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  #11  
Old 05-17-2009, 05:35 PM
FlyBack FlyBack is offline
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Default T.A. Heppenheimer OnLine

Quote:
Originally Posted by luke strawwalker
.... I highly recommend "The Space Shuttle Decision" by T. A. Heppenheimer. It details all the twists and turns and political machinations that can turn a technically challenging but feasible 'next step' engineering problem/solution into an overbudget, underperforming, compromised by compromises politically-derived vehicle that doesn't really satisfy ANYBODY'S requirements.


Yes, it is interesting how history repeats. Toward the end of my senior year in high school I was awarded a NASA internship at AMES in Sunnyvale, California. I spent most of my time working in the model shop and got to see many of the shuttle configurations being tested at the time (1969 Jan-Jun). Max Faget's straight wing design was my favorite. It seemed like every week they brought in a new model for the craftsmen there to put the finishing touches on. It was fascinating to watch it evolve over a very short period from a TSTO flyback booster/orbiter to something like what we have now.

Anyway... found the link to T.A. Heppenheimer's report online. Excellent read. Enjoy.

Regards,

FlyBack
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  #12  
Old 06-09-2009, 11:52 AM
Jeff Walther Jeff Walther is offline
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Quote:
Originally Posted by Nuke Rocketeer
The program as a whole. I found about the porking of the shuttle for employment from Jerry Pournelle's website. It was not widely publicized, but it was there. Certain powerful congresscritters wanted no shuttle caused drops in employment in their districts. Even with the DoD specs increasing the size/cross-range capability/etc, NASA projected that it would take far fewer people to run operations.


That would explain a few things. In May of 1984 I went to work at NASA JSC with my shiny new Aerospace Engineering B.S.. I was working in Attached Payload Integration in Space Shuttle Operations. After about six months I had figured out that we wrote documents describing payloads, and that the documents weren't actually read by anybody outside our group.

Our only other function seemed to be to supply a Payload Officer to Mission Control (in the big room on TV) and two or three Payload Systems guys (in a back room no-one ever saw). The attached payload would have its own...darn, can't remember what they were called. But basically, there was a control room for "guests" who were monitoring/operating the actual payload. Really, the only thing the Payload Officer did was to be in between the leader of the payload-operating guests and the Flight Control Officer. I could never see any reason our entire area couldn't be shut down and shot into the sun.

Fortunately, McDonnell Douglas lost it's part of that contract to Rockwell, and I was able to jump to Orbital Dynamics, until that contract also went to Rockwell, at which point I jumped to Structures, but by that time Challenger had exploded and we had even less meaningful work to do. Sigh. Not-so-good-times.

NASA JSC Shuttle Operations--what a great place for a spirited new engineer. (NOT.)
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  #13  
Old 06-09-2009, 12:03 PM
Jeff Walther Jeff Walther is offline
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One of the cooler concepts in TSTO (two stage to orbit) is the large air-breathing booster carrying the rocket or hybrid sustainer.

Oxidizer is a huge percentage of the mass of rocket fuel. If you can arrange to pick up your oxygen out of the atmosphere during ascent, you can vastly reduce your lift-off weight.

So, if you could somehow build your booster stage as a recoverable Ramjet/SCRAMjet powered aircraft you might garner some benefits.

Of course, one of the first obstacles is getting the thing up to Ramjet speeds without a set of turbine engines, but if you add the conventional turbine jet engines, then you've got extra weight you don't need.

Some kind of rocket assisted take off might work there. The initial velocity will be a little low for ramjets, but it will still be down where the air is pretty thick any way. One problem is that for any sizable vehicle, the take-off gear (the wheels) become massive. A sort of drop-away go-cart which never leaves the ground starts looking attractive for the take-off gear.
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  #14  
Old 06-09-2009, 12:58 PM
Jerry Irvine's Avatar
Jerry Irvine Jerry Irvine is offline
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Quote:
Originally Posted by Jeff Walther
One of the cooler concepts in TSTO (two stage to orbit) is the large air-breathing booster carrying the rocket or hybrid sustainer.


