Shipbucket

So, I'm a rocket scientist. I like playing around with these things.

Consider the following doodle in two frameworks. First, as a Space Launch System alternative, similarly leveraging Shuttle framework (on a 10m base, not an 8.4m one) but rejecting capsules in favor of a further-enlarged HL-42.

Alternately, think of it as something like Shuttle-C, where we're returning the engines and avionics but rejecting a payload-return capability. This gives us something like 150k to LEO, with only the tank and fairing as expendable. We can decouple the crew and lighter payload return capability and stick it on the top of the stack, where it's safe from foam damage. I think the engine pod is safe too, but if we lose one every now and again it's no big deal.

The engine recovery pod for Shuttle-C is something that was extensively studied, and I stole it and traced it directly from here: https://www.aiaa.org/uploadedFiles/Abou ... alAIAA.pdf

HL-60 could carry 20klb of crew and passengers to LEO with almost 800m/s of hypergolic dV, or something more like 35-40klb with Shuttle-like margins. There is a 10x25' payload bay (cf. 15x60 on Shuttle) that would, for ISS missions, be a pressurized passthrough to a tail docking adapter. For missions like Hubble repair or similar, one might imagine a pair of HL-60s docking on-orbit near the target, with one carrying a passenger cabin of about 1400ft3 (Shuttle is 2600) and the other with tools, replacement parts, a manipulation arm, and maybe a bit more crew space. There is a permanent space for two crew, an airlock, and additional lifesystem stuff, to the tune of about 600ft3, although one certainly presumes it could fly unmanned. The notional access tunnel is another 800-900ft3, although I don't think it'd be useful for much.

Pusher solids for abort through the entire launch profile. About 350m2 of solar panel, comparable to ATV. Tail skirts for relocation would fit through the nose door of a 747F, so we might imagine NASA would buy one or two of those and use them for transport. The docking mechanism is a notional 50"-diameter expanded version of the international berthing and docking mechanism, which would allow for transfer of large objects to the ISS (not all current automated cargo vehicles can do this). Note that the pressurized cargo volume would be very similar to that of ATV if used in this role, and substantially greater than any other supply systems. Payload by mass is about double.





Notional stack is three regenerative RS-68A with a pair of RSRM. Later blocks might do crazy things like a Delta IV Heavy parallel stack, which I suspect (I haven't run the numbers) could well exceed any SLS option yet proposed.

Anyway, I enjoyed playing with it!

Great art

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Wansui!

Brilliant. My first (and I will probably have more) is why the selection of the Nitrous Oxide - Ethane OMS/RCS propellants over something more classical such as HTP/RP-1?

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If I understand the technical literature, N2O/C2H6 is hypergolic, storable as liquid at STP, and non-toxic. That's a pretty great trifecta for a ~310s Isp bipropellant.

Fair enough. That's about 30s higher than the biprop I noted (as defined in the PLS/HL-20 study). Similar safety measures.

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𝐌𝐀𝐓𝐇𝐍𝐄𝐓- 𝑻𝒐 𝑪𝒐𝒈𝒊𝒕𝒂𝒕𝒆 𝒂𝒏𝒅 𝒕𝒐 𝑺𝒐𝒍𝒗𝒆

Great work Erik! Glad to see you in the orbit

Great drawings of an interesting concept.

I re-oriented everything around a comically oversized X-37, since this shape most accurately reflects the best hypersonic aerothermodynamics we think we can achieve with modern materials. We can now carry payloads of 10x35ft, which I note is larger than the original minimum required by the Shuttle as we knew it. Still something like 20-30klb of crew and cargo to orbit with something like 800m/s of dV once they get there. Note aft access tunnel can be installed to link up to back half of payload bay for (e.g.) crew transfer modules or ISS resupply. Built-in crew pressurized volume, not counting the aft tunnel, is about 1500 cubic feet.

I like this concept very much more than HL-60. Quite aside from the larger payload, performace should be improved at all speeds.





Also presented is a notional visible-light telescope configuration with about 5x the light-gathering of the James Webb Space Telescope. 10m fairings feel like cheating.

Very nice work on both of these concepts.

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Much more careful (read: less beer) number crunching led me to realize I could substantially optimize the design in the context of shuttle launching, at least working under the fundamental premise of a 70klb 3x RS-68A return vehicle that had to achieve at least a low orbit (so we can pick our landing spot and return it directly to KSC/Vandy).

In the case of the X-37D vehicle, we end up being able to put 250klb (!!) on-orbit, at least at low inclination. Limited practical experience suggests a spaceplane empty-weight scaling with about the 1.64 power of length. If we remove the 3x7klb from the Shuttle (no RS-25 here!), scaling gives us about a 90klb empty weight. In contrast, HL-42 specifies a 20% dry weight margin on 29.5klb, for a notional empty weight of 23.5klb, which scales to 95klb. Neat! Let's split the difference to 92.5klb.

Anyway, let's add back in a 10% margin to take us to 102klb. Figure 35klb of crew and cargo, and I want 500m/s of on-orbit dV off of 310s OMS (c.f. 300m/s STS). That takes me up to 200klb. HL-42 says I need about 27% margin for adapters and solids, which in turn takes me to a nice round 250klb LEO capability (which I note with some degree of horror is more than a space shuttle at full gross). This is the penalty we pay for an inline stack and a second re-entry vehicle for engine replacement and refurbishment. Note the laziness with which I assume we'd carry the solid abort motors all the way to orbit. You'd chuck 'em earlier than that, so treat that as a growth margin or whatever.

An interesting (to me, anyway) side detail is how inflexible this vehicle is to growth and shrinkage, something that I find frustrating because I was hoping to get Delta/Atlas-like flexibility out of the rocket family. It's not surprising if you think about it, though: because of the way we're seeking to recover the first stage engine pod, we need to carry those engines all the way up to orbital speeds. Solids only affect the design so much, really. Secondly, our recovery-pod concept really limits the base area available for engine carriage, and the RS-68 is (while the biggest hyrdolox engine ever) not that big in the context of a 10m-diameter launch vehicle. Indeed, my calculations suggest that after solid motor separation, our T/W is right at 1.0. This is okay (many vehicles actually drop under 1.0 after first-stage separation), but it means we can't play a Delta IV sort of game where a common booster core can be the one and only component of a launch vehicle.

All that said, we can boost as little as about 175klb to orbit (compared to 150klb for SLS Block 0) without a tank size change, and up to 450klb or thereabouts on a twin-parallel-stage concept (you could go beyond this to three or possibly four cores, but you'd lose a lot of design commonality). So that's pretty great. And everything is reusable except for the sheet metal of the tanks and adapters and fairings. That's pretty great too.