Someone has probably already asked this but I wouldn't know how to find it: How short could you plausibly make the full-diameter BFR? Im just thinking a lot shorter and symmetrically remove some engines.
Yes, if you could make it wide but short for a Mini-BFR with say 9 Raptors, then stretch the tanks and add the remaining engines for a full BFR. Same with a second stage, one Raptor and a short reusable stage, then stretch with more engines for an MCT or tanker. I would say at least 10-12m in diameter. 3.7m tankage could be made at Hawthorn to fit inside the upper stage with remaining space on a stretched MCT version for cargo or crew.
The only way I could see this being worthwhile is if it used almost all the same major components from the ITS spaceship.
convert the thrust structure to hold 21 Raptors
Quote from: envy887 on 10/03/2016 04:52 pmThe only way I could see this being worthwhile is if it used almost all the same major components from the ITS spaceship.Well that is the idea. Essentially the propulsion section of ITS (second stage) starts life as the first stage of smaller beast.Same tanks, same engines, same handling and transport systems.Quote from: envy887 on 10/03/2016 04:52 pmconvert the thrust structure to hold 21 Raptors21?
21 SL Raptors is based on the idea that the second stage is the same as the ITS ship. The total GTOW would be about 4500 tonnes, so at least 20 Raptors are needed. 21 packs a little better.I don't see the point of wasting resources making a smaller dedicated second stage. Just put the big ITS upper stage on top and stage lower. As long as the booster gets it up 30 km they can light the Raptor vacs.
It doesn't sound like everyone is on the same page as SpaceX. They intend to build and sub-orbitally test the Ship first. Once that's accomplished there will be time for them to decide whether going for the final Booster design, or building a shorter "Booster Block 0" makes more sense.
Quote from: sdsds on 10/09/2016 06:55 amThey intend to build and sub-orbitally test the Ship first.Does ship mean upper stage? Where can I read about this?
They intend to build and sub-orbitally test the Ship first.
Quote from: KelvinZero on 10/09/2016 07:33 amQuote from: sdsds on 10/09/2016 06:55 amThey intend to build and sub-orbitally test the Ship first.Does ship mean upper stage? Where can I read about this?Well yes it would mean that, if it were a standard launch system. It's an upper stage of a launch vehicle, a trans-planetary habitat, a planetary lander, and a single-stage-to-orbit (from Mars at least) ascent vehicle. You can hear more about it in ... the speech Musk gave announcing the ITS. Look particularly at the timeline graphic which shows which systems are developed when....
Quote from: sdsds on 10/09/2016 08:02 amQuote from: KelvinZero on 10/09/2016 07:33 amQuote from: sdsds on 10/09/2016 06:55 amThey intend to build and sub-orbitally test the Ship first.Does ship mean upper stage? Where can I read about this?Well yes it would mean that, if it were a standard launch system. It's an upper stage of a launch vehicle, a trans-planetary habitat, a planetary lander, and a single-stage-to-orbit (from Mars at least) ascent vehicle. You can hear more about it in ... the speech Musk gave announcing the ITS. Look particularly at the timeline graphic which shows which systems are developed when....I just meant the top bit (as distinguished from the bottom bit) Ok, I found the timeline inside the speech.https://www.youtube.com/watch?v=IFA6DLT1jBA?t=3157It is saying top bit first, possibly in 4 years, mentions vague possibility of suborbital flights as a service as well as for testing. Mentions possibility of at least tanker being single stage to orbit.I didn't see mention of a shorter block 0. Were you just referring to what is being discussed on this thread?I had been discounting the SSTO, especially due to the mention of not being able to bring it down, but I guess there is one reasonable use if you can just get the non-tanker version to orbit: You could avoid developing the tanker or booster at all until flight rate is high. Instead you launch SSTO with no cargo and use many launches of you F9R to refuel it. You could also use F9R to get 6 crew to orbit, plenty for an early mission. Maybe the safety would be the most important factor. The booster does sound pretty simple once you have the space ship and the F9R very likely would still not be fully reusable.
What kind of performance would you get out of a 9+1 Raptor, 12m diameter, TSTO launcher?
I didn't see mention of a shorter block 0. Were you just referring to what is being discussed on this thread?
Yes, someone should think about a refuelable SSTO excursion vehicle for interplanetary missions.
But what if the first Ship they build doesn't have quite the performance capability they currently say the final version will have? Wouldn't it then be interesting to supplement its capabilities with a minimalist, reusable version of the Booster? That would allow them to fly fully reusable missions to Earth-orbit....
It seems so sensible, if you assume 2 stage with SSTO just a nice-to-have. I wonder if the shuttle could have been this.
That's what should be striking about SpaceX's architecture. Nothing is particularly technically questionable except the raw scale and performance.
Quote from: KelvinZero on 10/10/2016 08:21 amI wonder if the shuttle could have been this.Shuttle didn't have the materials and manufacturing technology that make insane engine performance and mass fractions possible.
