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SpaceX successfully launches two humans into orbit

nasa.gov

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Re: SpaceX successfully launches two humans into orbit

#641

Post by Isinlor »

nabla9 wrote: post #415
Isinlor wrote: post #403

Earlier quoted context omitted.

You should listen to the astronauts. SpaceX is developing all of it with them and for them. They seem quite happy with UI because it allows rapid iteration on procedures. If they screw up something SpaceX can adjust interface within days. With space shuttle they would need to wait months and months.

Astronauts and pilots just talk PR to the public. "It's great, I'm so happy, we are all happy family. We had say on how these things work." Wait until they retire to find out the truth.

Astronauts are backed by NASA - no small agency mind you. If they would find things that they do not accept they can trigger safety reviews anytime.

BTW - On Soyuz they would need sticks, literal sticks, to interact with controls that are out of reach.

Re: SpaceX successfully launches two humans into orbit

#643

Post by jabl »

avmich wrote: post #614
sephamorr wrote: post #319

Earlier quoted context omitted.

Soyuz still uses UDMH and nitrogen tetroxide as its propellants. It simply jettisons the propulsion module before reentry so the reentry module has no thruster system and therefore no (toxic) fuel. With the return of a SpaceX vehicle, the recovery crew don't have suits on, that would be very unwieldy at sea, and they would just back off if trace gas detectors measure a toxic leak.

> Soyuz still uses UDMH and nitrogen tetroxide as its propellants. Right, but at least Soyuz doesn't have them in the returning capsule. Crew Dragon could be just as good in this aspect, but unfortunately isn't. So when moving the capsule from the sea the team has extra dangers.

Isn't the crew dragon using those hypergolic thrusters only in an abort scenario? IIRC they did test using them to do a propulsive landing, but the current plan is to use parachutes and land in the sea, no? And those thrusters had some ports to prevent seawater ingress, so I would guess that if they haven't been fired and there's no leak there's no danger.

Re: SpaceX successfully launches two humans into orbit

#644

Post by jasode »

colordrops wrote: post #579
jakswa wrote: post #540

Earlier quoted context omitted.

livestream still relevant? Docking with ISS tomorrow morning? All the tests they are doing?

Yes, live broadcast until docking at 10:30am EST.

To clarify, it's "EDT" not "EST":

https://www.google.com/search?q=spacex+dock+%22space+station...

Fyi that "Daylight Saving Time" instead of "Standard Time" is in effect in case someone miscalculates it by 1 hour.

Re: SpaceX successfully launches two humans into orbit

#645

Post by varjag »

adventured wrote: post #440
spopejoy wrote: post #357

Earlier quoted context omitted.

> brown-nosing speech towards the end of broadcast Was there any truth to the claims made that Trump has been exceptional in space support?

What does exceptional mean in this context? The Trump Admin has pushed for increasing NASA funding. Their funding had barely budged for the better part of a decade until Trump became president. From $19.2b the last Obama year (they got $18.7b in 2010, to show how little increase they received) to a requested $25.2b for 2021 (typically they get more than is requested). If that request sum comes through, much less high…

This is nothing compared to increases under Kennedy administration.

Re: SpaceX successfully launches two humans into orbit

#646

Post by varjag »

burfog wrote: post #378
varjag wrote: post #41

Why the MRAP though?

It replaces NASA's M113 armored personnel carrier, a tracked vehicle which dates back to the Vietnam War. The fire crew sits in there for protection from an exploding rocket. The vehicle is great for evacuating astronauts. https://www.nasa.gov/feature/mrap-rolls-through-pad-evacuati... If you want the closest view of a launch without being in the rocket, get some firefighting experience (preferably on an aircraft car…

OK, now that makes a lot more sense, thanks.

Re: SpaceX successfully launches two humans into orbit

#647

Post by varjag »

spopejoy wrote: post #357
varjag wrote: post #246

Earlier quoted context omitted.

To be fair they called the president by the last name and honorific, in that brown-nosing speech towards the end of broadcast.

> brown-nosing speech towards the end of broadcast Was there any truth to the claims made that Trump has been exceptional in space support?

He certainly isn't compared to mid-century administrations.

Re: SpaceX successfully launches two humans into orbit

#648

Post by jabl »

dralley wrote: post #389
avmich wrote: post #52

Earlier quoted context omitted.

> What would be the options? Soyuz uses straight hydrogen peroxide, I believe, 82% concentration. For 3 tons capsule it takes 30 kg of peroxide - monopropellant - to land. Buran is still the example of a high tech option - it used LOX and kerosene for RCS, the biggest trick was to keep LOX liquid for a month-long missions. It was done with mid-1980 technologies. Kliper planned to use LOX and ethanol. The craft wasn't…

HTP may be (comparatively) non-toxic but that doesn't mean it's necessarily less dangerous. The Kursk (Soviet ballistic missile submarine) was sunk by a malfunctioning HTP torpedo.

Having an oxidizer that easily starts to exothermically decompose sounds extremely dangerous. This was pointed out as the main factor why HTP "lost" to NTO/IRFNA as the storable oxidizer of choice already back in Clarks Ignition (1972).

The toxicity of NTO is bad, extremely so, and everyone knows it. But having your oxidizer tank suddenly go boom on its own accord is even worse.

Re: SpaceX successfully launches two humans into orbit

#649

Post by jabl »

orbital-decay wrote: post #57
avmich wrote: post #20

Earlier quoted context omitted.

Buran had non-toxic components for RCS. Kliper was planned with non-toxic RCS. Soyuz spacecraft at least has non-toxic components for capsule RCS, so when the capsule lands, it doesn't need to be approached in a chemical protection suit. It's not a question of choices - there are choices. I suspect it's a question which is considered less important so far, so SpaceX didn't pay that much attention to it, considering t…

Buran was using LOX, storing it for up to two weeks with a cryocooler and a complicated cooling system, Crew Dragon can be rated for hundreds of days and doesn't have the volume/mass/cost to spare. Dreamchaser with its propane/N2O thruster is a better counterexample. They avoided toxic components so it could theoretically land at any airport, making it a strong selling point. There are also new(-ish) hydroxylammonium…

Propane/N2O is an interesting combination. It needs to be pressurized quite a lot (the N2O in particular) to stay liquid, ruling it out for large systems like launchers. But for small thrusters, it means the system is self pressurizing, meaning (potentially) less mass and complexity for the entire thing.

HAN and ADN are also interesting options.

That being said, they should be tested and flown a lot more on cargo launches before they're ready to be put on crafts carrying humans.

Re: SpaceX successfully launches two humans into orbit

#650

Post by thu2111 »

londons_explore wrote: post #622
asdfasgasdgasdg wrote: post #573

Earlier quoted context omitted.

How pressing of a problem is the quality of optical fiber? Something tells me tells me that even if you imagine that all the capacity already existed, the mere shipping of raw goods up and finished goods down would probably eat any marginal profits over earth-manufactured fiber.

For regular data transmission, I can't imagine it to be worth it - far bigger gains could be made by just making repeaters smaller and cheaper by iterative design improvement. Perhaps there are scientific uses where loss in fiberoptics makes a project infesible? Or perhaps quantum entangled photons, which one can't amplify?

I suppose the issue is no matter how small and cheap the repeaters get, they will still need power, backups, replacements and all the complexity that implies.

I also have a feeling I've read the power needed for the repeaters generates magnetic fields that attract sharks. Shark bites are a not entirely trivial source of fiber cuts, which require very expensive fleets of cable repair ships to be maintained on standby and simply driving down the number of fiber cuts could be a fairly significant source of cost savings.

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