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SpaceX Vehicles and Missions => SpaceX Super Heavy/Starship (BFR/BFS) - Earth to Deep Space => Topic started by: KelvinZero on 10/03/2016 11:55 am

Title: Full diameter shortened ITS as FH replacement?
Post by: KelvinZero on 10/03/2016 11:55 am
This is a spin off of the SFR (mini-BFR) as fully reusable Falcon Heavy replacement (http://forum.nasaspaceflight.com/index.php?topic=36508.msg1564590#msg1564590) thread.

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.

I can't shake this idea. Now we have exact ITS numbers to deal with.

Im sure you would lose some efficiency; there is a reason rockets are tall and thin, but the Shuttle suggests it is not the only design consideration.

You would be testing so much of the final ITS. By past history im not sure I want to ride on any SpaceX rocket until they have blown up at least two of them  8) .

It could be simpler and cheaper than the FH: probably a bit more fuel but many less components. It would have huge volume advantages over the FH. Even without the Mars colonisation goal you would be developing a BFR of very adaptable performance without going back to the drawing board. No need for crossfeed. With half the number of engines, but still about as many as the FH, you still have redundancy but even less risk of one rocket taking out neighbours. It would let you start with much wider safety margins and evolve towards the requirements of the ITR.
Title: Re: Full diameter shorted ITS as FH replacement?
Post by: Paul451 on 10/03/2016 04:38 pm
What kind of performance would you get out of a 9+1 Raptor, 12m diameter, TSTO launcher?

It seems like a reasonable stepping stone to ITS, same engines, same diameter tanks, etc. And switching to 9 vac-Raptors, the mini-ITS first stage becomes the first version of an ITS second stage when you develop the BDB.

But Musk's timeline pretty much rules it out.
Title: Re: Full diameter shorted ITS as FH replacement?
Post by: envy887 on 10/03/2016 04:52 pm
The only way I could see this being worthwhile is if it used almost all the same major components from the ITS spaceship. Use the same tanks, convert the thrust structure to hold 21 Raptors: same gimballing center cluster of 3, and each of the 6 fixed vacuum engines replaced with a fixed cluster of 3 SL Raptors. Convert the cargo section into an interstage. The PICA layer could be a lot lighter.

That would still be big enough to put 150 tonne payloads in LEO, probably closer to 200t of fuel with the tanker version.
Title: Re: Full diameter shorted ITS as FH replacement?
Post by: Paul451 on 10/03/2016 05:14 pm
The 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.

convert the thrust structure to hold 21 Raptors

21?
Title: Re: Full diameter shorted ITS as FH replacement?
Post by: envy887 on 10/03/2016 06:25 pm
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.
Title: Re: Full diameter shorted ITS as FH replacement?
Post by: Impaler on 10/04/2016 05:30 am
Simply utilizing the amazing engine technology and carbon composite construction in the Falcon family seems like the more straightforward way to improved the existing vehicle performance and serve as sub-scale demonstrators at the same time.  Also allows Merlin engine to be retired which saves overhead
Title: Re: Full diameter shorted ITS as FH replacement?
Post by: hkultala on 10/04/2016 06:09 am
The 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.

convert the thrust structure to hold 21 Raptors

21?

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.


Title: Re: Full diameter shorted ITS as FH replacement?
Post by: guckyfan on 10/04/2016 10:17 am
To me it makes much sense to use the ITS, the upper stage and replace the vac engines with first stage engines. Keep the propulsion system basically the same as ITS  and put a second stage with 1 Raptor on top. Or fly with cargo section on top as SSTO with smaller LEO payloads.
Title: Re: Full diameter shorted ITS as FH replacement?
Post by: KelvinZero on 10/09/2016 02:17 am
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.
(Sorry for bumping this with such a late reply. Partially because a whole bunch of interesting proposals where thrown in that I hadn't thought of.. and that might drag this back to the mini-bfr thread.)

This above is probably the closest to what I was imagining. I was (probably naively) considering shortening both stages but that may be more like "just shortening" the space shuttle than a typical rocket tank.

I would still like to take some weight off the upper stage. 150 tons dry mass (90 tons for propellant variation) is not super absurd, only double the dry mass of the shuttle, which delivered less than 30 tons to orbit. I would like to start smaller if possible though. Between the fuel and mars version I think there could be room for a cargo version. It's goal is to do the same job as the falcon heavy but be totally reusable including the fairing. It also has room to grow to much much larger payloads.

