I hope its Donald Trump
SpaceX to Send Privately Crewed Dragon Spacecraft Beyond the Moon Next Year
321–330 of 513 posts
Re: SpaceX to Send Privately Crewed Dragon Spacecraft Beyond the Moon Next Year
#322Earlier quoted context omitted.
Right. SpaceX doesn't have a craft capable of lunar orbit rendezvous https://en.wikipedia.org/wiki/Lunar_orbit_rendezvous so they would need to return to the Earth directly from the surface of the moon https://en.wikipedia.org/wiki/Direct_ascent Direct ascent requires a much larger initial launch mass, i.e., a larger rocket than has ever been built. Since it took the massive Saturn V to complete the Apollo missions u…
SpaceX is already docking with the space station which is similar difficulty as launching from the moon and docking in lunar orbit. The problem is getting a rocket with enough fuel on the surface of the moon without damaging it, not the docking in orbit. Which is even easier than doing the same thing from the surface of Mars. The only advantage of Mars is you don't need to burn fuel slowing down but that's more than…
I don't think either of us know much about this, but I do know that docking with the ISS to unload supplies requires completely different equipment than doing a rendezvous between a lunar lander and a lunar orbiter for Earth return. (That's why I didn't say merely "docking".)
The only craft SpaceX has that can land on Earth or the Moon is Dragon. I am pretty sure Dragon does not have enough delta-v to do a full propulsive landing on the moon (no aerobraking available) and then return to orbit. And they definitely don't have the tech to re-fuel in lunar orbit for the return to Earth. None of this equipment exists.
Not to mention that this would be a totally new lunar strategy, since the Apollo mission returned to earth in the lunar orbiter (Command Module) rather than re-fueling and returning in the lunar lander.
Re: SpaceX to Send Privately Crewed Dragon Spacecraft Beyond the Moon Next Year
#323Earlier 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/
Still, you can get rid of most of the velocity for a Mars landing using aerobraking alone. To land on the Moon you'll be bringing all of that delta-V with you as fuel. Landing a Dragon on Mars already takes a lot of propellant: https://youtu.be/ZoSKHzziLKw
Re: SpaceX to Send Privately Crewed Dragon Spacecraft Beyond the Moon Next Year
#324> This presents an opportunity for humans to return to deep space for the first time in 45 years and they will travel faster and further into the Solar System than any before them.
Shocking that it's been this long. There is an entire generation that hasn't seen man make it into deep space.
Re: SpaceX to Send Privately Crewed Dragon Spacecraft Beyond the Moon Next Year
#325Earlier quoted context omitted.
>Except that these two private citizens are presumably absurdly wealthy. Whereas the nationalize space program which brought forth the Apollo mission gave all private citizens, as well as schoolchildren for generations, hope and aspirational outlooks. I doubt it's any more difficult to get absurdly wealthy than to become an astronaut.
I'm sure they only sell you a ticket if you pulled yourself up out of the slums by your own bootstraps. No old money allowed.
What's your point?
Re: SpaceX to Send Privately Crewed Dragon Spacecraft Beyond the Moon Next Year
#326Earlier quoted context omitted.
SpaceX is already docking with the space station which is similar difficulty as launching from the moon and docking in lunar orbit. The problem is getting a rocket with enough fuel on the surface of the moon without damaging it, not the docking in orbit. Which is even easier than doing the same thing from the surface of Mars. The only advantage of Mars is you don't need to burn fuel slowing down but that's more than…
I don't think either of us know much about this, but I do know that docking with the ISS to unload supplies requires completely different equipment than doing a rendezvous between a lunar lander and a lunar orbiter for Earth return. (That's why I didn't say merely "docking".) The only craft SpaceX has that can land on Earth or the Moon is Dragon. I am pretty sure Dragon does not have enough delta-v to do a full propu…
Yea, I am not a rocket guy.
However, the minimum delta V to land on the moon is ~1.72 km/s, and you need another 1.72 km/s to get back into orbit + some safety factor ~2.2-2.4 km/s. By comparison it takes ~8km/s to get from LEO to low moon orbit and back to earth. Though you can reduce this by how hard to hit the earth's atmosphere. So, having fuel to land and take off from the moon is not that much worse than getting to the moon and back.
Re: SpaceX to Send Privately Crewed Dragon Spacecraft Beyond the Moon Next Year
#327Re: SpaceX to Send Privately Crewed Dragon Spacecraft Beyond the Moon Next Year
#328Earlier quoted context omitted.
I don't think either of us know much about this, but I do know that docking with the ISS to unload supplies requires completely different equipment than doing a rendezvous between a lunar lander and a lunar orbiter for Earth return. (That's why I didn't say merely "docking".) The only craft SpaceX has that can land on Earth or the Moon is Dragon. I am pretty sure Dragon does not have enough delta-v to do a full propu…
Yea, I am not a rocket guy. However, the minimum delta V to land on the moon is ~1.72 km/s, and you need another 1.72 km/s to get back into orbit + some safety factor ~2.2-2.4 km/s. By comparison it takes ~8km/s to get from LEO to low moon orbit and back to earth. Though you can reduce this by how hard to hit the earth's atmosphere. So, having fuel to land and take off from the moon is not that much worse than gettin…
> By comparison it takes ~8km/s to get from Earth LEO to Moon LEO
No, from Earth LEO some 3.1 km/s will get you to TLO, and then some ~1 km/s will take you to Moon low orbit, so total about 4(+) km/s. 8 km/s is an approximate budget for a round-trip between low orbits.
Re: SpaceX to Send Privately Crewed Dragon Spacecraft Beyond the Moon Next Year
#329Earlier quoted context omitted.
That is a really surprising comparison, thanks for pointing it out! Do you have a source for that, it is something I expect to be repeating.
I agree. For some reason I imagined that orbital-capable rockets use order(s) of magnitude more fuel than airliners...
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, you can take 30k lbs, so 41.7 L/lb, for only 4X LEO, quite the bargain!
(Interestingly, the average cost of a 10 hr 747 flight is about $40k [about $14k for fuel, which is about 33% of costs], compared to $90m [estimated] for a Falcon Heavy launch. So one order of magnitude more fuel, but almost 4 orders of magnitude more price.)
[1] https://www.reference.com/vehicles/much-747-weigh-8b0c48a1d8... [2] https://en.wikipedia.org/wiki/Boeing_747-8 [3] https://en.wikipedia.org/wiki/Falcon_Heavy [4] https://www.quora.com/How-much-fuel-does-a-Boeing-747-or-777... [5] https://www.quora.com/How-much-of-the-cost-of-an-airline-tic...
Re: SpaceX to Send Privately Crewed Dragon Spacecraft Beyond the Moon Next Year
#330Absolutely incredible. This will be the furthest that humanity has journeyed away from Earth in a very long time. However it is worth noting that there hasn't been a single crewed Dragon flight yet. There are demonstator flights scheduled for this year though with the first NASA crewed mission slated for May 2018. That's an incredibly aggressive timeline but if anyone can achieve it, SpaceX can. The long duration fli…
They've already had Dragon flights where they've said "if there were humans aboard, they'd have been just fine", i.e. the Dragon's life-support capabilities have been tested. You don't have to have flown humans to test whether you can fly humans, you know you were able to maintain a breathable atmosphere, and you know you have enough fuel to launch a few hundred kilos of meatbags, food & water.
Note also that SpaceX is going to start flying cargo in a derived-from-Crew-Dragon Dragon, so they'll have more experience with the changes in Crew Dragon, and can practice propulsive landings on Earth for cargo before trying it for crew.