Thursday, October 29, 2009

Number 1 on the Runway

Yesterday NASA launched the Ares 1X test rocket, with spectacular results. As I saw it on the launch pad with the Space Shuttle on NASA’s other launch pad I was reminded of the old NASA quote that goes back to the Mercury Missions, “You’re Number One on the Runway”.

At the time that quote was a joke as obviously there were no other spacecraft ahead of them waiting to take-off.

It’s not so much of a joke anymore with two Spacecraft waiting to take-off (even if the launches are weeks apart).

With the Ares 1X successful test, and SpaceX’s Falcon 9 rocket moving along, in a few years we could see Cape Kennedy nearly always having two rockets waiting to launch, opening up great opportunities for the human presence in Low Earth Orbit.

Space Station Missions will become much simpler when they know the next flight is only days away instead of the current system of having to plan everything with the expectation that if something goes wrong the next flight might be months away.

If the Ares 1 and the Falcon 9 turn out to be even as reliable as the Space Shuttle, not a hard goal, America can start making real plans to use space.

By having 2 separate craft doing missions to space, the odds of continuous missions are exponentially improved. If they both had a 1 in 10 chance of a mission scrub that took them out of commission for months that would mean a 1 in 100 chance of something taking both of them out of the picture. (Not to mention the Russians and Chinese launches.)

Those are odds that make working in Low Earth Orbit practical.

I can’t wait until Mission Control has to seriously say to a crew on a manned flight, “You’re number two on the launch pad.”

To those people that are against having NASA go forward with building new spacecraft, I am reminded of the words of John F. Kennedy:

“the United States was not built by those who waited and rested and wished to look behind them. This country was conquered by those who moved forward, and so will space.”


Stephanie B said...

Actually, making something launch more reliably than the Shuttle is hard. Average launch failure rates are greater than 5%. The Shuttle's failure rate is better than half that.

It's not the launch scrubs that are the issue, it's the mission losses (missed orbit, launch abort, etc) and, worse, catastrophic losses that really hurt you. A scrubbed mission (like a leaky valve during cryoloading) might cause a month or so delay. A mission failure (like one requiring use of the launch abort system) might be months if not years delays. A catastrophic failure can cause stand-down for years.

What I'm saying is that I'm not sure your risk logic is indicative of the risk.

However, I think it's worth doing anyway. Not because it easy, but because it's worth it. In some ways, I think it's because it's not easy that it's worth doing.

If we can make it out there, we can make it anywhere.

Or so I think.

Project Savior said...

I love the "If we can make it out there, we can make it anywhere." LEO,LEO.
I grabbed the 1 out 10 out of thin air cause I didn't have time to look stuff up like I like to.
But using the 5% number. That's 1 out of 20, so two different types of spacecraft with the same scrub rate would have a 1 out of 400 chance of them both being out of commission at the same time.
10 launches each a year that makes it an event that happens once in twenty years.

Stephanie B said...

No, I don't agree. Not a scrub, a launch FAILURE where you lose your launch vehicle, your payload or both, and your logic is, in my opinion, too simplistic. That's 5% chance of failure EACH launch. At 10 launches/year, that's a 50% chance of a launch failure per year. And that's just as simplistic and just as misleading.

Let's say we have a six month down time for a launch failure - you've lost two-three launches that don't happen, your 20-sided die is effectively on the one FAIL side, meanwhile, you're still throwing the other 20-sided die 2-3 times. During any six months down time (and that's very optimistic), which you would expect every two years (from these stats), you have a 10-15% chance of losing one of other program's flights. Combining the two gives you about 5-7.5% chance, each year, of having them both out at the same time (that's 1:13-1:20). You'll notice, that, numerically, that's still close to your own value (1 time in 20 years) - as long as the amount of down time isn't greater than six months, and there's no damage to the facilities (like launchpads), and there's no common cause failure mode between the two programs.

I'm always leery of making too much of statistics or reading too much in them. Statistics are GREAT if you are working with millions of something (which is why insurance companies ALWAYS make money). But there is a world of difference between saying, I expect 1000 (and only 1000) of these 50,000 people of dying this next year (statistically quite likely true within a percentage point or two) and saying, I expect 1 (and only 1) of these 50 people to die next year (considerably less likely to be accurate) and saying only 1 (and only 1) of these 50 people will die per year over the next fifty years (demonstrably wrong), even though they all come from the same statistical ratio. The smaller your number of whatever, the greater the potential dispersion between the number you expect (average/median) and reality. I.e., predicting if a particular person (who isn't actively dying at the moment) will die in any given year is almost statistically meaningless.

Note that that 5% average encompassed programs that are mature and have been flying since the 1970's and programs that are just starting out. First five flight estimates are much worse.

Project Savior said...

Besides 400 being a so small a number that my margin of error is greater than the stat for Mission Failure I'm using, and the fact that both the actual Ares 1 and Falcon 9 are merely concepts at this point, not actual rockets, so any performance numbers are meaningless, and not taking into account catastrophic failures, and basically simplifying everything to nearly point of reductio ad absurdum and the other things that happen when I've only got 15 minutes to post (This response took longer than the original post).
I would still rather be on the ISS with two different types of American spacecraft and a Russian spacecraft for support than just one of each.

Stephanie B said...

You got the gist of it. The more baskets you have for your eggs, the better the chance of getting chicks.