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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."
(HAL 9000 on Discovery): "I am fully operational, and all my circuits are functioning perfectly. I have the highest enthusiasm for this mission."
This time the check engine light won't turn off...
You can tell I'm an aries because of my ram.
I'm afraid that NASA shuttles will never get in the air again, due to the now incredibly high standards of NASA. The last problem may have been pretty big, but we can't turn off every shuttle launch just because it's not absolutely perfect.
Believe me, I want the astronauts to survive. But you also have to understand that going into space is dangerous. Things go wrong even in the most tested of scenarios. The astronauts know the risk.
I think it might be time to rename this shuttle Longhorn
"I'm a leaf on the wind. Watch how I soar."
-Hoban Washburn
with plans to launch the orbiter spaceward on July 26
I think we all needed that clarified. I can never guess what those wacky people at NASA will think of next!
There are three possible outcomes to the launch attempt, only one of them is completely positive:
1. Discovery launches Tuesday during the launch window and has a routine and successful mission. After that, there will be plenty of time to determine the root cause of the sensor issue.
2. The weather does not co-operate or another tenchnical glitch surfaces, causing Tuesday's attempt to be scrubbed. NASA is hounded in the press for being unable to manage their spacecraft, when in fact they are doing exactly that according to their safety protocols, which have been generally tightened post-Columbia.
3. Disaster. Unthinkable and possibly the end of an American manned space presence until the Crew Exploration Vehicle is completed and launched in the next decade.
The Space Shuttle is an aging flying compromise that has been updated as much as possible, and it is what NASA has been given to work with. I almost expect Outcome #2, given their justifiable prudence in halting launches when they are not 100% satisfied that the system is as operationally ready as they can make it. NASA may be criticized for delays, but when seven lives and a multi-billion dollar spacecraft are on the line, not to mention all of their political capital, once can understand why they do what they do.
Bottom line is that all eyes will be back on the Cape come Tuesday morning. Godspeed Discovery.
I'll watch from a distance, thank you.
Thanks, I'll be sure to forward this info to NASA.
Now what I can't imagine is how many times more difficult that is when true "ground" ends up being over 100 kilometers away!
-- I'm not a pessimist, I'm a realist. It's not my fault that life sucks so much. --
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.