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Reused Dragons to start flying this year



 
 
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Old November 9th 17, 04:42 AM posted to sci.space.policy
Fred J. McCall[_3_]
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Default Reused Dragons to start flying this year

JF Mezei wrote:

On 2017-11-07 08:35, Fred J. McCall wrote:

mass tends to be higher. They need both actual landing gear and
something to generate that horizontal lift (wings, a lifting body, or
both). Those things are just parasitic weight during boost,


But so is the fuel needed for vertical landing. So it's a question of
which weighs the most.


Unless your horizontal lander is going to 'dead stick' in like the
Shuttle, it's going to need some fuel, too. Landing gear adds 4%-6%
to the weight of a vehicle. That in itself is a big chunk of mass
when you're talking about carrying it clear to orbit (or anywhere
close) and back. Now add in the dead weight of all that wing
structure.


Wings need not be dead weight. They can be used as tanks for liquids
such as kerosene. (this is what commercial aircraft do).


Very heavy tanks. They still increase dead weight because they need
sufficient structure to not rip off when they're out there doing all
those draggy things.


So the cost of having wings need not be as great as it was on the
Shuttle where wings were dead weight. This doesn't mean that wings with
fuel in them would be better than powered vertical landing, but the
difference may not be as great as it was with Shuttle.


Wings always increase dead weight if they're actually going to be used
as wings and provide lift on the way down. Whether it's better than
the Shuttle mass fractions is irrelevant to the question.


--
"Some people get lost in thought because it's such unfamiliar
territory."
--G. Behn
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