Author Topic: SpaceX tanker variant  (Read 38338 times)

Offline biosehnsucht

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Re: SpaceX tanker variant
« Reply #100 on: 11/29/2017 07:37 am »
If it wasn't coming back you could probably not install the sea level raptors used for landing in the first place. If that drops needed thrust to make orbit with full tanks somehow, just decrease fuel level until it makes it to orbit and top it off with regular tankers.

Probably not worth the effort until there are a LOT of flights going on.

Would a SL-less BFS have enough power to land and take off from the Moon at least? You could do limited servicing there.

Offline philw1776

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Re: SpaceX tanker variant
« Reply #101 on: 11/29/2017 12:59 pm »
Yes.  Plenty of thrust for lunar landing & takeoff.  Throttled down.
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Online guckyfan

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Re: SpaceX tanker variant
« Reply #102 on: 11/29/2017 03:04 pm »
With SL engines close to the center landing will be easier, especially dealing with engine out.

Offline Ludus

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Re: SpaceX tanker variant
« Reply #103 on: 11/29/2017 03:25 pm »

Question. Speaking of customizing a tanker for on orbit and deep space missions, would this customized tanker need to carry the mass of all of the engines? That is, once on orbit, would any significant mission capability be added by removing, say, six of the raptors?

No. The engines weight only few tonnes, but removing them would worsen gravity losses considerably.
I  believe this was an on orbit modification, and this vessel then would never return to a gravity well but instead stay in orbit. So gravity losses might not apply, although maybe I am confused?

If I’m following this, the variant I was talking about was a BFS built on earth with propellant tanks completely filling its volume rather than the large cargo space left over. It could launch only with those extended tanks partially filled. It might however have utility as a fuel depot/deep space Booster.

My notion was this would be an otherwise standard BFS with bigger tanks. I took the question about removing engines to be asking could it launch successfully and operate as an in space Booster if you left some engines off considering it wouldn’t land on earth again. I’m not sure what’s meant by gravity losses unless that’s assuming all the engines would be removed? I guess “propellant depot” sort of suggests it might have no engines but that’s not compatible with using it as a Booster too.

It’s really more about function than any modification to the BFS. Assigning a BFS to the specialized function of collecting propellant from the Tanker flights so it can load it in one go to a mission. The same BFS could also dock nose to tail with a mission BFS and act as a Booster. A BFS that happened to be modified so it’s entire OML was occupied by propellant tanks would work better in this function. Unlike a Tanker it would remain in space rather than landing and repeatedly launching. Maybe it could get along without some of the ordinary BFS hardware.

Online aero

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Re: SpaceX tanker variant
« Reply #104 on: 11/29/2017 04:35 pm »

Question. Speaking of customizing a tanker for on orbit and deep space missions, would this customized tanker need to carry the mass of all of the engines? That is, once on orbit, would any significant mission capability be added by removing, say, six of the raptors?

No. The engines weight only few tonnes, but removing them would worsen gravity losses considerably.
I  believe this was an on orbit modification, and this vessel then would never return to a gravity well but instead stay in orbit. So gravity losses might not apply, although maybe I am confused?

If I’m following this, the variant I was talking about was a BFS built on earth with propellant tanks completely filling its volume rather than the large cargo space left over. It could launch only with those extended tanks partially filled. It might however have utility as a fuel depot/deep space Booster.

My notion was this would be an otherwise standard BFS with bigger tanks. I took the question about removing engines to be asking could it launch successfully and operate as an in space Booster if you left some engines off considering it wouldn’t land on earth again. I’m not sure what’s meant by gravity losses unless that’s assuming all the engines would be removed? I guess “propellant depot” sort of suggests it might have no engines but that’s not compatible with using it as a Booster too.

It’s really more about function than any modification to the BFS. Assigning a BFS to the specialized function of collecting propellant from the Tanker flights so it can load it in one go to a mission. The same BFS could also dock nose to tail with a mission BFS and act as a Booster. A BFS that happened to be modified so it’s entire OML was occupied by propellant tanks would work better in this function. Unlike a Tanker it would remain in space rather than landing and repeatedly launching. Maybe it could get along without some of the ordinary BFS hardware.

My question had to do with removing some engines after reaching orbit. I doubt the ship could safely reach orbit with some engines removed but that is a different question. As for landing legs, those could be removed before the launch of course. There may be other massive items that could be removed before launch or after reaching orbit. What they are and how massive they are is still a different question. The point of my questions is to what extent could the mission capabilities as you gave them be increased by removing unneeded mass either before or after the modified BFS reaches orbit. Perhaps the "thrust structure" could be replaced with a less massive structure if engines are removed?
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