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SpaceX Crew Dragon Splashes Down After Historic Test Flight

scientificamerican.com

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Re: SpaceX Crew Dragon Splashes Down After Historic Test Flight

#71

Post by simonh »

bumby wrote: post #52
XorNot wrote: post #46

Earlier quoted context omitted.

Rockets and the rocket fuel are also in the "easy to substitute" category. They'll never not be hydrocarbons, but significant work has been done on producing rocket-compatible fuels from biological sources, and the marginal increase in cost if you scaled up to industrial production is possibly going to be entirely unnoticeable considering the general purity and refining requirements of anything you load into a spacec…

How do the biological propellants compare in terms of stability? Maybe not an issue for launches, but I'm curious about their viability in satellite thrusters that hang out for years/decades (although this is a digression from the GRG emission concern)

Satellite thrusters generally use stable hypergolics, to avoid the need for an ignition system, or electric systems such as ion or Hall thrusters.

Re: SpaceX Crew Dragon Splashes Down After Historic Test Flight

#72

Post by simonh »

Rebelgecko wrote: post #67
lostapathy wrote: post #23

Earlier quoted context omitted.

What other US-based company has had a man-rated rocket such that they owned the full stack, launch facility, etc? Sure contractors have been involved and built lots of components, but this is the first time a corporation has owned the fully, complete product as well as the facilities to launch and recover.

>What other US-based company has had a man-rated rocket such that they owned the full stack, launch facility, etc? No company does (including SpaceX)

This is in the context of the OP saying SpaceX will soon also own and operate their own launch facility, so that comment was contrasting the situation SpaceX will be in then to other companies. So I’m afraid your comment kind of misses the point.

Re: SpaceX Crew Dragon Splashes Down After Historic Test Flight

#73

Post by Rebelgecko »

simonh wrote: post #72
Rebelgecko wrote: post #67

Earlier quoted context omitted.

>What other US-based company has had a man-rated rocket such that they owned the full stack, launch facility, etc? No company does (including SpaceX)

This is in the context of the OP saying SpaceX will soon also own and operate their own launch facility, so that comment was contrasting the situation SpaceX will be in then to other companies. So I’m afraid your comment kind of misses the point.

Last I heard, SpaceX won't be using Boca Chica for Falcon 9/Heavy launches. So they do have their own launch facility, and they do have their own rockets, but they don't currently have any rockets that they can launch from their LF (which isn't ready yet)

Re: SpaceX Crew Dragon Splashes Down After Historic Test Flight

#74

Post by avmich »

robbiep wrote: post #58
geuis wrote: post #56

Earlier quoted context omitted.

Question about the inflight abort: Soyuz has this too. It was used a few months ago when a launch to the ISS went non-nominal. How is the one on Crew Dragon different?

You’re right. I believe the Soyuz uses two modes, the first is architecturally similar to the Apollo system (ie uses the ‘towed’ mode) whereas the crew dragon has abort built into the capsule.

Soyuz has one "tower", which can work both before liftoff https://en.wikipedia.org/wiki/Soyuz_7K-ST_No._16L and in flight.

Re: SpaceX Crew Dragon Splashes Down After Historic Test Flight

#75

Post by avmich »

willio58 wrote: post #28
pageandrew wrote: post #25

How do they plan to land it when humans are aboard?

Into the ocean just like the test. This is how it is always done with the exception of the space shuttle program I believe.

In addition to standard landings of Soviet and Russian spacecrafts on land the spacecraft designer always assumes the emergency landing may happen anywhere on the planet. Dense forests or rocky ridges can be problematic, but there is still demand to handle a wide variety of landing situations.

Re: SpaceX Crew Dragon Splashes Down After Historic Test Flight

#76

Post by avmich »

XorNot wrote: post #46
ceejayoz wrote: post #40

Earlier quoted context omitted.

https://www.smithsonianmag.com/science-nature/spacex-environ... says: > if the SpaceX’s plan for a rocket launch every two weeks comes to fruition, this amount of carbon (approximately 4,000 tonnes per year) will rapidly become a bigger problem So, that gives us a number... and it's also very weird for the Smithsonian to describe that as a "problem". 4,000 tonnes per year is about a thousand cars worth per the EPA's…

Rockets and the rocket fuel are also in the "easy to substitute" category. They'll never not be hydrocarbons, but significant work has been done on producing rocket-compatible fuels from biological sources, and the marginal increase in cost if you scaled up to industrial production is possibly going to be entirely unnoticeable considering the general purity and refining requirements of anything you load into a spacec…

Hydrogen as the only fuel was in the X-33 project, which technically had a lot of success (before finally closing).

