Author Topic: SNC outline Dream Chaser's Enterprise-style landing test approach  (Read 56031 times)

Offline Lee Jay

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What exactly is the challenge with tires in space ?

I assume they aren't inflatable tires, but one solid piece of rubber-like material.

They are inflatable tires, and they have to endure change to a vacuum and a pretty wide thermal environment.

Offline arachnitect

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It's good that we're getting some quality reports on Dreamchaser; thanks Chris and Lee Jay.

Is White Knight II the only fixed wing mothership available? SCA is the only other option I can think of.

Offline Orbiter

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Interesting to see that Lindsey will be doing ALT tests, reminds me of how Haise did ALT tests for Shuttle.

Orbiter
KSC Engineer, astronomer, rocket photographer.

Offline Lee Jay

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Thanks Lee Jay. FWIW - you are a generous person, thanks again.

Thanks, but any little bit that I can contribute is orders of magnitude less that I've received from the site from the site experts such as Jim and Jorge and Pete and Phillip and all the other regulars (you know who you are), not to mention Chris' remarkable expertise in turning volumes of L2 information into easy to understand bite-sized articles.

Offline tigerade

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Neat.  Looking forward to watching these tests.  :)

Offline Lee Jay

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It's good that we're getting some quality reports on Dreamchaser; thanks Chris and Lee Jay.

Is White Knight II the only fixed wing mothership available? SCA is the only other option I can think of.

They said there were other possibilities.  I'm not sure what they were referring to, but military planes such as the B-52 and even Orbital's L-1011 have carried and dropped aircraft or spacecraft.  Maybe they have something like that lined up?

Offline Lars_J

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The front tire on a DC would probably be more difficult than on the Shuttle, due to limited space between the pressurized composite structure and the outer thermal protection system. So there would be less of a thermal buffer, I would guess.

Offline Thorny

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Is White Knight II the only fixed wing mothership available? SCA is the only other option I can think of.

Orbital's L-1011?

Offline Downix

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Is White Knight II the only fixed wing mothership available? SCA is the only other option I can think of.

Orbital's L-1011?
Antonov An-225 comes to mind, strapped to the back.
« Last Edit: 06/09/2012 05:08 pm by Downix »
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Offline Lars_J

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It seems like the WKII or a B-52 are the only options for a simpler drop (compared to being carried on top). But it might be too much even for a B-52?

Offline Downix

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It seems like the WKII or a B-52 are the only options for a simpler drop (compared to being carried on top). But it might be too much even for a B-52?
Orbital's Stargazer also handles a similar drop:
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Offline Lars_J

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DC is much bigger than a Pegasus XL. (vertically) There won't be enough ground clearance, unless I am mistaken. (see image below)
« Last Edit: 06/09/2012 05:26 pm by Lars_J »

Offline TomH

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Regarding nose wheel steering, most ground steering (particularly during landing) on any aircraft is done by differential braking to starboard and port wheels.

Offline jnc

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Regarding nose wheel steering, most ground steering (particularly during landing) on any aircraft is done by differential braking to starboard and port wheels.

Yes, but the Shuttle had both differential braking and steerable nosewheels, and after 'issues' (a blowout) they started using the latter more. (More here.) Not sure if the causes for the Shuttle's issues would carryover to DC, though.

Noel

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Offline Go4TLI

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Not sure if the causes for the Shuttle's issues would carryover to DC, though.

Noel



With respect to the orbiter it was a very large, and heavy spacecraft.  At the speed and angle the vehicle touched down the wheels would warm significant very quickly.  The brakes also input additional heat into the system that lasted for some time due to thermal soack-back.  Using the breaks more just adds more heat.

With DC this will also be an issue but the vehicle is smaller and lighter.  Like the orbiter and many larger aircraft, "keep-out zones" will certainly be established until this heat soackback has disipated and the tires are again a more normal temperature. 

Offline TomH

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Regarding nose wheel steering, most ground steering (particularly during landing) on any aircraft is done by differential braking to starboard and port wheels.

Yes, but the Shuttle had both differential braking and steerable nosewheels, and after 'issues' (a blowout) they started using the latter more. (More here.) Not sure if the causes for the Shuttle's issues would carryover to DC, though.

