Author Topic: Starship Expendable Upper Stage?  (Read 43466 times)

Offline TomH

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Re: Starship Expendable Upper Stage?
« Reply #120 on: 09/18/2023 06:27 am »
How much would it cost for SpaceX to add a crew access arm to the launch tower for the Starship?

Elon recently tweeted that the full stack will likely grow by 10%-20% in height. This will require tower modifications. IDK for sure, but I believe this tower is much more easily modified than SLS tower. I think it was designed with simplicity of future modifications in mind.

Offline DanClemmensen

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Re: Starship Expendable Upper Stage?
« Reply #121 on: 09/18/2023 02:56 pm »
How much would it cost for SpaceX to add a crew access arm to the launch tower for the Starship?

Elon recently tweeted that the full stack will likely grow by 10%-20% in height. This will require tower modifications. IDK for sure, but I believe this tower is much more easily modified than SLS tower. I think it was designed with simplicity of future modifications in mind.
My guess: stretching an existing tower would be fairly expensive. The massive cap would need to be removed, and new section added, and the cap replaced. Changing the design prior to building a new tower would add very little cost. However, it is not clear that  a 10% stack stretch would need a taller tower. The lift points on the stretched SS would need to be the same distance from the SS base as they are now, which would put them farther from the nose. We have already seen how they handle an increase in SH height. All of this is actually relevant to this "expendable SS" thread. An expendable SS can be heavier than a non-expendable SS, and thus could might need to be taller to handle some large exotic payload.

A crew access arm for an Orion would be conceptually similar to the existing SS QD arm. I doubt it would be much if any heavier.

Offline Twark_Main

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Re: Starship Expendable Upper Stage?
« Reply #122 on: 09/25/2023 03:45 am »
If they can support 150+ tonnes at 4(?) g axially (FH payload & fuel at MECO), but can't support their own empty mass of 4 tonnes at 2 g laterally even with the aid of "highly specialized structures"... that would be quite a result for a horizontally-integrated LV

It's not that the Falcon upper stage can't support 2 g laterally in general. The question is more about where specifically you want to transfer 2 g laterally into the vehicle.

Unless you want to fill the entire payload bay with expanding foam and push on the whole outside surface of S2 evenly (and I'd love to have eight pages of discussion on that btw), then you'll need to figure out a set of hard points on S2 you'll use to attach it to Starship. All the complexity comes in how that structural adapter is designed and built, how it gets attached to S2 in orbit, and what happens in case of various off-nominal contingencies.
« Last Edit: 09/25/2023 03:51 am by Twark_Main »
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Offline Paul451

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Re: Starship Expendable Upper Stage?
« Reply #123 on: 10/14/2023 08:10 am »
If they can support 150+ tonnes at 4(?) g axially (FH payload & fuel at MECO), but can't support their own empty mass of 4 tonnes at 2 g laterally even with the aid of "highly specialized structures"... that would be quite a result for a horizontally-integrated LV

Examples of the required structures below.

First image in the internal support for the bottom of the upper stage and its engine, on the lower stage. Second image shows the external supports required.

Offline BitterJim

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Re: Starship Expendable Upper Stage?
« Reply #124 on: 11/19/2023 05:20 pm »
It will be interesting to see how SpaceX intend to land both vehicles to make the system fully reusable as stated.  The Super Heavy goes higher and faster than the Falcon 9 first stage but they haven't tested such a landing.  As far as the second stage is concerned assuming it will have the capability to do a controlled landing from LEO escape velocity is a different story.  Currently, a ballistic re-entry is the only possibility.

(Bold mine)

Isn't the opposite true? I thought Starship did more of the work than the Falcon 9 second stage, allowing the booster to stage lower/slower/not as far downrange

Offline Brigantine

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Re: Starship Expendable Upper Stage?
« Reply #125 on: 11/20/2023 11:04 am »
This telemetry comparison (from IFT-2 Updates thread) agrees with BitterJim (mostly).

SH burns longer, but F9 pulls more G's after Max Q and so gets more done in less time.

Eyeballing:
At staging, F9 velocity is ~1800 m/s (T~⁺140), SS is ~1600 m/s (T~⁺160)
However, F9 altitude is ~550 hm (i.e. 55 km) at staging, and although SS altitude is lower at a given time, it increases to ~600 hm (i.e. 60 km) in the extra time it has before MECO.

I don't know which F9 mission that was, YMMV depending on whether F9 is doing LEO or GTO etc.
« Last Edit: 11/20/2023 11:07 am by Brigantine »

Offline BringBackSuperHeavies!

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Re: Starship Expendable Upper Stage?
« Reply #126 on: 12/28/2023 09:18 pm »
You might need to expend the starship for higher delta-v, instead you could just fill the spacecraft inside with a big fuel tank and let that do some of the work.

Offline TomH

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Re: Starship Expendable Upper Stage?
« Reply #127 on: 12/28/2023 11:30 pm »
You might need to expend the starship for higher delta-v, instead you could just fill the spacecraft inside with a big fuel tank and let that do some of the work.

No reason to do that. The LV is designed such that they refill the propellant tanks from a fuel depot.

Offline JaimeZX

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Re: Starship Expendable Upper Stage?
« Reply #128 on: 12/29/2023 01:28 am »
Here's a fun one I don't recall seeing before, but may well have overlooked:

Could SH SSTO with a simple nose cone for low-altitude aerodynamics?

If so, with orbital refueling you could stack a payload after the fact and REALLY expend a booster.

Offline DanClemmensen

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Re: Starship Expendable Upper Stage?
« Reply #129 on: 12/29/2023 01:38 am »
Here's a fun one I don't recall seeing before, but may well have overlooked:

Could SH SSTO with a simple nose cone for low-altitude aerodynamics?

If so, with orbital refueling you could stack a payload after the fact and REALLY expend a booster.
You could also go completely crazy and stack an SS on your SH after the fact, but why do any of this? We need SH (33 engines) to get from Earth to space. After you are in space, it's mostly about the total energy (more or less, the total propellant mass), not about the number of engines. just send your payload (presumably in an SS), together with as many full depots as you wish, to whatever destination you wish.

 

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