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SpaceX to Send Privately Crewed Dragon Spacecraft Beyond the Moon Next Year

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Re: SpaceX to Send Privately Crewed Dragon Spacecraft Beyond the Moon Next Year

#441

Post by rtkwe »

varjag wrote: post #421
kworker wrote: post #414

Earlier quoted context omitted.

If it will be done. Musk isn't great at the "deliver" part, not to mention how dangerous this mission is.

Musk sends partially re-usable rockets into space for a few years now. A decade ago, all he had were some fancy powerpoint slides. We sure have different definitions of "delivering".

We're still not 100% that they're reusable in a meaningful way that actually reduces costs. The landings are awesome but if it costs too much to reuse them it's more a stunt than anything because as good as it is to not just chunk that hunk of metal in the ocean every launch if it's cheaper that's how it'll be done.

Re: SpaceX to Send Privately Crewed Dragon Spacecraft Beyond the Moon Next Year

#442

Post by andrepd »

ChuckMcM wrote: post #161

Wow. This sends so many thoughts cascading through my head that I'm dizzy. Some things to consider, China has been working up to getting a space capability to send people to the Moon with the full backing of the government funding, by 2035[1]. They started in 2003. SpaceX was founded in 2002 and they are saying they will fly someone around the moon next year? Dragon has the deltaV to land on the moon (not sure if it…

> All this time I imagined that some country would establish a base there, and grudgingly offer up some space for non-state use, and now there is this possibility of a private facility that states have to ask permission to visit? That is priceless.

That is scary, and dangerous, more like.

Re: SpaceX to Send Privately Crewed Dragon Spacecraft Beyond the Moon Next Year

#443

Post by vidarh »

nojvek wrote: post #376
Retric wrote: post #331

Earlier quoted context omitted.

Sorry, butchered that. I was trying to say the figures are less exact depending on how hard you want to hit the earths upper atmosphere. ~8.2km/s if you want to end up in earth LEO ~8km/s if you want to get back to the earth. You can also save a little if your sending an unmanned craft and don't care how long it takes or skip low moon orbit.

I wonder if spaceX is going to send a permanent colony of bots on moon to make a base there. The latency is a lot lower than Mars and would make a good start. Sending a couple of humans around moon for tourism is a waste of resources.

> Sending a couple of humans around moon for tourism is a waste of resources.

One persons waste of resources is another persons revenue. They're not doing it for charity.

Re: SpaceX to Send Privately Crewed Dragon Spacecraft Beyond the Moon Next Year

#444

Post by mikeash »

mozumder wrote: post #434
mulmen wrote: post #359

Earlier quoted context omitted.

Exactly the way it was described. People are on board the rocket for the minimal amount of time before launch and not during the most risky operations in order to mitigate the risk of explosion. While the people are on board the rocket there are systems in place to increase their chances of escape, again mitigating the risk. e: I realize you are saying none of this reduces the risk of the rocket exploding but at some…

> Two lost rockets in a year is a lot better than previous years. Uh no.. they're losing MORE rockets now than before, mostly because the rockets are getting bigger and more powerful - and they have the Heavy versions coming. Consider that 2 of their last 13 rockets exploded.. that's not a good track record. Compare that to ULA, which hasn't had an explosion over 100 Atlas/Delta launches.

I don't think either of the explosions were related to the rockets getting bigger or more powerful. The CRS-7 failure would have happened on any version of the Falcon 9. It happened on that particular one because that one happened to have a defective strut. The AMOS-6 explosion happened because of their experiments with supercooled propellants.

Two losses in two years is a lot better than the very early days when they lost their first three Falcon 1s in a row, but worse than the early years of Falcon 9 where the only failure was a single engine out that didn't hurt the primary payload, and is certainly not a good track record overall.

Re: SpaceX to Send Privately Crewed Dragon Spacecraft Beyond the Moon Next Year

#445

Post by Symmetry »

TheArcane wrote: post #401
prewett wrote: post #329

Earlier quoted context omitted.

Depending on how you count, it does. The 747-8 freighter can carry 240k L of fuel [1], and 308k lbs of cargo [2], so 1.3 L/lb. The Falcon Heavy can launch 120k lbs of cargo into low-Earth orbit [3], and according to the grandparent, is carrying 1250k L of fuel (including oxygen, which is an essential component of "fuel" in this case), so 10.4 L/lb. Still, that's better than I expected. And if you want to go to Mars,…

Would it be erreneous to say that no matter how 'green' our industries and power consumption on ground becomes, aviation and space flight would always require carbon based fuel?

