Author Topic: DARPA Experimental Spaceplane 1 (XS-1) Program  (Read 194807 times)

Online Comga

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Re: DARPA Experimental Spaceplane 1 (XS-1) Program
« Reply #740 on: 07/16/2017 03:01 AM »
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The X38 was slated to have a "flush mount" ADS with more pressure sensing pipes to cope with the surface geometry effects of being mounted in the nose. I think the X37b also uses such a system.

In principal these systems can operate to much higher Mach numbers, giving a much better idea of aerodynamic forces on the vehicle. I'm not sure if the X37b has been remote piloted during its landings or if this ability to more accurately generate air data has made that unnecessary.

I'm guessing some of the future vehicles like the SR-72 and any Reaction Engines Limited derivatives might use something like the BAE LASSI system, unless it's still 5 years away by the time those programs go into full development.  That's assuming that technology solves some of the high mach issues.  It might be coming too late for XS-1...
http://www.baesystems.com/en/blog/lassi-laser-air-speed-sensing-instrument

Ha!
"laser airspeed sensor "
I was offered a job to develop a system like this some 35 years ago.
Seemed beyond the technology then.  Seems intuitively obvious now.
But do we have any information that Boeing will actually use such a system?  For XS-1 or X-37? You are just guessing, you say.   
What kind of wastrels would dump a perfectly good booster in the ocean after just one use?

Offline john smith 19

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Re: DARPA Experimental Spaceplane 1 (XS-1) Program
« Reply #741 on: 07/16/2017 04:21 PM »
...
The X38 was slated to have a "flush mount" ADS with more pressure sensing pipes to cope with the surface geometry effects of being mounted in the nose. I think the X37b also uses such a system.

In principal these systems can operate to much higher Mach numbers, giving a much better idea of aerodynamic forces on the vehicle. I'm not sure if the X37b has been remote piloted during its landings or if this ability to more accurately generate air data has made that unnecessary.

I'm guessing some of the future vehicles like the SR-72 and any Reaction Engines Limited derivatives might use something like the BAE LASSI system, unless it's still 5 years away by the time those programs go into full development.  That's assuming that technology solves some of the high mach issues.  It might be coming too late for XS-1...
http://www.baesystems.com/en/blog/lassi-laser-air-speed-sensing-instrument
As I noted flush mount ADS is a real thing now. It's been built and was tested as far back as some of the early Shuttle test flights, also on some of the ET's . AFAIK it's being used on the X37b now.

In the context of XS-1 available-now beats very-accurate-but-needs-a-decade-of-work by a very wide margin.

For any sort of aero-space plane air data sensing is a tough problem.  A pitot probe is an excellent shape to induce lots of turbulent heating and is quite small, so not good at getting rid of heat.

My instinct for a design solution would be something like the system used by some gas meters, ultrasonic Doppler sensing. Sending the signals through the walls of the vehicle would complicate things, but those effects could be calibrated or nulled out. The issue would be at what point the air gets too thin to give a reliable signal. However at this point you would probably be leaving the atmosphere anyway. During re-entry ionisation would start to build up and you could probably borrow techniques from the plasma diagnostics people to measure a set of flows which would give you air data information.

Both such systems would be very short range, and hence more "stealthy" than a UV laser, which would be very alien in the night sky.  :(
« Last Edit: 07/17/2017 04:35 PM by john smith 19 »
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Online Comga

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Re: DARPA Experimental Spaceplane 1 (XS-1) Program
« Reply #742 on: 09/22/2017 02:27 AM »
(snip)
Both such systems would be very short range, and hence more "stealthy" than a UV laser, which would be very alien in the night sky.  :(

A UV laser would be far more than stealthy.  It wouldn't be a light show.  Perhaps a few watts with strong atmospheric scattering and attenuation, pointed in specific and changing directions.  No one is going to intercept that.

And it's on a rocket.  Rockets are as far from stealthy as one can imagine.

But this is all speculation with regards to the XS-1. 
What kind of wastrels would dump a perfectly good booster in the ocean after just one use?

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