In article ,
"The Enlightenment" wrote:

"Chad Irby" wrote in message
m...

Actually, skip-reentry relies on a somewhat higher initial reentry
speed, as compared to the "plunge" method, and while max temps can
be higher, the plunge method has some advantages. Note also that
the "skip" method relies heavily on radiative heat emission, and
that's not very effective for dumping large amounts of heat in a
short period of time.

Indeed but thats not a problem for winged re-entry vehicles that
unlike blunt bodies can fly and control their rate of entry hopefully
limiting the rate of hest buildup to that which can be radiated.

Nope. Velocity is velocity, and coming in out of vacuum means those
steel wings are just little flanges out in the Mach-20 airflow waiting
to be melted - or broken off altogether.

You still need some very high-temp metals (Inconel or titanium,
to start), instead of the normal stainless steel Sanger proposed.

Sangers aircraft the 'silver bird' was made of the high chrome steel
(stainless basically as used in the XB70 ) and I expect similar to
what was used in Boiler Tubes at the time. That can opperate at 600C
without loosing strength and beyond at reduced strength. Stainless
is more heat resistant than titanium and but less than inconel.

So the Silverbird could have managed about Mach 3 for a short period of
time, about 1/5 of the *necessary* speed for suborbital missions like
the one it was designed for... and then would have had to be scrapped
due to overheating of the structure.

Sanger never actually worked on the thermodynamic aspect of the
Silverbird, and that would have been a potential showstopper for
the program, even if he'd had more time to work on it. The plane
was a concept/mockup only, and very little actual engineering work
had been done when the war came to an end.

Sure, sanger didn't know that blunt bodies provide some thermal
protection.

Here is the Sanger Thermal protection system.

The Sanger silver bird is stainless steel. Pilot and critical
components such as tires, control and crew cabin are insulted from the
over 600C heat of re-entry for as long as necesaary.

Insulation of the insides isn't the problem. It's the skin melting off
in a very short period that's the issue, combined with the lack of time
to re-radiate the heat before hitting the atmosphere again. When a
spacecraft hits the atmosphere at Mach 20, the temps reach 9500 degrees.

At a "mere" Mach 6, the X-15 skin reached 650 to 700 degrees C, in a
minute and a half of powered flight. This would have happened to the
Sanger several times per mission, with a skin that didn't have the heat
resistance of the X-15's.

This is how I think it would have been tested:

(Magical handwaving imaginary ten year test program deleted)

....you also left out the two or three Silverbirds that would have been
lost due to the control problems inherent in supersonic flight. And
then the one or two they would have lost due to the skin peeling off.
And then one or two due to not knowing about how to support a man in
space...

...if the program had ever gotten that far.

The wedge shapped wing profile shows a keen understanding of
supersonic aerodynamics.

No, it just showed a basic understanding of high-speed flight.
Small wings = high wing loading = higher speeds and lower
maneuverability. Landing speeds would have been high, even when
empty.

It had a flat body to help both hypersonic re entry and landing and
braking parachutes.

....and would have come in at 200 MPH or so, like the Shuttle. So add
"develop high speed high load tires" to your development program. And
"redesign aircraft to really handle hypersonic flight."

If you look at the wings they are like triangular wedges like a
Sparrow missile.

Um, no. They're closer to the F-104 in shape and cross-section in every
image I've seen of the Silverbird. Much like the X-15 wings, as a
matter of fact.

The Germans had solved the hypersonic and heat shielding re-entry
problems of the V2

...by not flying it at high hypersonic speeds for very long. The
V-2 topped out at about 3500 MPH on reentry, and only managed that
for a very short time, in uncontrolled ballistic flight.

They had a heat shield. Graphite and plywood that turned to graphite.

....for the minute or two it took to reenter and impact.

No doubt other materials were in development. Eg dibule walled skins,
ablatives etc.

Replace "were" with would have to be once they started actually thinking
about it."

They had a problem defined and thus they could set about solving it.

....in several years. Which they didn't have, and had *not* anticipated
in the original idea.

Nothing like the 13,000 MPH the Sanger was supposed to hit.

Maybe Sanger would only have handeled a lower speed. say Mach 6 or
mach 10 instead of Mach 20.

....and been unable to complete its mission, which relied on long periods
of coasting in between moderate periods of slamming into the atmosphere
at 8,000 to 12,000 MPH and melting that stainless steel skin right off.

Then having to be redesigned for massive amounts of fuel to make up for
not being able to handle the original mission profile.

And a ten-year nuclear program to make a nuke small enough to carry in
the darned thing...

Sanger MkII on the otherhand?

Sure, and when they got the Ark of the Convenant out of that secret
American storage facility, they would have been unbeatable.

--
cirby at cfl.rr.com

Remember: Objects in rearview mirror may be hallucinations.
Slam on brakes accordingly.