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Author Topic: OT - AEHF-2 launch  (Read 2024 times)

Online Brett Buck

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OT - AEHF-2 launch
« on: May 05, 2012, 07:13:10 PM »
Here's a link to our launch (delayed to Friday after someone forgot to open a valve on Thursday):

http://www.space.com/15549-air-force-satellite-launch-aehf2.html

   There are a bunch of youtube videos of it.

    That's why I wasn't at the Stunt 25 Debut...

   

   Brett


Online Dan McEntee

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Re: OT - AEHF-2 launch
« Reply #1 on: May 05, 2012, 07:48:22 PM »
  It's like Kennedy said, " There is always some SOB that doesn't get the word!" 
  Very cool. I'll have to watch the launch footage later. We won't get to see much of this kind of stuff from here on out I guess.
  Thanks a lot,
  Dan McEntee
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Offline Douglas Ames

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Re: OT - AEHF-2 launch
« Reply #2 on: May 05, 2012, 08:31:20 PM »
I'm curious, the article stated that it will reach GS orbit in the next three months or so. Do you put it in orbit at a faster speed than req'd and let it drift (or steer it) to a pre-determined altitude, and then sync the speed/ orbit? Lots of space junk whizzing about!
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Online Brett Buck

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Re: OT - AEHF-2 launch
« Reply #3 on: May 05, 2012, 09:19:36 PM »
I'm curious, the article stated that it will reach GS orbit in the next three months or so. Do you put it in orbit at a faster speed than req'd and let it drift (or steer it) to a pre-determined altitude, and then sync the speed/ orbit? Lots of space junk whizzing about!

  The rocket put it into an orbit that is highly elliptical, with a perigee of about 120 miles and an apogee of about 26000 miles (a little higher than geosynchronous). What is supposed happen is that we do three maneuvers with the spacecraft 100 lb thrust engine to boost the perigee up to about 11,000 miles. It is still pretty highly inclined and still elliptical. Then we use on-board ion engines (Hall Current Thrusters) with a thrust of about 1/2 ounce and then thrust for many hours a rev, or multiple revs, pointing the spacecraft in the right direction to take out the inclination, raise perigee, lower apogee, and then stop in geosynchronous at the right spot. The best direction to thrust is continually changing and determining that on a second-to-second basis is a pretty tricky problem. The acceleration is low (spacecraft weights a little less than 14000 lbs right now, and you are pushing it with around 1 once of thrust) so that's what takes the 3 months.

   What happened on the first one is that the 100 lb engine failed after about 13 second of total run time (instead of the intended 3 and a half hours). We used some 5 lb thrust chemical thrusters until we used up most of the fuel for that (saving enough for the on-orbit mission of wheel desaturation), then the ion engines for the next year and 2 months in the most optimal way possible, and got it to orbit. We won an Aviation Week laureate award for saving the mission. It launched in August 2010 and got there in October 2011.

    We are pretty sure the 100 lber is going to work this time, and we will find out in about 8 hours. That's why I am in Colorado Springs right now. I am the lead engineer for the attitude control subsystem which is what determines where the spacecraft it pointed, drives the attitude to the desired direction, and fires the engines (100 lber, 5 lbers .2 lbers and ion engine and associated gimbals). I am here to make sure that it is working correctly and determine that if it isn't, what we should do.

    We do have to concern ourselves about space junk and space "no junk" like the Space Station. Particularly now, when the perigee is down in the upper atmosphere - so close we have to select the thrusters for attitude control because the aerodynamic forces are too high to handle with the reaction wheels. There is a whole lot of stuff (junk and otherwise) in low Earth orbit. After the first 100-lb engine burn the perigee is high enough that we aren't close to very much in the way of junk at the low side. On the high side we are going through geosynchronous altitude but at an inclination that means there's not a lot to worry about there, either. So while there are guys who figure out the close approaches and adjust the maneuvers to avoid close-misses, it's only a significant problem until the first maneuver, which is a few hours away.

     Brett


Offline Clint Ormosen

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Re: OT - AEHF-2 launch
« Reply #4 on: May 05, 2012, 09:25:07 PM »

    That's why I wasn't at the Stunt 25 Debut...

   Brett

We're probably going to have to reschedule due to wind. You didn't miss a thing. Except wind. A lot of it.
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Online Brett Buck

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Re: OT - AEHF-2 launch
« Reply #5 on: May 05, 2012, 10:10:49 PM »
We're probably going to have to reschedule due to wind. You didn't miss a thing. Except wind. A lot of it.

  So I hear - Jim said he was having trouble *driving*, much less flying.


    Brett

Online Dennis Adamisin

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Re: OT - AEHF-2 launch
« Reply #6 on: May 05, 2012, 10:38:13 PM »
Brett
Thanks for the explanation on the orbital manuvering - amazin stuff.  Certainly sounds like more fun than car/truck partz...   ~^
Denny Adamisin
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Offline Mike Keville

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Re: OT - AEHF-2 launch
« Reply #7 on: May 05, 2012, 10:47:13 PM »
Yes, absolutely amazing.  Sitting here tonight looking at the moon at its closest approach (221,000 mi.) recently...wishing I could get out there, but alas, was born WAY too soon for that.

