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SpaceX wins $440M contract with NASA to develop Space Shuttle successor

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Re: SpaceX wins $440M contract with NASA to develop Space Shuttle successor

#91

Post by wamatt »

physcab wrote: post #53
natep wrote: post #39

Earlier quoted context omitted.

From TFA: "This is a decisive milestone in human spaceflight and sets an exciting course for the next phase of American space exploration," said SpaceX CEO and Chief Designer Elon Musk. "SpaceX, along with our partners at NASA, will continue to push the boundaries of space technology to develop the safest, most advanced crew vehicle ever flown." So yes, he is claiming it is the safest, and I think he has good reason…

Safety isn't as much determined by your aspirations, as it is by your record. 37% failure is an acceptable milestone considering all the SpaceX has achieved in its short lifetime, but I doubt would satisfy NASA's safety regulations for human spaceflight.

Suspect you may be confusing the state of 'being safe', with the measurement of 'being safe'. Empirical methods are not the only way to quantify something.

Either world view relies on

"Just trust me, I know" or "The numbers never lie"

Would be potentially problematic.

This debate has been going on for centuries.

http://en.wikipedia.org/wiki/A_priori_and_a_posteriori

Re: SpaceX wins $440M contract with NASA to develop Space Shuttle successor

#92

Post by joshuahedlund »

alpine wrote: post #43

I would hate to see SpaceX become an acquisition of NASA, or a nationalised company of the US Federal Government. Stranger things have happened, of course, but if Musk wants to retire to Mars, he had best be concerned with this.

I'm pretty sure I've read (though I could be wrong) that SpaceX is already profitable from contracts to launch commercial satellites, even without NASA's budget dollars.

Re: SpaceX wins $440M contract with NASA to develop Space Shuttle successor

#93

Post by ceejayoz »

btilly wrote: post #84
ceejayoz wrote: post #74

Earlier quoted context omitted.

> So what you're telling me is that they have a more sophisticated system than previous ones with sophisticated backups. Given that the shuttle's SRBs were "once they start, they don't stop until they're empty", sometimes more complicated is a good thing. > Until you have actual experience with the weird stuff that goes wrong in the field, you do not really know what is going to go wrong. And the more complicated the…

You're wrong that the same argument can be used on cars. Because one thing that we have with cars is lots and lots of real data from the field. We don't say that cars today are safer than cars from the 70s because we have a list of safety features. We can say it because we have actual accident statistics and casualty rates. Yet even with cars, even with the fact that they have experienced designers, when you build a…

OK, let's put it this way.

You have to options:

Option 1: Ride in a car with a single button labeled "press to start engines, you will not be able to stop until they run out of fuel". This car has been driven about a hundred times.

Option 2: Ride in a car with a "start engine" button and a "stop engine" button, plus a throttle. This car has been driven several times plus extensive testing on the ground.

"Option 2 is a safer setup" seems like a fair statement.

Re: SpaceX wins $440M contract with NASA to develop Space Shuttle successor

#94

Post by alpine »

joshuahedlund wrote: post #92
alpine wrote: post #43

I would hate to see SpaceX become an acquisition of NASA, or a nationalised company of the US Federal Government. Stranger things have happened, of course, but if Musk wants to retire to Mars, he had best be concerned with this.

I'm pretty sure I've read (though I could be wrong) that SpaceX is already profitable from contracts to launch commercial satellites, even without NASA's budget dollars.

That's wonderful - the more private contracts they win the better - and the brighter all private space initiatives will hopefully be. Unfortunately, accepting several million dollars from the US government leaves SpaceX (and other Musk ventures) vulnerable to government meddling. When the government starts to meddle in your business, they are the ones that decide where to stop. You cede control of your company's destiny often when you accept the first cheque.

Re: SpaceX wins $440M contract with NASA to develop Space Shuttle successor

#95

Post by danielweber »

zevets wrote: post #86
danielweber wrote: post #80

Earlier quoted context omitted.

This is the big deal with air-launch or dirigible-launch or whatever you call it. The air resistance of the atmosphere is significant. IIRC, it takes 9 km/s of delta-v to get from ground to LEO. LEO is only orbitting at ~7.7 km/s, though, so you can save at least 1 km/s of fuel. As others have said, schemes like Stratolaunch or SpaceShipOne also get horizontal velocity from the mothership.

It's not that high. A lot of the losses in take-off aren't the consequence of drag. I think I saw on wikipedia that the aerodynamics losses are only 1-200 m/s of the delta-v budget.

I surely don't want to use this site as gospel (especially since I can't pull up a better version of that graph) but it claims that the losses are around 25% at sea level. http://www.nasaspaceflight.com/2012/07/commercial-shows-reig...

Going by raw math, if the Earth were a perfect magic sphere with no atmosphere, you could attain "orbit" at ground-level by accelerating to 7.90 km/s. Then you could Hohmann to LEO with one 0.06 km/s burn to transfer up and another 0.06 km/s burn to achieve a circular orbit, so that's only 8.02 km/s in an ideal world. [Oh, I forgot that you start with about 0.40 km/s from rotation if you are near the equator.]