Noel



During a landing, both brakes are being applied for negative Delta V, and the difference in the amount of braking applied to the two sides in order to maintain center-line alignment is negligible. I would not expect there to be even 1% difference between the amount of friction applied to the port and starboard brakes for the purpose of maintaining center-line alignment; if cross-winds were that powerful, the mission would not be given a go for de-orbit burn prior to landing. It is a stretch for me to believe that use of port and starboard brakes to steer caused any problem on STS. In that the brakes are being applied mainly for the purpose of deceleration, I would think that brake heat or a tire defect would have more to do with it. I can see how the need to crab at a vectored angle in a cross-wind would cause a tire to burst if the wheels are rigidly fixed and not allowed to pivot and stay in alignment with the runway during the landing. That friction would chew a tire to pieces quickly and easily. A center-front wheel on something like DC would not need to be actively steerable from the stick, it would only need to be able to pivot on its own (to maintain alignment with the runway center-line) while the port/starboard brake differential did the steering.

The B-52 is a good example of an airplane on which the entire gang of wheels has to pivot. As a large and heavy high-wing plane (with no left and right wheels other than small outriggers-high wings dictate wheel gangs going fore and aft of bomb bay) that had to be able to take off and land in heavy cross-winds, the plane might be crabbed 10 degrees into the wind while the wheel gangs remained lined-up with the runway. If the wheels could not pivot, landing at a crabbed angle would chew them to pieces instantly.
« Last Edit: 06/10/2012 12:29 am by TomH »

Offline Rocket Science

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Lifting Body Air and Spacecraft Q & A

With all the interest generated by Dream Chaser and its direct ancestor the HL-20 and all the other lifting body vehicles, the thread linked below is to discuss, inform and exchange general questions, ideas and answers as to what exactly a Lifting Body is. This is to keep the Dream Chaser threads clean and without clutter and OT topics as things get busier now. :)

http://forum.nasaspaceflight.com/index.php?topic=29126.msg914401;topicseen#new
« Last Edit: 06/10/2012 12:56 am by Rocket Science »
"The laws of physics are unforgiving"
~Rob: Physics instructor, Aviator

Offline Rocket Science

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Lifting Body Air and Spacecraft Q & A

With all the interest generated by Dream Chaser and its direct ancestor the HL-20 and all the other lifting body vehicles, I created this thread to discuss, inform and exchange general questions, ideas and answers as to what exactly a Lifting Body is. This is to keep the Dream Chaser threads clean and without clutter and OT topics as things get busier now. :)

http://forum.nasaspaceflight.com/index.php?topic=29126.msg914401;topicseen#new


O.K., you are not being clear enough in whatever you are trying to imply and what you want us to infer. You state here that the thread was "created to discuss...what exactly a lifting body is."  In the same sentence you include "...discuss, inform, and exchange general questions..."  The thread title clearly references "...landing test..."

Are you saying that brakes and steering are not part of landing? Are you saying that because you started the thread you feel the prerogative strictly to control the posts if they do not meet your definition of being on-topic or off-topic? Just asking, because I want to understand you with complete clarity before I respond further.
Hey Tom,

No much more basic than that: Only related to basic lifting bodies in general ie) aerodynamics.

You don't need my permission to discuss anything, for example DC brakes... Ultimately Chris has the Last say... ;)

Regards
Robert
"The laws of physics are unforgiving"
~Rob: Physics instructor, Aviator

Offline TomH

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Lifting Body Air and Spacecraft Q & A

With all the interest generated by Dream Chaser and its direct ancestor the HL-20 and all the other lifting body vehicles, I created this thread to discuss, inform and exchange general questions, ideas and answers as to what exactly a Lifting Body is. This is to keep the Dream Chaser threads clean and without clutter and OT topics as things get busier now. :)

http://forum.nasaspaceflight.com/index.php?topic=29126.msg914401;topicseen#new


May I suggest you change this thread to say the thread linked below?  Chris created this thread and at first read it sounded like you were chastising us for posts we have made immediately above. I had figured out what you meant and deleted the post you quoted before you finished your reply.
« Last Edit: 06/10/2012 12:54 am by TomH »

Offline jnc

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It is a stretch for me to believe that use of port and starboard brakes to steer caused any problem on STS.

Hey, I'm just passing on what that NASA web site I linked to said - take it up with them.

Noel
"America Needs - Space to Grow"

(old bumper sticker)

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