Author Topic: Pre-Launch History: Atlas V - OTV X-37B - April 22, 10  (Read 261106 times)

Offline Jim

  • Night Gator
  • Senior Member
  • *****
  • Posts: 32426
  • Cape Canaveral Spaceport
  • Liked: 11164
  • Likes Given: 331
Re: Pre-Launch History: Atlas V - OTV X-37B - April 22, 10
« Reply #680 on: 04/24/2010 01:59 PM »


Could this imply reboost after hypersonic upper-atmospheric maneuvering?

It is not that type of vehicle.

Offline TrueBlueWitt

  • Space Nut
  • Senior Member
  • *****
  • Posts: 2005
  • Mars in my lifetime!
  • DeWitt, MI
  • Liked: 78
  • Likes Given: 72
Re: Pre-Launch History: Atlas V - OTV X-37B - April 22, 10
« Reply #681 on: 04/24/2010 02:40 PM »


Could this imply reboost after hypersonic upper-atmospheric maneuvering?

It is not that type of vehicle.

That was my thought.. a little atmospheric skip for an orbital plane change.. Oh well.. It was an interesting thought.

Offline Jim

  • Night Gator
  • Senior Member
  • *****
  • Posts: 32426
  • Cape Canaveral Spaceport
  • Liked: 11164
  • Likes Given: 331
Re: Pre-Launch History: Atlas V - OTV X-37B - April 22, 10
« Reply #682 on: 04/24/2010 02:46 PM »


Could this imply reboost after hypersonic upper-atmospheric maneuvering?

It is not that type of vehicle.

That was my thought.. a little atmospheric skip for an orbital plane change.. Oh well.. It was an interesting thought.

wrong shape, it is has bad hypersonic L/D

Offline simonbp

wrong shape, it is has bad hypersonic L/D

Well, not bad, just no better than STS orbiter. So, eyeballing it, maybe a L/D of 0.4, which would make it better than Apollo (~0.2-0.3), but worse than a lifting body (up to 0.8 ).

Granted, they don't need much cross-range (and thus hypersonic L/D), as the landing sites are pretty close to each other...
« Last Edit: 04/25/2010 05:12 PM by simonbp »

Offline edkyle99

  • Expert
  • Senior Member
  • *****
  • Posts: 12882
    • Space Launch Report
  • Liked: 3939
  • Likes Given: 752
Re: Pre-Launch History: Atlas V - OTV X-37B - April 22, 10
« Reply #684 on: 04/25/2010 06:53 PM »
Back when it was a NASA program, it had two 100 kb OME's and was biprop with tanks on each end of the payload bay.

2,500 ft/sec  was the spec for delta V

Returning to this question, if X-37B uses something like the STS Marquardt R-40A N2O4/MMH primary RCS thrusters as its main maneuvering engines (T = 394.6 kfg, ISP = 289 sec), augmented by vernier thrusters burning the same propellant, and if the total delta-v is 2,500 ft/sec (762.2 meters/sec), then the propellant load would only be about 1,180 kg, or less than one-quarter of gross vehicle weight.  The propellant would be divided in a 1.65:1 mass ratio (N2O4:MMH).

762 meters/sec is still a healthy delta-v allotment.  STS only has 300+-ish meters/sec delta-v.  It still seems to me that propellant could be traded for upload mass - and quite a bit of upload mass - if desired.  (I wonder, could this thing have an ability to transfer propellant to on-orbit satellites?)

R-40A thrusters, by the way, are rated for 50,000 starts and up to 20,000 seconds of cumulative firing.  A full load of X-37B propellant would only use up 860 seconds of an R-40A life if it were burned through just one thruster.  The bird obviously has numerous vernier thrusters as well, so an R-40A would never use all of the propellant.

 - Ed Kyle
« Last Edit: 04/25/2010 06:58 PM by edkyle99 »

Offline Jim

  • Night Gator
  • Senior Member
  • *****
  • Posts: 32426
  • Cape Canaveral Spaceport
  • Liked: 11164
  • Likes Given: 331
Re: Pre-Launch History: Atlas V - OTV X-37B - April 22, 10
« Reply #685 on: 04/25/2010 07:07 PM »
I think the thruster is like the 100 lb apogee thrusters on many comsats.

