Poll

What diameter do you think the Mini-ITS will have?

3.7 m (12 ft) like Falcon 9
0 (0%)
5 m (16.4 ft) like Delta IV
3 (2.8%)
8.4 m (27.6 ft) like the Shuttle ET
50 (46.3%)
10.1 m (33.0 ft) like the Saturn V
45 (41.7%)
12.2 m (40 ft) like the Falcon Heavy width
3 (2.8%)
Even bigger!
3 (2.8%)
None, it won't be built at all.
4 (3.7%)

Total Members Voted: 108

Voting closed: 08/20/2017 03:09 PM


Author Topic: POLL: Mini-ITS Diameter  (Read 4800 times)

Offline FutureSpaceTourist

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Re: POLL: Mini-ITS Diameter
« Reply #20 on: 07/21/2017 12:22 PM »
Jon has given a great set of reasons for 8.4 (I'm not qualified to comment on the BOTEs, but sounds good to me!).

I too went for 8.4 and one of the reasons was that anything bigger I felt was too close to the original 12m BFR proposal. Given the economic issues Elon has admitted with going that large, I feel the small version has to be notably smaller to change the economics. 5m feels to small to be a meaningful step-up from F9, so that leaves 8.4.

Edit: typos
« Last Edit: 07/21/2017 12:23 PM by FutureSpaceTourist »

Offline blasphemer

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Re: POLL: Mini-ITS Diameter
« Reply #21 on: 07/21/2017 12:27 PM »
We know 12m ITS should be able to put 300 tonnes to LEO with reuse. 7m New Glenn should launch 45 tonnes. What would be the figure for other diameters?
« Last Edit: 07/21/2017 12:29 PM by blasphemer »

Offline rsdavis9

Re: POLL: Mini-ITS Diameter
« Reply #22 on: 07/21/2017 12:55 PM »
10m because of pad limits discussed elsewhere.
Has anybody thought of components being manufactured at hawthorne and then airlifted to ports. Engines can be trucked. The tank(s) would probably be light enough to airlift with helicopters? Isn't there buildings at the port that are owned by aerospace companies? Boeing? LM?
With ELV best efficiency was the paradigm. The new paradigm is reusable, good enough, and commonality of design.
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Online envy887

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Re: POLL: Mini-ITS Diameter
« Reply #23 on: 07/21/2017 01:10 PM »
We know 12m ITS should be able to put 300 tonnes to LEO with reuse. 7m New Glenn should launch 45 tonnes. What would be the figure for other diameters?

It depends on height, propellant density, mass fraction, engine thrust, thrust density, and impulse, and many other things.

But roughly speaking, a vehicle with subcooled methalox and best in class mass fraction / engine performance should get:
3.6 m: 10 to 20 t
5.0 m: 25 to 60 t
7.0 m: 40 to 80 t
8.4 m: 50 to 150 t
10 m: 75 to 250 t
12 m: 200 to 400 t
15 m: 400 to 800 t
« Last Edit: 07/21/2017 01:12 PM by envy887 »

Offline rsdavis9

Re: POLL: Mini-ITS Diameter
« Reply #24 on: 07/21/2017 01:33 PM »
We know 12m ITS should be able to put 300 tonnes to LEO with reuse. 7m New Glenn should launch 45 tonnes. What would be the figure for other diameters?

It depends on height, propellant density, mass fraction, engine thrust, thrust density, and impulse, and many other things.

But roughly speaking, a vehicle with subcooled methalox and best in class mass fraction / engine performance should get:
3.6 m: 10 to 20 t
5.0 m: 25 to 60 t
7.0 m: 40 to 80 t
8.4 m: 50 to 150 t
10 m: 75 to 250 t
12 m: 200 to 400 t
15 m: 400 to 800 t

Most of the ranges are double.
Why is 8.4m and 10m   3 to 1?
With ELV best efficiency was the paradigm. The new paradigm is reusable, good enough, and commonality of design.
Same engines. Design once. Same vehicle. Design once. Reusable. Build once.

Online envy887

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Re: POLL: Mini-ITS Diameter
« Reply #25 on: 07/21/2017 02:36 PM »
We know 12m ITS should be able to put 300 tonnes to LEO with reuse. 7m New Glenn should launch 45 tonnes. What would be the figure for other diameters?

It depends on height, propellant density, mass fraction, engine thrust, thrust density, and impulse, and many other things.

But roughly speaking, a vehicle with subcooled methalox and best in class mass fraction / engine performance should get:
3.6 m: 10 to 20 t
5.0 m: 25 to 60 t
7.0 m: 40 to 80 t
8.4 m: 50 to 150 t
10 m: 75 to 250 t
12 m: 200 to 400 t
15 m: 400 to 800 t

Most of the ranges are double.
Why is 8.4m and 10m   3 to 1?

I considered a wider range of heights for those diameters, assuming they wouldn't start with a rocket much shorter than F9. The lower bound for height increases slower with diameter than the upper bound, leading to a wider range for rockets in the middle. But height gets really unwieldy up around 150-200 m tall. 7.0 m could be more like 40-100 t, though a 100t version would be a bit skinny.

