One of the reasons why I’ve started doing these “Random Thoughts” blog posts was in order to toss out some ideas that I just don’t have the time to research completely, yet still sound interesting. On some of my more detailed posts, I can often spend 4-6 hours writing, doing math, looking figures up, etc. Because of that hurdle I post less frequently, and unfortunately I was noticing that some interesting ideas were falling completely by the wayside. It’s generally considered bad to sacrifice quality for the sake of quantity, but I look at it more as it being better to let out an idea that is half-baked and get early feedback than to sit on it until I’ve forgotten about it.
So without further ado, my latest musing.
In case you haven’t noticed, I don’t like the Shuttle. I don’t like Shuttle Derived Boosters. I spent half my life in Northern Utah, but I really don’t like SRBs, and have never been that impressed with them. I’d really like to have a reason to retire the Shuttle sooner rather than later. I know it isn’t going to happen, but a guy can wish can’t he?
One of the key problems with retiring the Shuttle sooner (or even in 2010) is that there are many ISS modules and payloads that were designed specifically to be launched on the Shuttle, and can’t just be launched on a standard EELV. The argument has gone that if we don’t keep Shuttle flying, we can’t complete ISS, and without ISS there won’t be a market for COTS. Never mind the fact that NASA just undercut COTS by signing a contract with Russia for crew and cargo services out through, was it 2011?
So, for a long time I’ve been noodling alternatives to the Shuttle for launching such payloads.
So here’s the idea. Well, here’s some background first. CSI recently unveiled their LEOExpress idea for cargo delivery to space stations (ISS as well as Bigelow). The basic idea is you make a cargo canister that has a “Progress Nose” on both ends, and a cargo section in the middle. You launch this canister on any existing LV (Atlas, Delta, eventually Falcon or K-1 as well). The upper stage of the LV holds the canister in place until a Progress can undock from the space station, and rendezvous and dock with the canister. The LV upper stage then separates and deorbits, and the Progress hauls the cargo up to the station where the free-end of the cargo canister then docks into the Progress’s original docking port. After use the progress then disposes of the canister and itself. It’s a kind of cool idea that really doesn’t feature a lot of new technologies, while still opening up a bunch of new capabilities.
Currently the canisters envisioned all have the same OD as the existing progress module. But what if you expanded those canisters? Say to the same internal volume and shape as the Shuttle payload bay? Use composite structures to transmit the loads from the ISS modules into the canister in the exact same manner as on Shuttle. Provide all the services packaged in so none of the modules have to be redesigned. Sure it’s wasteful to toss away such a payload canister after each mission, but these are just stripped down payload bays with the minimum number of services for the job.
What most people don’t realize is that while the Shuttle can put almost 30 tons into a due-east, minimal Low Earth Orbit, it can only put about half of that (~32,600lb IIRC) all the way to the station. This is because Shuttle has a very low MR “upper stage” and is operating at the bad end of the Rocket Equation. Vehicles like Atlas V 552 and Delta IVH could likely launch more to ISS, even once you take the hit for the “shuttle bay canister”.
Anyhow, that’s the idea. I’ve run the numbers, and the payload is heavy enough compared to the Progress tank capacity that you would need to deliver the cargo to just outside of the ISS operating area, and just have the Progress supply the “last-mile” so to speak. And I don’t have specific numbers on how much Delta-IVH or Atlas V 551 or 552 can deliver to an ISS altitude and inclination, but at least from preliminary investigations such an idea could be doable. Since we’re going to retire the Shuttle soon anyway, reverse engineering one of their cargo bays to make such an expendable cargo-bay-canister might actually be a good idea. There are some modules that are never planning on flying as is, and this might provide them a second chance. Plus if it were done quick enough, you might be able to retire the orbiters a year sooner, and funnel some of that money into more productive purposes.
Just a thought.