Candrea Thomas/NASA Launch Commentator: This is Shuttle Launch Control at T-3
hours and holding. I have NASA Test Director Steve Payne here. He's going to discuss a
little bit about what the teams are doing since the "red team" has been sent by Launch
Director Mike Leinbach out to the pad to manually adjust the ground systems valve in the
mobile launcher platform. Steve, could you give us a little synopsis of what the issue is
and, and what this, this helium pressure is for?
Steve Payne/NASA Test Director: Yes, absolutely. What we found, we have, let me give
you a little bit about where this is so you know what, what it's all about once I explain
that. Between the external tank and the belly of the orbiter there are 17-inch pipes that
carry the liquid hydrogen and liquid oxygen to and from the tank into the engine
compartment. Where that belly of the orbiter meets the external tank there's an interface
it's a flat plate on the orbiter and a flat plate on the external tank and where the two meet
there's a, an area that we purge with helium. We purge it with helium for a couple of
reasons. Just one in case there's any leakage out there we get rid of it with an inert gas
and the other one is because all the piping in there is going to be extremely cold with all
the liquid hydrogen going through. That's also the interface where our electrical
connections go through. So we feed in helium gas, which does not freeze in the presence
of liquid hydrogen, and it regulates the temperature of the electrical connectors on there
so they don?t get too cold, and it purges out the area in between the two plates to make
sure we have an inert environment between the two. In this case, the pressure in that gap
between the two plates was a little too low. It was on the low side of our acceptable
limits. We were still within limits, but it was low enough that we figured we need to
increase the supply pressure. We had done a little bit of that using our secondary systems,
but we were still towards our low end of it. So what we came up with is there's a way to
adjust it using a panel that's inside the mobile launcher platform -- in compartment 33B
inside -- but it takes people to go adjust it. It's not a remote control adjust, so we,
generally what we call a red crew -- and a red crew is a group of technicians, engineers
and safety personnel that go out after tanking has started and they go address whatever
technical issues we have. In this case, in order to get to that panel inside the mobile
launcher platform, we needed to send a team out to go manually adjust this regulator
panel. What they're doing, and I don't know if you saw them tracking on the camera, we
send a team of three -- they take two vehicles because just in case one of the vehicles
breaks you have another way to get out and they observe the buddy-system so that they're
never alone. They're on radio contact and they're on intercom system contact once they're
inside the mobile launcher platform. And they're talking to our main propulsion system
engineers, and they're adjusting the regulator to the appropriate pressure so we have
plenty of margin, and we don't have to worry about it going back down to the low limit.
We can't go to high on it because the seals around that cavity will, will come loose and if
we go too low we don't have enough purge. So we're going to try to put it right in the
middle so that we have a little margin for when the temperature changes up and down or
if the tank moves -- because as you fill it and you cool it, and change in pressure, and
open and close the valves -- the tank has a little bit of movement on it, we want to make
sure we have plenty of pressure in that gap.
Candrea Thomas/NASA Launch Commentator: That's a wonderful explanation.
Thank you. I understand that this is not going to interfere with the launch attempt tonight.
Is that correct?
Steve Payne/NASA Test Director : No, this does not interfere, this, we do this every now
and then as necessary. It is a procedure we've done many times in the past when we've
had to go into the pad to retrieve something or to adjust something last minute. And I
fully expect they'll be out of here in probably about another 10 minutes and we'll be done.
Candrea Thomas/NASA Launch Commentator: Well Steve, thank you so much.
We really appreciate it. I know you're busy, we'll get you
back to work.
Steve Payne/NASA Test Director: Thank you, Candrea.
Candrea Thomas/NASA Launch Commentator: Thank you.