Author Topic: Boeing Submits Proposal for NASA Commercial Crew Transport System  (Read 12683 times)

Offline Star-Drive

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Yeah, my post was too simplistic. Wings are not categorically an obsolete technique in a launch / re-entry vehicle.

It's just that one can't say capsules are bad because they are old-fashioned. (Maybe you didn't mean that but that's the gist of what I understood.)

You could likely quite easily soft-land capsules with parawings / parafoils. This seems to me to be the optimal path: very small mass and still precision landings. (Maybe not thousands of kilometers of cross range but tens of kilometers anyway.)
http://gravityloss.wordpress.com/2008/05/09/the-last-five-kilometers/

Capsules can be extremely light. This solves so many other problems it's a very good idea to look at them hard. Lifting bodies are heavy and things with wings are elephants. Capsules have great margins in control and thermal issues and are very easy to build.

I'm not dismissing winged vehicles out of hand. Just saying they start with a significant weight disadvantage, which effects everything down below in the hierarchy, the launcher, ground infrastructure... There are  good reasons why all operational re-entry vehicles but one have been capsules.

Like there are reasons why airplanes were airplanes and not airships, re-entry craft are not spaceplanes automatically - the environment is different and requires a clean sheet thinking to find the best approach.

There is a midway ground between winged and capsule reentry vehicles and that is the one Lockheed Martin took back in the June 2005 article in Popular Mechanics.  And please note, L-M proposed to use titanium for the reentry vehicle, which greatly reduces the mass of the required heat-shield, even for lunar reentry profiles.  I think that a titanium based capsule design could come in a bit lighter, but at the expense of hypersonic cross range capability.  I still wish though that NASA had allowed an open competition between this L-M stub-wing vehicle and Boeing's Apollo Capsule redo to see who would really come out on top overall operationally, but Griffin had already stacked the deck to meet his and his controller's requirements.

http://www.popularmechanics.com/science/air_space/1534782.html

"May 3, 2005 -- When NASA requested designs for a Crew Exploration Vehicle (CEV), two major teams--one headed by Lockheed Martin and one by Northrop Grumman and Boeing--took on the challenge. The winning concept will be chosen in 2008, and the manned vehicle flown in 2014.

The agency's primary requirement is to "ensure crew safety through all mission phases." The Lockheed team--consisting of six companies--came up with a CEV in three parts.  The titanium crew module holds four to six astronauts and launches separately from the mission module and the propulsion stage.  They rendezvous in orbit to create a 70-ft.-long vehicle that weighs just under 40 metric tons.

The team scrapped foam insulation in favor of a redundant Thermal Protection System that includes a backed-up carbon-carbon heat shield. In an emergency, a rescue module designed into the top 22 ft. of the crew module can be fired off at any time. The CEV is not designed to glide upon re-entry like the shuttle; rather, it will be equipped with parachutes and airbags to set down on land or water. Interchangeable computer systems will increase adaptability between modules."

Star-Drive

Offline meiza

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Yeah, that's quite heavy though. What's the weight of the "CM"?
A lifting body might weigh double that of a capsule CM, and a winged vehicle triple. Or something in that vein.

In a sense, a lifting body is taking the worst of both worlds - you still have to hard or wet land with parachutes like a capsule, but you have the control and possibly heating problems of a non-capsule... (don't know for sure how bad, having lift helps some...)

Offline Lars_J

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...
Dragon is the only one of the present crop of capsule vehicles that at least tries to do something better.
It did move most of the service module systems into the reentry vehicle and claims to have a reusable LV.
...

What is Dragon doing differently in an ops concept?  It launches on a rocket, orbits earth, the service module separates, the capsule lands in the ocean.....sounds real familar.

Well technically Dragon does't have a service module per se. Sure it will have a separating trunk with solar arrays, but that's it. All orbital maneuvering and deorbit burns are accomplished with the thrusters in the capsule.
« Last Edit: 09/30/2009 12:32 AM by Lars_J »

Offline Lars_J

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That L-M lifting body looks nice... But that thing would have been extremely heavy. Not to mention the added complexity of a lifting body splitting in half in an emergency to just pull the front half away. (I thought first the whole lifting body would have separated, but according to the article above posted by Star-Drive, the lifting body separated in the middle)

But the concept of steerable parachutes is a good one. Wasn't that an early suggested landing mode for Big Gemini? (Landing on extendable struts using a steerable parachute)

EDIT - I found the Big Gemini landing picture: http://www.astronautix.com/graphics/b/biglandg.jpg
« Last Edit: 09/30/2009 12:38 AM by Lars_J »

Offline A_M_Swallow

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But the concept of steerable parachutes is a good one. Wasn't that an early suggested landing mode for Big Gemini? (Landing on extendable struts using a steerable parachute)

Can steerable parachutes be tested cheaply using mini-capsules dropped from aircraft and sounding rockets?

Offline Lars_J

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Yes, why not? They would be tested just like any other parachute.

Offline Star-Drive

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That L-M lifting body looks nice... But that thing would have been extremely heavy. Not to mention the added complexity of a lifting body splitting in half in an emergency to just pull the front half away. (I thought first the whole lifting body would have separated, but according to the article above posted by Star-Drive, the lifting body separated in the middle)

But the concept of steerable parachutes is a good one. Wasn't that an early suggested landing mode for Big Gemini? (Landing on extendable struts using a steerable parachute)

EDIT - I found the Big Gemini landing picture: http://www.astronautix.com/graphics/b/biglandg.jpg

Per Astronautix.com all the 2005 CEV entries had to be in the 15 to 18 metric ton range for their total mass, which includes LM's lifting body design.  Think titanium...

 http://www.astronautix.com/craftfam/cev.htm
Star-Drive

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