In article ,
says...

"Fred J. McCall" wrote in message
...

wrote:

"In 1961, an American astronaut reached space for the first time and
soared
through the heavens in a gumdrop-shaped capsule.

Since then, people have flown to the moon, created space planes and
designed
rockets that return to Earth for precision landings. But when astronauts
lift off
next year from U.S. soil for the first time in six years, their vehicle of
choice
will be another capsule."

See:

http://www.latimes.com/business/la-f...htmlstory.html




How do the benefits of capsules and spaceplanes compare?


Capsules have lower dry mass for the cargo they carry, since you're
not carrying along all that lifting structure. I was rather
disappointed to see SpaceX back away from a powered landing on land
for the Dragon V2, since that would have addressed one of the
advantages of spaceplanes in that they don't require 'recovery forces'
to fish them out of the water. Small spaceplanes tend to be more
'reusable' than capsules. However, the fiasco that was the Space
Shuttle backed everyone away from the idea of spaceplanes.



My understanding is that NASA is the one insisting on a water landing for
Dragon V2, but SpaceX for its own missions still plans to ultimately do land
landings.

This has changed somewhat recently. Reportedly SpaceX is the one who
shelved development of Dragon V2 vertical landing. The reasons for this
aren't terribly clear, but there are hints from SpaceX that this is
because they've decided to change the (Mars) landing mode of their
(eventual) Mars vehicle.

Also, SpaceX is supposed to have a press briefing about the changes in
their Mars program sometime this fall. Hopefully we'll get more
information then which will allow us to "connect the dots".

I expect we'll eventually see us move back towards small
spaceplans/lifting body designs in a few decades, but it'll
take some time.

Possibly. Sierra Nevada Corporation is still working on Dreamchaser,
but it's only under a cargo contract with NASA, so it will lack the
ability to carry people. Also, SNC isn't exactly a "big player" in
aerospace. You're playing (quite) long odds if you think they'll
eventually dominate manned space travel.

The USAF is funding Experimental Spaceplane program (XS-1), which sounds
really cool, but it's nothing more than a (smallish) winged reusable
first stage. It's very hard for me to see this thing being cheaper than
a reusable Falcon 9 first stage. There are several reasons for this.
First the contractor is Boeing. Second, the thing will use what's left
of the parts of old SSMEs assembled into working engines (i.e. the bits
NASA isn't planning on using for SLS) and the SSME is not known for
being a "cheap" engine by any stretch of the imagination. Third, LH2 is
not a very dense fuel so this will result in a quite large "space
plane" when compared to say a LOX/kerosene stage. Fourth, winged
landing vehicles are more complex than a VTVL in aerodynamics,
structures, dynamics and control, and etc. Costs scale more closely
with complexity than size, but in the case of the XS-1, it's got
complexity and size as its drawbacks.

So, any way you run the accounting, I have a feeling XS-1 is going to be
a dismal (economic) failure. Despite the prejudices of the USAF, there
is nothing magic about wheels on a runway that will make "spaceplanes"
inexpensive to operate.

So, from my point of view, we're not sitting on the cusp of a resurgence
in "space planes". They're just too expensive to develop and too
expensive to fly compared to their simpler, cheaper, VTVL counterparts.

I'd also note that in the consumer world, the market of small flying
machines is dominated by quad copters, not fixed wing aircraft. VTVL
tech has literally matured to the point where it's cheap enough and easy
enough to fly that you can buy one in the children's toy aisle for less
than $100.

Jeff
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