Author Topic: Speculation: what will be the first ITS hardware to fly?  (Read 4611 times)

Online envy887

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Re: Speculation: what will be the first ITS hardware to fly?
« Reply #20 on: 04/18/2017 12:53 PM »
Another thought:
What would be the largest payload that could be placed on top of a FH core+boosters stack?
Using their existing heavy launcher, SpaceX could fly a subscale ITS stage as a reusable combined US/payload, and validate the OML. If adding CH4 to thr pad was possible, then it could also test fly the Raptor- otherwise it would use Merlins.
This would get flight experience on a large lifting body, without needing to build the BFR and its pad first.

I don't think that upper stage mass would be the limiting factor. Peak stresses are almost certainly in flight, not sitting on the pad, and flight stresses might actually go down with a larger upper stage because the vehicle accelerates slower and hits trans-sonic and MaxQ later and higher in the atmosphere. Wind shear is also less stressful due to lower speeds in the dense part of the atmosphere.

IMO, bending moments from a large upper stage under aero loads will be the limiting factor.

Online envy887

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Re: Speculation: what will be the first ITS hardware to fly?
« Reply #21 on: 04/18/2017 12:57 PM »
...
Another thought is that the FH US/payload should total around 175t, and the dry mass of the BFS is supposed to be 150t- and the tanker presumably a bit less than that. So in fact it would be, in theory, possible to launch a short-fuelled full size BFS onto a suborbital trajectory. The aero loads for the poor little Falcon would perhaps be too much, and operating the BFS as a single stage suborbital (or even orbital) vehicle is probably more likely- but it's fun to run through the different options.

A BFS would look preposterous sitting on top of Falcon Heavy. Falcon Heavy boosters next to a BFS might work, but are entirely unnecessary if the goal is suborbital flight.

Offline OneSpeed

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Re: Speculation: what will be the first ITS hardware to fly?
« Reply #22 on: 04/18/2017 01:07 PM »
Neat, but the argument against is that it's a huge development project in its own right.

It would be a logical first step in the ITS development process, and retire many risks early. It would have one eighth of the material costs, and potentially be a money earner in the shorter term. That is why it is a good candidate for the first ITS hardware to fly. The updated SpaceX plans for ITS can't come soon enough ;)
« Last Edit: 04/18/2017 09:29 PM by OneSpeed »

Online guckyfan

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Re: Speculation: what will be the first ITS hardware to fly?
« Reply #23 on: 04/18/2017 01:24 PM »
Coming back to a methane upper stage for F9/FH. Just one Raptor vac, scaled or full size. Make it the weight of the present upper stage, so slightly more diameter, but same height. How much can the TE take without shape modification? 50 or 60cm more diameter should do it. Carbon fiber body, autogenous pressurized. With the winglike extensions of ITS or without, but with the flaps. Nozzle extension small enough to fit into the existing interstage.

This should give the reusable upper stage for F9 and FH without payload penalty for most orbits plus plenty of ITS related experience. It could even fit the end of next year timeline for reusable upper stage, or almost, if they have been working the idea for a while.

Offline OneSpeed

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Re: Speculation: what will be the first ITS hardware to fly?
« Reply #24 on: 04/18/2017 09:44 PM »
Coming back to a methane upper stage for F9/FH. Just one Raptor vac, scaled or full size. Make it the weight of the present upper stage, so slightly more diameter, but same height. How much can the TE take without shape modification? 50 or 60cm more diameter should do it. Carbon fiber body, autogenous pressurized. With the winglike extensions of ITS or without, but with the flaps. Nozzle extension small enough to fit into the existing interstage.

This should give the reusable upper stage for F9 and FH without payload penalty for most orbits plus plenty of ITS related experience. It could even fit the end of next year timeline for reusable upper stage, or almost, if they have been working the idea for a while.

Everything in the current launch process assumes a 3.66mØ rocket, including tooling, road transport, and the TE. If you are going to change all of those, why not go straight to a half scale (6mØ) BFS, and learn a lot more?

Also, the split body flaps would be integrated with the strakes, not a separate option.

Online guckyfan

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Re: Speculation: what will be the first ITS hardware to fly?
« Reply #25 on: 04/18/2017 09:59 PM »
Road transport is not important for reusable stages. The airframe would be produced where ITS would be produced later. I was suggesting a very moderate diameter increase, just enough that the same propellant weight fits. The idea being that the TE does not need modifications. If I am wrong and the TE can really not handle 50cm additional diameter, that would be 25cm/10 inch closer to the TE, then indeed the idea is not feasible. But that is why I am not suggesting something much larger, optimized for FH.

The idea is just getting experience with the new materials and technology and at the same time gaining enough performance to compensate for reusability losses, no more.

