XCOR and the Lynx rocket

[Robotbeat]

Isn't that exactly what XCOR is already planning? From the article: "Greason won’t say much about more about the orbital vehicle than that it is planned as two rocket-powered stages launched from a carrier aircraft"

3 stages, just the first one is air breathing.

Yeah, you're right. I misread that quote.

I thought I read that sub-orbital Lynx starts out with a air breathing engine as well.
If they "launch" Lynx from a carrier aircraft, that would actually make 2 air breathing stages, right ?

Or they just drop the jet engine from Lynx, and increase the fuel for the rocket engine in Lynx, going back to a 2-stage launcher.

They aren't going to launch Lynx from a carrier aircraft, and Lynx never had a jet engine.

[a_langwich]

If the first stage of the future orbital vehicle is HTHL, why not make it a three-stage-to-orbit architecture?

Isn't that exactly what XCOR is already planning? From the article: "Greason won’t say much about more about the orbital vehicle than that it is planned as two rocket-powered stages launched from a carrier aircraft"

3 stages, just the first one is air breathing.

Wait...the article goes in great length to explain that they chose Lynx to take off under its own power from the ground in view of a future two-stage-to-orbit design, how their design choices were ultimately driven with orbital craft in mind, and how that's a very different approach to Spaceship Two which is air-launched...then it ends with a short paragraph stating their future orbital design will be air-launched from a carrier aircraft, exactly like SS2 and its proposed orbital extensions.  Did I miss something there? 

Does that represent a radical shift in direction, or did they spent a lot of time designing a craft to go from runway to the Karman line knowing that wouldn't be useful for the next design?

The observation that XCOR's engines and Scaled's airframes and Richard Branson's money and marketing skills would make a good combination is still very apt.  It's better for the industry to have multiple players, though, and hopefully both companies will complete these projects.

[fatjohn1408]

3 stages, just the first one is air breathing.

Does the "carrier aircraft" really need to be air breathing? Could it not simply be a scale-up of the Lynx?

I hope you are right. Air breathing carriers do not give enough oomph in altitude and velocity and initial fligth path angle to make it worth it from a performance point of view IMO.

[Lurker Steve]

Isn't that exactly what XCOR is already planning? From the article: "Greason won’t say much about more about the orbital vehicle than that it is planned as two rocket-powered stages launched from a carrier aircraft"

3 stages, just the first one is air breathing.

Yeah, you're right. I misread that quote.

I thought I read that sub-orbital Lynx starts out with a air breathing engine as well.
If they "launch" Lynx from a carrier aircraft, that would actually make 2 air breathing stages, right ?

Or they just drop the jet engine from Lynx, and increase the fuel for the rocket engine in Lynx, going back to a 2-stage launcher.

They aren't going to launch Lynx from a carrier aircraft, and Lynx never had a jet engine.

How does it take off from the ground (HTHL) if there isn't an air-breathing engine ??

Was this just bad reporting ?

[bubbagret]

 Watch the video for the answer.

[zt]

Isn't that exactly what XCOR is already planning? From the article: "Greason won’t say much about more about the orbital vehicle than that it is planned as two rocket-powered stages launched from a carrier aircraft"

3 stages, just the first one is air breathing.

Yeah, you're right. I misread that quote.

I thought I read that sub-orbital Lynx starts out with a air breathing engine as well.
If they "launch" Lynx from a carrier aircraft, that would actually make 2 air breathing stages, right ?

Or they just drop the jet engine from Lynx, and increase the fuel for the rocket engine in Lynx, going back to a 2-stage launcher.

They aren't going to launch Lynx from a carrier aircraft, and Lynx never had a jet engine.

How does it take off from the ground (HTHL) if there isn't an air-breathing engine ??

Was this just bad reporting ?

Lynx is (and always was) a rocketplane. LOX onboard, no air intakes.

http://www.airspacemag.com/space-exploration/The-Lynxs-Leap-223968551.html?c=y&story=fullstory

[Robotbeat]

3 stages, just the first one is air breathing.

Does the "carrier aircraft" really need to be air breathing? Could it not simply be a scale-up of the Lynx?

I hope you are right. Air breathing carriers do not give enough oomph in altitude and velocity and initial fligth path angle to make it worth it from a performance point of view IMO.

That isn't their greatest performance advantage. They increase initial Isp far higher than sea level.

[baldusi]

What about it taking off towed by some other airplane? It would save a lot of LOX.

[Joel]

What about it taking off towed by some other airplane? It would save a lot of LOX.

I can't see how it would save "a lot" of LOX.

