Author Topic: Mars Precursor Vehicle  (Read 6497 times)

Offline meekGee

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Mars Precursor Vehicle
« on: 06/26/2017 07:13 AM »
There's a lot of arguing over in the SpaceX general forum about a "Raptor Upper Stage", with some people correctly pointing out that RUS gives limited benefits if all we're doing is replacing a Merlin with a Raptor and changing fuel types.

But there's something a lot more ambitious they can do, which coincidentally will also provide a RUS...

Since ITS won't be built tomorrow, SpaceX could benefit from A) risk mitigation and B) early access to Mars which has lineage to ITS architecture (instead of RD, which is a dead end).

So - build a "Mars Precursor Vehicle" that acts like BFS - it's a second stage, but can also be a refuelable Mars vehicle.

It launches on FH, but with a RUS instead of the current Merlin, can take maybe 70 tons to orbit.

Now this stage can be used (in one variation) to launch satellites and be fully reusable, or (in a second configuration) do Mars missions.

SpaceX gets to test (in earth orbit)
- Raptor
- Composite tanks
- Autogenous pressurization
- Refueling

And then test on a Mars mission:
- long duration interplanetary flight
- EDL

---

Basically with a modest development effort, we can have Mars missions with a departure mass of say 3x the payload of FH/RUS.

I am perfectly happy with that as a "stop gap" until ITS, or mini-ITS, or whatever comes afterwards.

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Online guckyfan

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Re: Mars Precursor Vehicle
« Reply #1 on: 06/26/2017 08:14 AM »
This is the only setup that could possibly be ready to go to Mars in 2020 instead of RedDragon.

Should it not be able to do a Mars landing even without refuelling? Though refuelling would greatly increase payload.

Offline DreamyPickle

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Re: Mars Precursor Vehicle
« Reply #2 on: 06/26/2017 08:24 AM »
Another key feature a new upper stage should have is a non-detachable fairing, because if you want to land a payload on Mars you can't expose it during entry. But perhaps it might still be detached and recovered separately in LEO missions?

I don't know why you expect a reusable upper stage on top of Falcon Heavy to have a 70 ton payload, that is higher than the maximum for a fully-expendable Falcon Heavy stack. I'd expect that the performance gain from switching to Raptor will be much less that what is lost in attempting to make it reusable and the difference will have to made up from using a larger booster.

It's also very dubious that they would build a special stage only for a few flights as it sort of defeats the purpose of reusability. Maybe if they somehow manage to build it to the same diameter as the early ITS and still fit it on the Heavy?

Perhaps a Falcon Heavy + Reusable Upper Stage could be cheaper to operate than a Falcon 9 + Expendable Upper Stages. This would require very fast and cheap refurbishment of multiple boosters.

Offline meekGee

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Re: Mars Precursor Vehicle
« Reply #3 on: 06/26/2017 09:30 AM »
Another key feature a new upper stage should have is a non-detachable fairing, because if you want to land a payload on Mars you can't expose it during entry. But perhaps it might still be detached and recovered separately in LEO missions?

I don't know why you expect a reusable upper stage on top of Falcon Heavy to have a 70 ton payload, that is higher than the maximum for a fully-expendable Falcon Heavy stack. I'd expect that the performance gain from switching to Raptor will be much less that what is lost in attempting to make it reusable and the difference will have to made up from using a larger booster.

It's also very dubious that they would build a special stage only for a few flights as it sort of defeats the purpose of reusability. Maybe if they somehow manage to build it to the same diameter as the early ITS and still fit it on the Heavy?

Perhaps a Falcon Heavy + Reusable Upper Stage could be cheaper to operate than a Falcon 9 + Expendable Upper Stages. This would require very fast and cheap refurbishment of multiple boosters.
Let's dial it down to 40-50 tons even.  This is a larger vehicle, 5m diameter, it should carry more fuel, and carry significantly more than today's (tomorrow's) FH.

I don't think it'll fly just a few times.  I think as a reusable deployer (with cargo bay instead of fairing) it will be a workhorse untill BFR or SFR get deployed several years later.

Of all intermediate steps, this one makes the most sense to me.
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Offline Bob Shaw

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Re: Mars Precursor Vehicle
« Reply #4 on: 06/26/2017 10:06 AM »
The trouble with a small precursor to ITS is that it doesn't benefit from the mass/volume equation in the same way, making EDL quite a different thing. Additionally, keeping cryogenic fluids cold on a trip to Mars would be much harder. I think a smaller-than-ITS Mars ship would just about work for a flags and footprints mission, but a tiny craft isn't a goer. Fine for LEO, good as an alternative to SLS locally, but that's it.

Offline MATTBLAK

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Re: Mars Precursor Vehicle
« Reply #5 on: 06/26/2017 10:50 AM »
Scaled-up Dragon - about 7 meters in diameter across the base? Or slightly larger even than that? I'm thinking something that would fit inside an 8.4 meter SLS style payload fairing. Or a similar sized fairing on another BFR.
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Offline MATTBLAK

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Re: Mars Precursor Vehicle
« Reply #6 on: 06/26/2017 11:03 AM »
...I'm thinking of a 'Mars Direct' based concept - based that is on the soon to be fully-proven form factor of the crewed 'Dragon 2.0'. Several versions of the same hull - Mars Transit, EDL & Surface Habitat, and an Ascent version that refuels after landing via ISRU: it climbs to Martian orbit where another ERV Dragon is attached to an Earth Return propulsion stage and an expendable, attached extra Habitat augmentation module. The Propulsion stage - either hypergolic or LOX/CH4 pushes the Dragon & Hab Earthwards and is ejected after TEI. Shortly before Earth interface, the Hab is jettisoned and the Dragon does either a direct entry to the Earth's surface for a propulsive landing, or aerocaptures into Earth orbit for a 'taxi' rendezvous to return the crew to Earth.

Basing the above ideas on variations of the Zubrin Direct or the NASA 'Semi-Direct' architectures.
« Last Edit: 06/26/2017 11:04 AM by MATTBLAK »
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Offline envy887

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Re: Mars Precursor Vehicle
« Reply #7 on: 06/26/2017 12:15 PM »
Scaled-up Dragon - about 7 meters in diameter across the base? Or slightly larger even than that? I'm thinking something that would fit inside an 8.4 meter SLS style payload fairing. Or a similar sized fairing on another BFR.

No. Dragon doesn't scale up very well, and SpaceX is moving to BFS-style entry so I can't see them building anything new that doesn't move in that direction.

The trouble with a small precursor to ITS is that it doesn't benefit from the mass/volume equation in the same way, making EDL quite a different thing. Additionally, keeping cryogenic fluids cold on a trip to Mars would be much harder.

You have this backwards. Smaller vehicles have a much BETTER mass/area ratio for EDL, and big vehicles are harder to get through entry. This (and not launch vehicle capability) is why MSL is the largest thing to land on Mars to date.

The cryo problem is about the same either way.

...
I don't know why you expect a reusable upper stage on top of Falcon Heavy to have a 70 ton payload, that is higher than the maximum for a fully-expendable Falcon Heavy stack. I'd expect that the performance gain from switching to Raptor will be much less that what is lost in attempting to make it reusable and the difference will have to made up from using a larger booster.

It's also very dubious that they would build a special stage only for a few flights as it sort of defeats the purpose of reusability. Maybe if they somehow manage to build it to the same diameter as the early ITS and still fit it on the Heavy?

Perhaps a Falcon Heavy + Reusable Upper Stage could be cheaper to operate than a Falcon 9 + Expendable Upper Stages. This would require very fast and cheap refurbishment of multiple boosters.

With aggressive ITS-like mass fractions and full Raptor specs FH could do about 70t fully reusable. The biggest difference isn't that Raptor is so much better, but that the F9 upper stage is woefully undersized for FH. A 6m stage massing 300+ tonnes wet would allow FH to accelerate slower (less throttling losses) and stage sooner (easier recovery) while still putting far more mass in orbit. But 60-65 tonnes fully reusable is probably a better target, to allow for mass overruns and performance shortfalls.

