For Aron: Honoring the Shuttle

Aron asked: I have another nooby question, what do you think of the idea I posted on the Space Tweep Blog, should I go after it?

I think it's an excellent idea. For those that never follow links, Aron's proposal was to give homage to the last Shuttle flight (which keeps being put off) by carrying a torch through all of the communities that have supported it, which will cover probably every NASA center (and their surrounding communities) and many military and contractor facilities. The torch (symbolic since I think NASA will still use electronics to ignite the engines and solid rocket boosters) would not only remind us how many people have contributed to the Shuttles in their nearly thirty year lifespan, but also allow people to show that the Shuttle and its contributions have touched them.

The Shuttle is not a perfect beastie (I've talked about her before here and here), but it is still a technological marvel, even today. It cannot take us out of low earth orbit, but it has carried humans into space more than all other US space vehicles combined, more than all of the manned missions that the Soviet Union/Russia have ever launched. We have launched her 132 times, each time manned. 131 times she took her precious cargo to space. 130 times she brought them back safely. Even Soyuz does not have such a record (with regards to human spaceflight). Who knows when we will ever have a vehicle so capable of transporting

She has served this country well, humankind well.

All honor to her and to those who designed, built, service and fly her.

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For Aron: Aerogel instead of Shuttle Tiles?

Aron asked: So...I have the most insane idea for the shuttle, ever. Do you think it would be possible to strip all the tiles from the shuttle and replace it with aerogel and a thin ceramic to keep the aerogel in place. (It's insane and would increase the chance of damage to the shuttle) This could cut the weight.

It could cut the weight, in theory, given the density of aerogel. Aerogel has a density of 1.9 kg/m^3. Most of the tiles weigh in at ~144 kg/m^3 and, given that aerogel is pretty structurally strong and a great insulator, you might not even need the same volume to have the same thermal protection.

However, we might want to be careful before we get our Shuttle scrapers out and do the work.

First off, aerogel is hydrophilic (attracts and absorbs water), which means a couple of months sitting in Florida's humidity is unlikely to be good. Absorbing water not only drastically increases weight, but also cause it to deteriorate rapidly. Still, the Shuttle tiles also have to be waterproofed and there is a process for making aerogel hydroscopic (water repelling).

It's also friable which means it shatters like glass. I know it was used to gather space dust, so it can take tiny fast impacts, but I'm not sure how it would handle blunt trauma, handling, foam impact, etc.

Truthfully, we've known about aerogel for some time but I've never seen any suggestions or designs that use aerogel for a proposed spacecraft thermal protection system except early on; when the design matures, aerogel is taken off the table. I don't know why but I assume there good reasons for it. Perhaps it can't take the cold (as opposed to the heat). Perhaps it does poorly in high UV situations or is susceptible to atomic oxygen.

If whatever the problems are can be overcome (without degrading the thermal/density properties) of aerogel, perhaps some future designs will use it.

However, even if it were perfect, it might not be worth our while to change the Shuttle. As you know, there aren't many missions left for the Shuttle. Removing all the tile and replacing it (which hasn't I believe, been done in their lifetimes) would take months and probably force a recertification of the Shuttle. That's millions/billions of dollars. I'm not sure they could all be removed without potential damage to the underlying structure.

And Shuttle has some limitations - vendors no longer in business, limited spares and equipment, aging infrastructure and avionics - that replacing the tiles won't fix. Nor do I know that aerogel would better withstand foam. That makes extending the Shuttle to make the huge investment worthwhile (and to take advantage of the weight difference) a pretty bad deal I would think.

But, then, it's all speculation.

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For Aron: Tell Me What it Means

Aron asked: What does this mean? Orbiter: OV-105 / ET-134 / SRB BI-141 / RSRM 109 (VAB HB-1)

Let's break it down:

The first bit, OV-105, is the Orbiter Vehicle Designation, the one that tells us which Orbiter it is (as we still have three). In this case, OV-105 designates, for instance, Endeavour, the newest Orbiter, constructed as a replacement for Challenger in 1992. Only five space-worthy operational Orbiters were built: OV-099 (Challenger), OV-102 (Columbia), OV-103 (Discovery), OV-104 (Atlantis) and OV-105 (Endeavour). There were two other developmental prototypes: OV-098 (Pathfinder - a structural model) and OV-101 (Enterprise). Enterprise was designed to be the original Orbiter design, but without engines or heat shield; i.e. not spaceworthy. However, they did tests with Enterprise, including vibration tests, mated (to the Boeing) flight tests, and detached landing tests.

Why "Orbiter" and not "Shuttle" - well the part that comes back, the plane-like part, that lands some 4-24 days after launch is technically called an Orbiter in the Shuttle world. The whole system, Orbiter, External Tank, Solid Rocket Boosters, is called the Shuttle Transport System (hence the STS in the flight designation: STS-107, for instance). Just so you know

That leads us to the ET-134. That designates which External Tank it is. Each flight requires a new ET (they are not reusable and burn up in reentry). I think they are just numbered in order of construction, though they are not always flown in that order.

Similarly, I believe the SRB (which stands for Solid Rocket Booster) now called the RSRM for Reusable Solid Rocket Motor (also Redesigned Solid Rocket Motor) are just listed by number. I often hear the terms RSRM and SRB used interchangeably (even in technical circles), but, technically the RSRM is a redesign of the original SRBs. The SRBs/RSRMs have always been reusable and the cases are plucked from the drink not long after launch, refurbished, reloaded with solid rocket fuel and reshipped to KSC.

The last bit, I believe, has to do with where it sits in the Vertical Assembly Building (VAB), as in which High Bay (HB). But I'm speculating there.

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