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bjbjD This is the Earth Departure stage, and this is gonna be a real challenge. It's a
very, very large stage, about 550,000 pounds of propellant. But it has some very, very
unique requirements. No large stage has ever had to loiter for more than a few hours. This
one will have to loiter, under our plan, it's gonna have to loiter for up to four days on
orbit with hydrogen, and no one has ever done anything like that. I can tell you a little
of the history, in fact I dug this out of the very database that, uh, that was discussed
earlier this morning and one of the lessons learned. The, uh, Saturn 5 launched nine times
to the Moon. ...In those nine times, in every case it went through orbit and then restarted.
The shortest that it ever loitered was 2 hours 22 minutes. The longest was 3 hours. The average
was 2 hours 38 minutes. We're talking about loitering for 4 days. That is an enormous
requirement on the stage. Now, it's one thing to build like a thermos bottle and put lots
of multilayer insulation around it but the problem is, if you've ever looked at a stage,
the stage is -- it looks more like a porcipine You've got structure attached to it. You've
got feed lined attached to it, pressure sensors attached to it, all the pressurization. Everything
is attached to that Every one of those is a heat leak. ...this is a real challenge and
we're not sure yet how, this is an engineering--job's gotta be done. But it's gonna be a real, real
challenge. That 4 day loiter, it puts a magnificent burden on that. So it means, this has gotta
act as a spacecraft in orbit, it's gotta have attitude control while it's wating, It's got
to be able to handle its propellant. It's got to have MMOD protection. All the things
spacecrafts do, so all of that's got to be there. uh, this is the J-2, and I'll just
use this chart to show you what the uh, why some of the things have to be different. The
main thing is, it's got to loiter for 4 days and nobody's ever done that with an engine
like that and restarted it, and it's got to restart on orbit. And with a tank, getting
it to the start box on that engine, with a tank that big that's half empty, you get it
to the right pressure, the right temperature to start that engine is, is a real challenge.
So there will be some further testing, development testing beyond what we, what we do... gdUP
gdUP gdUP This is the Earth Departure stage, and this is gonna be a real challenge hstephenson
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