I wonder if the shuttle could have been this.
Quote from: KelvinZero on 10/10/2016 08:21 amIt seems so sensible, if you assume 2 stage with SSTO just a nice-to-have. I wonder if the shuttle could have been this.Shuttle didn't have the materials and manufacturing technology that make insane engine performance and mass fractions possible. The key to ITS is the Raptor engine, composite tanks, and lightweight heatshield.
Quote from: KelvinZero on 10/09/2016 12:25 pmI didn't see mention of a shorter block 0. Were you just referring to what is being discussed on this thread?Yes, I should have been clearer on that. Neither the "block 0" terminology nor the concept come from anything SpaceX has said. It's only a thought experiment!But what if the first Ship they build doesn't have quite the performance capability they currently say the final version will have? Wouldn't it then be interesting to supplement its capabilities with a minimalist, reusable version of the Booster? That would allow them to fly fully reusable missions to Earth-orbit....Then they could develop and fly a Tanker to validate their plan for on-orbit "refilling."
the Ship is first on the timeline because out of the two parts it will need the most testing
Quote from: envy887 on 10/10/2016 01:04 pmQuote from: KelvinZero on 10/10/2016 08:21 amIt seems so sensible, if you assume 2 stage with SSTO just a nice-to-have. I wonder if the shuttle could have been this.Shuttle didn't have the materials and manufacturing technology that make insane engine performance and mass fractions possible. The key to ITS is the Raptor engine, composite tanks, and lightweight heatshield.I probably shouldn't drag this to a shuttle debate, although this does sort of look like a shuttle replacement rather than a FH replacement......but my point was that the insane performance claims are not that important. For a SSTO, sure, but im talking about a conventional TSTO. The design just seems to have insane margins. I don't care about 500 tons to orbit. The shuttle only did about 30 and didn't weigh that different. You can evolve this. If you eke more performance out of the rockets later, great. If power doesn't match your requirements you can stretch the booster a bit, add some more engines. You really want more cross range? You could consider a winged version later like dreamchaser and stretch your booster again or lower your cargo. You are not trapped.To me the shuttle just looks so so complicated. So difficult. Two solids in balance with the shuttle main engine. Maximum surface area shared between solids and hydrogen tank and wings so that if anything goes wrong with one of them it is bound to hit one of the others.I know I am just an arm chair rocket scientist but a TSTO just seems so much more straightforward that it should also be cheaper to develop.. and be fully reusable. Or at least you can land it and consider reuse.
Minor aside:"Full diameter shorted ITS as FH replacement?"Can the thread creator or a suitably empowered mod change the thread name to "shortened"? It makes my eye twitch every time I see it.
21 means just dropping the outer ring of engines of ITS booster. More compatibility with it.In ITS booster there is 1 center engine, 6 other around it. And 14 on the next ring. This makes 21.
Although, by the standards of the day, everything about the Shuttle was insane, so far beyond the state of the art. A 130 tonne to LEO spaceplane? Having never developed an orbital spaceplane before? With no preliminary versions? Crewed on its first launch? On a declining budget and shrinking workforce? Ouch. That's what made it so expensive and fragile.(And why SDLV's (from Shuttle-C to SLS) were always such a dumb idea. If they'd started with Shuttle-C and then added a crew component... mmmaybe. But going the other way? No.)
On a declining budget and shrinking workforce? Ouch. That's what made it so expensive and fragile(And why SDLV's (from Shuttle-C to SLS) were always such a dumb idea. If they'd started with Shuttle-C and then added a crew component... mmmaybe. But going the other way? No.)
the military wouldn't have diluted it with insane cross range requirements,
Integrating the second stage propellant tanks and spacecraft would have the been the natural choice then and a big first stage instead of the SRBs as well as hydrocarbons instead of LH2 too.
And everybody stop talking as though ITS is a given. A reusable first stage has yet to fly. And even if it does, 1, 2 or 3 times stills doesn't prove the effort.
Quote from: Jim on 10/17/2016 06:27 pmAnd everybody stop talking as though ITS is a given. A reusable first stage has yet to fly. And even if it does, 1, 2 or 3 times stills doesn't prove the effort.New Shepard.
It is not that ITS has to be fake either. That could be the honestly intended end point, but what happens in between exactly? I just keep expecting something to pop out and fill in the "underpants" stage, even if it is a bit smaller than advertised.
Quote from: KelvinZero on 10/19/2016 02:40 amIt is not that ITS has to be fake either. That could be the honestly intended end point, but what happens in between exactly? I just keep expecting something to pop out and fill in the "underpants" stage, even if it is a bit smaller than advertised. The timeframe given is much too short for a useful fake. It could be a trick if the timeframe for first hardware would be 2025 or beyond. But the timeframe is real hardware before the end of this decade and we are near the end of 2016.
Maybe [a shortened first stage] is the sort of intermediate step [...] that could also serve some launch market