It doesn't have to be strictly cheaper per launch than F9: if the larger payload allows constellation deployment in fewer launches, it would be worth operating if the total cost is less.

Offline Robotbeat

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Re: Mars Precursor Vehicle
« Reply #8 on: 06/26/2017 12:21 PM »
I've personally been using RUS interchangeably with a mini BFS.
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Offline envy887

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Re: Mars Precursor Vehicle
« Reply #9 on: 06/26/2017 12:31 PM »
I've personally been using RUS interchangeably with a mini BFS.

This is not the only possible interpretation, but it's the only one that's plausible to me.

Offline Jim

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Re: Mars Precursor Vehicle
« Reply #10 on: 06/26/2017 02:03 PM »
RUS, the thing that I am vehemently against, is either a stock stage with methane or a wider one with methane that operates like the existing stage.  There is no point to these configurations.

An mini BFS/ITS as MG describes has some merit but......

a.  It would only operate out of LC-39A
b.  SLC-41 and/or Boco Chica have be up and running smoothly to keep the cash coming
c.  It would be after FH and Dragon 2 are flying smoothly. 
d.  DOD is not going to use F9 or FH for vertically integrated payloads
e.  It won't happen for 2020 because of c & d, unless LC-39B is used.

Offline meekGee

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Re: Mars Precursor Vehicle
« Reply #11 on: 06/26/2017 02:03 PM »
The trouble with a small precursor to ITS is that it doesn't benefit from the mass/volume equation in the same way, making EDL quite a different thing. Additionally, keeping cryogenic fluids cold on a trip to Mars would be much harder. I think a smaller-than-ITS Mars ship would just about work for a flags and footprints mission, but a tiny craft isn't a goer. Fine for LEO, good as an alternative to SLS locally, but that's it.
Correct, it wouldn't be an efficient Mars vehicle as BFS would be - you need size.

But it'd be better than RD or anything else, it'd be enormous compared to any current or planned Mars missions  and you can test basics even when the system is very different.  You validate your model, not the actual end design.

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Offline meekGee

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Re: Mars Precursor Vehicle
« Reply #12 on: 06/26/2017 02:06 PM »
I've personally been using RUS interchangeably with a mini BFS.
I know, and I did the same, but that was the reason for some of the RUS arguments.  Some people are talking about a 3.6 m engine replacement RUS with no Mars ambitions, and I felt this is sufficiently different that it merits it's own thread.
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Offline meekGee

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Re: Mars Precursor Vehicle
« Reply #13 on: 06/26/2017 02:22 PM »
RUS, the thing that I am vehemently against, is either a stock stage with methane or a wider one with methane that operates like the existing stage.  There is no point to these configurations.

An mini BFS/ITS as MG describes has some merit but......

a.  It would only operate out of LC-39A
b.  SLC-41 and/or Boco Chica have be up and running smoothly to keep the cash coming
c.  It would be after FH and Dragon 2 are flying smoothly. 
d.  DOD is not going to use F9 or FH for vertically integrated payloads
e.  It won't happen for 2020 because of c & d, unless LC-39B is used.
I don't know if "vehemently", but I don't see those other two options as likely at all.

Mostly because if SpaceX were thinking about them, they would naturally migrate the design towards this.

Timing wise, I wouldn't be surprised if they aimed at 2020, but hit 2022.  Lots of factors here, including pad availability, other missions, funding, etc.

This is assuming of course that FH is successful operationally and they like flying it. If not, then it's a while new ballgame.

What the big IAC plan was missing was steps. I appreciated the audacity, and maybe "bigger is easier", but in the grand scheme of things this MPV can give them a lot of knowledge for considerably​ less effort, and might actually accelerate the schedule for ITS compared to what it would have ended up being in reality.

My guess is we won't hear about any of it until FH flies.
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Offline Jim

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Re: Mars Precursor Vehicle
« Reply #14 on: 06/26/2017 02:29 PM »
RUS, the thing that I am vehemently against, is either a stock stage with methane or a wider one with methane that operates like the existing stage.  There is no point to these configurations.

An mini BFS/ITS as MG describes has some merit but......

a.  It would only operate out of LC-39A
b.  SLC-40 and/or Boco Chica have be up and running smoothly to keep the cash coming
c.  It would be after FH and Dragon 2 are flying smoothly. 
d.  DOD is not going to use F9 or FH for vertically integrated payloads
e.  It won't happen for 2020 because of c & d, unless LC-39B is used.

Actually, I am wrong about a.  It can't operated from 39A.  A mini BFS/ITS would be incompatible with the existing TEL. It would be too disruptive for the existing FH and it would interfere with manned Dragon 2 flights.  Both these are priorities for Spacex.  It would need to go to another pad.

Online jpo234

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Re: Mars Precursor Vehicle
« Reply #15 on: 06/26/2017 03:06 PM »
e.  It won't happen for 2020 because of c & d, unless LC-39B is used.

LC-39B is the SLS pad. Do you know or suspect that something bad will happen to this plan?

Offline Jim

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Re: Mars Precursor Vehicle
« Reply #16 on: 06/26/2017 03:08 PM »
e.  It won't happen for 2020 because of c & d, unless LC-39B is used.

LC-39B is the SLS pad. Do you know or suspect that something bad will happen to this plan?

It is a multi user pad

Offline Semmel

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Re: Mars Precursor Vehicle
« Reply #17 on: 06/26/2017 03:17 PM »
d.  DOD is not going to use F9 or FH for vertically integrated payloads

That is interesting. I would be inclined to believe that SpaceX does not want to develop vertical integration for the Falcon family, but that they would do it if DOD asks. However I have never heard before that DOD does not WANT SpaceX to develop that capability. Thats a pretty strong statement. Do they simply put all VI payloads on Atlas and Delta?

Offline Jim

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Re: Mars Precursor Vehicle
« Reply #18 on: 06/26/2017 03:23 PM »
d.  DOD is not going to use F9 or FH for vertically integrated payloads

That is interesting. I would be inclined to believe that SpaceX does not want to develop vertical integration for the Falcon family, but that they would do it if DOD asks. However I have never heard before that DOD does not WANT SpaceX to develop that capability. Thats a pretty strong statement. Do they simply put all VI payloads on Atlas and Delta?

No, I am saying that for  mini BFS/ITS to happen, DOD would not use F9 or FH for vertically integrated payloads.

If LC-39A is modified for mini BFS/ITS, it is likely incompatible with stock F9 or FH and hence not DOD vertically integrated payloads.

Offline meekGee

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Re: Mars Precursor Vehicle
« Reply #19 on: 06/26/2017 03:33 PM »
How come?  Won't any modifications be made in a backward compatible way?

Since a hypothetical MPV is not defined yet, any interface (mechanical or otherwise) is free to be designed so that it does not interfere with current TEL components for the current US.

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Offline Jim

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Re: Mars Precursor Vehicle
« Reply #20 on: 06/26/2017 03:39 PM »
How come?  Won't any modifications be made in a backward compatible way?

Since a hypothetical MPV is not defined yet, any interface (mechanical or otherwise) is free to be designed so that it does not interfere with current TEL components for the current US.



It then would be constrained to the same diameter, length and common bulkhead location as the existing second stage.

Offline meekGee

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Re: Mars Precursor Vehicle
« Reply #21 on: 06/26/2017 04:06 PM »
How come?  Won't any modifications be made in a backward compatible way?

Since a hypothetical MPV is not defined yet, any interface (mechanical or otherwise) is free to be designed so that it does not interfere with current TEL components for the current US.



It then would be constrained to the same diameter, length and common bulkhead location as the existing second stage.

If they use the current TEL upper section, then yes, of course.

But if they replace the TEL upper section to accommodate an MPV, that new upper section can be made to still support the existing U/S.  Actually if the two are different sizes, it makes it easier, since the different functional bits of the interface occupy different areas.



