Quote from: AncientU on 07/04/2018 07:20 pm*Note: For calibration, the BFS is approximately the size and double wet mass of the SLS core stage with approaching double the propulsive thrust. This is a B-I-G F'n Spaceship.https://www.nasa.gov/sites/default/files/thumbnails/image/core_stage_infographic_reboot.jpgIn all the discussions of refueling I haven't seen an estimate of how may BFS tankers it takes to refuel an empty BFS in LEO. Is it 150 tons of fuel per tanker? How many does it take?
*Note: For calibration, the BFS is approximately the size and double wet mass of the SLS core stage with approaching double the propulsive thrust. This is a B-I-G F'n Spaceship.https://www.nasa.gov/sites/default/files/thumbnails/image/core_stage_infographic_reboot.jpg
Quote from: marsbase on 07/04/2018 08:49 pmIn all the discussions of refueling I haven't seen an estimate of how may BFS tankers it takes to refuel an empty BFS in LEO. Is it 150 tons of fuel per tanker? How many does it take?Sorry for the error above; corrected in original post. (Should be 130% the wet mass of SLS core stage, not double.) The IAC 2017 presentation mentioned 4-5 tankers, I believe... something around 200-250t per tanker.
In all the discussions of refueling I haven't seen an estimate of how may BFS tankers it takes to refuel an empty BFS in LEO. Is it 150 tons of fuel per tanker? How many does it take?
Quote from: AncientU on 07/04/2018 09:03 pmQuote from: marsbase on 07/04/2018 08:49 pmIn all the discussions of refueling I haven't seen an estimate of how may BFS tankers it takes to refuel an empty BFS in LEO. Is it 150 tons of fuel per tanker? How many does it take?Sorry for the error above; corrected in original post. (Should be 130% the wet mass of SLS core stage, not double.) The IAC 2017 presentation mentioned 4-5 tankers, I believe... something around 200-250t per tanker.It is possible they won't make tanker variants for some considerable time.See this thread on tankers.In short - if the BFS is actually readily reusable, and the tanker costs around the same to make, but its only benefit is to save 20% on launch cost, you need to have quite a lot of launches to justify it.
Quote from: marsbase on 07/04/2018 08:49 pmIn all the discussions of refueling I haven't seen an estimate of how may BFS tankers it takes to refuel an empty BFS in LEO. Is it 150 tons of fuel per tanker? How many does it take?... The IAC 2017 presentation mentioned 4-5 tankers, I believe... something around 200-250t per tanker...
<snip my comment>On your point of having tanker versions... there will likely be tankers in time to support the second Mars visit where four BFSs (two cargo, two crew) are planned. Main advantage is that tankers will fly much more often than any other version and will be the least expensive BFS configuration -- just a flying tank. If you are going to wear something out, might as well be the cheapest version. The 20% or whatever more fuel per trip also minimizes wear and tear -- which will become a consideration as launch frequency climbs.
There might be issues with even getting near the surface. Exhaust gas velocities are well above orbital speeds so a landing anywhere will contaminate the entire moon with fast dust particles. There was a great post by a post-Apollo researcher recently about an instrument returned by an Apollo mission. They were told to look for a white box but when they found it it was brown. Years later they found out that millions of dust particles had lodged themselves into the paint after flying around the moon for a bit.
New internal view of BFS with huge windows.
Quote from: Robotbeat on 07/05/2018 01:21 pmNew internal view of BFS with huge windows.I can't make the scale work for a BFS, unless perhaps she's three feet tall.Even if you make the whole top half of the upper BFS glass.
I’m sure it was posted on a thread SOMEwhere, but can’t find it.
Uh, I don't think there will be real windows. Too heavy and a safety risk. The view outside will be projected onto a thin film screen. And of course the violinist could be a superimposed projection as well. CGI or real. The point is to distract the colonists from the existential danger of the propellant refueling going on under their feet. Or above their feet. Oh, you know what I mean.
Quote from: speedevil on 07/05/2018 02:51 pmQuote from: Robotbeat on 07/05/2018 01:21 pmNew internal view of BFS with huge windows.I can't make the scale work for a BFS, unless perhaps she's three feet tall.Even if you make the whole top half of the upper BFS glass.I can't work out how she'd remain in the correct orientation to the audience, is the dress fitted with a RCS?
Uh, I don't think there will be real windows. Too heavy and a safety risk.
Quote from: marsbase on 07/05/2018 03:11 pmUh, I don't think there will be real windows. Too heavy and a safety risk. I guess you've never heard of transparent aluminium?
Quote from: marsbase on 07/05/2018 03:11 pmUh, I don't think there will be real windows. Too heavy and a safety risk. I guess you've never heard of transparent aluminium?And no, I don't mean the stuff Scotty mentioned on Star Trek IV.See here: https://en.wikipedia.org/wiki/Aluminium_oxynitrideAnd here: https://hackaday.com/2018/04/03/whats-the-deal-with-transparent-aluminum/Actual windows on BFS, made from Aluminium_oxynitride, could very well work and would be lighter than windows made from fused silica (aka glass).