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Crew Dragon Docks with ISS

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Re: Crew Dragon Docks with ISS

#161

Post by sandworm101 »

bane wrote: post #15

SpaceX runs basically as a giant R&D program that also happens to accomplish useful things as byproducts of its approach (with the miracle of insurance to cover costs if things get explody). Every flight is data for incremental improvement. If you think of all SpaceX has ever done was try to get to this point, with somewhere around 80 flights on the Falcon 9, but for a variety of mission buyers (NASA, USAF, Commercia…

>> We now have the capability to put up another ISS today, resupply it, and staff it, at a fraction of the cost,

Capacity to put mass into low orbit, but building a multipart space station requires far more than cobbling modules together KSP-style. Shuttle and the Canadarm(s) built the space station. SpaceX doesn't have that construction/manipulation capacity. It doesn't have the spacewalk capacity. To match Shuttle and build another ISS SpaceX would need to send people and cargo on the same flight, something that is certainly physically possible but remains logistically complex. NASA doesn't spend millions training astronauts in that giant swimming pool because they like the water.

Re: Crew Dragon Docks with ISS

#162

Post by helldritch »

gfodor wrote: post #132
toyg wrote: post #72

Earlier quoted context omitted.

The problem of getting to Mars is bigger than “just do more spacey stuff in space” though. There are some massive physical limits, in terms of fuel efficiency, that make it really really hard to get there and come back . That’s the main challenge and I don’t think SpaceX moved us particularly closer on that point. I’m in my forties and I don’t expect to see us on Mars in my lifetime, except on some poetic suicide mis…

Why is coming back particularly challenging? Isn't it by definition easier because Mars is less massive than Earth? It seems like what you're talking about here is a different problem: getting enough resources and manpower to Mars to be able to bootstrap what's needed for return trips. But it seems like that is pretty inductive and just a matter of time once an economically sustainable one-way flow of people and good…

It's also worth mentioning that coming back isn't necessarily a fixed requirement. I would happily live a shorter live on Mars - with the risk overhead of being stranded in the event of a catastrophic failure - for the chance to be one of the first Martian settlers.

Foreign colonists in the Americas (ignoring any political aspect of this) faced disease, starvation and attacks from natives but still colonised America because of a dream they had.

Re: Crew Dragon Docks with ISS

#164

Post by bobwaycott »

jandrese wrote: post #96
elliekelly wrote: post #55

From NASA's Mission Updates: > The Crew Dragon arrived at the station’s Harmony port, docking at 10:16 a.m. EDT while the spacecraft were flying about 262 miles above the northern border of China and Mongolia. It's hard for me to wrap my brain around this. They seem so far away but 262 miles above earth is about the distance from NYC to DC which doesn't seem far at all.

There is a fantastic what if that talks about this. https://what-if.xkcd.com/58/

You’re right. That was fantastic. Hadn’t seen that one before. Thank you.

Re: Crew Dragon Docks with ISS

#165

Post by pbhjpbhj »

hansoolo wrote: post #151

Why is it such a big deal this time? Don't the Russians fly to ISS all the time?

Yes, it seems they do - I assume that the fact all other countries relied on Russia for the last decade to ferry astronauts and cosmonauts to ISS doesn't fit with the narrative of them being the sworn enemy of the West?

Re: Crew Dragon Docks with ISS

#166

Post by cdash »

raverbashing wrote: post #86
calaphos wrote: post #75

Earlier quoted context omitted.

Turns out it is a lot more useful to (potentially) reuse the first stage than to carry a lot of additional weight to reuse the last stage.

Well, but the Shuttle SRBs were reusable. The only non-reusable part was the external fuel tank. But yeah, sending something as big as a bus up and down was probably the bane of it.

If you call rebuilding an engine every time reusable. SRBs and reusable do not go together at all.

Re: Crew Dragon Docks with ISS

#167

Post by pbhjpbhj »

helldritch wrote: post #162
gfodor wrote: post #132

Earlier quoted context omitted.