I think that a rocketplane first stage and a two non-lifting body vacuum-optimized cross-feeding rocket stages would be pretty awesome. You would get a really great pmf and all stages could return to launch site (first stage after gliding, second stage without gliding and third stage after orbital alignment).

[simonbp]

Not all aircraft are airplanes. If your goal is to lift something heavy to altitude, and you don't care about forward speed, a dirigible would seem to be the best option.

[baldusi]

What about it taking off towed by some other airplane? It would save a lot of LOX.

I can't see how it would save "a lot" of LOX.

Well, I thought of propellent and wrote LOX. And LOX would clearly boil off, while RP-1 won't. But my guess was that if you could tow it to 700km/h, at 10km of altitude, and extended a bit the nozzles, that's 200m/s of speed, plus another 30m/s (WAG) of drag losses, plus some isp improvement of expansion ratio. But the more important issue is that if you want to go closer to the equator, you can do it for "cheap", isp wise, since you use atmospheric optimized engines.
The secret, of course, is only if you can use a stock passenger line or cargo aircraft that you can rent on a per mission and optional basis. Preferably one with a home base close to the normal launch site. In other words, I'm not proposing to base it on a towed architecture, just to have the option of enhancing the performance when the mission has a small negative margin, or to get to closer to the equator missions.

[simonbp]

A commercial airliner will not be able to lift an orbital vehicle the size that Xcor is talking about. Even a C-5 can only lift 120 tonnes. They're going to need a bigger boat plane.

[Joel]

A commercial airliner will not be able to lift an orbital vehicle the size that Xcor is talking about. Even a C-5 can only lift 120 tonnes. They're going to need a bigger boat plane.

If it's a glider, why lift it? Better tow it.

What about towing an orbital vehicle without fuel to an equatorial launch site (e.g. high in the Andes), fuel and take off from there?

[fatjohn1408]

3 stages, just the first one is air breathing.

Does the "carrier aircraft" really need to be air breathing? Could it not simply be a scale-up of the Lynx?

I hope you are right. Air breathing carriers do not give enough oomph in altitude and velocity and initial fligth path angle to make it worth it from a performance point of view IMO.

That isn't their greatest performance advantage. They increase initial Isp far higher than sea level.

That can be endlessly discussed and should not be done in this thread. However, I stand by my earlier position that I hope lynx does not go that way.

[RanulfC]

A commercial airliner will not be able to lift an orbital vehicle the size that Xcor is talking about. Even a C-5 can only lift 120 tonnes. They're going to need a bigger boat plane.

Maybe, maybe not. Consider Dan Delong's previous work assumed a 747 sized carrier aircraft and it's lift has gotten better since then:
http://www.xcor.com/products/vehicles/frequent_flyer_and_teledyne_brown_spaceplane.html

Randy

[Danderman]

Getting back to the Lynx, if I understand the concept correctly, it will lift off the runway, using standard jet engines, and then fire a rocket engine at altitude.

Does this mean the Lynx uses the jet engines for landing?

[Lars_J]

Getting back to the Lynx, if I understand the concept correctly, it will lift off the runway, using standard jet engines, and then fire a rocket engine at altitude.

No - what could possibly give you that idea? Where?

Lynx has been 100% rocket powered from the beginning. Watch the video linked to in this post: http://forum.nasaspaceflight.com/index.php?topic=19033.msg1106835#msg1106835

[Joel]

I think that there is a confusion between the XCOR's suborbital vehicle "Lynx", which is and has always been a single-stage rocket plane, and XCOR's future orbital vehicle.


According to http://www.airspacemag.com/space-exploration/The-Lynxs-Leap-223968551.html?c=y&story=fullstory, the future orbital vehicle consists of "two rocket-powered stages launched from a carrier aircraft", but that's not a direct quote. That carrier aircraft may or may not have jet engines.

[deltaV]

Does anyone know if XCOR has an exclusivity agreement with ULA banning XCOR from selling their LH2/LOX engine to anyone else?

[jongoff]

I chatted with Jeff Greason yesterday, and it sounds like the subscale pump-fed LOX/LH2 demo engine they're doing with ULA is in the same size-range as the Lynx engines. It would be kind of neat to do a four engine mini-taur/mini-ACES. Also, I didn't realize, but apparently the 25klbf RL-10 replacement is high enough pressure compared to the 7500lbf LOX/Methane engine they were testing with ATK back in the day, that the chambers for the two are probably really close to the same size. Sounds like they're making a lot of progress on that front.

I'm just looking forward to seeing pictures of their first test firings. So many commercial space people are knee-jerk anti LOX/LH2, but it seems like XCOR feels they've found a way to tame the stuff at a much lower cost point than had previously been assumed possible.

~Jon