What tools do you use to model the boost to orbit phase of various candidate designs?

Jerry
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  #15  
Old 06-09-2009, 02:58 PM
Jeff Walther Jeff Walther is offline
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Quote:
Originally Posted by Jerry Irvine
What tools do you use to model the boost to orbit phase of various candidate designs?


When we did this as a senior design project (1st Runner up, 1984 Bendix Design Competition) we wrote our own flight/trajectory simulator in Fortran on the dual CDC6700 at UTexas.

I wrote the propulsion subroutine which calculated thrust and fuel consumption, based, in part, on atmospheric conditions during ascent. My first run generated nonsense. I checked and checked the code and couldn't find any errors. It turns out one of my team mates had converted the atmosphere modeling subroutine from english units to metric units so whenever my routine asked, "How's the air at this altitude?" it got figures which made no sense.

Ten or so years later, JPL crashed a probe into Mars by making the same mistake...
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  #16  
Old 07-24-2009, 01:14 PM
Jeff Walther Jeff Walther is offline
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Quote:
Originally Posted by GregGleason
There was a link to a PPT in the news link. Not great dimensional information but it is interesting.

In the 2nd pic, the lower right vehicle looks similar the Centuri Space Shuttle.


That "Heavy" version would never make it through a safety evaluation. With two boosters separating at similar times, there are too many ways to have a collision after separation.
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  #17  
Old 07-24-2009, 01:27 PM
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Doug Sams Doug Sams is offline
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Quote:
Originally Posted by Jeff Walther
With two boosters separating at similar times, there are too many ways to have a collision after separation.
Jeff,

What am I missing? That is, how is that event any different than the current shuttle with two boosters separating at the same time? Or for that matter, don't the Deltas and Atlases also shed boosters?

Doug

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  #18  
Old 07-24-2009, 04:03 PM
Jeff Walther Jeff Walther is offline
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Quote:
Originally Posted by Doug Sams
Jeff,

What am I missing? That is, how is that event any different than the current shuttle with two boosters separating at the same time? Or for that matter, don't the Deltas and Atlases also shed boosters?.


Well, I could be wrong, of course. :-) Shooting off my keyboard and all that.

The difference in this case is that the two boosters are also either gliders or airplanes. So instead of just following a ballistic path, which is pretty predictable, they have the opportunity to use their aero surfaces to fly into each other. A little pitch in the nose down direction and the two will hit each other. Two much pitch in the nose up postion and they'll loop around and hit each other. Odd winds or effects from the vehicles passage, and perhaps those big wings will drag them into each other.

I guess with a careful gentle nose up pitch they could predictably fall away from each other... It would definitely get a lot of scrutiny, I think.
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  #19  
Old 07-26-2009, 04:17 PM
FlyBack FlyBack is offline
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Quote:
Originally Posted by Jeff Walther
It would definitely get a lot of scrutiny, I think.


... it has, and you are abslolutely correct. It is a very difficult problem to solve. A quick literature search on the separation dynamics of hypersonic vehicles yielded the following:

UNSTEADY AERODYNAMICS OF A HYPERSONIC VEHICLE DURING A SEPARATION PHASE

exerpt - "At high altitude and
high Mach number the orbital stage is released and
the ”Separation Phase” starts. The separation phase
is mainly dominated by aerodynamic interference ef-
fects, hence safety considerations in order to achieve a
certain distance between both vehicles as fast as pos-
sible are of great interest."


Also, found at aiaa.org:

Wind tunnel tests for separation dynamics modeling of a two-stage hypersonic vehicle

Lateral Separation Dynamics and Stability of a Two-Stage Hypersonic Vehicle


For those of you who like a little light reading before bed.. enjoy.


Regards,

FlyBack

Last edited by FlyBack : 07-26-2009 at 11:40 PM.
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