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Offline meekGee

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Re: Mars Precursor Vehicle
« Reply #22 on: 06/26/2017 04:08 PM »
For a company that has innovation in its blood, running another fuel up the T/E is peanuts. It's not even a deep cryogen and if the US has no Helium tanks, even better.

For a (hypothetical) company that is used to think in terms of "minimizing change to existing assets/technology" - yeah, it's a high visibility issue.

SpaceX was never shy about changing things.  See the F9 1.1 and 1.2 arguments...

This kind of rhetoric is used a lot to justify any pet idea of a poster; "SpaceX will do this because it's the New Space way!"
So I might as well use it too:
To me, postponing ITS in order to make incremental improvements to Falcon, which a RUS would do, is less 'SpaceX-y' than just going full bore straight to ITS asap.  They'll learn more from ITS failures than RUS failures.

(Replying to a post from the general RUS thread:)

Well SpaceX hasn't started with a 9-engine cryo-propellant reusable top-of-its class booster, right?

It was F1 with an ablative engine, then F1 with a regenerative engine, then F9 1.0, then after only 6 flights it was F9 1.1 and reusability development, then  1.2 with cryo, reusability implementation, and some recovery-based learning, now we're seeing a transition to blocks 4 and 5 (is it 1.3?) which implement lessons learned and more "second round" improvements (e.g. new legs)...

SpaceX has ferocious goals, but to date they pursued them using a gradual implementation.  (!!!)

BFR/BFS was a departure from this pattern.

I do agree with your point though that any "midway step" is also a detour - so it's not a no-brainer.

In order to justify itself, the interim stage must have either A) value in and of itself (like being a reusable commercial constellation sat launcher) or B) have such a low cost-of-failure that overall, it's worth failing in "small scale".
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Offline envy887

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Re: Mars Precursor Vehicle
« Reply #23 on: 06/26/2017 04:14 PM »
RUS, the thing that I am vehemently against, is either a stock stage with methane or a wider one with methane that operates like the existing stage.  There is no point to these configurations.

An mini BFS/ITS as MG describes has some merit but......

a.  It would only operate out of LC-39A
b.  SLC-40 and/or Boco Chica have be up and running smoothly to keep the cash coming
c.  It would be after FH and Dragon 2 are flying smoothly. 
d.  DOD is not going to use F9 or FH for vertically integrated payloads
e.  It won't happen for 2020 because of c & d, unless LC-39B is used.

Actually, I am wrong about a.  It can't operated from 39A.  A mini BFS/ITS would be incompatible with the existing TEL. It would be too disruptive for the existing FH and it would interfere with manned Dragon 2 flights.  Both these are priorities for Spacex.  It would need to go to another pad.

Is it not possible to add a second HIF and TEL to 39A without interrupting FH and Crew?

Offline Jim

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Re: Mars Precursor Vehicle
« Reply #24 on: 06/26/2017 04:16 PM »
Is it not possible to add a second HIF and TEL to 39A without interrupting FH and Crew?

They did not place the current HIF in the proper location to allow for this. It is right at the base of the pad incline.

Offline envy887

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Re: Mars Precursor Vehicle
« Reply #25 on: 06/26/2017 04:16 PM »
e.  It won't happen for 2020 because of c & d, unless LC-39B is used.

LC-39B is the SLS pad. Do you know or suspect that something bad will happen to this plan?

It is a multi user pad

Would this be a new HIF and TEL at 39B, or modify a MLP and crawler and use the VAB?

Offline Jim

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Re: Mars Precursor Vehicle
« Reply #26 on: 06/26/2017 04:18 PM »

Would this be a new HIF and TEL at 39B, or modify a MLP and crawler and use the VAB?

whatever works

Offline envy887

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Re: Mars Precursor Vehicle
« Reply #27 on: 06/26/2017 04:22 PM »
Is it not possible to add a second HIF and TEL to 39A without interrupting FH and Crew?

They did not place the current HIF in the proper location to allow for this. It is right at the base of the pad incline.

How about a pass-though  with a Y split to the south side. One fork for storing the existing TEL while the new one passes through, and the other fork leading to a new HIF south of the current one?

Offline envy887

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Re: Mars Precursor Vehicle
« Reply #28 on: 06/26/2017 04:22 PM »

Would this be a new HIF and TEL at 39B, or modify a MLP and crawler and use the VAB?

whatever works

So there's no first order issues preventing either option?

Offline JasonAW3

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Re: Mars Precursor Vehicle
« Reply #29 on: 06/26/2017 04:29 PM »

Would this be a new HIF and TEL at 39B, or modify a MLP and crawler and use the VAB?

whatever works

      In theory, couldn't they build a erector specifically for the subscale ITS and booster?  While expensive, I'm not totally certain that there are any technical reasons that it couldn't be done.

      I can see how expensive it would be, but couldn't that be written off as developmental expenses?
My God!  It's full of universes!

Offline Jim

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Re: Mars Precursor Vehicle
« Reply #30 on: 06/26/2017 04:44 PM »
Is it not possible to add a second HIF and TEL to 39A without interrupting FH and Crew?

They did not place the current HIF in the proper location to allow for this. It is right at the base of the pad incline.

How about a pass-though  with a Y split to the south side. One fork for storing the existing TEL while the new one passes through, and the other fork leading to a new HIF south of the current one?

That stops existing launches.  The south end of the HIF is a clean room

Offline envy887

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Re: Mars Precursor Vehicle
« Reply #31 on: 06/26/2017 04:54 PM »
Is it not possible to add a second HIF and TEL to 39A without interrupting FH and Crew?

They did not place the current HIF in the proper location to allow for this. It is right at the base of the pad incline.

How about a pass-though  with a Y split to the south side. One fork for storing the existing TEL while the new one passes through, and the other fork leading to a new HIF south of the current one?

That stops existing launches.  The south end of the HIF is a clean room

So they would have to widen the ramp and allow the new TEL to split off part way down the incline. Some dirt and concrete work, but not on the level of what they are doing at Boca Chica.

Speaking of Boca Chica, it could be dedicated to this type of vehicle. It's higher performance would be useful for the GTO/lunar/interplanetary missions which are the only reason the launch facility exists.

Offline Zed_Noir

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Re: Mars Precursor Vehicle
« Reply #32 on: 06/26/2017 07:43 PM »
Can meekGee's Mars Precursor Vehicle be use as a mid size Lunar lander? Presumably with Lunar orbital refueling.

Offline envy887

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Re: Mars Precursor Vehicle
« Reply #33 on: 06/26/2017 08:32 PM »
Can meekGee's Mars Precursor Vehicle be use as a mid size Lunar lander? Presumably with Lunar orbital refueling.

In theory, sure. There would be some challenges with thermal management, comms, power, etc. The usual trivialities of spaceflight :D

Offline Jim

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Re: Mars Precursor Vehicle
« Reply #34 on: 06/26/2017 10:00 PM »
Is it not possible to add a second HIF and TEL to 39A without interrupting FH and Crew?

They did not place the current HIF in the proper location to allow for this. It is right at the base of the pad incline.

How about a pass-though  with a Y split to the south side. One fork for storing the existing TEL while the new one passes through, and the other fork leading to a new HIF south of the current one?

That stops existing launches.  The south end of the HIF is a clean room

So they would have to widen the ramp and allow the new TEL to split off part way down the incline. Some dirt and concrete work, but not on the level of what they are doing at Boca Chica.

NASA isn't going to allow that

Offline watermod

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Re: Mars Precursor Vehicle
« Reply #35 on: 06/26/2017 10:17 PM »
The trouble with a small precursor to ITS is that it doesn't benefit from the mass/volume equation in the same way, making EDL quite a different thing. Additionally, keeping cryogenic fluids cold on a trip to Mars would be much harder. I think a smaller-than-ITS Mars ship would just about work for a flags and footprints mission, but a tiny craft isn't a goer. Fine for LEO, good as an alternative to SLS locally, but that's it.

What about using a Metal-Organic-Framework material instead of a cryogenic tank?

https://en.wikipedia.org/wiki/Metal-organic_framework

I don't know about oxygen but am told the materials can be designed to hold more methane or more hydrogen then a liquid tank of the same size.





