Author Topic: F9 Second Stage Reusability  (Read 351383 times)

Offline redneck

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Re: F9 Second Stage Reusability
« Reply #1060 on: 05/20/2023 10:31 pm »
Would it? You lose a fair amount of surface area with the truncated nozzle. The deleted part is extremely thin and not very heavy.

Counter intuitive, but a spent upper stage with a truncated nozzle is likely a smidge denser.

I was imagining a base first re-entry like a stubby very light version of the first stage. Is the bell wider than the diameter of the tank? (I was wondering if an upper-stage is fluffier than a dragon capsule.)

A shortened bell would be lighter and stronger for handling the re-entry stresses.

Or possibly jettison the expansion bell (det cord?) before base first reentry. Definitely not a smooth entry surface in any case. Removing the bell should at least slightly improve the characteristics.

I have wondered if SpaceX has some instrumentation on those stages gathering proprietary information. Or possibly undeclared  reentry test shapes deployed after the reentry burn. These under no obligation to disclose?

Offline TrevorMonty

Re: F9 Second Stage Reusability
« Reply #1061 on: 05/30/2023 09:02 pm »
How viable it is to reuse US depends on launch cost of reusing booster. There is also payload reduction for cost of US reuse.

Here are some costing examples for launch costs, the numbers are just show cost ratios.
Reuseable booster $50(B), expendable US $50(EUS) for 100kg so $1kg.
Now we apply reuse to US but with 25% payload reduction for 50% saving on US costs.
$50(B) +$25 (RUS) = $75 for 75kg or $1kg.

Now assume cheaper booster costs.
$25(B) +$50(EUS) = $75 for 100k = $0.75kg
$25(B) +$25(RUS) = $50 for 75k =$0.67kg
$10(B) +$50(EUS) =$60 for 100k = $0.6kg
$10(B)+$25(RUS) =$35 for 75k =0.47kg

Lets change US reuse costs.
$25 + $15(RUS) = $40 for 75kg = $0.53kg
$25  + $10(RUs) =$35 for 75k = $0.47kg
$10 + $15 =$25 =$0.334kg
$10 +$10 =$20 = $0.27kg

These costs ratios are important when deciding how viable reuse of US is. While reduction in payload mass also reduces addressablemarket in most cases the expendable US would've been developed first and is still available for higher payload missions.

For small RLVs like Electron its never going to be viable. Dawn reuseable Auroa 3 spaceplane booster on the other hand maybe viable. The goal is aeroplane like operational costs for the Auroa. Achieve that and $10 example above for booster reuse is starting to look viable assume payload hit version reuse costd on RUS aren't to high.

« Last Edit: 05/30/2023 09:03 pm by TrevorMonty »


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