Air Launch LLC

[Antares]

Sigh. Cost doesn't matter if it can't get to first flight because of low Isp.  No argument that technology choice drives cost.  But all the money in the world can't break physics.  And if it can't make Isp, an awful lot of money is spent redesigning.  Any operational vehicle development I manage won't have new technology in the critical path.  Integration is hard enough.  I suppose X-33/VS marked me for life.  Promising technologies like vapak need to get to high TRL/IRL before going into an operational vehicle.  The investment should be made, by the government if the private sector won't.

10sec was not arbitrary.  I think that within 10sec (for a CxHy, 15 for LH2), designers can tweak settings or accept some of it and decrease payload to orbit.  Beyond 10sec, a rocket (not just the engine) starts having real problems with its overall performance and sizing.

I don't doubt the capability or fundamental physics of the vapak concept to run an engine.  My questions are: 1) Will it make thrust, Isp and MR as predicted?  2) Can it make those 3 numbers when integrated into a launch vehicle where temperature control of the propellants (which dictates P_vap) is non-trivial?  Designing a vehicle around an engine before those two questions are answered repeatably is asking for COST increases - or complete cancellation.

Please relax before going all attack-mode.  I missed no point.  Just because I don't mention cost doesn't mean I don't consider it.

Dan Moser - 17/5/2007  11:38 PM

Antares - 13/5/2007  6:42 PM
Any idea if they hit their Isp target?  By hit, I mean within 10sec.  Vapak is dubious to me.

Isp is important.. but you totally miss the real point.  Achieving your COST target is of far greater importance.  NASA missed the cost target on the Shuttle by a factor of 50 (!) ... now would you be OK with that because they "hit" their Isp target?  Sheesh!

And your arbitrary "within 10 sec" target and "dubious" assessment.. sound like something an uninformed detractor might say.  The Vapak system has been shown to be a viable concept with outstanding potential for enabling substantial launch cost reductions, whether air or ground launched.  A growing body of test data continues to demonstrate this.

Now consider the SSME... very impressive Isp numbers, granted !... yet it is going extinct in less than 3 years in spite of the tens of billions of American taxpayers dollars that have been poured into its development..  .  It's too expensive even for non-cost conscious NASA to deal with. .. talk about dubious!!

[aero313]

Antares - 18/5/2007  1:25 AM

Sigh. Cost doesn't matter if it can't get to first flight because of low Isp.  No argument that technology choice drives cost.  But all the money in the world can't break physics.  And if it can't make Isp, an awful lot of money is spent redesigning.  Any operational vehicle development I manage won't have new technology in the critical path.  Integration is hard enough.  I suppose X-33/VS marked me for life.  Promising technologies like vapak need to get to high TRL/IRL before going into an operational vehicle.  The investment should be made, by the government if the private sector won't.

This is a fair assessment, but I have to agree with Dan.  If Isp is good enough to get a useable payload for the price, then the vehicle can be successful.  Now, is the ability to predict and model performance important?  Absolutely.  A prudent designer will keep significant margins on both performance and mass at this point in a program.  One of the mistakes that inexperienced rocket companies continually make is to overlook or just ignore the need to hold large margins early in the design.  

AirLaunch has (in my opinion) a very clever system design that admittedly relies heavily on the details of Vapak working as advertised.  The company is still in the early stages of development - what they are attempting to do is a lot harder than just building another pump fed LOX/RP engine.  The difference with Vapak is that while it takes more development effort and money up front, the potential payoff in lower recurring costs is great.  Unfortunately, a lot of misinformation about the program has been spread.

By the way, the whole point of DARPA IS to do development of promising, high risk technologies.  Unfortunately they often need to tie that technology to an "operational" system (ie, the FALCON - all caps - program).  Is there risk in this approach?  Sure, but it has also worked for them in the past.

[jongoff]

BTW, I've talked with some people around here and got more info on their most recent firing.  Apparently they were being extra cautious (since they only have one stage to test with, and if it breaks they're screwed), and aborted the firing prematurely when someone got spooked by the transient as the LOX switches over to GOX flow.  They inspected afterward, and had no sign of equipment damage or malfunction, they just were being over-cautious.  They still had propellant left in both tanks, so they probably could've come a lot closer to meeting their goal had someone been a little less twitchy.  Overcaution when you don't have a lot of spares is perfectly reasonable in a test program.

~Jon

[Antares]

aero313 - 18/5/2007  11:40 AM

Antares - 18/5/2007  1:25 AM
...And if it can't make Isp, an awful lot of money is spent redesigning.  Any operational vehicle development I manage won't have new technology in the critical path.  Integration is hard enough...

...A prudent designer will keep significant margins on both performance and mass at this point in a program.  One of the mistakes that inexperienced rocket companies continually make is to overlook or just ignore the need to hold large margins early in the design.  

AirLaunch has (in my opinion) a very clever system design that admittedly relies heavily on the details of Vapak working as advertised.  The company is still in the early stages of development - what they are attempting to do is a lot harder than just building another pump fed LOX/RP engine.  The difference with Vapak is that while it takes more development effort and money up front, the potential payoff in lower recurring costs is great.  Unfortunately, a lot of misinformation about the program has been spread.

By the way, the whole point of DARPA IS to do development of promising, high risk technologies.  Unfortunately they often need to tie that technology to an "operational" system (ie, the FALCON - all caps - program).  Is there risk in this approach?  Sure, but it has also worked for them in the past.

I'm perfectly content with DARPA doing this since they aren't tasked with developing a fieldable system.  However, and this is not a leading question, do you think t/Space-AirLaunch would have met COTS milestones had they been chosen?