Offline Bob Shaw

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Re: Mars Precursor Vehicle
« Reply #36 on: 06/26/2017 10:37 PM »

The trouble with a small precursor to ITS is that it doesn't benefit from the mass/volume equation in the same way, making EDL quite a different thing. Additionally, keeping cryogenic fluids cold on a trip to Mars would be much harder.

You have this backwards. Smaller vehicles have a much BETTER mass/area ratio for EDL, and big vehicles are harder to get through entry. This (and not launch vehicle capability) is why MSL is the largest thing to land on Mars to date.

The cryo problem is about the same either way.


Read my post again. I was pointing out that a mini-ITS wouldn't behave like the big chap during EDL, not specifying the difference. I also don't agree with you about the cryogenic sustainability issue being the same for a small, low-volume vehicle as a large, low surface area one - relatively speaking, the small ship suffers more heating, and must work harder to remain cool.

Offline MATTBLAK

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Re: Mars Precursor Vehicle
« Reply #37 on: 06/26/2017 10:50 PM »
Scaled-up Dragon - about 7 meters in diameter across the base? Or slightly larger even than that? I'm thinking something that would fit inside an 8.4 meter SLS style payload fairing. Or a similar sized fairing on another BFR.

No. Dragon doesn't scale up very well, and SpaceX is moving to BFS-style entry so I can't see them building anything new that doesn't move in that direction.

The trouble with a small precursor to ITS is that it doesn't benefit from the mass/volume equation in the same way, making EDL quite a different thing. Additionally, keeping cryogenic fluids cold on a trip to Mars would be much harder.

You have this backwards. Smaller vehicles have a much BETTER mass/area ratio for EDL, and big vehicles are harder to get through entry. This (and not launch vehicle capability) is why MSL is the largest thing to land on Mars to date.

The cryo problem is about the same either way.

...
I don't know why you expect a reusable upper stage on top of Falcon Heavy to have a 70 ton payload, that is higher than the maximum for a fully-expendable Falcon Heavy stack. I'd expect that the performance gain from switching to Raptor will be much less that what is lost in attempting to make it reusable and the difference will have to made up from using a larger booster.

It's also very dubious that they would build a special stage only for a few flights as it sort of defeats the purpose of reusability. Maybe if they somehow manage to build it to the same diameter as the early ITS and still fit it on the Heavy?

Perhaps a Falcon Heavy + Reusable Upper Stage could be cheaper to operate than a Falcon 9 + Expendable Upper Stages. This would require very fast and cheap refurbishment of multiple boosters.

With aggressive ITS-like mass fractions and full Raptor specs FH could do about 70t fully reusable. The biggest difference isn't that Raptor is so much better, but that the F9 upper stage is woefully undersized for FH. A 6m stage massing 300+ tonnes wet would allow FH to accelerate slower (less throttling losses) and stage sooner (easier recovery) while still putting far more mass in orbit. But 60-65 tonnes fully reusable is probably a better target, to allow for mass overruns and performance shortfalls.

It doesn't have to be strictly cheaper per launch than F9: if the larger payload allows constellation deployment in fewer launches, it would be worth operating if the total cost is less.
I was only advocating the Dragon shape - internally, it would be quite different. But I suppose developing such a big, derivative vehicle would cost most of what ITS is going to anyway, so....  Probably best if the Zubrin/Baker 'tuna can' Hab & semi-blunt biconic ERV 'Mars Direct' vehicles were done in the traditional manner, if done at all. Perhaps Zubrin could persuade the rather wealthy Jeff Bezos to launch his designs on the 'New Glenn' when it appears... ;) Twinned launches of the NG should roughly fit the Mars Direct mass estimates.
« Last Edit: 06/28/2017 10:59 AM by MATTBLAK »
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Offline DreamyPickle

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Re: Mars Precursor Vehicle
« Reply #38 on: 06/27/2017 01:14 AM »
I think the concerns about ground support are overblown for several reasons:

* The changes for a methane upper stage are much less than those for the full BFS. Remember how their intro video showed stacking the second stage right on the pad with a crane?
* Flying with different upper stages has been done before. The Atlas V is flying with multiple fairing diameters right now.
* They might be able to afford taking 39A out for a few months, and Boca Chica is being built in the same timeframe.

The biggest problem I see is building the business case. SpaceX is not very open about their costs but I'd guess the current upper stage is <10M per flight, and this is partially because it shares so much with the first stage booster. The fairing is not included in that but they've stated they are close to figuring out recovery for that.

In order for a methane upper stage to make sense it needs to cost much less than 10M per flight, including the design phase. The only way this could make is if the stage is fully reusable and has a larger diameter and mass (to preserve payload capacity). Has anyone done any simulations on how much a Falcon Heavy could lift in fully reusable mode with a different and larger upper stage?

I still think it's more likely that they'll just jump to a full methane-only rocket of uniform diameter instead of worrying around cross-compatibility.

Offline envy887

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Re: Mars Precursor Vehicle
« Reply #39 on: 06/27/2017 01:50 AM »
Is it not possible to add a second HIF and TEL to 39A without interrupting FH and Crew?

They did not place the current HIF in the proper location to allow for this. It is right at the base of the pad incline.

How about a pass-though  with a Y split to the south side. One fork for storing the existing TEL while the new one passes through, and the other fork leading to a new HIF south of the current one?

That stops existing launches.  The south end of the HIF is a clean room

So they would have to widen the ramp and allow the new TEL to split off part way down the incline. Some dirt and concrete work, but not on the level of what they are doing at Boca Chica.

NASA isn't going to allow that

NASA let them build a HIF right on the crawlerway. Why wouldn't they allow improvements to the pad?

Offline envy887

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Re: Mars Precursor Vehicle
« Reply #40 on: 06/27/2017 02:01 AM »

The trouble with a small precursor to ITS is that it doesn't benefit from the mass/volume equation in the same way, making EDL quite a different thing. Additionally, keeping cryogenic fluids cold on a trip to Mars would be much harder.

You have this backwards. Smaller vehicles have a much BETTER mass/area ratio for EDL, and big vehicles are harder to get through entry. This (and not launch vehicle capability) is why MSL is the largest thing to land on Mars to date.

The cryo problem is about the same either way.


Read my post again. I was pointing out that a mini-ITS wouldn't behave like the big chap during EDL, not specifying the difference. I also don't agree with you about the cryogenic sustainability issue being the same for a small, low-volume vehicle as a large, low surface area one - relatively speaking, the small ship suffers more heating, and must work harder to remain cool.

And why is easier EDL a 'trouble' that 'doesn't benefit'?

Passive cooling at steady state is the same for either. I think passive cooling will be the primary cooling mechanism. And it might be the only necessary mechanism, depending what pressure the tanks can hold.

Offline Jim

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Re: Mars Precursor Vehicle
« Reply #41 on: 06/27/2017 02:10 PM »
NASA let them build a HIF right on the crawlerway. Why wouldn't they allow improvements to the pad?

The pad mound was untouched and there was no environmental impact to use the crawler way

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Re: Mars Precursor Vehicle
« Reply #42 on: 06/27/2017 02:17 PM »
I think the concerns about ground support are overblown for several reasons:

1.   The changes for a methane upper stage are much less than those for the full BFS. Remember how their intro video showed stacking the second stage right on the pad with a crane?
2.   Flying with different upper stages has been done before.

3. The Atlas V is flying with multiple fairing diameters right now.

4. They might be able to afford taking 39A out for a few months, and Boca Chica is being built in the same timeframe.


The concerns for ground support are well justified unlike those "reasons"

1.  that is just a video and doesn't mean it is going to happen.  And no one is comparing this to the BFS.

2.  Not from the same pad

3. Meaningless point.  Fairings don't interface with the TEL unlike second stages

4. no, 39A is for Dragon 2 launches and others that can't move to other pads.
« Last Edit: 06/27/2017 02:18 PM by Jim »

Offline Lobo

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Re: Mars Precursor Vehicle
« Reply #43 on: 06/27/2017 03:30 PM »
RUS, the thing that I am vehemently against, is either a stock stage with methane or a wider one with methane that operates like the existing stage.  There is no point to these configurations.

An mini BFS/ITS as MG describes has some merit but......

a.  It would only operate out of LC-39A
b.  SLC-40 and/or Boco Chica have be up and running smoothly to keep the cash coming
c.  It would be after FH and Dragon 2 are flying smoothly. 
d.  DOD is not going to use F9 or FH for vertically integrated payloads
e.  It won't happen for 2020 because of c & d, unless LC-39B is used.

Actually, I am wrong about a.  It can't operated from 39A.  A mini BFS/ITS would be incompatible with the existing TEL. It would be too disruptive for the existing FH and it would interfere with manned Dragon 2 flights.  Both these are priorities for Spacex.  It would need to go to another pad.

e.  It won't happen for 2020 because of c & d, unless LC-39B is used.

LC-39B is the SLS pad. Do you know or suspect that something bad will happen to this plan?

It is a multi user pad

Yes, I think 39B seems like probably the only plausible location for such a MiniBFR.  As Jim points out, SpaceX needs their Falcon pads launching Falcon to handle their commercial business.  39A will be launching the occasional FH, as well as crews and goverment payloads.  39B is a multi user pad.  A MLP could be purchased/leased and modified for such vehicle to be vertically integrated in the VAB. 

Depending on it's size, it could offer some favorable optics next to SLS for SpaceX, potentially giving a visual "alternative" right on the same pad.

« Last Edit: 06/27/2017 04:16 PM by Lobo »

Offline Lobo

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Re: Mars Precursor Vehicle
« Reply #44 on: 06/27/2017 04:11 PM »

So - build a "Mars Precursor Vehicle" that acts like BFS - it's a second stage, but can also be a refuelable Mars vehicle.

It launches on FH, but with a RUS instead of the current Merlin, can take maybe 70 tons to orbit.


I think they could go the other way with it.  A new wider Raptor power booster to replace FH, with a FUS on top.  Especially for going to Mars, how would you reuse an upper stage that wasn't going there, landing, refueling, and returning to Earth?  I'm no expert in orbital mechanics but in order to have a reusable upper stage going to Mars you need to do like ITS would do, or do a 2 year orbital loop back to Earth (which would get into loiter times), or perhaps it takes Red Dragon to some sort of Mars Transfer Oribt?  But then Red Dragon would need to provide a certain amount of dV in order to get to full escape.

Personally, from some of Musk's comments over time, that the upgrades and growth of F9, along with their continuing learning about reusability, seem to have mostly worked FH out of a job by the time it flies.
Its not needed any longer for most of the EELV-heavy payloads it originally was needed for years ago with Falcon v1.0.
But, it's -is- still needed to cover that D4H payload range.  But that's a pretty small market.  I think D4H has only flown maybe 8 payloads in it's history? 
And a tri-core booster isn't very good for reuse, hence why ITS isn't a tri-core.  And to get like 70 tons to orbit, I'm pretty sure at least the center core would be expended, and perhaps the side boosters too?

So perhaps a new subscale Raptor powered big dumb booster that is RTLS, which starts off with an expendable FUS (perhaps with some upgrades to optimize it for this purpose)  that can start dropping Red Dragons on Mars.  After that work on developing a new reusable upper stage, a mini-BFS, that would then also be the biconic spacecraft and lander for the first crews to Mars.  Red Dragons are one way tickets, so you need something that can come back before you start sending people there.
This could be of sufficient size for the initial exploration class missions, which would only have smaller crews anyway.  Then the full ITS would come later after SpaceX has cut their teeth on a smaller vehicle.

And 39B would be the logical location to operate the new booster, so as not to interfere with the Falcon pads that SpaceX needs to be launching Falcons.
« Last Edit: 06/27/2017 04:17 PM by Lobo »

Offline Ludus

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Re: Mars Precursor Vehicle
« Reply #45 on: 06/27/2017 05:08 PM »
If they had the money to do both, it would be compatible with plans expressed to build the full sized ITS Ship with 9 Raptor engines and use it for suborbital flights before building the ITS Booster.

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Re: Mars Precursor Vehicle
« Reply #46 on: 06/27/2017 05:53 PM »

So - build a "Mars Precursor Vehicle" that acts like BFS - it's a second stage, but can also be a refuelable Mars vehicle.

It launches on FH, but with a RUS instead of the current Merlin, can take maybe 70 tons to orbit.


I think they could go the other way with it.  A new wider Raptor power booster to replace FH, with a FUS on top.  Especially for going to Mars, how would you reuse an upper stage that wasn't going there, landing, refueling, and returning to Earth?  I'm no expert in orbital mechanics but in order to have a reusable upper stage going to Mars you need to do like ITS would do, or do a 2 year orbital loop back to Earth (which would get into loiter times), or perhaps it takes Red Dragon to some sort of Mars Transfer Oribt?  But then Red Dragon would need to provide a certain amount of dV in order to get to full escape.

Personally, from some of Musk's comments over time, that the upgrades and growth of F9, along with their continuing learning about reusability, seem to have mostly worked FH out of a job by the time it flies.
Its not needed any longer for most of the EELV-heavy payloads it originally was needed for years ago with Falcon v1.0.
But, it's -is- still needed to cover that D4H payload range.  But that's a pretty small market.  I think D4H has only flown maybe 8 payloads in it's history? 
And a tri-core booster isn't very good for reuse, hence why ITS isn't a tri-core.  And to get like 70 tons to orbit, I'm pretty sure at least the center core would be expended, and perhaps the side boosters too?

So perhaps a new subscale Raptor powered big dumb booster that is RTLS, which starts off with an expendable FUS (perhaps with some upgrades to optimize it for this purpose)  that can start dropping Red Dragons on Mars.  After that work on developing a new reusable upper stage, a mini-BFS, that would then also be the biconic spacecraft and lander for the first crews to Mars.  Red Dragons are one way tickets, so you need something that can come back before you start sending people there.
This could be of sufficient size for the initial exploration class missions, which would only have smaller crews anyway.  Then the full ITS would come later after SpaceX has cut their teeth on a smaller vehicle.

And 39B would be the logical location to operate the new booster, so as not to interfere with the Falcon pads that SpaceX needs to be launching Falcons.

The upper stage would be reusable on earth, with the nice advantage that it could also fly a one-way trip to Mars unmanned similar to the idea for Red Dragon and the first ITS.  Reusing the particular stage that flew a demonstration mission to Mars would not be a priority. 

I agree that a Raptor-powered booster smaller than the full BFR would be useful, but paring it with FUS doesn't make much sense.  You still have the drawback of different fuels, but flying a low-ISP upper stage without the ability to coast for more than a few hours wouldn't be very useful, and you still don't get any experience using Raptor in deep space - better to go to an all methalox vehicle right away. 

Offline envy887

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Re: Mars Precursor Vehicle
« Reply #47 on: 06/27/2017 06:05 PM »

So - build a "Mars Precursor Vehicle" that acts like BFS - it's a second stage, but can also be a refuelable Mars vehicle.

It launches on FH, but with a RUS instead of the current Merlin, can take maybe 70 tons to orbit.


I think they could go the other way with it.  A new wider Raptor power booster to replace FH, with a FUS on top.  Especially for going to Mars, how would you reuse an upper stage that wasn't going there, landing, refueling, and returning to Earth?  I'm no expert in orbital mechanics but in order to have a reusable upper stage going to Mars you need to do like ITS would do, or do a 2 year orbital loop back to Earth (which would get into loiter times), or perhaps it takes Red Dragon to some sort of Mars Transfer Oribt?  But then Red Dragon would need to provide a certain amount of dV in order to get to full escape.

