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Space Shuttle Discovery to Launch July 26
thhamm writes "According to Space.com: 'NASA will restart the countdown for the space shuttle Discovery Saturday, with plans to launch the orbiter spaceward on July 26 after more than a week of work to pin down a fuel sensor glitch, mission managers said late Wednesday'. In the meantime, technicians will work with grounding wiring associated with the liquid hydrogen engine cutoff sensor system, as well as adjust the configuration of components within Discovery's point sensor box."
Actually, it's more like the check engine light went on, but by the time you get the car to the mechanic, it's gone off and won't come on again.
In the shuttle's case, they can't repeat the problem. The theory now is that it only occurs when the tanks are loaded (and thus at cryo temperatures versus ambient).
I can only hope and pray that this isn't another example of government administrators scheduling a shuttle flight (ala Challenger), thinking that they know more about the problem than engineers. To a degree, this is also what brought down Columbia. Godspeed, STS-114..
Throughout 40 years of manned space flight, there were no fatalaties.
0 4/
Which 40 year period was this?
There was this tragedy in 1967, perhaps not often mentioned since it was an on-pad test and not part of an actual space flight:
http://www.hq.nasa.gov/office/pao/History/Apollo2
Tag lost or not installed.
A couple things:
1) Destroying the shuttle, like the parent hoped for, would be disastrous. Not only would we see NASA cuts, as others have suggested, but there'd be another multiyear downtime in which nothing occurs: Including the development of a replacement vehicle.
2) The focus on complete re-usability.
What focus on complete reusability? The external tank is disposable.
3) The reliance on the tiles alone, without any ablative shielding
Ablatives are just as problematic for a reusable craft. Ablatives, too, can chip, and have to be reapplied with care and detailed inspection. They're even more problematic around moving parts, btw, than tiles and RCC panels are. Lastly, they weigh more, something that the shuttle simply couldn't afford.
The shuttle's main problem isn't something that you stated: it is having such a huge reentry vehicle. A huge, *dense* reentry vehicle (dense because it doesn't have big empty voids where large drained fuel tanks would normally be). This means a lot of energy to dissipate over a proportionally small surface area. Even with its low beta entry (it takes almost an hour from the LEO deorbit burn to landing), well, you know how much heat it has to deal with.
Heat problems don't scale linearly. A material with 500MPa tensile strength at 500 degrees may be down to 200MPa at 600, 40MPa at 700, 4MPa at 800, and molten shortly thereafter. It becomes a *lot* harder the higher the temperatures you have to deal with; your options quickly become quite limited.
3) tiles alone
The shuttle's TPS (Thermal Protection System) involves two different types of tiles, reinforced carbon-carbon leading edges, and insulating blankets.
4) fragile to the point of being delicate
I doubt you could damage a tile without tools short of throwing it as hard as you can onto a hard surface (in which case, you'd probably just chip it). They're nothing like steel or even aluminum in terms of resistance to damage, but they're not nearly as delicate as people around here pretend, especially given their density. The problem is, when you go hundreds to thousands of meters per second (depending on where you're at in ascent/descent), even raindrops become fierce impactors.
The biggest problems with the tiles are that they have to be repaired at all. Attaching a tile (or RCC panel, for that matter) to a metal frame, securely so that it won't fall off, when the metal is expanding at a different rate than the tile, is no simple task (it was resolved with the SIP - Strain Isolation Pad). You can't have any significant loose spaces, because at hypersonic speeds cracks tend to funnel in plasma like a blowtorch. The tiles have to endure the large vibrational loads of ascent as well. Consequently, it's a huge task to make sure that they're all A) intact, and B) securely attached.
5) Why use a vehicle in LEO to launch a satelite
It's called a stage. Even vehicles that we "launch from the ground" typically use a separate stage to get to GEO. Now, why you'd want to use a *manned* craft for the first few stages is a good question; however, the shuttle usually doesn't deal with such missions, and leaves them to things like Atlas and Delta rockets.
Point of interest. Offering to shoot us might not work so well as an incentive as you might imagine.
His ashes will go into space, according to http://www.startrek.com/startrek/view/news/article /12920.html, just probably not on the shuttle.