(Of course if it WAS possible for me to go out there they'd need to have a smoking section....which probably ain't gonna' happen.)  LL~  LL~  LL~  LL~  LL~
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Offline BillLee

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Re: OT - AEHF-2 launch
« Reply #8 on: May 06, 2012, 05:40:35 AM »
Yes, absolutely amazing.  Sitting here tonight looking at the moon at its closest approach (221,000 mi.) recently...wishing I could get out there, but alas, was born WAY too soon for that.

(Of course if it WAS possible for me to go out there they'd need to have a smoking section....which probably ain't gonna' happen.)  LL~  LL~  LL~  LL~  LL~


Or way too late. Unless you're Chinese.

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Offline john e. holliday

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Re: OT - AEHF-2 launch
« Reply #9 on: May 06, 2012, 07:52:19 AM »
Brett, this is very interesting and way beyond the capabilities of this old man.   

Mike, this old man has been off cigarettes since Thanksgiving eve of 1988.  I still have the urge once in a while after this many years.
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Online Brett Buck

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Re: OT - AEHF-2 launch
« Reply #10 on: May 06, 2012, 08:05:14 AM »
Brett, this is very interesting and way beyond the capabilities of this old man.

  Oh, I doubt it is beyond you at all. Just different knowledge, not better.

   Our engine ran fine this time, so no year-and-a-half of heroics.

    Brett

Offline pat king

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Re: OT - AEHF-2 launch
« Reply #11 on: May 06, 2012, 08:35:09 AM »
Brett,
Does the Atlas V still use RP1 and Liquid Oxygen the same as the old Atlas ICBMs we supported?

Pat
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Offline FLOYD CARTER

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Re: OT - AEHF-2 launch
« Reply #12 on: May 06, 2012, 10:04:58 AM »
Brett:  Good to know that the MILSTAR (bis) project is still successful.  You seem to have come a long way since I worked on MILSTAR #2 (Test Director for ground testing and post-launch at Falcon AFB).

Keep up the good work.

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Offline Mike Keville

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Re: OT - AEHF-2 launch
« Reply #13 on: May 06, 2012, 08:35:50 PM »
Or way too late. Unless you're Chinese.

Actually, no.  "Born too late" would indicate that I'd be too young to participate in a moon flight today.  "Born too SOON" (1940), as I said above, means that I'm too danged OLD to be considered....even if they were taking applications (which they're not).
"I have always abhorred change of any kind."
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Offline Douglas Ames

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Re: OT - AEHF-2 launch
« Reply #14 on: May 06, 2012, 08:46:21 PM »
Interesting stuff. Thanks.  H^^
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Offline Mike Callas

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Re: OT - AEHF-2 launch
« Reply #15 on: May 12, 2012, 01:08:42 PM »
Brett,
A couple of months ago I read how the first AEHF finally made it up into proper orbit after the biprop(?) thruster failed. It was simply amazing to read how it was saved. You guys probably have the world record for time to station. And (I assume) that all the antennas and solar panels deployed after spending that much time in limbo is no small feat.

At least the Navy doesn't have to use up a Standard missile to go "fetch" it.

Now, Hughes Space (Ok, Boeing) is ditching the biprop and using XIPs (Xenon ion prop) for it's small sats. 2-up on a Space X rocket and then Ion propulsion to geo. Apparently they are saving a bunch of mass. Much cheaper too.

Oh, and thanks for saving us taxpayers half a billion dollars!

Mike

Online Brett Buck

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Re: OT - AEHF-2 launch
« Reply #16 on: May 12, 2012, 04:16:40 PM »
A couple of months ago I read how the first AEHF finally made it up into proper orbit after the biprop(?) thruster failed. It was simply amazing to read how it was saved. You guys probably have the world record for time to station. And (I assume) that all the antennas and solar panels deployed after spending that much time in limbo is no small feat.

    The engine that failed was a 100 LB biprop. liquid apogee engine. We used as much hydrazine as possible using the 5 LB monoprops normally used only for ullage control to boost the apogee (which wasn't too far), and then switched to the HCT ion engine. The oxidizer is with us forever, as ballast.

 Payload wings and antennas deployed with no problem after that amount of time. The Solar Array, however, was deployed early on. The engines, while very fuel efficient, manage it by sucking up heroic amounts of electricity. They are about 3x what it takes to run the regular mission, just to supply the HCTs.

Quote
Now, Hughes Space (Ok, Boeing) is ditching the biprop and using XIPs (Xenon ion prop) for it's small sats. 2-up on a Space X rocket and then Ion propulsion to geo. Apparently they are saving a bunch of mass. Much cheaper too.

    Cheaper on paper, at least. They have already had several XIPS failures with associated drastic reduction in life, but that doesn't get into the press releases. They are a mixed bag - particularly XIPs, which are a particular crude version of the engine, much like what the russians have been using for decades and like NASA used on Deep Space 1, with metal screen accelerators, etc. Efficient but marginally reliable. The HCT is a much more sophisticated design, but ours was the first use, which is not what you would want in a rescue situation.


Quote
Oh, and thanks for saving us taxpayers half a billion dollars!

  All in a days, er, nights work. The part of it my attitude control buddies and I worked on were pretty proud that we *never missed a single maneuver because of attitude control or determination reasons*, which was no small feat. 

Brett


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