Offline Darkseraph

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Re: POLL: Mini-ITS Diameter
« Reply #26 on: 07/21/2017 03:01 PM »
8.4 because:

1. I've guessed this figure previously.
2. Similar size to another Methlox Super Heavy Rocket, New Glenn. SpaceX's next system needs to stay  competive with that.
3. Could be potentially manufactured at Michoud, something that has been hinted at by Musk before.
4. A rocket this size with a distributed launch architecture is more than enough to handle early Mars missions for the next decade or more. Going to 10 or even 12 metres is probably overkill until traffic to and from Mars is at gargantuan volumes.


One reason I don't share for voting 8.4 metres is manufacturing at Hawthorne. It would be very difficult and disruptive to get a stage that large to a port from their current Californian factory. The vehicle will probably undergo final assembly at a new facility close to the launch site or with easy access to a water way so that stages can be barged to the launch site with ease. I'd even go as far as guessing a new facility will be placed in one of the traditional space states to gain political support in Congress, similar to Blue Origin's decision to manufacture BE4 in Alabama.   
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Online philw1776

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Re: POLL: Mini-ITS Diameter
« Reply #27 on: 07/21/2017 06:06 PM »
8.4 m makes the most Hawthorne etc. logistics sense but I'm voting somewhat wishfully for 10m.

10m allows for an initial Nova class booster with N engines suitable for 39A today possibly upgraded with M more engines for higher thrust over its lifetime as a modified or additional launch facility has time to become available.  SpaceX got lots of growth out of the F9 template and I think that they may try to plan for an even more extensible next gen platform.

Arguing against my stubby 10m is that Elon seems to like his rockets and his women tall and willowy.
« Last Edit: 07/21/2017 06:08 PM by philw1776 »
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Offline Lar

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Re: POLL: Mini-ITS Diameter
« Reply #28 on: 07/21/2017 06:45 PM »
Note: I added ":none" as a poll option somewhat late. (I didn't set up the poll initially) so, sorry if some folk didn't get to vote for it... but resetting all the votes seems like a bad idea.
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Offline guckyfan

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Re: POLL: Mini-ITS Diameter
« Reply #29 on: 07/22/2017 06:54 AM »
Voted 10m because Elon Musk said "A little bit smaller". That seems to signal maxing out present capacity of LC-39A. It is also big enough to get some serious equipment to Mars for building a base. They can then take their time to build the big ship. That may then have 15m, the value mentioned before Elon announced the 12m ITS.

It is really hard to move that out of Hawthorne. So maybe they do prototyping there and move production elsewhere quickly. They can keep one booster and one spaceship in Hawthorne for fitchecks, when they move out production.

I also believe, they will build something in the New Glenn class as well, though more capable due to better Raptor performance and better dry mass. It could speed up starting to earn money by at least 2 years and facilitate cislunar operation and launching of the constellation.

Offline Nomadd

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Re: POLL: Mini-ITS Diameter
« Reply #30 on: 07/22/2017 07:15 AM »
 8.4, because that's what it will take to launch all the BA 2100s Bigelow is going to build, but still be small enough to avoid breaking my windows.
« Last Edit: 07/22/2017 07:17 AM by Nomadd »

Offline RotoSequence

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Re: POLL: Mini-ITS Diameter
« Reply #31 on: 07/22/2017 05:58 PM »
Elon's hinting that they're leaning somewhere at/under the 9 meter range.

https://twitter.com/elonmusk/status/888813713800785923

Quote from: Elon Musk
A 9m diameter vehicle fits in our existing factories ...
« Last Edit: 07/22/2017 06:17 PM by RotoSequence »

Offline Robotbeat

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Re: POLL: Mini-ITS Diameter
« Reply #32 on: 07/22/2017 06:36 PM »
Voted 8.4m as it's closest to 9m that Musk just tweeted. :D
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Offline QuantumG

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Re: POLL: Mini-ITS Diameter
« Reply #33 on: 07/22/2017 10:39 PM »
hehe... and the whole "existing facilities" part sounds Hawthorney... could be reading too much into it.
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Offline go4mars

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Re: POLL: Mini-ITS Diameter
« Reply #34 on: 07/28/2017 08:54 PM »
Even bigger.
I assume that the future version is really big. 
Easier to add length to the cylinder later than girth.
Not sure what the transportation limitations are.
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Offline cro-magnon gramps

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Re: POLL: Mini-ITS Diameter
« Reply #35 on: 07/28/2017 11:12 PM »
I figure the 9m Mini-ITS is the smallest ITS size that can be built, the next size up, the mid-size is the 12m - 100 passenger model announced last year... for the FULL size 200-300 passenger ITS i'm going with a 15-18m

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Offline deadman719

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Re: POLL: Mini-ITS Diameter
« Reply #36 on: 07/31/2017 12:58 AM »
I voted 8.4 because there wasn't a 9 meter option. 8.4 meters enables use of existing manufacturing facilities to construct the vehicle.

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