Why is coming back particularly challenging? Isn't it by definition easier because Mars is less massive than Earth? It seems like what you're talking about here is a different problem: getting enough resources and manpower to Mars to be able to bootstrap what's needed for return trips. But it seems like that is pretty inductive and just a matter of time once an economically sustainable one-way flow of people and good…

It's also worth mentioning that coming back isn't necessarily a fixed requirement. I would happily live a shorter live on Mars - with the risk overhead of being stranded in the event of a catastrophic failure - for the chance to be one of the first Martian settlers. Foreign colonists in the Americas (ignoring any political aspect of this) faced disease, starvation and attacks from natives but still colonised America…

Wasn't it more that trying things in [the continent of] America seemed more likely to yield success than staying with what they had where failure was relatively certain. Like religious persecution at home was certain for the Pilgrim Fathers, but in all likelihood they could form colonies where they could freely practice their religion by risking it in North America. For others it was abject poverty at home, or try carving out a piece of frontier.

Seems like colonising Mars is the other way around, we stand more chance of fulfilment on Earth and failure going to Mars?

Some of us have an explorational spirit, a desire to be pioneers at all costs - isn't that why we want to go? Maybe it's toxoplasmosis.

Re: Crew Dragon Docks with ISS

#168

Post by barbegal »

pfdietz wrote: post #114
7thaccount wrote: post #22

Earlier quoted context omitted.

Incredibly impressive, but you have to take into account both more modern technology, as well as the fact that they were able to build off the shoulders of giants. It is still amazing of course, but I doubt they could've done the same thing during the era of the mercury program, so not really apples to apples comparison.

Guidance systems are vastly less expensive now, and can take advantage of things like MEMs, fiber laser gyros, and GPS (and, of course, modern computing power). The tanks on Falcon are welded using Friction Stir Welding, which was invented in the early 1990s. The landing algorithm for the first stage uses convex optimization algorithms based on interior point methods, which were not available in the 1960s. However, s…

> The landing algorithm for the first stage uses convex optimization algorithms based on interior point methods, which were not available in the 1960s.

Is this level of optimisation really needed? I thought most of the landing was having enough fuel margin and then running a PID control algorithm during the landing burn.

Re: Crew Dragon Docks with ISS

#169

Post by 725686 »

jes wrote: post #122
pfdietz wrote: post #114

Earlier quoted context omitted.

Guidance systems are vastly less expensive now, and can take advantage of things like MEMs, fiber laser gyros, and GPS (and, of course, modern computing power). The tanks on Falcon are welded using Friction Stir Welding, which was invented in the early 1990s. The landing algorithm for the first stage uses convex optimization algorithms based on interior point methods, which were not available in the 1960s. However, s…

I had not heard of Friction Stir Welding previously. Video that demonstrates the technique is here: https://www.youtube.com/watch?v=aNbQH8XBgxQ

Smarter Every Day has a very interesting video[1] inside the factory of United Launch Alliance in which, among a lot of other things, shows the friction stir welding used in their Atlas Rocket[2]:

[1] https://youtu.be/o0fG_lnVhHw

[2] https://youtu.be/o0fG_lnVhHw?t=1933

Re: Crew Dragon Docks with ISS

#170

Post by chipsa »

paulryanrogers wrote: post #101
trixie_ wrote: post #90

Earlier quoted context omitted.

Maybe not during Mercury, but definitely during the 70s all the technology was there to build a cheap, reusable rocket and capsule. The dream was that the shuttle could be that system, but it did not turn out that way. And giving in to the 'sunk cost fallacy' they supported the shuttle for the next 40 years. Arguably you could say we are 50 years behind where we should be. Unfortunately driving down costs is probably…

Didn't Space X also benefit from NASA launch facilities? I imagine their payroll also includes quite a few NASA trained people too. They certainly aren't doing rocket science from scratch or in a vacuum. Not too say this isn't a big deal. Just that it's not all Elon and his wunderkind.

SpaceX leases the launch pad and Eastern Range, but those are paid either on a yearly basis, or per use. The NASA/DoD personnel that support the launch are getting paid whether there's a launch or not, because they're needed for any launch from the Cape.
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