completely follow the optics here, but it sounds like a solar powered laser would have more success as a weapon than a mirror.
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On Jan 25th it sounds like SLS definitively lost Clipper:
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Clipper formally no longer making SLS compatibility efforts. It's likely to be FH:
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Wow, a whole tonne. As a separate mission to crew. How ambitious.
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8 minutes ago, CatastrophicFailure said:
Now, where I am that’s actually extremely competitive, I pay Comcast around $180 for cable and broadband. Local phone company has options from $60-$90 but, well, they suck too. Did your buddy get the same “mid to late 2021” estimate?
Same for you, eh?
Maybe that timeframe is just general and they’ll actually be shipping to early orderers sooner?
As I understand, and I could be wrong, StarLink should not really be affected by weather much, as the frequency it operates at can get through clouds/moisture, and the phased array antenna can compensate a great deal for any wind jostling of the dish.
As well as picking an alternative satellite in an alternative direction, once the constellation is mature, which should give some protection from passing storms.
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3 minutes ago, RuBisCO said:
Called my step-father up, told him I want to get him starlink for the family farm, he is paying $180 a month for 2 phones lines and 20 Mbs DSL and he wants to get rid of the phone lines and replace them with Voip (he has been saying he wants to replace them with Voip for years now, needs a kick in the butt to do it). Minnesota is high enough latitude we should get good early coverage.
That's exactly the sort of situation Starlink is optimal for.
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With 1 engine out allowed on ascent and landing, at 2% chance of failure per burn the Starship upper stage would have a 99.4% chance of successful ascent (6 failures in 1000) on 6 engines and a 99.9% chance of a successful landing on 3 engines. That's 7 failures in 1000 due to engines.
With 4 engines out allowed on ascent, the Superheavy booster, the Superheavy booster has a 99.98% chance of successful ascent. That's 2 failures in 10,000.
Loss of crew due to engines would therefore be 72 in 10,000 missions.
The booster landing on 4 engines would land successfully (up to 1 engine out) 99.77% of the time. ~25 lost boosters total ascent and landing per 10,000 flights.
If the engines are more reliable than 2% chance of failure then things improve a lot. Merlin 1D has flown 110 (990 engines) missions with 2 engine failures on ascent. Failures during static fire/landing are unknown and therefore excluded. That's 0.2%.
If Raptor can achieve Merlin level reliability of 2 failures in 990, then Superheavy might be expected to fail 24 in a million landings and suffer no failed ascents. The Starship upper stage would suffer critical engine related failures on 72 of a million flights.
That's not a very long way off where it needs to be TBH. In 1960 Boeing alone suffered over 40 accidents per million flights. Sure, engines are not everything that can go wrong with a rocket, but they are the most critical.
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The right thing to do in a developing incident 99.9% of the time is to throw on the brakes to the limit of grip, and do so as quickly as possible.
If you still hit the vehicle in front then that's your problem for being too close. Self-driving cars don't do that.
If someone rear-ends you that's their problem for being too close. Self-driving cars don't do that.
Any case that isn't covered by the above that might involve dodging would require superhuman reflexes and perfect situational awareness. Dodging out of lane doesn't help if there are oncoming vehicles or obstacles you're not aware of. It involves a lot of hope and desperation. Humans don't actually dodge very well.
Whereas self-driving cars might actually be capable of dodging to a higher degree of capability, but they won't, because 99.9% of the time applying the brakes in good time is the least risky option, which they do very well, and any accidents caused by dodging opens questions of liability.
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13 hours ago, sevenperforce said:
The tiles have gaps between them, so it's fairly straightforward to wrap the tile matrix around a cone as long as you mind the gap.
As you can see, the angle starts four tiles down but the gaps are large enough that the bent-over tile sections (unbent tiles on right) don't collide. Wherever there is a collision you take out that tile and you use a large, single, customized tile to fill that particular space.
If you don't want to use a customized piece then you can just tile the space irregularly and allow larger gaps.
As always an impressive diagram, but I'm pretty sure this ends up with a large number of different custom tiles.
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The problem is you can't tile a curved surface with regular hexagons.
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33 minutes ago, tater said:
Wow, I guess my sarcasm detector needs a retune.
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Ultimately, the engines have to relight.
They can't depend on 3/2 redundancy because whatever it is giving problems is probably a common mode failure. If one won't light, chances are more than one won't light. Or possibly none will light.
That's not something you can really band-aid with extra engine ignitions and sooner starts.
They just have to get it right. Whatever the problem is, they'll find it and fix it. Just needs more flight tests.
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RIP SN5. I had hoped you'd be used for the mock up.
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Starship navigates to its destination using lift. Drag is parallel to the airstream. Without lift Starship would be unable to steer.
Most of the lift comes from the body. A little comes from the flaps. Yes, these surfaces are stalled. That doesn't mean they produce no lift, only that the lift to drag ratio is poor.
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1 hour ago, YNM said:
Is it correct though that SN8 went to 12.5 km and SN9 only went up to 10 km ? I know that SN9's altitude was announced in the livestream but for SN8 there wasn't any.
Flight comparison:
Looks like SN9 went a little over 10km, and SN8 was a little under 12.5km. SN9 had a slower ascent. SN8 started descending before pitch and flip, whereas SN9 flipped straight from apogee.
Interesting that descent was much faster than Ascent, which it doesn't really look like.
SN9 also had a higher peak velocity, which may have been a result of it going a bit nose-down after flip.
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Good slo-mo:
Oof. Much fire where fire should not be.
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Sure those are legs? Maybe looks like engine bell debris to me.
Maybe that timeframe is just general and they’ll actually be shipping to early orderers sooner?
SpaceX Discussion Thread
in Science & Spaceflight
Posted
Yup.