Old Content:
Space Shuttle External Tanks – Ignored Resources?
May 14, 2009 by Kyle BradyTags: NASA, Space, Space Shuttle, Space Station, Spaceflight, U.S.
As required by the FTC, a Full Disclosure is available - this piece adheres to the Code of Ethics
But there's an important point to be made from this document: NASA appears to be wasting potentially valuable resources for unknown reasons, a practice that has occurred for over two decades now. This discovery (if it is actually a discovery) comes to my attention when a Presidential review of NASA is looming and the much-lauded (by NASA's top officials) "new" generation of rocket delivery is actually the focus of much skepticism and rising internal complaints.
The Gist
The gist of the paper, so far as I understand it (which is hopefully at a fairly high level), is that since the space shuttle has been in operation, materials have been wasted on each launch: the external fuel tank (the giant orange cylinder, known as "ET") is released as the shuttle leaves Earth, gets partially disintegrated by reentry heat, and lands in the Indian Ocean or Pacific Ocean, depending on launch path. Every launch.
Imagine, for a second, the cost that this adds up to: the ET has to be replaced every launch - resulting in $X spent on retrieval and replacement for all missions, and X is not a trivial number.
What if the ET were instead launched into space itself, rather than falling back to earth, and repurposed? The tanks would still have to be replaced for each mission, but they would have a second life after being drained of most of their fuel.
The Options
The paper presents a number of options that the ETs could be used for, but the most important ones are:
- raw materials for space-based construction projects
- enclosures for assorted projects
- safe havens for astronauts
- fuel/gas storage units
As the report mentions, the fuel tank would have to be flushed or cleaned before use, so let's ignore that fact and look at the options instead.
Raw Materiel
Everything used in space has to be lugged up via some method, and it's usually via rocket payloads. This is expensive, and turns out to be even more so when you have to carry alot upstairs for your project... they charge by weight.
However, if there were raw materials already available for purchase in space, assuming at a lower cost than launching your own, this could be highly useful. ETs are made of an aluminum/lithium alloy, and carry both liquid hydrogen fuel and liquid oxygen oxidizer. According to the report, anywhere from 10% to 25% of these liquids-turned-mostly-gases remain after engine shutoff (depending on the launch path), and could be turned into liquids again with some effort.
This means that aluminum-lithium would be available for purchase, as well as liquid hydrogen and liquid oxygen. NASA could have a revenue stream from any number of contractors immediately, in addition to the obligatory entrepreneurs that would be interested.
Project Enclosures
Because it's original purpose is as a fuel tank, the ETs are rather spacious and rugged, clocking in at 46.9m long and 8.4m in diameter, with an empty weight of 26,500kg. That' s just under 2,600 cubic meters of space. As a reference, my "one bedroom, one bathroom, full kitchen, living room, and dining room" apartment is ~1835 cubic meters.
Which means that the fuel tank of the shuttle has more space than I live in.
Anyways, the point is that there's alot of room, and it's built strong enough to be usable in orbit. The report adds that attitudinal thrusters could easily be fixed on the external surface of the tank, creating maneuverability and stability. The empty tank could house experiments, act as "orbital storage", or have any number of other uses.
Safe Havens
This is the point that the report pushes the most: the empty ET could be used as a "safe haven" for astronauts in orbit, or be used as easily-added-after-some-quick-modification structures for the basis of a space station or the ISS.
When would a safe haven be necessary? If there was a solar storm approaching, and an astronaut was vulnerable in naked space, this might be an option. Others situations could include space debris, damaged spacecraft, damaged space stations, and alien attacks.
The authors of the report seem to be most interested in the use of ETs as modules for a space station. With their large size, they could be used either as the structural basis for a space station to be built on (like a pier holds boats tied to it), or as actual modules for a space station itself.
This is an interesting proposal, and suggests that the large cost of assembling the space station modules here on Earth, and their subsequent launch, could have been significantly cut if the tanks were used in any sort of fashion. As modern consumers are no doubt aware, "some assembly required" would be branded on each module, but it would cost less and allow for a larger project scope.
Fuel/Gas Storage Units
As I mentioned previously, a non-trivial amount of fuel remains after launch, which could be accumulated via transfer to a collection container, resulting in an energy store for use in space operations. The report acknowledges that such a transfer would require a special device, and would not in itself be an easy process, but could nonetheless be achieved with enough initial preparation.
The tanks could also be used to store other assorted gases or fuel, sort of as an orbital gas station.
Need hydrogen? Just fill 'er on up at SpaceGas Depot!
Potentiality vs. Drawbacks
Only a few options have been listed here, and the report goes into much more detail - I suggest reading it. But such activities don't come without certain drawbacks, limitations, and potential problems, which the report also covers in large detail.
I find it interesting, however, that NASA is ignoring such a large potential resource, which would both benefit their own projects and missions, as well as double as a means of income. The saying goes that "if it weren't for the Dark Ages, we'd be colonizing space today" - the same applies to NASA.
With a little more creativity, a product they already have/use could be the driving force in expanding humanity's foothold in space.
Even if it's only in Earth's orbit.
The NASA report is obviously property of NASA (even the locally hosted copy), and some of the details on the shuttle and the ETs are courtesy of Wikipedia.
Kyle can be found on Twitter and MySpace, or reached via email.