[aero313]

Antares - 18/5/2007  3:19 PM
  However, and this is not a leading question, do you think t/Space-AirLaunch would have met COTS milestones had they been chosen?

Not knowing anything about their COTS proposal or milestones, I really can't comment.  Clearly they don't have 200+ employees, four buildings in El Segundo, or a personal checking account with a few hundred million bucks.  Of course, that's no guarantee of success either.

Since you've already noted your aversion to new technolgy in an operational program like COTS, I don't need to point out that nine engine clusters and uncrewed RLVs are not at TRL 9 yet either.

[CentEur]

jongoff - 18/5/2007  7:03 PM

BTW, I've talked with some people around here and got more info on their most recent firing.  Apparently they were being extra cautious (since they only have one stage to test with, and if it breaks they're screwed), and aborted the firing prematurely when someone got spooked by the transient as the LOX switches over to GOX flow.  They inspected afterward, and had no sign of equipment damage or malfunction, they just were being over-cautious.  They still had propellant left in both tanks, so they probably could've come a lot closer to meeting their goal had someone been a little less twitchy.  Overcaution when you don't have a lot of spares is perfectly reasonable in a test program.

~Jon

Good news. Waiting for successful firing and positive DARPA decision.

[Antares]

aero313 - 18/5/2007  4:07 PM
I don't need to point out that nine engine clusters and uncrewed RLVs are not at TRL 9 yet either.

Amen.  Probably the top integration risk for F9, though I have only best wishes and high hopes for the testing in McGregor.  But: try explaining how a 9-engine, 9-nozzle F9 is, without going into an actual reliability exercise, probably more complex than a 5-engine, 32-nozzle Soyuz to people who work the other end of the rocket.  It's the turbopumps, man, the turbopumps.

[yinzer]

S-IB used an 8-engine cluster.  Worked OK.

[aero313]

yinzer - 20/5/2007  9:47 PM

S-IB used an 8-engine cluster.  Worked OK.

Yes, with much more development money and labor invested and absolutely no corners cut.   The first four Saturn I flights were suborbital, first stage only development flights.

CentEur - 20/5/2007  9:12 AM  

jongoff - 18/5/2007  7:03 PM  BTW, I've talked with some people around here and got more info on their most recent firing.  Apparently they were being extra cautious (since they only have one stage to test with, and if it breaks they're screwed), and aborted the firing prematurely when someone got spooked by the transient as the LOX switches over to GOX flow.  They inspected afterward, and had no sign of equipment damage or malfunction, they just were being over-cautious.  They still had propellant left in both tanks, so they probably could've come a lot closer to meeting their goal had someone been a little less twitchy.  Overcaution when you don't have a lot of spares is perfectly reasonable in a test program.  ~Jon

 Good news. Waiting for successful firing and positive DARPA decision.

Had heard that they were very cost conscious and cautious - guess you can get in a bind both ways here!

Glad to hear it wasn't the technology - the utter simplicity of what they have is a thing of beauty. If they get it to work it will be more valuable to DARPA by far than half the crazy things past funded.

[William Graham]

What year is the maiden flight scheduled for?

Update:
http://www.airlaunchllc.com/News.htm

DARPA continued them to Phase 2C. Apparently we'll see more results.

[Danderman]

nobodyofconsequence - 10/8/2007  10:12 PM  Update: http://www.airlaunchllc.com/News.htm  DARPA continued them to Phase 2C. Apparently we'll see more results.

 

The results should be some test firings of their engines.

 

[CentEur]

nobodyofconsequence - 11/8/2007  7:12 AM

Update:
http://www.airlaunchllc.com/News.htm

DARPA continued them to Phase 2C. Apparently we'll see more results.

No word about "the design and development of the onboard propellant conditioning system" they previously planned for phase 2C. Looks like DARPA is interested in propulsion system, not in a launch vehicle.

[meiza]

The propulsion system and launch vehicle are very linked though in this pressure fed VAPAK approach.

[gin455res]

IIRC the Quickreach airlaunch concept used a parachute to reorient the rocket as it exited the aircraft.


So it lost speed and changed direction. And, the speed of the velocity vector parallel to its ignition angle was less than the carrier aircraft.


Out of curiosity, if it had been launched vertically (by, say, a VTOL jet-powered carrier-vehicle) at the same speed, what would the effective pressure have been?


--Ram-pressure has an inverse, I'm guessing (velocity-suck?, venturi vacuum? eductor vacuum? what? is the terminology for this effect..).  Not exactly wake-shield but similar.


How much of the effective pressure/vacuum felt by the base of a vertically launched rocket travelling up at the same speed as the Quickreach carrier aircraft, and releasing at the same altitude would be due to altitude and how much due to 'velocity-vacuum-effects'?


My intuition... tells me that it requires more and more energy to compress, and (theoretically) less and less 'negative-energy' to expand.


<OT> Does this mean subsonic ramjets derive more of their pressure-ratio from the 'velocity-vacuum-effect' than from ram pressure?</OT>


Intuition... tells me that the 'velocity-vacuum-effect' would potentially have more effect to pressure-ratio at speeds lower than mach 1 than ram-pressure.


So when launching low pressure rockets can speed increase 'effective altitude' (and designed-for exit pressures) at fairly low speeds?


<OT> How do vacuum-effects and altitude effects impact on sustainer power-plant design in hybrid-electric aircraft destined to never run below 20,000 ft and < 200mph? - due to changes in potential pressure-ratios available to low compression engines (at altitude, with sucking exhaust conditions)</OT>

[HMXHMX]

This paper might  help with your questions.