Offline Paul451

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Re: Speculation: what will be the first ITS hardware to fly?
« Reply #26 on: 04/19/2017 11:26 AM »
Hard to imagine that SpaceX would hesitate to modify the TE again, if they thought a wider diameter upper-stage had a market.



Generally:

No methalox launch vehicles smaller than ITS. No Raptors smaller than the ITS-version. No intermediate-sized versions of anything. (This is not my preference. I'd prefer them to go the other way, but I see nothing to suggest they will.)

[Exception: if someone like the USAF wants to pay (directly or through significant contract launches) for an upper-stage development, and Musk thinks there's a profit in it. He'll use it to further practice building recoverable upper-stages, vacuum versions of Raptor, etc.]

First, a dumb but full-diameter variant of the ITS-Orbiter created within 2yrs as a Grasshopper (more like a kangaroo) to test engines and landing systems, eventually to test the recovery cradle. This is the first vehicle that Musk referred to.

Then the ITS-Booster, possibly skipping right past a Grasshopper test-vehicle step for that. This tests the launch infrastructure. If the ops cost is comparable with the multi-core complexity of FH, ITS will immediately replace FH as SpaceX's heavy lift launch vehicle. Let customers pay for recovery tests. (If not, no harm done.)

(I suspect the first version of the recovery/capture system will be separate from the launch pad. Same site, but far enough apart that a failed landing doesn't take out the launch pad.)

Then a simplified cargo-carrying ITS-Orbiter, launching on the ITS-Booster, for launch & recovery tests.

Then the ITS-Tanker, that allows orbital docking tests and higher-rate ground-ops practice. Now they have the parts necessary to deliver a payload or two to surface of Mars. I suspect they'll test a couple of versions of their fuel-production system in-situ, rather than try to sim everything to death on Earth. But its likely this flight (or flights) will be sold to someone like NASA, early 2020's for a next-gen rover, sample-return missions, etc, letting SpaceX effectively fly their test missions for free.

Then a man-rated version of the ITS-Orbiter, flown into space a couple of times to test, maybe flown unmanned to Mars once. Maybe. But the moment SpaceX is comfortable with the orbital propellant transfer system, the in-situ Martian propellant manufacturing system, and the reliability of the manned Orbiter, they will fly humans to Mars. Even if the early versions can only support a handful of people for a short-duration mission, they'll fly volunteer researchers and bring them back. (And I suspect they'll be able to sell seats to existing agencies.)

[Nomenclature: ITS (the whole thing). ITS-Orbiter (AKA "BFS", the top bit). ITS-Tanker (the other version of the top bit). ITS-Booster (AKA "BFR", the bottom bit.)]

Online guckyfan

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Re: Speculation: what will be the first ITS hardware to fly?
« Reply #27 on: 04/19/2017 11:57 AM »
Hard to imagine that SpaceX would hesitate to modify the TE again, if they thought a wider diameter upper-stage had a market.

They will not want to cause significant downtime. The TE will need to be modified to carry methane for the new upper stage. But it would need to be compatible with the existing upper stage for a while.

Offline Robotbeat

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Re: Speculation: what will be the first ITS hardware to fly?
« Reply #28 on: 04/19/2017 01:21 PM »
They've probably built at least 10 different variants of the TE. I remember that in the early days it seemed they used a new TE variant for every launch.
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Offline spacenut

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Re: Speculation: what will be the first ITS hardware to fly?
« Reply #29 on: 04/19/2017 01:51 PM »
Does anyone have an idea of the time frame for any of SpaceX's equipment?  Raptor?  Raptor vacuum?  ITS? BFR? 

Online guckyfan

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Re: Speculation: what will be the first ITS hardware to fly?
« Reply #30 on: 04/19/2017 01:53 PM »
They've probably built at least 10 different variants of the TE. I remember that in the early days it seemed they used a new TE variant for every launch.

Yes, we all remember the downtime. Or the time between flights. They will not want that back.

Offline Kaputnik

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Re: Speculation: what will be the first ITS hardware to fly?
« Reply #31 on: 04/19/2017 03:31 PM »

First, a dumb but full-diameter variant of the ITS-Orbiter created within 2yrs as a Grasshopper (more like a kangaroo) to test engines and landing systems, eventually to test the recovery cradle. This is the first vehicle that Musk referred to.

The BFS doesn't land on a cradle, it has legs. Are you suggesting they might make a one-off version that would be different?
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Offline philw1776

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Re: Speculation: what will be the first ITS hardware to fly?
« Reply #32 on: 04/19/2017 04:05 PM »
1) ITS boilerplate.  Maybe aluminum.  Purpose to test SL Raptors.  Grasshopper style flights.  Maybe 3 Raptors.
Tests methalox engines in flight and some avionics.

