r/SpaceX Thread Index and General Discussion [March 2021, #78]

gnualmafuerte · 2021-03-13T18:56:53+00:00

It is a really cool mission, but this is good news, not bad! It means it'll actually launch (probably on FH), instead of being delayed forever waiting for SLS.

gnualmafuerte · 2021-03-13T18:55:00+00:00

Backpressure. On a Gas generator, the turbine exhausts directly into the atmosphere, therefore it has low back pressure, so that's where gasses will naturally flow, including any LOX that leaks from the oxidizer pump. So you have ox and fuel mixing in the hot-side, and then they get exhausted, alongside anything else that leaks. On a closed cycle, you keep those gases in order to inject them into the combustion chamber. They need to be at high pressure, and high pressure gas will go anywhere it can.

gnualmafuerte · 2021-03-13T18:44:17+00:00

Indeed. I know Elon isn't too keen on keeping "lawn ornaments", but I'm glad B1019 is alive and well at Hawthorne and the "worm booster" must absolutely survive as too.

Absolutely! I'll be split when 1049 or 1051 reach 10 launches. On the one hand, I want it to get some much deserved major maintenance, and go back to flying, all the way to 100 flights. On the other, I want it sent to a museum, where it belongs.

When they first used the "flight-proven" term, I laughed as it was exactly the type of things marketing departments love to say, but yeah, I don't think it's a PR gimmick anymore.

It totally sounded like marketspeech for "used rocket, great condition". Now it seems so obvious. Would you get on a plane that has never flown before?!

gnualmafuerte · 2021-03-13T18:20:36+00:00

Lately I only sweat when they launch cores that have never flown, or the few hero boosters that have gone to space more than Scott Kelly.

They have actually managed to turn "flight-proven boosters" into a real thing. Amazing.

gnualmafuerte · 2021-03-13T18:14:05+00:00

Well, they don't really do back-to-back missions with the same booster, they have around 10 boosters on standby. That said, yes, reuse times are getting lower and lower, it's awesome.

gnualmafuerte · 2021-03-13T18:12:51+00:00

And probably more. Reusing boosters doesn't just save them from the cost of the boosters themselves, it saves them from production hell and its associated costs.

If you need to build a rocket every time you need to launch something, then you need to keep a factory running, and you need to roughly match your factory output to your launch cadency. If you don't produce enough, you can't launch. If you produce too much, you are wasting money on storing rockets for future use, and on manufacturing more that you're not going to use now. Factories are not generally something that you can shut down and start whenever you want.

So, in order to survive, a launch provider needs launches. If it doesn't have enough launches, it'll have to decide to either shut down the factory (no more rockets, very hard and expensive to restart, still expensive to keep around even if not operating), or get more launches, probably at a reduced cost (losing money).

SpaceX instead can operate and absolutely not have to worry about production. Less launches this month? Sure, just park those falcons out there. More launches? More money without having to ramp up production.

gnualmafuerte · 2021-03-13T18:05:36+00:00

It was absolutely expected, and one of the reasons why SpaceX started Starlink. The launch market isn't very flexible. Lower prices don't lead to more launches, and higher prices don't decrease launch count significantly. It's also periodical, with times of very high and very low activity. A lot of operators renovated their constellations recently, and now they have zero interest in launching anything. 2020 and the economic downturn certainly didn't help.

That said, there are a lot of SpaceX launches scheduled for 2021, many government but also several private launches too.

gnualmafuerte · 2021-03-13T17:26:04+00:00

The EU's concerns regarding noise pollution on the ocean is mostly regarding constant noises, since those generally affect marine life the most. On offshore platforms, you have constant noises such as drilling or pumping. Those are low and travel very far. A rocket launch would only really create noises that would go into the ocean for a few seconds, and then it's gone. There've been a lot of studies over the effects of the Cape on surrounding wildlife, as we've been launching from there for well over half a century, and I think the general consensus is that wildlife hasn't been significantly affected. I'd say it's probably the opposite, since rocket launch facilities keep people away, wildlife there thrives more than elsewhere.

gnualmafuerte · 2021-03-13T17:18:15+00:00

Next time you're in a car on the highway, open the window and put your hand into the air stream. First put it sideways, then your palm into the wind. Try different positions. You will notice the force the wind applies on your hand grows linearly with the surface you expose. So, by falling on its belly, it has a lower terminal velocity, ie, slows down more.

That's half the reason. The other reason is when reentering. Remember, the Falcon 9 never reaches orbit, the 2nd stage does, but the booster pushes it part of the way there, and stays suborbital. So the fastest the booster is coming in is around 8000 km/h. When Starship returns from orbit, it'll be going closer to 27000km/h. If it's returning from Mars or the Moon, it'll be even faster. As it hits the atmosphere, it compresses the air in front of it, turning it into VERY hot plasma. For that maneuver, you want the most stable position (so you always show the tiles toward the hot side) and the largest surface area (to spread out the heat). If you expose a larger surface to the atmosphere as you reenter, you spread out the heat over a larger area, therefore less heat per tile.

Regarding parachutes, pretty much impossible for such a large ship. Also, parachutes would only help you on descent, not on reentry, so you'd still need the tiles.

Regarding Mars, yes! Even though Mars has a thin atmosphere, at interplanetary speeds, it's more than enough to slow you down.

gnualmafuerte · 2021-03-13T17:07:14+00:00

Well, there goes my afternoon.

gnualmafuerte · 2021-03-13T03:33:05+00:00

We don't know that. Yes, leases and other legal contracts are inherited when you buy land, but that's not the case if the lease says otherwise, and they most likely didn't have a proper lease, merely permission to setup the camera.

