Someone was digging around the ULA publications section, and stumbled on a very interesting paper I hadn’t heard about yet discussing a shuttle alternative for resupplying the space station. While I don’t agree with everything in it, it’s worth a good read.
One of the main ideas presented in the paper is a “Payload Bay Fairing” that would allow a heavy EELV to interface and launch payloads originally designed to launch on shuttle. The EELV would deliver the PBF with its encapsulated payload to just outside the ISS “visiting vehicle stay-out zone”, and then a tug of some sort would provide “last mile” services, hauling the PBF and its payload to the station, where it would be unloaded. They mentioned using Soyuz/Progress as the tug (like Constellation Services proposed), but decided to focus on ATV due to concerns about ITAR and INKSNA issues.
The PBF would be derived from the current 5m payload fairing used on the Atlas V. The PBF would have docking/berthing mechanisms on both ends, and would have structure to allow it to transfer loads into the payloads in a manner similar to the shuttle payload bay. I imagine it would also provide the necessary services for maintaining those payloads until they were ready to be installed at the ISS. By launching this on Delta-IV, you could pretty much deliver any payloads that the Shuttle was supposed to deliver, and probably at a far cheaper price. This includes the MPLMs, the AMS module that has received so much attention, and any other modules that isn’t going to get a shot at getting launched due to the 2010 shuttle retirement.
This is an interesting idea in several ways:
- For small payloads that the COTS providers can deliver, a Delta-IV/ATV derived solution isn’t going to be cost competitive so it doesn’t necessarily step on toes as much. If the Shuttle is kept running after 2010, being a government jobs program it doesn’t have to be economically competitive with COTS, and therefore could easily squash the nascent efforts by SpaceX, OSC, and others in this area. With a Delta-IV based system, procurements would have to be handled in a competitive manner if the payload is one that could be flown on other commercial options, and therefore it’s much less likely to interfere in that key initial market.
- This provides a commercial method for replacing the key functionality that we’ll be losing when the space shuttle retires. This might allow us to drop the albatross sooner. More importantly it might allow for some of the other modules that were deselected to be restarted and launched. If Atlas V ever gets built there would even be some redundancy. Building a station out of 20 tonne chunks isn’t a crazy idea so long as all those chunks aren’t stuck flying on the same system.
- Space Tugs for proximity ops are an idea whose time has come. If you start with an ATV-based tug system, that might provide enough of a market for other more affordable competitors to start filling that niche. Once you have space prox-ops tugs available, lots of things become much, much easier. Most of the mass launched with Shuttle or Progress (or even ATV or HTV) ends up being used to handle things like prox-ops, rendezvous and docking, cargo handling, reentry, etc. The more of those functions can be offloaded to something that can stay in orbit and not have to be relaunched every time, the higher a percentage of your delivered mass can actually go to paying cargo, propellants, or passengers. Also, by removing offloading a lot of the Visiting Vehicles requirements to the tug, it makes it removes a big barrier to entry by new suppliers.Space tugs would also benefit people like Bigelow. If he didn’t have to design each of his modules as maneuvering, independently operable spacecraft, I bet his task would be a lot easier. Also, tugs would make it much easier for different groups that want to dock/berth with his stations to do so.
It’s also amusing to note that I tossed out such an idea on usenet back in 2003 right after Columbia. Now, I’ll admit that at the time, I really had no clue of all the challenges involved. And accusations that I sounded like an “engineering undergrad with lots of imagination but very little experience with real world considerations?” were probably more accurate than I’d like to admit now. But it’s always cool finding out that one of my ideas I had years ago actually was a good one after all.
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