People have also mentioned using the upper stage as a SSTO, which technically fits on this thread. I haven't done the numbers but it is the opposite of the philosophy Im aiming for here: Start easy with large margins. Feel your way forwards. If an SSTO pops out at the end, great.

Im wondering if the reasons that make 12 meters absurd are not such a big deal now that SpaceX is confident of returning to landing site. Could a squat kettle of a rocket serve current uses (ie FH cargos) competitively while being evolvable to a full size ITS? I don't think Elon has ever said the ITS was other than an ultimate goal, but at the same time there does not seem to be room for a totally different intermediate rocket as part of the learning process.
Title: Re: Full diameter shorted ITS as FH replacement?
Post by: guckyfan on 10/09/2016 06:41 am
It seems to me that using only the propulsion unit of the upper stage/ITS and replacing the vac engines with sea level engines would be a good first stage for a smaller vehicle though still large. Then put a new second stage on top with one vac Raptor and 3 of the 10t RCS thrusters as landing engines.

Not an optimal design but utilizing much "existing" capabilities.
Title: Re: Full diameter shorted ITS as FH replacement?
Post by: sdsds on 10/09/2016 06:55 am
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.
Title: Re: Full diameter shorted ITS as FH replacement?
Post by: KelvinZero on 10/09/2016 07:33 am
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.
Oh, ok. I missed that. Does ship mean upper stage? Where can I read about this?
Title: Re: Full diameter shorted ITS as FH replacement?
Post by: sdsds on 10/09/2016 08:02 am
They 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....
Title: Re: Full diameter shorted ITS as FH replacement?
Post by: KelvinZero on 10/09/2016 12:25 pm
They 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=3157

It 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.
Title: Re: Full diameter shorted ITS as FH replacement?
Post by: HMXHMX on 10/09/2016 03:43 pm
They 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=3157

It 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.

Yes, someone should think about a refuelable SSTO excursion vehicle for interplanetary missions.  :)
Title: Re: Full diameter shorted ITS as FH replacement?
Post by: DOCinCT on 10/09/2016 09:08 pm
What kind of performance would you get out of a 9+1 Raptor, 12m diameter, TSTO launcher?
FH triples the booster thrust, but with a standard 2nd stage barely doubles the LEO performance of a F9, gets better to Mars (triple). 
With 9 raptors you get 6M+ lbf at launch vs. 5.1M lbf  a 20% boost.  Vacuum 787K vs 210K about 4x.
So maybe triple the overall performance?   (I think the 2nd stage is more important than booster - a F9 is 80% of a Delta IV Heavy to LEO with less booster thrust but a 2nd stage engine 8-9 time the thrust of a RL-10)
But I'm no rocket scientist/space engineer.
Title: Re: Full diameter shorted ITS as FH replacement?
Post by: sdsds on 10/09/2016 11:06 pm
I 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."
Title: Re: Full diameter shorted ITS as FH replacement?
Post by: Robotbeat on 10/09/2016 11:19 pm
I could see this as a possible SpaceX development timeline:

1) F9R-Dev1-like version of ITS with just 3 Raptors initially mounted for suborbital testing in 2018, maybe without TPS at first.
2) later, extra engines are added to get closer to the flight vehicle. Let's say they're Vacuum-optimized ones. Still just suborbital tests, but they test operation of the Vacuum Raptors this time. TPS needed for these tests. 2019-2020. 2021 sees the tanker version doing tests and Mars-entry-like tests for spaceship.
3) Booster testing, initially just 7 Raptors, could be even fewer. 2020. Mainly to test launch cradle concept.
4) Add 14 more engines. 2021
5) 21 more engines 2022. They put the ITS on top, do refueling tests and go to Mars uncrewed.

To be continued...
Title: Re: Full diameter shorted ITS as FH replacement?
Post by: KelvinZero on 10/09/2016 11:25 pm
Yes, someone should think about a refuelable SSTO excursion vehicle for interplanetary missions.  :)
Well I did hear about something like that somewhere :) I just meant there is an example where SSTO from earth is not totally useless even if it can manage no cargo, no crew, and has used up every drop of fuel so can't return to earth by itself.
Title: Re: Full diameter shorted ITS as FH replacement?
Post by: KelvinZero on 10/09/2016 11:47 pm
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....
For a while I thought the OP of this thread was thrown out by this test vehicle concept. I think this is reasonable though. The test vehicle is going to test this new sideways glide and flip for landing. Maybe there will be just a grasshopper version first but I think this gliding (or sideways falling) is a big new thing.