Offline JimO

  • Veteran
  • Full Member
  • ****
  • Posts: 1871
  • Texas, USA
  • Liked: 311
  • Likes Given: 74
Re: Pre-Launch History: Atlas V - OTV X-37B - April 22, 10
« Reply #686 on: 04/25/2010 11:16 PM »
So where IS it?

Does anybody know of anybody who's seen it? 

Why not?


Offline Blackstar

  • Veteran
  • Senior Member
  • *****
  • Posts: 11378
  • Liked: 2892
  • Likes Given: 1
Re: Pre-Launch History: Atlas V - OTV X-37B - April 22, 10
« Reply #687 on: 04/26/2010 04:01 AM »
The amateurs were looking, but they all had poor viewing conditions.  Most of them are in Europe, which can be cloudy.

Offline Ben the Space Brit

  • Senior Member
  • *****
  • Posts: 7140
  • A spaceflight fan
  • London, UK
  • Liked: 662
  • Likes Given: 771
Re: Pre-Launch History: Atlas V - OTV X-37B - April 22, 10
« Reply #688 on: 04/26/2010 09:43 AM »
So where IS it?

Does anybody know of anybody who's seen it? 

Why not?

Experimental active optical detection interdictor ('Cloaking Device')? ;)

More seriously, expermental passive optical low-observability technolgy (to the point where it is practically invisible up to nearly point-blank range).  This is more than possible using known and predicted refractive and light-absorbing materials, especially against the dark background of space.  Unless it transits the Moon or Sun, it would be effectively undetectable to ground optical tracking in the same way the F-117 and B-2 are to most types of radar.
"Oops! I left the silly thing in reverse!" - Duck Dodgers

~*~*~*~

The Space Shuttle Program - 1981-2011

The time for words has passed; The time has come to put up or shut up!
DON'T PROPAGANDISE, FLY!!!

Online Mike_1179

  • Member
  • Full Member
  • ****
  • Posts: 562
  • New Jersey
  • Liked: 230
  • Likes Given: 51
Re: Pre-Launch History: Atlas V - OTV X-37B - April 22, 10
« Reply #689 on: 04/26/2010 11:43 AM »
Low visibility solar arrays?  That would be a neat trick

Offline kevin-rf

  • Elite Veteran
  • Senior Member
  • *****
  • Posts: 8652
  • Overlooking the path Mary's little Lamb took..
  • Liked: 1123
  • Likes Given: 243
Re: Pre-Launch History: Atlas V - OTV X-37B - April 22, 10
« Reply #690 on: 04/26/2010 12:40 PM »
Low visibility solar arrays?  That would be a neat trick

Why? Idealy they are pointed at the sun, if built right everything behind them is in shadow, in LEO near sunrise/sunset tilt them so that nothing glints off them towards ground. Takes some design work, but not unsolvable.

Wasn't on of the rumor's about Misty that it had some sort of sunshade which keeps the payload in shadow making it dificult for ground observers to track. Thought there was a patent about the sun shade that could be used on it floating around the US patent servers.
If you're happy and you know it,
It's your med's!

Offline Blackstar

  • Veteran
  • Senior Member
  • *****
  • Posts: 11378
  • Liked: 2892
  • Likes Given: 1
Re: Pre-Launch History: Atlas V - OTV X-37B - April 22, 10
« Reply #691 on: 04/26/2010 03:14 PM »
Before getting all exotic with the explanations as to why it has not yet been spotted, perhaps one should use the simpler default position that it has not been spotted because of cloudy weather.

Offline joema

  • Regular
  • Full Member
  • **
  • Posts: 260
  • Liked: 25
  • Likes Given: 0
Re: Pre-Launch History: Atlas V - OTV X-37B - April 22, 10
« Reply #692 on: 04/26/2010 11:37 PM »
Has anyone noticed how much larger the X-37B tail section is vs the X-37? It's interesting the only images of the X-37B on a runway are from the front, which minimizes this difference.


