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Seer
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« Reply #495 on: 03/18/2012 07:06 AM » |
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Electric satellites of the 702sp mass would also be able to be launched on Antares.
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jcm
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« Reply #496 on: 06/23/2012 12:38 AM » |
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If Antonio's still reading this thread: I realize I always misunderstood the nature of the APEX (Aug 1994) and SEASTAR (Aug 1997) Pegasus launches - the press at the time made it sound like the third stage was part of the Pegastar spacecraft, but now I realize it was just that (some of?) the third stage
avionics functions were moved to the spacecraft bus (or something?) but the third stage still separated as usual.
Can you comment on what was different about the third stage for these missions, and whether there was or was not an advantage to doing whatever was done?
- Jonathan
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antonioe
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« Reply #497 on: 06/25/2012 04:22 PM » |
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If Antonio's still reading this thread: I realize I always misunderstood the nature of the APEX (Aug 1994) and SEASTAR (Aug 1997) Pegasus launches - the press at the time made it sound like the third stage was part of the Pegastar spacecraft, but now I realize it was just that (some of?) the third stage
avionics functions were moved to the spacecraft bus (or something?) but the third stage still separated as usual.
Can you comment on what was different about the third stage for these missions, and whether there was or was not an advantage to doing whatever was done?
- Jonathan
APEX incorporated the Pegasus avionics as its own avionics, so the satellite steered the rocket intil it separated from the avionicsless third stage. That was not the case for SeaStar. No, it was not a good idea. Trust me, it was MY idea!
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jcm
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« Reply #498 on: 06/29/2012 10:14 PM » |
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If Antonio's still reading this thread: I realize I always misunderstood the nature of the APEX (Aug 1994) and SEASTAR (Aug 1997) Pegasus launches - the press at the time made it sound like the third stage was part of the Pegastar spacecraft, but now I realize it was just that (some of?) the third stage
avionics functions were moved to the spacecraft bus (or something?) but the third stage still separated as usual.
Can you comment on what was different about the third stage for these missions, and whether there was or was not an advantage to doing whatever was done?
- Jonathan
APEX incorporated the Pegasus avionics as its own avionics, so the satellite steered the rocket intil it separated from the avionicsless third stage. That was not the case for SeaStar.
No, it was not a good idea. Trust me, it was MY idea!
Thanks for the insight!! (As it happens, I spent much of today working around the results of an idea I had ten years ago that seemed like a really good one at the time :-))
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gin455res
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« Reply #499 on: 06/30/2012 08:40 AM » |
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Hi Antonio,
I read earlier in the thread that you inspected a B52 (one that carried the x15) before settling on the final launch aircraft.
This was hung off the wing and not underneath.
Do you know if the size of a rocket-plane suspended from a wing is limited by the asymmetry of this arrangement?
And if it is, do you know of any air launch concepts where the rocket plane is hung under one wing and a dead mass counter weight is slung under the opposite wing to balance this asymmetry?
(I'm assuming hanging two rocket-planes off the opposite wings of a carrier plane, and releasing them at the same time is madness?)
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antonioe
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« Reply #500 on: 07/13/2012 06:48 PM » |
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We didn't just inspect the B-52, we flew 6 mission with it! (I was the LPO on missions 1 and 4)
B-52 s/n 0008 (good ol' "balls 8") had a large fuselage tank on the centerline as well as tanks on the the wings (but no tip tanks like later B-52 versions). Pegasus was hung from the pylon on the starboard (right) wing.
After towing the Pegasus-carrying trailer under the wing, but before attaching the rocket, we transfered fuel to the starboard wing tanks to lower the starboard wing.
We then raised the trailer a bit and attached Pegasus to the pylon.
Next, we transfered fuel to the port side to lift the Pegasus up from the trailer (we also lowered the trailer bed.)
We then took off with more fuel on the port side to balance the Pegasus on the starboard side, making the B-52 weight-symmetric at takeoff.
Before drop, we transfered fuel to the starboard side to make the aircraft heavy on the rocket side by about ONE HALF THE ROCKET WEIGHT.
When the rocket was dropped, the aircraft became instantly port-heavy by the same amount (on-half the rocket weight). The lateral aerodynamics of the B-52 were more than sufficient to handle these asymmetries. Also, the left-turning tendency was used by the pilot to acheive lateral separation from the release flight path.
Before landing, the fuel was equalized so, again, the aircraft was weight-symmetrical.
Neat, uh?
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Robotbeat
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« Reply #501 on: 07/13/2012 07:18 PM » |
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Great explanation! Thanks. 
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gin455res
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« Reply #502 on: 07/29/2012 08:17 PM » |
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We didn't just inspect the B-52, we flew 6 mission with it! (I was the LPO on missions 1 and 4)
B-52 s/n 0008 (good ol' "balls 8") had a large fuselage tank on the centerline as well as tanks on the the wings (but no tip tanks like later B-52 versions). Pegasus was hung from the pylon on the starboard (right) wing.
After towing the Pegasus-carrying trailer under the wing, but before attaching the rocket, we transfered fuel to the starboard wing tanks to lower the starboard wing.
We then raised the trailer a bit and attached Pegasus to the pylon.
Next, we transfered fuel to the port side to lift the Pegasus up from the trailer (we also lowered the trailer bed.)
We then took off with more fuel on the port side to balance the Pegasus on the starboard side, making the B-52 weight-symmetric at takeoff.
Before drop, we transfered fuel to the starboard side to make the aircraft heavy on the rocket side by about ONE HALF THE ROCKET WEIGHT.
When the rocket was dropped, the aircraft became instantly port-heavy by the same amount (on-half the rocket weight). The lateral aerodynamics of the B-52 were more than sufficient to handle these asymmetries. Also, the left-turning tendency was used by the pilot to acheive lateral separation from the release flight path.
Before landing, the fuel was equalized so, again, the aircraft was weight-symmetrical.
Neat, uh?
Yes, thanks for answering. So the you halved the asymmetry, clever.
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fatjohn1408
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« Reply #503 on: 08/23/2012 09:24 AM » |
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Dear Antonio, Thank you for this informative thread. I want to ask a general question about subsonic assisted launch. Why are all concepts multi-stage designs? It has even been said that the Titan 2 first stage could reach orbit from the ground. In the links provided it gives data indicating a 28 construction mass ratio and a specific impulse of 258. http://en.wikipedia.org/wiki/LGM-25C_Titan_IIhttp://www.braeunig.us/space/specs/titan.htmAdding 300 m/s as assist velocity and 450 due to the rotation of the earth, one gets 9175 m/s of delta-V. Having less drag losses and less gravitational losses than the average launcher. Now why didn't you try to optimize a single stage vehicle for assisted air launch? I am asking this question because I am optimising launch assist vehicles for assisted launch and right now my optimisation shows that subsonically assisted launchers can reach orbit with a payload. Is the extra payload brought by a multi stage vehicle worth that much more risk and complexety or am i forgetting something and is it actually close to impossible to bring a single stage into orbit from a subsonic assist. Thank you.
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modemeagle
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« Reply #504 on: 09/23/2012 02:22 AM » |
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Antonio,
Finally ran the Pegasus though my simulator. Solids are very time consuming to simulate and adding lift from the wing was the hardest part. The simulator is really designed for one to three stage liquid engines without solids. I did a lot of these for the Falcon series for SpaceX and did not want to leave Orbital out. Will try the Antares when more data is released on the system.
Edit: corrected drag vs angle of attack
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jcm
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« Reply #505 on: 09/26/2012 11:22 PM » |
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I read an item in Space News this week that took me to an Orbital press release back in August that we seem to have missed on this forum: http://www.orbital.com/NewsInfo/release.asp?prid=825"Dr. Antonio L. Elias, currently Executive Vice President and General Manager of Orbital’s Advanced Programs Group (APG), will become Executive Vice President and Chief Technical Officer, responsible for the company’s overall technical operations. In this new corporate capacity, Dr. Elias will oversee a 2,600-person functional organization consisting of the company’s engineering, production, supply chain, test and operations staff, as well as its safety and mission assurance professionals, in Virginia, Arizona and other locations." Congratulations, Antonio! I hope that comes with a nice pay raise and a swankier office ;-)
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jcm
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« Reply #507 on: 09/27/2012 10:58 PM » |
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I read an item in Space News this week that took me to an Orbital press release back in August that we seem to have missed on this forum:
It wasn't missed: http://forum.nasaspaceflight.com/index.php?topic=15457.msg947180#msg947180
Ah ok ... sorry about that. There is so much stuff on this site and the threads overlap enough that it's really easy to miss important stuff!
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modemeagle
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« Reply #508 on: 10/15/2012 05:22 PM » |
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Antonio,
Finally ran the Antares though my simulator. All masses were estimated and excluded from the output to not spread bad information. Only the payload is shown. Had some interesting results trying to get a good trajectory and think I may have found how to get more accuracy of insertion using a liquid first stage and a solid second stage. Being only a 2D simulator I can't use Yaw maneuvers to burn off excess velocity. Unless ATK publishes a new curve for the Castor 30XL then I won't be able to model the uprated version in a future simulation.
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Kabloona
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« Reply #509 on: 03/24/2013 05:25 AM » |
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Antonio, when your benevolent overlords give you some free time away from Antares, could you please post your promised next installment "Run Silent, Run Deep," in your story of how Pegasus was developed?
And thank you for sharing so generously of your time and knowledge on this forum; it's great to hear straight from the horse's mouth, as it were!
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