If we can make renewable energy cheap enough it'll start making economic sense to synthesize fuel oil out of the air and water rather than mining it out of the ground, leading to no net carbon consumption.

Re: SpaceX to Send Privately Crewed Dragon Spacecraft Beyond the Moon Next Year

#446

Post by varjag »

rtkwe wrote: post #441
varjag wrote: post #421

Earlier quoted context omitted.

Musk sends partially re-usable rockets into space for a few years now. A decade ago, all he had were some fancy powerpoint slides. We sure have different definitions of "delivering".

We're still not 100% that they're reusable in a meaningful way that actually reduces costs. The landings are awesome but if it costs too much to reuse them it's more a stunt than anything because as good as it is to not just chunk that hunk of metal in the ocean every launch if it's cheaper that's how it'll be done.

It's a lot easier to go from a stage that lands to one that has to be ditched than the opposite. Worst case, Musk has the same tech that the rest of the world does, although to me it's clear he has quite an advantage.

Re: SpaceX to Send Privately Crewed Dragon Spacecraft Beyond the Moon Next Year

#447

Post by Symmetry »

gravypod wrote: post #121
beojan wrote: post #82

Earlier quoted context omitted.

There's gravity and a rock on Earth too. Just going up into orbit, then landing back on Earth, is a much better way of testing a Mars landing.

The Earth has a full atmosphere with winds, an expansive array of magnetic and electric fields, and a much much higher gravitational pull then Mars or the moon. About a factor of 10 removed from mars and about a further factor of 10 removed from the moon. You'd obviously need more fuel, and fuel that can burn in a completely different atmosphere then it's intended to run in. It's an invalid test for the kind of usefu…

You're wrong about the gravity. The escape velocity of Mars is 5 km/s, half of Earth's and twice the Moon's. The surface gravity is also .4G which is about half the Earth's and two and a half times the Moons. So they're all a lot closer together than you said.

Re: SpaceX to Send Privately Crewed Dragon Spacecraft Beyond the Moon Next Year

#448

Post by Symmetry »

jobu wrote: post #221
nickik wrote: post #96

Earlier quoted context omitted.

Sure, if you ignore all the other problems. Why not fly to the Venus and test there? Why not on Saturn? The reason is simple, the cost of doing so outweighs the benefits of doing so. Look, its simply almost as expensive to make such a test on the moon, as it is on mars. If mars is your goal, then testing on the moon makes absolutely no sense. People seem to believe that because the moon is closer, it means its much e…

> plus mars gives nice tools to actually land, like an atmosphere. Actually Mars is a pretty difficult place to land. The atmosphere is just thick enough to require heavy heat shields, but too thin for parachutes to be sufficient. Here's a Wired article that talks about some of the issues - https://www.wired.com/2011/11/landing-on-mars/

Even if Mars's atmosphere only kills 90% of your orbital velocity instead of the 99% you'd get on Earth[1] you're still saving a humongous amount of fuel, far more than the mass of the heat shield you have to carry along. If you're designing a new heat shield for each mission then the added complexity might make that not worth while but SpaceX is reusing the same heat shield design they've been testing on Earth so that isn't a concern.

[1] numbers vague guesses

Re: SpaceX to Send Privately Crewed Dragon Spacecraft Beyond the Moon Next Year

#449

Post by Symmetry »

palunon wrote: post #377
nickik wrote: post #184

Earlier quoted context omitted.

You can repeat that as often as you want, that does not make it true. SpaceX clearly did not think that for their mars architecture needed a moon testing step. Mars concepts such as Mars Direct did not include such a step. Unless you have extreme time pressure its much, much, much preferable to test on Earth and Mars, rather then the Moon. Earth because it's by far the cheapest, and it shares a reasonable amount with…

Isn't Earth closer to Mars half a (lunar) month ?

No. The Moon is in orbit around the Earth and both the Earth and Mars are in orbit around the sun. The Moon varies between 360,000 and 400,000 km away and the closest Mars gets to us is 54,600,000 kilometers. Those numbers are a bit of an exaggeration because how much fuel you need is just as important as absolute distance/time to travel and for that you need 4 km/s of delta-v to get from Earth orbit to Moon orbit and 5.7 km/s to get to Mars orbit.

Re: SpaceX to Send Privately Crewed Dragon Spacecraft Beyond the Moon Next Year

#450

Post by mikeash »

kworker wrote: post #414
mrb wrote: post #349

Earlier quoted context omitted.

Except today it will be done at less than 1/10th the cost. So yeah, progress.

If it will be done. Musk isn't great at the "deliver" part, not to mention how dangerous this mission is.

He's pretty good at the "deliver" part, where he has trouble is "on time."
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