I think given you have tested all the hard stuff, a short booster would be easy to whip out towards the end. It is almost a subset of the problems, except that it needs attachments for more engines.
Title: Re: Full diameter shorted ITS as FH replacement?
Post by: Robotbeat on 10/10/2016 04:18 am
By the way, that maneuver has already been (subsonically, partially) tested by the DC-X swan-dive test:
https://m.youtube.com/watch?v=wv9n9Casp1o

That's what should be striking about SpaceX's architecture. Nothing is particularly technically questionable except the raw scale and performance. And performance is not critical except you need more refueling flights.
Title: Re: Full diameter shorted ITS as FH replacement?
Post by: KelvinZero on 10/10/2016 08:21 am
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.
Title: Re: Full diameter shorted ITS as FH replacement?
Post by: envy887 on 10/10/2016 01:04 pm
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.

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.
Title: Re: Full diameter shorted ITS as FH replacement?
Post by: Paul451 on 10/10/2016 03:09 pm
That's what should be striking about SpaceX's architecture. Nothing is particularly technically questionable except the raw scale and performance.

Until they fly, all we'll hear from critics is how unrealistic it is.

And after they fly, all we'll hear is how SpaceX hasn't really done anything new.

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.

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.)
Title: Re: Full diameter shorted ITS as FH replacement?
Post by: KelvinZero on 10/10/2016 09:46 pm
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.

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.

Title: Re: Full diameter shorted ITS as FH replacement?
Post by: Lumina on 10/13/2016 12:37 am
I 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."

My guess is that the Ship is first on the timeline because out of the two parts it will need the most testing and because a real flight-tested Ship would be an amazing marketing tool to get a country or a billionaire to pay SpaceX in advance to commission the construction of a city on Mars and to charter some flights. These advance payments can then take SpaceX all the way.
Title: Re: Full diameter shorted ITS as FH replacement?
Post by: sdsds on 10/13/2016 05:43 am
the Ship is first on the timeline because out of the two parts it will need the most testing

That's a good way to say it! Another way is to say it has the most uncertainty. By doing it first, they "buy down" risk.
Title: Re: Full diameter shorted ITS as FH replacement?
Post by: uhuznaa on 10/13/2016 10:43 am
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.

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.


If there would have been a shuttle 2.0 in the 90ies and NASA wouldn't have been obsessed with it landing like an airplane and the military wouldn't have diluted it with insane cross range requirements, a fully reusable TSTO shuttle would easily (for rocket science values of "easy") have been possible. 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.

In fact scaled down to 60 tons of payload or so and with 30 tons of this going into more pedestrian mass fractions ITS would make a great TSTO reusable shuttle with no need for composite tanks.

But in fact this would have never happened, because this would have been a totally different craft that would have just been a bad fit for the usual porky suspects.

Anyway, if you look at ITS at a scale more familiar for launch vehicles, there's nothing crazy about it, it's an eminently sane and straight design as soon as you accept powered vertical landings so you can do away with wings. The scale and the mass fractions to arrive at the payloads SpaceX wants though are a bit crazy.
Title: Re: Full diameter shorted ITS as FH replacement?
Post by: Paul451 on 10/13/2016 09:08 pm
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.
Title: Re: Full diameter shorted ITS as FH replacement?
Post by: KelvinZero on 10/14/2016 04:08 am
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.
Done :) Verbing weirds language.
Title: Re: Full diameter shortened ITS as FH replacement?
Post by: Manabu on 10/17/2016 05:39 pm
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.
I think it would still mean a complete redesign of the thrust structure, as the outer ring engines were the best located to transfer the thrust to the outer walls of the booster, that ultimately supports the BFS on top. F9 first stage was able to fly with only the center engine, but it never carried significant load on top while doing that.

If you want to partially populate the booster stage, a 5-6-10 or 5-0-16 arrangement, from center to outer, is probably better. If the booster turns off some engines during ascent, then the best would be to remove those, as the thrust structure would already be projected to function w/o those.

However

I'm not sure if all this design effort and lose of commonality is better than just sending the bigger version with larger margins to reduce risk and maintence costs. The total capital cost if you keep the second stage the way it is wouldn't drop that much. The booster is the thing projected to be re-used a thousand of times in the first place. SpaceX only needs to make one booster by launchpad it expects to use and use it until it becomes obsolete or explodes. Even this reduced version's total mass/thrust would still be way too high for other launch pads unmodified.

I only see real merit in a mini-BFR if it is much smaller, around Falcon Heavy payload in fact. This would need a new vehicle from ground up. And that can be left to SpaceX competitors, like ESA and Blue Origin.
Title: Re: Full diameter shortened ITS as FH replacement?
Post by: Patchouli on 10/17/2016 06:06 pm

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.)