Offline Jim

  • Night Gator
  • Senior Member
  • *****
  • Posts: 32426
  • Cape Canaveral Spaceport
  • Liked: 11164
  • Likes Given: 331
Re: Pre-Launch History: Atlas V - OTV X-37B - April 22, 10
« Reply #693 on: 04/26/2010 11:59 PM »
Has anyone noticed how much larger the X-37B tail section is vs the X-37? It's interesting the only images of the X-37B on a runway are from the front, which minimizes this difference.

There is no difference, they are the same

Offline iamlucky13

  • Full Member
  • ****
  • Posts: 1660
  • Liked: 102
  • Likes Given: 93
Re: Pre-Launch History: Atlas V - OTV X-37B - April 22, 10
« Reply #694 on: 04/27/2010 12:03 AM »
So where IS it?

Does anybody know of anybody who's seen it? 

Why not?

Experimental active optical detection interdictor ('Cloaking Device')? ;)

More seriously, expermental passive optical low-observability technolgy (to the point where it is practically invisible up to nearly point-blank range).  This is more than possible using known and predicted refractive and light-absorbing materials, especially against the dark background of space.  Unless it transits the Moon or Sun, it would be effectively undetectable to ground optical tracking in the same way the F-117 and B-2 are to most types of radar.

Perhaps, but that makes thermal control more difficult. I'm going with the weather explanation combined with a limited number of eyes looking for an object in an unknown orbit.

Offline Blackstar

  • Veteran
  • Senior Member
  • *****
  • Posts: 11378
  • Liked: 2892
  • Likes Given: 1
Re: Pre-Launch History: Atlas V - OTV X-37B - April 22, 10
« Reply #695 on: 04/27/2010 12:59 AM »
As someone explained to me, the observation problem gets harder over time.  In other words, if the amateurs don't spot it immediately and get an orbit track, it is harder for them to spot it later.  Not impossible, just harder.  So there's probably a curve to this, where it's easy to spot within a few days, and if not spotted by then, it could take quite awhile.  Thus, bad weather in the observing areas soon after launch hurts.

Offline edkyle99

  • Expert
  • Senior Member
  • *****
  • Posts: 12882
    • Space Launch Report
  • Liked: 3939
  • Likes Given: 752
Re: Pre-Launch History: Atlas V - OTV X-37B - April 22, 10
« Reply #696 on: 04/27/2010 03:53 AM »
Has anyone noticed how much larger the X-37B tail section is vs the X-37? It's interesting the only images of the X-37B on a runway are from the front, which minimizes this difference.

It looks about the same size to me.  Even the X-40A seemed to have approximately the same shape (see image below).  The differences seem to be due to viewing angle, and the available photos provide limited viewing angles.  I've also added a couple of side-view comparisons of X-37A and B.

IMO

 - Ed Kyle
« Last Edit: 04/27/2010 04:02 AM by edkyle99 »

Offline edkyle99

  • Expert
  • Senior Member
  • *****
  • Posts: 12882
    • Space Launch Report
  • Liked: 3939
  • Likes Given: 752
Re: Pre-Launch History: Atlas V - OTV X-37B - April 22, 10
« Reply #697 on: 04/27/2010 04:31 AM »
I think the thruster is like the 100 lb apogee thrusters on many comsats.

If so, I would expect more than just one firing at a time.  The thrust-to-weight ratio of Soyuz is 0.088, of Shenzhou 0.13, and of Shuttle 0.05.  If X-37B weighs 5,000 kg, it needs at least 250 kgf (551 lbf) thrust to equate with Shuttle's OMS.  I suspect that a deorbit burn requires more thrust for a given mass than a GTO apogee burn, since the apogee burns are usually broken up over a series of orbits.

 - Ed Kyle
« Last Edit: 04/27/2010 04:32 AM by edkyle99 »

Offline Danderman

  • Extreme Veteran
  • Senior Member
  • *****
  • Posts: 9629
  • Liked: 362
  • Likes Given: 464
Re: Pre-Launch History: Atlas V - OTV X-37B - April 22, 10
« Reply #698 on: 11/23/2012 02:02 AM »
I can't find whether this document has already been uploaded (it is over 10 years old), but it is of interest to X-37 fans.

Independent Assessment of
X-37 Safety & Mission Assurance
Processes and Design Features

Tags: