Pegasus

[georgeniebling]

Does anyone have a link for video of a Pegasus release and launch sequence?

 

[Testing]

It's on this page<br /><br />http://www.nasa.gov/mission_pages/dart/main/index.html <div class="Discussion_UserSignature"> </div>

 

[georgeniebling]

in the five seconds of freeefall ... how far does Pegasus get away from the L-1011?

 

[jurgens]

f = ma<br /><br />mg = ma<br /><br />g = a<br /><br />d = 1/2at^2<br />d = (4.9)(5^2)<br />d = 125m

 

[najab]

Except it's not freefall - the Pegasus has aerosurfaces. Judging from the pictures I've seen, it's probably a bit less than 125m.

 

[padrat]

The wing produces very little lift, particularly at the airspeed of the vehicle at release. It is only when the vehicle is supersonic that any appreciable lift is generated, and even then it's not that great. <br /><br />Some coworkers who work on NASA Peg missions have told me the OSC designers put the wing on it because it was "cool looking", not because it was needed.<br /><br />-Pad Rat-

 

[drwayne]

Wings/winglets/canards generally appear because someone needs to make adjustments to the Cp or give additional control authority.<br /><br />Wayne <div class="Discussion_UserSignature"> <p>"1) Give no quarter; 2) Take no prisoners; 3) Sink everything."  Admiral Jackie Fisher</p> </div>

 

[padrat]

>>Wings/winglets/canards generally appear because someone needs to make adjustments to the Cp or give additional control authority.<<<br /><br />For most aero vehicles that's true. However, in the case of Peg, the wing is not required. It reportedly creates less than 1K lb. of lift, which is inconsequential for a vehicle like that. The tail surfaces do provide control authority during first stage, but the wing is mostly (if not completely) for show, producing just enough lift to cancel out its component weight. <br /><br />-Pad Rat-

 

[padrat]

No. At the moment and speed of release the "airfoil" section of that wing is useless. The Peg would drop cleanly without it.<br /><br />-Pad Rat-

 

[padrat]

I'd have to disagree with that. At the moment of release the fins are no different from those on a free-fall weapon. If you examine the airfoil design used on that wing, you'll see that it is not able to develop lift at drop speed. <br /><br />-Pad Rat-

 

[drwayne]

Actually, subtle adjustments in the center of pressure can have dramatic effects on vehicle controllability. I don't have any facts in the case of Pegasus, but my gut tells me that they would not really put something on a multi-million dollar vehicle that doesn't need to be there for some reason.<br /><br />Even the fins for the Saturn 5, which were mostly useless, and might have been removed had the Saturn evolved, had a function in terms of making certain failure modes survivable.<br /><br />Wayne <div class="Discussion_UserSignature"> <p>"1) Give no quarter; 2) Take no prisoners; 3) Sink everything."  Admiral Jackie Fisher</p> </div>

 

[padrat]

>>A free fall weapon pitches down after release. <<<br /><br />Ever watch a B-52 release its load of 500lb. bombs?<br /><br />There's also the fact that the Peg's fins are its flight controls, and trim the vehicle's attitude during drop and flight.<br /><br />-Pad Rat-

 

[jurgens]

it was just an estimate najaB =)