Oh, finally found a nice reference, on Wiki: http://en.wikipedia.org/wiki/Low_Earth_orbit#Human_use The delta-v needed to achieve low earth orbit starts around 9.4km/s. Atmospheric and gravity drag associated with launch typically adds 1.5–2.0 km/s to the delta-v launch vehicle required to reach normal LEO orbital velocity of around 7.8 km/s (28,080 km/h). It doesn't break those out, unfortunately.

Re: SpaceX wins $440M contract with NASA to develop Space Shuttle successor

#96

Post by Florin_Andrei »

JoeCortopassi wrote: post #21

Every time I see something like a rocket or space shuttle launch, I can't help but wonder how much of the weight and cost could be saved using alternative methods . Even helium/hydrogen filled balloons could get them a good chunk of the way there. I know that would be horribly impractical for something the size of the shuttle and it's rocket boosters/fuel tanks, but if a balloon rig can get them to 120,000 ft they ha…

The ARCA team, one of the competitors in the Google Lunar X Prize, had the same idea. I'm not sure if they're following the same design now, or whether they changed it.

http://www.googlelunarxprize.org/teams/arca

Re: SpaceX wins $440M contract with NASA to develop Space Shuttle successor

#97

Post by stcredzero »

btilly wrote: post #46
ceejayoz wrote: post #25

Earlier quoted context omitted.

> It is easy to use superlatives like "safest rocket ever designed". But a lot of stuff can go wrong - fast - when you're sitting on a big pile of potential explosives that under other circumstances you'd keep a safe distance from. Until they actually achieve it, you shouldn't throw the superlatives around. This claim revolves more around the fact that the rocket can do a powered abort at any time, I think. It's pure…

So what you're telling me is that they have a more sophisticated system than previous ones with sophisticated backups. When it comes to reliability sophisticated can go either way - it can be better or can just give more things than can go wrong. For instance what happens on your vertical landing if a sensor malfunction causes the software to decide that the rocket is not vertical unless it is at a 20% tilt? (Don't l…

> Until you have actual experience with the weird stuff that goes wrong in the field, you do not really know what is going to go wrong. And the more complicated the system is, the more true this fact is.

A great lesson for software devs.

Re: SpaceX wins $440M contract with NASA to develop Space Shuttle successor

#99

Post by arrrg »

btilly wrote: post #59
rbanffy wrote: post #54

Earlier quoted context omitted.

> It is easy to use superlatives like "safest rocket ever designed" Well... Considering its predecessor, the shuttle, was one of the least safe rockets ever designed, it's not very hard to improve upon. Use multiple engines, avoid solid rockets (at least the ones that cannot be throttled down), mount your heatshield where nothing crashes on it, keep it simple...

Considering its predecessor, the shuttle, was one of the least safe rockets ever designed... According to http://www.futurepundit.com/archives/000940.html as of 2003, the space shuttle had the best safety record of any rocket design that had been flown to space at least 100x. That fact would argue strongly against your claim.

Those comparisons make no sense and are just plain wrong.

First point: When looking at safety we care about injuries and deaths, not the launch failure rate. A broken parked car might not be reliable but it certainly is safe. Don’t confuse reliability and safety.

The two are certainly related – but not one and the same. The biggest problem with the Space Shuttle, for example, is that there is no plan B (most of the time). If you have a launch abort system you can decrease the reliability of your rocket (and thus change the failure rate for the worse) while still being just as safe.

Second point: It just makes no sense to compare manned and unmanned launch systems. Bringing Atlas and Ariane in the mix just makes no sense at all. You can’t meaningfully compare the safety between those launch systems and the Shuttle, if only because it’s impossible for humans to be injured or killed in those rockets.

On a deaths per humans brought to space metric the Shuttle is a horrible performer and very unsafe.

Re: SpaceX wins $440M contract with NASA to develop Space Shuttle successor

#100

Post by wtracy »

alpine wrote: post #88
natep wrote: post #79

Earlier quoted context omitted.

By what mechanism, exactly do you think this will happen? He has no plans to sell. He'd like to go to Mars himself, but not if he doesn't think the mission of SpaceX would continue without him. So...that leaves it becoming 'a nationalised company of the US Federal Government"....aka, the gov't takes it over by force? How likely do you really think that is? It only took over Ford because they were bankrupt, so all he…

He has no plans to sell It is a brave man that gets in to bed with the government thinking he can withstand the intolerable pressure they can bring, if they decide, to bend his will. Nationalisation... How likely do you really think that is? Surely, it is for the oracles to strike a claim on future events, but when you consider gold confiscation in the 1930s, oil nationalisation in the 1950s, the absurd nationalisati…

How many NASA contractors have been nationalized in the past?
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