The Shuttle didn't explore any new territory in terms of payload as the Apollo stack with S-IVB could weigh up to 140tons.
As far as aerodynamics and materials they had the Dyna-Soar,ASSET,and PRIME programs to draw experience from.
The two hardest parts of the development of the shuttle were the TPS and SSME which caused numerous delays.

Title: Re: Full diameter shortened ITS as FH replacement?
Post by: Jim on 10/17/2016 06:20 pm

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.)


wrong.  Not one thing in that post is true.


Title: Re: Full diameter shortened ITS as FH replacement?
Post by: Jim on 10/17/2016 06:23 pm
the military wouldn't have diluted it with insane cross range requirements,

That has been proven wrong so many times.
Title: Re: Full diameter shortened ITS as FH replacement?
Post by: Jim on 10/17/2016 06:25 pm
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 that is wrong too. 
Title: Re: Full diameter shortened ITS as FH replacement?
Post by: Jim on 10/17/2016 06:27 pm
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.
Title: Re: Full diameter shortened ITS as FH replacement?
Post by: sdsds on 10/17/2016 08:15 pm
On the topic of a fully reusable vehicle for FH-like payloads....

I once pitched a design to my manager and he said something like, "With enough effort you could probably get it to work that way." Implicitly he was saying, "There's likely a better way to get the same result."

It depends though on how you measure whether the two results are the same. It turns out his approach was quicker and simpler. Mine would have provided capabilities on which we could have built lots of other nifty things.

Maybe a fully reusable vehicle for FH-like payloads is rather like that....
Title: Re: Full diameter shortened ITS as FH replacement?
Post by: envy887 on 10/17/2016 08:41 pm
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.

Maybe a little OT, but how much money do you think SpaceX has spent on efforts that only benefit reuse? Half of what it cost then to develop F9v1.0? Just as much?
Title: Re: Full diameter shortened ITS as FH replacement?
Post by: rakaydos on 10/18/2016 10:55 pm
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.
New Shepard.
Title: Re: Full diameter shortened ITS as FH replacement?
Post by: Jim on 10/19/2016 12:03 am
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.
New Shepard.

it didn't go to orbit
Title: Re: Full diameter shortened ITS as FH replacement?
Post by: Robotbeat on 10/19/2016 01:49 am
Someone should invent self-walking goal posts.
Title: Re: Full diameter shortened ITS as FH replacement?
Post by: KelvinZero on 10/19/2016 02:40 am
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.
Speaking for myself, the motivation for threads like this is that we don't accept ITS as a given. The plan seems to be "F9R, underpants, ITS". I feel like I am watching a shell game where is Elon Musk is moving around apparently real pieces: the Raptor development and that massive 12 meter tank thing, and wondering what the trick is.

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.  :)
Title: Re: Full diameter shortened ITS as FH replacement?
Post by: guckyfan on 10/19/2016 08:04 am
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.  :)

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.
Title: Re: Full diameter shortened ITS as FH replacement?
Post by: KelvinZero on 10/20/2016 03:50 am
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.  :)
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.
Thats why im playing around with this idea of a shortened first stage. Maybe that is the sort of intermediate step (between here and 200k tickets) that could also serve some launch market without requiring a whole new vehicle development.

I would like it if we could just shorten the upper stage too though I guess that is a lot more like producing a whole new vehicle due to its sideways reentry.

I found this timeline: http://futurism.com/elon-musk-mars-colony-all-his-key-points-from-todays-announcement/
but it didn't say when the 200k ticket was meant to arrive. If a shortened version could fit the bill then it could evolve towards the ultimate size and price performance. There are all sorts of ways to begin Mars flights without the full size 200k/ticket ITS.
Title: Re: Full diameter shortened ITS as FH replacement?
Post by: sdsds on 10/20/2016 04:10 am
Maybe [a shortened first stage] is the sort of intermediate step [...] that could also serve some launch market

I agree!

I think quite a bit depends on whether Musk is willing to risk putting people aboard the Ship soon. Because if he can offer LEO tourism without refilling and around-the-Moon tourism with refilling, that could be huge both in market share and in mind share.

A shortened first stage capable of enabling that (rather than FH equivalent payloads) would be the bold move....
Title: Re: Full diameter shortened ITS as FH replacement?
Post by: IainMcClatchie on 10/20/2016 05:30 am
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.  :)

Thousands of stadium sized direct-to-cellphone LEO comsats.

It's an existing trillion-dollar-per-year market.