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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

#361

Post by mulmen »

ctdonath wrote: post #135
Udik wrote: post #13

So, hmm, we wants to send people around the moon, a year and a half from now, with a rocket he never tested and with a capsule that never flew? I expect half of the directors of SpaceX to resign in the next two days...

Musk's #1 goal from the beginning is to put a lot of people on Mars, and do it in a rather short time (per human-history scale). We're talking a guy who literally invented PayPal just to make enough money to really get the project started. His other endeavors are as well, while laudable in their own right, really just ways of accumulating the resources to achieve that goal.

Musk did not invent PayPal. He founded x.com which merged with PayPal two years after PayPal was founded.

He has also been clear that he had three goals:

1) Expanding solar power use.

2) Popularizing electric vehicles.

3) Making human life multi-planetary.

I am paraphrasing and perhaps understating his desired level of success.

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

#362

Post by jboggan »

matthewmcg wrote: post #242
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…

I certainly hope they allow permission for any emergency landings required at Clavius...could create a bit of a diplomatic row if not.

Nasty flu this time of year, or so I've heard.

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

#363

Post by cptskippy »

avmich wrote: post #328
Retric wrote: post #326

Earlier quoted context omitted.

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.

So is it possible for them to launch multiple vehicles into Earth LEO, rendezvous with one another and then transfer to Moon LEO?

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

#364

Post by chatterbeak »

solidr53 wrote: post #41
runesoerensen wrote: post #5

> We are excited to announce that SpaceX has been approached to fly two private citizens on a trip around the moon late next year. They have already paid a significant deposit to do a moon mission. Can't wait to hear who booked this trip! Definitely one of the coolest ways to spend a lot of superfluous money :)

Same! I also think that spending money on a roundtrip to the moon is way better for humanity than spending it on champagne, caviar and cars.

Quite a few jobs are created by demand for champagne, caviar, and cars. And also jobs with living wages for farmers, fishermen, production line workers, drivers, and even engineers. While I'm all for space exploration, I wouldn't make any judgement calls on what activities are "better" for humanity.

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

#365

Post by cptskippy »

strmpnk wrote: post #296
skookumchuck wrote: post #286

Earlier quoted context omitted.

Jet fighters routinely use so much fuel taking off that the first thing they do after gaining altitude is refuel. Rockets can use the same idea.

This is partly because they don't always take off with full tanks which allows for shorter runways and/or safer takeoff. Depending on the ordinance that a jet may have to carry, it starts making more sense to stay a bit lighter until a minimum airspeed is achieved. The idea of docking modular components in space is a good one though. Perhaps all you really need to do is lift a bunch of fuel tanks since there is plent…

The SR71 literally leaked fuel until it reached operating temperature. It had something crazy like 2 minutes to rendevous with a tanker after takeoff.

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

#366

Post by NickNameNick »

skookumchuck wrote: post #355
ChuckMcM wrote: post #294

Earlier quoted context omitted.

Yes but as the ULA whitepaper pointed out there are some challenges to doing so in orbit. For one, the lack of gravity makes it hard to pump fuel. You can spin the tanker to achieve fuel settling but now you are both spinning bodies. Then there is handling cryogenic propellants in space, you get nominal bleed off from warming and again ULA had a really interesting design of an internal combustion engine using the ble…

> the lack of gravity makes it hard to pump fuel Evidently this problem is solved, because liquid fuel rockets have been working fine in space since the 60s. (Liquid fuel rockets have their propellants pumped into the chamber.) > nominal bleed off from warming Launch the tanker just beforehand. There won't be time for the fuel to bleed off.

Liquid fuel rockets use Surface tension against the slosh baffles to hold fuel in partially full fuel tanks in place.

Ullage motors are used to settle the fuel at the bottom of the tanks, so the main motor pumps can get to it.

Once the main motor starts providing acceleration, the ullage motors are no longer required.

For cross tanking, keeping the ullage motors running for long enough to transfer all the fuel, without the main motors running might be prohibitive.

https://en.wikipedia.org/wiki/Ullage_motor

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

#367

Post by mulmen »

ChuckMcM wrote: post #294
skookumchuck wrote: post #286

Earlier quoted context omitted.

Jet fighters routinely use so much fuel taking off that the first thing they do after gaining altitude is refuel. Rockets can use the same idea.

Yes but as the ULA whitepaper pointed out there are some challenges to doing so in orbit. For one, the lack of gravity makes it hard to pump fuel. You can spin the tanker to achieve fuel settling but now you are both spinning bodies. Then there is handling cryogenic propellants in space, you get nominal bleed off from warming and again ULA had a really interesting design of an internal combustion engine using the ble…

Do the fuels have to remain in a cryogenic state in space? Can much larger containers with warmer fuel be used once the fuel is in orbit? I have no idea if this makes any sense.

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

#368

Post by pheldagryph »

yellowapple wrote: post #275
ChuckMcM wrote: post #270

Earlier quoted context omitted.

I believe this (mating tanks given multiple missions) is what they were considering. Imagine you have your reusable falcon 9 boost into orbit a 'fuel only' second stage. Land the first stage, put another one on it, and send it up again. Once you have your 'boost pack' up in orbit, presumably docking with each other into a single unit, you launch your crew which attaches to the 'tug' that takes them to the moon. ULA h…

This can be applied to much more than just fuel, mind you. Interplanetary manned vehicles might very well end up looking like space stations, with a bunch of modules docked together in order to provide the necessary creature comforts to sustain a crew for months on end. In fact, a permanently-in-orbit transfer vehicle might make sense here; have this vehicle run the actual Earth Mars transfers, then just shuttle in f…

> a permanently-in-orbit transfer vehicle might make sense here

Buzz Aldrin is a big proponent of this approach: https://buzzaldrin.com/space-vision/rocket_science/aldrin-ma...

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

#369

Post by lucaspiller »

TeMPOraL wrote: post #298
maxerickson wrote: post #272

Earlier quoted context omitted.

Historically rocket research has been funded to develop the capability to deliver bombs.

Which seems to imply that military spending is pretty beneficial for humanity as long as it's spent on researching new cool ways of killing each other, and not on actually using them .

Military spending in WWII led to the invention or development of (to name a few) penicillin, radio navigation, synthetic oil and rubber, jet engines, nuclear power and computers. However some of these were pretty close to being invented even before the war, so it's hard to say how much the war progressed technology.

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

#370

Post by skookumchuck »

NickNameNick wrote: post #366
skookumchuck wrote: post #355

Earlier quoted context omitted.

> the lack of gravity makes it hard to pump fuel Evidently this problem is solved, because liquid fuel rockets have been working fine in space since the 60s. (Liquid fuel rockets have their propellants pumped into the chamber.) > nominal bleed off from warming Launch the tanker just beforehand. There won't be time for the fuel to bleed off.

Liquid fuel rockets use Surface tension against the slosh baffles to hold fuel in partially full fuel tanks in place. Ullage motors are used to settle the fuel at the bottom of the tanks, so the main motor pumps can get to it. Once the main motor starts providing acceleration, the ullage motors are no longer required. For cross tanking, keeping the ullage motors running for long enough to transfer all the fuel, witho…

I didn't know about ullage motors, thanks for the link. The link also says that only very tiny accelerations are needed - so this shouldn't be a big problem for a tanker. Like I hypothesized, the problem has been solved.
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