Re: SpaceX Crew Dragon Splashes Down After Historic Test Flight

#77

Post by computerex »

mitchellgoffpc wrote: post #64
computerex wrote: post #57

Earlier quoted context omitted.

> I would like to reiterate the point made before which is that SpaceX is on the verge of being in a place that no company has ever been before with regard to space. Excuse my ignorance, but what have they done that's so revolutionary? We have been putting people into LEO for decades. What's so groundbreaking about this test?

What’s special isn’t so much putting people into LEO, so much as a private company having done it! It’s one thing for a nation-state to send a mission across the Atlantic or to the moon, but it’s a VERY different thing for companies to begin doing those things — developing rockets has always been enormously expensive, and this test (among others) signals that companies are finding ways to do it profitably. If this tr…

I think you are getting ahead of yourselves. For one thing, SpaceX is a launch provider. Whether there is even demand for Mars launches remains to be seen. I think SpaceX itself has said that it can't/won't be funding the Mars launches.

And secondly, this was an unmanned test launch to LEO. I think it'd be more prudent to wait till we get reliable manned launches to LEO before dreaming about other planets.

It's very cool that private companies are now doing this type of stuff. But imo the technical challenges still remain.

Re: SpaceX Crew Dragon Splashes Down After Historic Test Flight

#78

Post by politician »

politician wrote: post #63
neuronexmachina wrote: post #36

Earlier quoted context omitted.

SpaceX actually showed a mock-up of what point-to-point travel might look like in one of their videos.

The vomit-comet ICBM video? I'm a big fan of SpaceX, but I think they'll get to Mars before governments on Earth allow that concept to happen. Your passengers do multiple g's to altitude, then go weightless, then go back to taking g-forces on descent. That's the vomit part. Not a great customer experience. Meanwhile, the Starship looks like an ICBM to every early warning radar on the planet. It's only during reentry…

Ok, I did some rough math. The W88 has a diameter of 55cm, a length of 175cm, and a blast yield of 475 kilotons. The unpressurized cargo hold of the Starship per Wikipedia is 88m^3, and the diameter of the vehicle is 9m. Let's assume that the unpressurized cargo hold is a cylinder 9m in diameter with a length of 9m.

It looks like a hold of that size could fit 15 units per 200cm length, or 60 units, with space for structural rails and deployment gear. For comparison, that's 7.5x the capacity of the Trident II SLBM which was designed to accommodate 8 W88s.

In terms of potential, one W88 detonated in an airburst would produce a fireball over 1.56 sq km, an air blast to 5psi overpressure over 91.9 sq km, and 3rd degree burns over 233 sq km.

The scale of the human tragedy involved in a first-strike deployment of 60 of these things is too gruesome to write down here, but you can play with it on NukeMap [1] if you're so inclined. Suffice it to say that no sane government on the planet will want Starship to land anywhere nearby unless we're living in a global utopia where this sort of thing is unthinkable.

[1] https://nuclearsecrecy.com/nukemap/

Re: SpaceX Crew Dragon Splashes Down After Historic Test Flight

#80

Post by oh_sigh »

Tuna-Fish wrote: post #7
ChuckMcM wrote: post #4

This is a better article on the recovery than the one I linked from TechCrunch. I would like to reiterate the point made before which is that SpaceX is on the verge of being in a place that no company has ever been before with regard to space. The are on the cusp of having a capsule that they can send into orbit for days and then return to Earth. They already have rockets capable of putting tons of material into ever…

They are unlikely to do this at this point. The big problem is that while the capsule will be reusable, since NASA killed the propulsive landing for Dragon 2, it now needs to splash down in saltwater and therefore is not considered safe for humans after the first use. This makes Dragon 2:s too expensive for large-scale space tourism. Unless there is suddenly a huge market for this, I think SpaceX would prefer to sell…

How big of an area could they splash down in? Could they target Lake Victoria, being the largest freshwater lake near the equator? Obviously, you don't want to miss...
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