Personally, from some of Musk's comments over time, that the upgrades and growth of F9, along with their continuing learning about reusability, seem to have mostly worked FH out of a job by the time it flies.
Its not needed any longer for most of the EELV-heavy payloads it originally was needed for years ago with Falcon v1.0.
But, it's -is- still needed to cover that D4H payload range.  But that's a pretty small market.  I think D4H has only flown maybe 8 payloads in it's history? 
And a tri-core booster isn't very good for reuse, hence why ITS isn't a tri-core.  And to get like 70 tons to orbit, I'm pretty sure at least the center core would be expended, and perhaps the side boosters too?

So perhaps a new subscale Raptor powered big dumb booster that is RTLS, which starts off with an expendable FUS (perhaps with some upgrades to optimize it for this purpose)  that can start dropping Red Dragons on Mars.  After that work on developing a new reusable upper stage, a mini-BFS, that would then also be the biconic spacecraft and lander for the first crews to Mars.  Red Dragons are one way tickets, so you need something that can come back before you start sending people there.
This could be of sufficient size for the initial exploration class missions, which would only have smaller crews anyway.  Then the full ITS would come later after SpaceX has cut their teeth on a smaller vehicle.

And 39B would be the logical location to operate the new booster, so as not to interfere with the Falcon pads that SpaceX needs to be launching Falcons.

At this point, the marginal effort to get and keep FH flying is tiny. compared to getting a whole new larger booster flying. A new booster REQUIRES a new factory and a new test facility. A sufficiently small mini-BFS might not.

Eventually they will build a larger booster, but it won't be paired with the Merlin upper stage. That just makes no sense at all. If you can build a new booster you're 95% of the way to a new upper stage. And the Merlin upper stage is way too underpowered for FH already.

Offline envy887

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Re: Mars Precursor Vehicle
« Reply #48 on: 06/27/2017 06:09 PM »
Yes, I think 39B seems like probably the only plausible location for such a MiniBFR.  As Jim points out, SpaceX needs their Falcon pads launching Falcon to handle their commercial business.  39A will be launching the occasional FH, as well as crews and goverment payloads.  39B is a multi user pad.  A MLP could be purchased/leased and modified for such vehicle to be vertically integrated in the VAB. 

Depending on it's size, it could offer some favorable optics next to SLS for SpaceX, potentially giving a visual "alternative" right on the same pad.

Boca Chica is also plausible, as it's ideal for GTO, cis-lunar, and interplanetary flights.

Offline MickQ

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Re: Mars Precursor Vehicle
« Reply #49 on: 06/28/2017 10:08 AM »
What's the possibility / likelihood of 39C being constructed as a multi vehicle pad with 2 opposing TEL/HIF sets ?

Offline envy887

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Re: Mars Precursor Vehicle
« Reply #50 on: 06/28/2017 12:01 PM »
What's the possibility / likelihood of 39C being constructed as a multi vehicle pad with 2 opposing TEL/HIF sets ?

There is only one ramp, from the south. The flame trench exhausts to the north, so they can't put a HIF there. And Jim says NASA would frown on even minor modifications to the ramp.

It would be much easier to add a HIF and TEL to the west of 40, where the old Titan service towers were. 40 was used to launch the 4 Mlbf Titan IV, so a Falcon Heavy launch wouldn't be that impractical if they approach from the right direction.

Edit: I totally thought that you said 39A, sorry.

Falcon Heavy has to approach 180 degrees away from the flame trench exhaust, so it cannot have multiple approaches to the same pad/trench. But a new pad could certainly have multiple HIFs at the bottom of a single ramp.
« Last Edit: 06/29/2017 01:20 AM by envy887 »

Offline Robotbeat

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Re: Mars Precursor Vehicle
« Reply #51 on: 06/28/2017 12:40 PM »
I seem to recall Musk or someone saying they would have two TELs on LC39a, one for Falcons and one for ITS.
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Offline rsdavis9

Re: Mars Precursor Vehicle
« Reply #52 on: 06/28/2017 03:37 PM »
Quote
So perhaps a new subscale Raptor powered big dumb booster that is RTLS, which starts off with an expendable FUS (perhaps with some upgrades to optimize it for this purpose)  that can start dropping Red Dragons on Mars.  After that work on developing a new reusable upper stage, a mini-BFS, that would then also be the biconic spacecraft and lander for the first crews to Mars.  Red Dragons are one way tickets, so you need something that can come back before you start sending people there.
This could be of sufficient size for the initial exploration class missions, which would only have smaller crews anyway.  Then the full ITS would come later after SpaceX has cut their teeth on a smaller vehicle.

So this new BFS like mini
1. Has multiple uses. Thats good because it isn't a throw away intermediate development step.
a. Launch constellation
b. Launch earth stuff
c. EDL mars.

2. Big problem.
Has all the development tech of BFS.
a. Raptor and LOX/CH4
b. Composite
c. autogenous pressurization
d. Combined fairing/US/Biconic reentry vehicle.

So my question is why is it easier to develop a small version?
b. Is composite easier if smaller?
a. I don't think it makes any difference to the raptor. Just more of them.
c. shouldn't be any difference for autogenous
d. Shouldn't be any different for biconic reentry vehicle

So where is the saving? 

We need an intermediate step with less tech to develop that isn't throw away.

1. I still like booster first because it eliminates d. above.
With raptor and composite booster it could stage at a greater m/s and still RTLS.
With the extra boost for S2, S2 could still do reusable with Dragon tech for reentry.

2. How could we take the 2nd stage proposed in the first post and reduce the tech needed to make it?
« Last Edit: 06/28/2017 03:49 PM by rsdavis9 »
bob

Offline envy887

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Re: Mars Precursor Vehicle
« Reply #53 on: 06/28/2017 04:03 PM »
...
So my question is why is it easier to develop a small version?
b. Is composite easier if smaller?
a. I don't think it makes any difference to the raptor. Just more of them.
c. shouldn't be any difference for autogenous
d. Shouldn't be any different for biconic reentry vehicle

1) They don't have to use composites, but if they do it's definitely faster, easier and cheaper to develop a 5 or 6 meter vehicle than a 12 meter one.

2) They can use the existing demo Raptor design without scaling it up, if they want. Using a 3,500 kN engine limits the minimum size of the upper stage. And the demo engine is a lot closer to flying.

3) They can make far more use of existing manufacturing, transport, test, and launch facilities.
« Last Edit: 06/28/2017 04:04 PM by envy887 »

Offline rsdavis9

Re: Mars Precursor Vehicle
« Reply #54 on: 06/28/2017 04:24 PM »
...
So my question is why is it easier to develop a small version?
b. Is composite easier if smaller?
a. I don't think it makes any difference to the raptor. Just more of them.
c. shouldn't be any difference for autogenous
d. Shouldn't be any different for biconic reentry vehicle

1) They don't have to use composites, but if they do it's definitely faster, easier and cheaper to develop a 5 or 6 meter vehicle than a 12 meter one.

2) They can use the existing demo Raptor design without scaling it up, if they want. Using a 3,500 kN engine limits the minimum size of the upper stage. And the demo engine is a lot closer to flying.

3) They can make far more use of existing manufacturing, transport, test, and launch facilities.

So keep it road transportable by limiting to 3.6m.
So if they adopt all three for making it easier/faster to first flight do we still get a useful vehicle?
Sounds like it to me.
Could it only be launched on FH?
bob

Offline Lobo

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Re: Mars Precursor Vehicle
« Reply #55 on: 06/28/2017 04:31 PM »

At this point, the marginal effort to get and keep FH flying is tiny. compared to getting a whole new larger booster flying.