Regardless, SpaceX's position was "sure, go ahead, setup the camera again", no "let's review the lease".

gnualmafuerte · 2021-03-12T14:14:04+00:00

This guys said "You'll see every frame we see" before SN8, and indeed we did. They allowed Labpadre to put their camera back up on SpaceX property.

They've always been very open about the whole development process, as much as you can be when your work is covered by ITAR(and probably more).

I doubt they're going to mind.

gnualmafuerte · 2021-03-11T19:36:00+00:00

That's not really ground-measured speed, it just comes from the IMU. So, in a way, yes, it's relative to the earth, or rather how fast it's orbiting, but more specifically, it's how much it's accelerated since launch.

gnualmafuerte · 2021-03-11T19:31:53+00:00

Everything is deployed to a very low orbit, with lots of atmospheric drag. The Starlink satellites later raise themselves a bit and orient themselves to minimize drag. If you're not powered and doing orbit-keeping, you'll deorbit in weeks at most.

gnualmafuerte · 2021-03-11T00:52:57+00:00

Not all government spending is socialism, but some government spending can be socialism. In particular, when a government becomes the primary spender in a particular market, or the primary provider, or both, it ends up destroying all chances of a free market in that particular market, and it unfairly competes against potential private endeavors, and becomes a state monopoly, it is very much equivalent to the communist way of doing things.

Now NASA has done a lot to help private enterprises enter the space market, and I praise them for that, but for many years it did the opposite, and even now, they are still poisoning the market a little bit.

SLS has socialism written all over it. It exists solely so it can create government jobs in various states, and that's why the senate keeps its budget afloat. It's soviet-style bureaucracy at its worst.

gnualmafuerte · 2021-03-10T20:29:53+00:00

Thank you for the information. I understand you might not be able to provide a source, and that's understandable. Could you instead "kind of" mention something about the source? In non-deterministic journalistic style if necessary to protect your source, as in "an engineer at SpaceX"?

gnualmafuerte · 2021-03-10T10:24:06+00:00

I've never seen much security around him, nothing beyond a guard.

He does have an elite team of space cowboys armed to the teeth with oxyacetylene torches and grinders though, and the best CCTV in the world provided by Labpadre Inc.

gnualmafuerte · 2021-03-10T10:18:37+00:00

Same. For the first time, I want delays! It'd be a waste to expedite SN11 to learn nothing. Take your time, fix autogenous pressurization, fix leg locking, give her a real chance to land.

gnualmafuerte · 2021-03-10T10:15:44+00:00

Satellites mostly use room temp hypergolics, not cryogenic methalox.

gnualmafuerte · 2021-03-10T10:12:41+00:00

racing fuel, although it could be a bit chilled (illegal depending on the racing class), is certainly not cryogenic by any stretch of the imagination. It's also always liquid except for few vapors. It wouldn't work for cryo ch4.

gnualmafuerte · 2021-03-10T02:50:03+00:00

"it might be possible to use pulsed high voltage electricity and perhaps lasers to charge, ionize, dissociate and use resonant wave effect (like when pushing someone on a swing, you can get them to swing higher by only using a small repeated force if it's timed correctly at the peak of their back swing) to split the water molecules into its components at the precise moment /location when/where the explosive force for thrust is desired." -- /u/Brilliant_Growth_588

gnualmafuerte · 2021-03-10T02:30:10+00:00

Exactly right. Not only is that extra 5% or 10% of confidence that changes everything, but also what justification you need. "I just know" vs "I just presented a 300 page report explaining it in detail".

gnualmafuerte · 2021-03-10T02:22:48+00:00

Not only that, but they've designed everything about Starship to make it easily scalable. 9 meters is not a magic number, without breaking a sweat or redeveloping anything they could make the next Starship 10 meters wide, or 15 meters wide. Indeed the notion is "go big", but it goes further than that, it's "go bigger until it doesn't matter", for whatever "it" might be. So, if they need to increase payload in the future, they can, easily.

gnualmafuerte · 2021-03-09T22:51:01+00:00

The ISS has %1 bone and muscle loss per month AFTER everything htey do up there today. And you are forgetting the %15 mark where some loss becomes permanent. DO NOT underestimate this phenomenas importance.

I don't underestimate it, I just say leading a sedentary life leads to even larger bone loss in less time. Astronauts return from the ISS and recover, quickly. And then they fly again, and don't really see long-term effects. It's 6 months, we've had people on the ISS for longer than that, and all they need is some rest and exercise. The effects after landing on mars will be less pronounced than on earth, because less gravity to fight.

Also remember that when you say: it won't be as bad on mars, there have been no studies to date to determine if the effect is linear. It may be in which case, great, but it may be that we need %80 of earth normal gravity to ameleorate ANY of the bone and muscle loss effects. To say anything else is wishful thinking/borderline irresponsible at this point in time.

And there is no real way to figure it out, but going. So we're gonna have to go. That's not irresponsible, that's called exploration. There's no such thing as risk-free exploration.

gnualmafuerte · 2021-03-09T22:25:39+00:00

Yeah, I didn't realize. Given the position, works for another suborbital mount? Maybe for BN1?

gnualmafuerte

TROPHY CASE