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Science and Technology "Somewhere, something incredible is waiting to be known." - Carl Sagan.

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Old February 7 2014, 10:45 AM   #121
gturner
Admiral
 
Location: Kentucky
Re: US retreat leaves China leading way in race to return to Moon

It turns out to be very hard to achieve orbit with a winged vehicle that takes off like an airplane, because it's very difficult to achieve a high mass ratio with a craft that has to have heavy wings, landing gear, and air breathing engines. It's certainly not impossible, but it takes a whole lot of development and many projects get canceled when the numbers indicate they won't deliver a useful payload, if they can even achieve orbit.

For example, the MUSTARD proposal's lift-off weight is nearly as much as the Falcon 9 rocket but it was only planned to deliver about a fifth as much payload to orbit. Yet the vehicle acted like a conventional two-stage rocket with flyback capability.

Given the estimates of the Skylon's development and operational costs and payload given to Parliament, if its launches are priced competitively (in $/kg) to the existing SpaceX Falcon 9, it would have to fly 411 missions before it hits break-even, and that's ignoring the time-value of money and assuming no cost overruns or accidents. If the SpaceX Falcon 9R succeeds and lowers their launch costs, the Skylon might not ever be competitive.

One of the issues such vehicles face is simple launch weight. No supersonic aircraft has ever been built that has a gross lift-off weight of more than about 600,000 pounds, half the lift-off weight of even a medium rocket. And of the large supersonic aircraft (Concorde, B-70, B-1, and Soviet designs) none has carried a fuel fraction of more than about 40%. This can no doubt be improved on, but no such vehicle (mere supersonic, not even suborbital) has been remotely cheap to develop or operate.
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Old February 7 2014, 06:18 PM   #122
sojourner
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Re: US retreat leaves China leading way in race to return to Moon

Shaka Zulu wrote: View Post

What the frack ever happened to the dream of a manned reusable spacecraft that could lift off from an airport (civilian or millitary) like the National Aerospace Plane or the British one(s) like MUSTARD and Skylon (at least the British one is going ahead)?
Everyone realized the math doesn't work out using current technologies.
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Old February 9 2014, 10:15 PM   #123
publiusr
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Re: US retreat leaves China leading way in race to return to Moon

It was SLI and the Boeing bimese plan that was going to be most costly, that and Venture Star


Crazy Eddie wrote: View Post

SLS was designed by congress critters, not engineers.
Got any pix of Richard Shelby at the drafting table? That's funny. Last I heard Dan Dumbacher is the engineer, and he and other support SLS.

Engineers were pushing for HLVs for years ALS/NLS, Aquila, Jarvis...
http://www.wired.com/wiredscience/20...iew-1989-1993/
http://ntrs.nasa.gov/archive/nasa/ca...18890.pdf[
https://www.aiaa.org/uploadedFiles/About-AIAA/History_and_Heritage/Final_Space_Shuttle_Launches/ShuttleVariationsFinalAIAA.pdf

There was Magnum as well
http://www.wired.com/wiredscience/20...-nuclear-2001/

SLS will use a Delta IV second stage as a ready made insertion stage.

There was this line from Doctor Who which states that the soufflé isn't the soufflé, the recipe is the soufflé. SLS is not the rocket, but an engaged corps of dedicated men like what we had in Apollo, who existed beyond the lifespan of any one private company--like Marquardt or--who knows--Space X.

This in-house capability is not a liability, but an asset that acts as a force driver, a constituency. The one thing MSFC was put on this Earth to do is build big rockets. That they gave up on Venture Star--a real cost hog, and are working on something much more do-able in recovering the Saturn mojo, is to be lauded.

Here is an interesting post that you may find persuasive http://voices.yahoo.com/who-right-sp...-12305322.html

Nice quote from the comment section here, not that I agree with Spudis on everything--but...
"Many of these limits and assumptions placed on progress seem to me either arbitrary or instigated by the constant howling of private space advocates that 'it’s too expensive.'”

http://www.spudislunarresources.com/...tier-of-space/


For the folks who don't hate SLS , here are some other resources:
http://www.thespacereview.com/article/2445/1
http://newpapyrusmagazine.blogspot.c...r-highway.html
http://www.beyondearth.com/spotlight...launch-system]
http://www.americaspace.com/?p=51685
http://www.americaspace.com/?p=51730
http://forum.nasaspaceflight.com/ind...075#msg1158075
http://whnt.com/2014/01/31/sls-progr...iggest-rocket/
http://blog.al.com/breaking/2014/01/...ys_goodby.html

Russia feels it needs to answer with its own, so the heavy lift bandwagon is growing
http://www.space-travel.com/reports/...ocket_999.html
http://www.russianspaceweb.com/rockets_launchers_2010s.html#superheavy
http://forum.nasaspaceflight.com/ind...topic=3321.225

Last edited by publiusr; February 9 2014 at 10:29 PM.
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Old February 25 2014, 01:28 AM   #124
publiusr
Commodore
 
Re: US retreat leaves China leading way in race to return to Moon

China's CZ-9
http://www.globalsecurity.org/space/...china/cz-x.htm

http://www.newsmax.com/LarryBell/NAS...1/06/id/545396

It’s important to note that China’s lunar lander is far too big to have been designed for tiny rovers. Its size is 40 percent larger than a NASA Apollo module descent stage, suggesting that it must have been engineered for the addition of an ascent stage and crew cabin module to carry astronauts. The Chinese are building as many as six of such landers on an assembly line basis.
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Old February 25 2014, 07:47 PM   #125
gturner
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Location: Kentucky
Re: US retreat leaves China leading way in race to return to Moon

You left out an important quote from your second link:

Any effective policy requires committed leadership, a destination goal, and a carefully conceived long-term roadmap with achievable, worthwhile milestones. Since none of these prerequisites presently exist, the U.S. Space program is adrift without any real vision, goal, or determination.
Currently the fastest way to provide appropriately massed payloads for the SLS, since none are under current development, is to launch locomotive engines. Locomotive engines generally weigh from 100 to 250 tons, and after selection their weight can be tailored by removing some of the traction wheels, which are of course useless in orbit.
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Old March 1 2014, 08:52 PM   #126
publiusr
Commodore
 
Re: US retreat leaves China leading way in race to return to Moon

Nah--the space elevator people will find a use for them
Payloads followed R-7 development, not the other way around. But it helps if space advocates run things like the Chief Designers did. In the Pentagon, space advocates rank below the janitor. Now the A-10 is under assault, not JSF/F-35.

Air Force gets what Air Force wants.

China isn't alone--India wants in:
http://en.wikipedia.org/wiki/ISRO_Orbital_Vehicle

The text of the article seems to contradict the art. The art depicts the capsule as being atop their standard GSLV. The text tells us it will rest atop their mini-me SLS, the new GSLV III.

This will make the launch stack actually look like the Ariane 5 ARV concept
http://www.spaceflightnow.com/news/n1009/29arv/
http://www.astronautix.com/craft/mulpsule.htm

Hermes was thought too large and complex, so they went for a capsule. Ariane 6 may be too small for either ARV or ATV, but I think Europe washed its hands of manned spaceflight--with ARV research--already bought and paid for--going to Orion.
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