Forgot your password?
typodupeerror

Comment: Re:Would this kind of system have saved Challenger (Score 2) 44

by gman003 (#48195803) Attached to: A Look At Orion's Launch Abort System

You basically described Orion on top of SLS. SLS takes the Shuttle launch system, scales it up a bit (adds another fuel "segment" to the boosters, and a fourth SSME), and puts it into a regular stack.

This would probably have saved the Challenger crew. The scariest thing about Challenger is that the crew actually did survive the explosion - they died when they hit the water, possibly unconscious from the lack of air pressure at altitude. The crew compartment also remained mostly-intact.

In a similar failure on SLS, it's likely the capsule would also have survived. Even if LES doesn't get them away from the explosion, they could probably survive the fireball (particularly since they're now above it, rather than beside it). The parachutes can then bring them down safely.

In an emergency like this, the LES might be triggered by computer. In that case, the LES would be able to safely pull them away from the explosion. If it relies on crew or ground-control to abort, it would need someone that can instantly tell the problem is dire enough to abort.

Comment: Re:Would this kind of system have saved Challenger (Score 5, Interesting) 44

by gman003 (#48192707) Attached to: A Look At Orion's Launch Abort System

Possibly. Probably not.

The failure modes for the Shuttle are unlike any other spacecraft's - even the near-clone of it, Buran. And any theoretical abort mode for it has to account for that weirdness.

First, the Shuttle has to remain intact. You can't just eject the "pilot area", because the whole thing is really monolithic. You might be able to get away with ejection seats, but that works only for a very small period of spaceflight (probably not Challenger - they'd have ejected into a fireball and coasted up to 60,000ft). They did, in fact, have some ejection seats on the early test flights, with partial crews, but they did away with them in use (letting some escape while leaving others to die was inhumane, and making all seats eject was far too heavy for the marginal benefit).

Second, the boosters cannot be shut off. That's the big safety drawback of solid rockets - you light them, and they aren't going out until they're out of fuel. This means detaching the boosters isn't going to work, because (without the drag and mass of the Shuttle holding them back) they'll just blow past the Shuttle, bathing it in hot exhaust. If my memory is correct, the Shuttle is the only manned rocket in history to use solid engines, in no small part because of this sort of problem. Even the Soviet shuttle clone, Buran, used all-liquid engines.

Third, the Main engines are nearly useless in-atmosphere. They're lit mainly because they sometimes fail to light, and having that failure occur halfway to orbit would suck. The "boosters" provide about 80% of the thrust, if memory serves. The SSMEs aren't even at full throttle for much of the flight - Challenger had just set them to full when the stack exploded. So any idea of "just floor the main engines to outrun the boosters" is ludicrous.

Fourth, these sorts of disasters happen with very little notice. Rocket fuels are generally extremely volatile - even the least exotic combo, LOX+RP1, is still liquid oxygen and high-grade kerosene. LH2 is safer than some things (ClF3 was, and still is, considered for rocket use), but it's still pretty dangerous, and when a tank of LH2 and LOX decides to explode, it's not going to give you even a second's warning. So the escape systems they did add after Challenger probably wouldn't have been usable, because it literally involved jumping out of the Shuttle.

Fifth, the Shuttle is HEAVY. Really goddamn heavy, especially since you're not going to be able to dump the payload during an abort. So you've got the crew, all their supplies, whatever they were carrying to orbit, and all the vehicle mass. Any rocket that could accelerate the Shuttle away from an exploding stack would be itself enormous, not something you could really justify launching into orbit every mission.

Because of these peculiarities, the Shuttle abort modes are along the lines of "pick where to crash" instead of "run away from the explosion". The four post-launch modes are "return to launch site", "trans-atlantic landing", "abort to once-around" and "abort to orbit" - all of which require a mostly-working Shuttle and must be used after the boosters are exhausted.

An LES like this could not have saved them, because you couldn't really use an LES such as this on the Shuttle. Modifying the Shuttle enough that an LES like this makes sense would basically require making it not a Shuttle - in fact, you'd basically end up with an Orion-like capsule on top of an SLS-like stack, because they're literally reusing that much of the technology.

Comment: How on earth? (Score 1) 84

by gman003 (#48185681) Attached to: IBM Pays GlobalFoundries $1.5 Billion To Shed Its Chip Division

How on earth do they find "pay someone a billion and a half to take this business" to be cheaper than just shutting the entire thing down? Even if the division is losing more money than that, I think you could do better by just firing everyone and burning any physical assets to the ground. The only way I think it could be otherwise is if it costs more than $1.5 billion just to shut down the division. Unless IBM is running a nuclear reactor somewhere and I just never heard of it, that just doesn't seem plausible.

Comment: Look at the orbital mechanics (Score 3, Informative) 219

by gman003 (#48137765) Attached to: When will the first successful manned Mars mission happen?

The way the orbits work, there's a period every sixteen years or so where the journey between Earth and Mars is shortest. There's a similar cycle for the longest path, eight years offset. Using this close approach is crucial - it means less fuel is needed (very important in rockets), and it shortens the crew's exposure to radiation.

The next close approach is in 2018 (it's still a two-year journey, so you'd actually want to launch in 2017). Barring a massive undertaking, bigger than Apollo, we will not be ready in time. I'd like it to happen, but it just isn't.

After that, missions become harder up to 2026, then become easier until the next close approach in 2035. That's when I think we will be ready. So my money is on a 2030's Martian mission.

Comment: Re:No worse than AIDS, are you kidding? (Score 1) 421

by gman003 (#48127079) Attached to: Texas Health Worker Tests Positive For Ebola

Ebola is weird.

It doesn't spread easily. The virus is basically content to sit in a corpse and multiply. It doesn't spread through air, or aerosol, or even a lot of fluids. Just blood and bile - which, granted, it does like to make you spew out, but it's not too hard to avoid unless you're trying to treat infected people or lugging corpses around.

On the other hand, just a small initial infection can be lethal. Most diseases don't spread from one particle of the virus or bacterium entering your body - most need quite a lot, otherwise they get smashed by your immune system before you even show symptoms. Ebola doesn't need much of an initial infection to turn into a full-blown case.

Given those two things, there's no surprise that Ebola so often infects the doctors who are treating it. But that's on outlier on its infectiousness - it's still not going to be a massive plague, because outside medical and funeral services, it just doesn't spread well.

To err is human -- to blame it on a computer is even more so.

Working...