But it's still complex to operate (Elon has said that, and it's been said about D4H), and difficult to reuse, and really not needed by more than small number of payloads, due to the growth of F9.  Back when there was F9 v1.0, it was needed for many payloads due to F9's performance at that time.  Reusability wans't an issue then, so a tri-core 1.5 stage booster was a fine idea.  And it seemed like it'd be as easy as just strapping 3 F9 cores together and launching it.  But that has turned out to not be the case.  Cross feed went away for that reason, and it was no longer needed with the upgraded F9.  Then F9 was upgraded again and most of the need for FH at all went away.
You are correct that FH is close to flying, and as they have nothing else in that class close to ready, and they want those USAF/DoD contracts, some of which will reqire D4H performance, they still -need- it.  But they'll have this complex and hard to reuse LV that will only be needed once in awhile, and is basically an evolutionary dead end.  Shotwell said they've tested Merlin up to 190klbs, with margin for higher.  They could even upgrade F9 again, and stretch the FUS a bit more, and they may even be able to cover D4H payloads with that.   So I think they've become less and less excited about FH as it's got closer and closer to flying.  It'll almost be obsolete by the time it flies, ironically.



A new booster REQUIRES a new factory and a new test facility. A sufficiently small mini-BFS might not.

Eventually they will build a larger booster, but it won't be paired with the Merlin upper stage. That just makes no sense at all. If you can build a new booster you're 95% of the way to a new upper stage. And the Merlin upper stage is way too underpowered for FH already.

Well, my point isn't that I think a FUS on a larger Raptor booster is the new LV itself, but that a new "dumb" booster could be the first element developed.  If they put a FUS on top of that, they could have an interim vehicle that could cover the occasional payloads that would need the FH.  As well as provide testing for the booster, ahead of the development of a mini-BFS. 

A new booster REQUIRES a new factory and a new test facility. A sufficiently small mini-BFS might not.

If you can build a new booster you're 95% of the way to a new upper stage. And the Merlin upper stage is way too underpowered for FH already.

Huh?
No, I think when you develop the booster you are maybe 20% of the way to a new upper stage.  Remember, for a mini-BFR/BFS, the upper stage will be a resuable spaceship...and lander.  It will need to be a lander at first only on Earth, but later on the Moon and Mars presumably.  It will be a biconic lifting body, with a new TPS system on ti's nose and side, and perhaps some sort of shuttle-like internal payload bay.  And likely have the ability to put a crew cabin in it later.  It'll need solar power for long loiter times, etc.
No, I think the mini-BFS will be definitely be the long pole item, IMO.  And be the much longer item to develop.  The Booster will more or less just be a larger version of F9 booster.  That's pretty well understood by SpaceX now.  Definitely the easier of the two pieces.  The biconic spaceship will be the new cutting edge difficult bit.

If they wanted to just build a larger version of FUS with Raptor power, then you might be correct.  But I'm pretty sure they aren't going to put such an expendable upper stage on a new vehicle like that as the final product.

However, they -could- put a FUS on it to get some launches under it's belt, and retire FH, while flying those payloads fully reusably, and dropping Red Dragons on Mars.

It would just be an interim configuration pending the development of a mini-BFS to mate with it.
Again, just an idea of a different way they could go about things, as opposed to using the FH booster for more uses.  They may want to move on from it as soon as it's absolutely not needed any more, for the reasons I mention above.  No idea if they'd actually go this way, but regardless I still have a hunch that FH may not have a long service life.

Offline envy887

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Re: Mars Precursor Vehicle
« Reply #56 on: 06/28/2017 04:43 PM »
...
So my question is why is it easier to develop a small version?
b. Is composite easier if smaller?
a. I don't think it makes any difference to the raptor. Just more of them.
c. shouldn't be any difference for autogenous
d. Shouldn't be any different for biconic reentry vehicle

1) They don't have to use composites, but if they do it's definitely faster, easier and cheaper to develop a 5 or 6 meter vehicle than a 12 meter one.

2) They can use the existing demo Raptor design without scaling it up, if they want. Using a 3,500 kN engine limits the minimum size of the upper stage. And the demo engine is a lot closer to flying.

3) They can make far more use of existing manufacturing, transport, test, and launch facilities.

So keep it road transportable by limiting to 3.6m.
So if they adopt all three for making it easier/faster to first flight do we still get a useful vehicle?
Sounds like it to me.
Could it only be launched on FH?

Road transport isn't necessarily a limit for an upper stage, since leasing a super-large airlifter is an option up to about 7m diameter and 25m long.

It's more capable if limited to FH. Like 50 tonnes of payload to Mars surface capable. However, a mini-BFS sized for F9, which would be about the same size as the existing upper stage and fairing, would still be pretty capable and much more useful for dispensing constellation satellites thanks to F9 flight rates.
« Last Edit: 06/28/2017 04:52 PM by envy887 »

Offline Negan

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Re: Mars Precursor Vehicle
« Reply #57 on: 06/28/2017 04:49 PM »
But they'll have this complex and hard to reuse LV that will only be needed once in awhile, and is basically an evolutionary dead end.

So if F9 and FH are so different cost wise, why wasn't the circumlunar mission a lot more? Although we've never received an exact figure, it still looks to be less than $200 million, and that includes the Dragon 2 and all the support to go with it. Seems like they would have been far enough along on the development of FH when they announced this mission, they would have a handle on what would be involved.
« Last Edit: 06/28/2017 04:51 PM by Negan »

Offline envy887

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Re: Mars Precursor Vehicle
« Reply #58 on: 06/28/2017 04:51 PM »

At this point, the marginal effort to get and keep FH flying is tiny. compared to getting a whole new larger booster flying.

But it's still complex to operate (Elon has said that, and it's been said about D4H), and difficult to reuse, and really not needed by more than small number of payloads, due to the growth of F9.  Back when there was F9 v1.0, it was needed for many payloads due to F9's performance at that time.  Reusability wans't an issue then, so a tri-core 1.5 stage booster was a fine idea.  And it seemed like it'd be as easy as just strapping 3 F9 cores together and launching it.  But that has turned out to not be the case.  Cross feed went away for that reason, and it was no longer needed with the upgraded F9.  Then F9 was upgraded again and most of the need for FH at all went away.
You are correct that FH is close to flying, and as they have nothing else in that class close to ready, and they want those USAF/DoD contracts, some of which will reqire D4H performance, they still -need- it.  But they'll have this complex and hard to reuse LV that will only be needed once in awhile, and is basically an evolutionary dead end.  Shotwell said they've tested Merlin up to 190klbs, with margin for higher.  They could even upgrade F9 again, and stretch the FUS a bit more, and they may even be able to cover D4H payloads with that.   So I think they've become less and less excited about FH as it's got closer and closer to flying.  It'll almost be obsolete by the time it flies, ironically.

F9 is nowhere near DIVH payloads to high energy missions and never will be with the current upper stage or any kind of reuse. While FH can likely put more payload to GTO than DIVH can, while still reusing all the boosters. I'm sure that FH with reuse will be cheaper than F9 expendable within a few years.

Also, SpaceX seems pretty excited about heavy GTO commsats, which also require expending F9, and about the lunar Dragon mission which has apparently gotten a lot of interest and also requires FH. I doubt FH is going away all that quickly

Quote


A new booster REQUIRES a new factory and a new test facility. A sufficiently small mini-BFS might not.

Eventually they will build a larger booster, but it won't be paired with the Merlin upper stage. That just makes no sense at all. If you can build a new booster you're 95% of the way to a new upper stage. And the Merlin upper stage is way too underpowered for FH already.

Well, my point isn't that I think a FUS on a larger Raptor booster is the new LV itself, but that a new "dumb" booster could be the first element developed.  If they put a FUS on top of that, they could have an interim vehicle that could cover the occasional payloads that would need the FH.  As well as provide testing for the booster, ahead of the development of a mini-BFS. 

A new booster REQUIRES a new factory and a new test facility. A sufficiently small mini-BFS might not.

If you can build a new booster you're 95% of the way to a new upper stage. And the Merlin upper stage is way too underpowered for FH already.

Huh?
No, I think when you develop the booster you are maybe 20% of the way to a new upper stage.  Remember, for a mini-BFR/BFS, the upper stage will be a resuable spaceship...and lander.  It will need to be a lander at first only on Earth, but later on the Moon and Mars presumably.  It will be a biconic lifting body, with a new TPS system on ti's nose and side, and perhaps some sort of shuttle-like internal payload bay.  And likely have the ability to put a crew cabin in it later.  It'll need solar power for long loiter times, etc.
No, I think the mini-BFS will be definitely be the long pole item, IMO.  And be the much longer item to develop.  The Booster will more or less just be a larger version of F9 booster.  That's pretty well understood by SpaceX now.  Definitely the easier of the two pieces.  The biconic spaceship will be the new cutting edge difficult bit.