2) ITS prototype with design goal carbon-fiber tanks & skin.  Rvac & SL Raptors, flies downrange & back RTLS.
Completes Block 1 Raptor engine design validation for build out & qualifies basic tank & airframe technology.

3) Booster prototype with ~21 engines. Inner ring & central cluster.  Flies downrange & RTLS but not on cradle for initial flights; temporary "legs".  Followed by cradle landing tests.

The goal of this approach is to allow rapid prototyping and flight experience without large expense building lots of early prototype engines that get ECOed and discarded.

4) Booster with ~21 engines with ITS (minimal "payload") 6 Rvac & 3 SL engines to LEO.
I've run #s based on Musk's September reveal and a 21 Raptor booster lifts a low payload ITS to LEO.
ITS orbital velocity re-entry qualified.

5) All-up all engines testing to LEO with ITS tanker re-fueling.  5b: Possible crew config ITS around the moon flight ECLSS etc. qualification.

6) Un-crewed cargo ITS re-fueled in LEO; lands on Mars with cargo, e.g. in-situ propellant equipment.
« Last Edit: 04/19/2017 04:08 PM by philw1776 »
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Online envy887

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Re: Speculation: what will be the first ITS hardware to fly?
« Reply #33 on: 04/19/2017 04:46 PM »
1) ITS boilerplate.  Maybe aluminum.  Purpose to test SL Raptors.  Grasshopper style flights.  Maybe 3 Raptors.
Tests methalox engines in flight and some avionics.

2) ITS prototype with design goal carbon-fiber tanks & skin.  Rvac & SL Raptors, flies downrange & back RTLS.
Completes Block 1 Raptor engine design validation for build out & qualifies basic tank & airframe technology.

3) Booster prototype with ~21 engines. Inner ring & central cluster.  Flies downrange & RTLS but not on cradle for initial flights; temporary "legs".  Followed by cradle landing tests.

The goal of this approach is to allow rapid prototyping and flight experience without large expense building lots of early prototype engines that get ECOed and discarded.

4) Booster with ~21 engines with ITS (minimal "payload") 6 Rvac & 3 SL engines to LEO.
I've run #s based on Musk's September reveal and a 21 Raptor booster lifts a low payload ITS to LEO.
ITS orbital velocity re-entry qualified.

5) All-up all engines testing to LEO with ITS tanker re-fueling.  5b: Possible crew config ITS around the moon flight ECLSS etc. qualification.

6) Un-crewed cargo ITS re-fueled in LEO; lands on Mars with cargo, e.g. in-situ propellant equipment.

Part 1 isn't necessary. All the relevant testing can be done on the test stand.

I think part 2 will be the first ITS hardware to fly (unless a FH upper stage appears). Might include downrange landings until the flight and landing characteristics of the ITS ship are verified.

Part 3 is also unnecessary, there is no reason to launch the booster without an upper stage.

Part 4 would be a natural step, much like building a F9 v1.0 before jumping to the final Falcon 9. Could use fewer and derated Raptors, and the same tanks as the upper stage. They could even crew-rate this "short" ITS booster and start cislunar and Mars flights with it. Fully reusable payload should be ~175t to LEO launching the crewed upper stage and ~225t to LEO launching the tanker upper stage.

Offline oldAtlas_Eguy

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Re: Speculation: what will be the first ITS hardware to fly?
« Reply #34 on: 04/19/2017 07:05 PM »
If the ITS has the thrust to weight ratio to liftoff the ground with 0 payload, then a flight of just the ITS without the 1st stage BFR to sub-orbital or orbital once around test flight to test the ITS systems and it's ability to reenter and land.

Once a ITS can do this then they would be ready to build and test the BFR. Then the full stack 0 payload or even a possibility of the ITS being the tanker version is sent to LEO with its tanks full.

Followed by another BFR/ITS launch this time a cargo/personnel one loaded with cargo (or payload simulators at 1/4 total payload mass simulating the payload that the ITS would have on it's return from Mars) would then refuel from the tanker go to a higher orbit and then perform a high velocity reentry (not quite Mars return speed but much higher than just a LEO return).

Now all the elements except the long duration to Mars, Mars landing, and Mars liftoff with return journey to Earth has been tested.

Offline sanman

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Re: Speculation: what will be the first ITS hardware to fly?
« Reply #35 on: 04/25/2017 08:15 PM »
So are there going to be Grasshopper-style test flights for ITS? Will they likely start at McGregor?

Online envy887

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Re: Speculation: what will be the first ITS hardware to fly?
« Reply #36 on: 04/25/2017 08:31 PM »
So are there going to be Grasshopper-style test flights for ITS?

IMO yes. That's my take based on the IAC presentation.

Quote
Will they likely start at McGregor?

Probably not. I think McGregor has some noise and altitude restrictions that would make that kind of testing more difficult. Check the past McGregor threads, there's more of a discussion there.

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