If they wanted to just build a larger version of FUS with Raptor power, then you might be correct.  But I'm pretty sure they aren't going to put such an expendable upper stage on a new vehicle like that as the final product.

However, they -could- put a FUS on it to get some launches under it's belt, and retire FH, while flying those payloads fully reusably, and dropping Red Dragons on Mars.

It would just be an interim configuration pending the development of a mini-BFS to mate with it.
Again, just an idea of a different way they could go about things, as opposed to using the FH booster for more uses.  They may want to move on from it as soon as it's absolutely not needed any more, for the reasons I mention above.  No idea if they'd actually go this way, but regardless I still have a hunch that FH may not have a long service life.

At least 95% to a dumb upper stage. Certainly much more than 20% towards a mini-BFS upper stage. I'm including all the manufacturing, transport, test, integration and launch infrastructure, in addition to development costs. A FH-replacement single stick booster can't use any of the existing infrastructure.

Offline Negan

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Re: Mars Precursor Vehicle
« Reply #59 on: 06/28/2017 05:11 PM »
I'm sure that FH with reuse will be cheaper than F9 expendable within a few years.

So it has already been established that currently FH with reuse cost more than F9 expendable?
« Last Edit: 06/28/2017 05:14 PM by Negan »

Offline envy887

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Re: Mars Precursor Vehicle
« Reply #60 on: 06/28/2017 05:17 PM »
I'm sure that FH with reuse will be cheaper than F9 expendable within a few years.

So it has already been established that currently FH with reuse cost more than F9 expendable?

No, that has not been established. But if it is (and it might be), it won't be for long IMO.

Offline Lobo

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Re: Mars Precursor Vehicle
« Reply #61 on: 06/28/2017 05:41 PM »
But they'll have this complex and hard to reuse LV that will only be needed once in awhile, and is basically an evolutionary dead end.

So if F9 and FH are so different cost wise, why wasn't the circumlunar mission a lot more? Although we've never received an exact figure, it still looks to be less than $200 million, and that includes the Dragon 2 and all the support to go with it. Seems like they would have been far enough along on the development of FH when they announced this mission, they would have a handle on what would be involved.

Well FH is almost already developed and paid for now.  And I don't know that it's really more costly to launch, I said more "complex".  Meaning, more tricky with more modes of failure than the single core...as well as more complex to recover boosters as there's more than one, but you do it with the same personnel and support, so that'd be more a fixed cost I'd think.

But like I said, they still need it for now.  There isn't anything else close to being ready for that upper payload range that F9 can't do.  They need to have an offering in that D4H range.  Scrapping it when it was already in development when they didn't have an alternative doesn't seem like it would make much sense?

And I could be completely misreading the tea leaves here.
I was just noting Elon's past comments, and considering the delays in it's development, as well as others' comments about the complexities of launching D4H, the only US all liquid tri-core that we have to compare with, makes it seem like it's quite a bit more invovled  than a single core F9.

But, how much SpaceX may or may not want to replace FH is a tangential discussion.  To get back to my original point, I don't know that they'll want to put a new big Raptor Mars upper stage on the FH booster, as discussed upthread, for some of these reasons.  And Maybe instead they build a new Raptor booster, and fly a FH upper stage on it as an interim (FH class) precursor vehicle while developing the upper stage/spacecraft for it.  Once that was developed, then that full stack would be the true Mars Precursor vehicle.
Just a wild-eyed alternative.  :)

« Last Edit: 06/28/2017 05:45 PM by Lobo »

Offline Negan

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Re: Mars Precursor Vehicle
« Reply #62 on: 06/28/2017 05:41 PM »
I'm sure that FH with reuse will be cheaper than F9 expendable within a few years.

So it has already been established that currently FH with reuse cost more than F9 expendable?

No, that has not been established. But if it is (and it might be), it won't be for long IMO.

Makes sense. I can also see how a reused expendable F9 could also really muddy the waters too.

Online Lars-J

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Re: Mars Precursor Vehicle
« Reply #63 on: 06/28/2017 06:16 PM »
Given how complex FH is turning out to be, I think one things is clear: SpaceX won't be doing any multi-core vehicles anytime soon.

Any vehicle that replaces FH and/or is an ITS precursor will be single-core.

Offline envy887

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Re: Mars Precursor Vehicle
« Reply #64 on: 06/28/2017 06:35 PM »
Given how complex FH is turning out to be, I think one things is clear: SpaceX won't be doing any multi-core vehicles anytime soon.

Any vehicle that replaces FH and/or is an ITS precursor will be single-core.

True, but also OT here. The vehicle described by the OP is specifically "a second stage, but can also be a refuelable Mars vehicle". Not a complete FH replacement.

Offline rsdavis9

Re: Mars Precursor Vehicle
« Reply #65 on: 06/28/2017 08:20 PM »
But the title of the thread is "mars precursor vehicle".
Which to me means any means to implement some of BFR/BFS(to reduce development) and make it useful to the current business/mars.
So any vehicle that reduces some of the technology development for BFR/BFS and produces something useful at the same time.

If it isn't useful, i.e. make money, then it doesn't make sense as and intermediate vehicle.
The OP chose the upper stage with raptor as the obvious place to make something.
bob

Offline watermod

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Re: Mars Precursor Vehicle
« Reply #66 on: 06/28/2017 09:18 PM »
A totally different idea for a precursor vehicle to test out the technology in a minimally invasive way.

First, it depends on the Omelek Island test site still being in relatively good shape.
If it is then they could test their small experimental version of the Raptor in a Falcon 1 or 1e form factor.
This gives a small 1 engined rocket easier to modify in a form factor they might still have manufacturing jigs for.
SpaceX could do tests and modification at a remote location with no footprint on their current infrastructure.   
They could in the process get a nice small sat launch vehicle.
This would provide confidence for the larger changes in existing form factors and for the ITS.

Just my off beat thought of the day.

Offline stcks

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Re: Mars Precursor Vehicle
« Reply #67 on: 06/28/2017 09:26 PM »
First, it depends on the Omelek Island test site still being in relatively good shape.

FWIW there is nothing left on Omelek except memories

Online Lars-J

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Re: Mars Precursor Vehicle
« Reply #68 on: 06/28/2017 09:32 PM »
Given how complex FH is turning out to be, I think one things is clear: SpaceX won't be doing any multi-core vehicles anytime soon.

Any vehicle that replaces FH and/or is an ITS precursor will be single-core.

True, but also OT here. The vehicle described by the OP is specifically "a second stage, but can also be a refuelable Mars vehicle". Not a complete FH replacement.

Ok, I guess I misunderstood then, it seemed like some were suggesting a Methane FH.

Offline TomH

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Re: Mars Precursor Vehicle
« Reply #69 on: 06/29/2017 12:16 AM »
What's the possibility / likelihood of 39C being constructed as a multi vehicle pad with 2 opposing TEL/HIF sets ?

39C was recently developed, but for small LVs. The original map for Complex 39 designated possible locations for 39D and 39E however.

Offline su27k

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Re: Mars Precursor Vehicle
« Reply #70 on: 06/29/2017 03:04 AM »
What's the possibility / likelihood of 39C being constructed as a multi vehicle pad with 2 opposing TEL/HIF sets ?

39C was recently developed, but for small LVs. The original map for Complex 39 designated possible locations for 39D and 39E however.

The recent developed 39C is actually part of 39B I believe. The original planned 39C and 39D area are merged together and are now called LC-49 which can be developed into a super heavy pad, although I imagine it would be a pretty expensive operation.

Reference: https://masterplan.ksc.nasa.gov/Future-State/Future-Land-Use/Vertical-Launch

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