SpaceShipOne and reentry heat

I'm just an average person with an English degree, so I'm unfamiliar
with the science and physics and space craft reentry, so this is
likely a very stupid question.

But it's my uneducated understanding that returning space craft, like
all objects entering our atmosphere, super-heat from the friction of
falling through our atmosphere.
Which is why all crafts from Apollo to the space shuttles must have
carefully crafted heat shields and enter at a VERY narrow angle to
prevent either burn-up or "skipping" off the atmosphere.

Now, correct me if I'm wrong, but didn't the commercial SpaceShipOne
reach the very edge of the atmosphere? Doesn't it also need the
observe the same careful considerations for reentry?
If not, why? In simple "Physics for English Majors" language. =)

Thanks!
Liam

Doesn't it also need the
observe the same careful considerations for reentry?
If not, why? In simple "Physics for English Majors" language. =)



Not going nearly as ast, mach 3 instead of mach 25, and from lower/deeper in
the atmosphere. And when it activates it's novel "shuttlecock" drag system, it
slows the craft down in a place where the air is very very thin, by the time it
hits thicker air, it has already slowed considerably. There IS reentry heating,
but orders of magnitude below what a capsule or shuttle sees. The goofs who
talk about the same craft becomeing orbital don't "get it" about the SS-1: it
was designed for a very narrow mission, which it obviously performs well. To
make the leap to orbit, will require a redesign that takes into account the
much much more difficult factors involved. The system may look similar, in the
way a forumula one race car has four wheels like your family commuter. But
really it's a different breed of cat altogether.

On 21 Jun 2004 08:40:08 -0700, (LRW) wrote:
But it's my uneducated understanding that returning space craft, like
all objects entering our atmosphere, super-heat from the friction of
falling through our atmosphere.
Which is why all crafts from Apollo to the space shuttles must have
carefully crafted heat shields and enter at a VERY narrow angle to
prevent either burn-up or "skipping" off the atmosphere.

Now, correct me if I'm wrong, but didn't the commercial SpaceShipOne
reach the very edge of the atmosphere? Doesn't it also need the
observe the same careful considerations for reentry?
If not, why? In simple "Physics for English Majors" language. =)

It was going very much slower than a re-entering orbital craft.
Top speed was Mach 3.

In other words, it was at relative rest with respect to the Earth at
the top of its arc while a re-entering orbital craft would be moving
5 miles per second or faster at that point.

Gary

LRW wrote:
I'm just an average person with an English degree, so I'm unfamiliar
with the science and physics and space craft reentry, so this is
likely a very stupid question.

But it's my uneducated understanding that returning space craft, like
all objects entering our atmosphere, super-heat from the friction of
falling through our atmosphere.
Which is why all crafts from Apollo to the space shuttles must have
carefully crafted heat shields and enter at a VERY narrow angle to
prevent either burn-up or "skipping" off the atmosphere.

Now, correct me if I'm wrong, but didn't the commercial SpaceShipOne
reach the very edge of the atmosphere? Doesn't it also need the
observe the same careful considerations for reentry?
If not, why? In simple "Physics for English Majors" language. =)


SpaceShipOne dropped down from a height of 100km, while a shuttle drops
down from a height of some 400km AND has additionally a horizontal
velocity of some 8km/s. And an Apollo spacecraft dropped down from some
400000km. That's in both cases a *LOT* of kinetic energy more to kill
than SSO had to.

In article you wrote:
snip
Now, correct me if I'm wrong, but didn't the commercial SpaceShipOne
reach the very edge of the atmosphere? Doesn't it also need the
observe the same careful considerations for reentry?
If not, why? In simple "Physics for English Majors" language. =)

Basically, as it's going much, much slower.
Craft reentering from low-earth orbit come in at around mach 30.
The SS1 reenters at mach 3 (?).
Heating is more or less proportional to the cube of speed, so the
heating will be around a thousandth of that coming in from orbit.
The RS-71 flew at mach 3, and was fine with just a titanium skin.
If you tried to put a titanium skin on a craft coming in at orbital
velocities, you get little more than a bright shower of sparks
as it atomises.

In article , LRW wrote:
I'm just an average person with an English degree, so I'm unfamiliar
with the science and physics and space craft reentry, so this is
likely a very stupid question.

But it's my uneducated understanding that returning space craft, like
all objects entering our atmosphere, super-heat from the friction of
falling through our atmosphere.
Which is why all crafts from Apollo to the space shuttles must have
carefully crafted heat shields and enter at a VERY narrow angle to
prevent either burn-up or "skipping" off the atmosphere.

Now, correct me if I'm wrong, but didn't the commercial SpaceShipOne
reach the very edge of the atmosphere? Doesn't it also need the
observe the same careful considerations for reentry?
If not, why? In simple "Physics for English Majors" language. =)

Thanks!
Liam

It's all a matter of speed. Vehicles returning from the moon (Apollo)
are doing about Mach 35; Orbital vehicles are doing about Mach 25;
SpaceShip 1 did about Mach 3.5 today. Reentering vehicles are using
the atmosphere to absorb their kinetic energy (velocity) and slow them
down to touchdown speed at ground level - and that's what generates the
re-entry heat. The faster you're going, the more energy there is to
dissapate, the more heat is produced.

So SS1 has to deal with some heating, true - but it's not the same
level of heating as a shuttle or Apollo spacecraft. And since it's
on a ballistic (suborbital) trajectory, it can't "skip" off the
atmosphere - it's not going fast enough or heading in the right
direction to do that. SS1 does have to pay attention to it's re-enty
profile and make sure it can handle the heat and ends up back at the
runway - but the constraints are milder than shuttle or Apollo dealt
with.

(LRW) wrote:
Now, correct me if I'm wrong, but didn't the commercial SpaceShipOne
reach the very edge of the atmosphere? Doesn't it also need the
observe the same careful considerations for reentry?
If not, why? In simple "Physics for English Majors" language. =)

It flies much lower and *MUCH* slower than orbital craft (SS1 is
sub-orbital), and thus does not require the same considerations and
protection.

D.
--
Touch-twice life. Eat. Drink. Laugh.

"LRW" wrote in message
om...
Now, correct me if I'm wrong, but didn't the commercial SpaceShipOne
reach the very edge of the atmosphere? Doesn't it also need the
observe the same careful considerations for reentry?
If not, why? In simple "Physics for English Majors" language. =)

Basically, SpaceShipOne was not moving all that fast when it left the
atmosphere. If something is in orbit, it is moving around Mach 25 (compared
with SSO's top speed of less than Mach 3).

In article ,
LRW wrote:
Now, correct me if I'm wrong, but didn't the commercial SpaceShipOne
reach the very edge of the atmosphere? Doesn't it also need the
observe the same careful considerations for reentry?
If not, why? In simple "Physics for English Majors" language. =)

Mostly, because it didn't go very high and wasn't in orbit, so it
reentered at quite low speed.

To reach an altitude of 100km, which SS1 (just barely) did, it needed a
speed of 1.5-2km/s (depending on how steep the ascent was), and it would
have come back down at around the same speed. Orbital velocity, on the
other hand, is 8km/s, and return from the Moon brings you in at 11km/s.

Moreover, a lot of the reentry issues scale with kinetic energy, which is
proportional to the *square* of velocity, so 8km/s is not four times as
bad as 2km/s, it's more like sixteen times as bad.

Between the low speed and the clever design of SS1, the reentry was quite
a mild one. The designers couldn't quite ignore the heating issue, but
they didn't have to do anything very elaborate about it.

If SS1 had gone two or three times as high, reentry heating would have
needed more attention. If SS1 had been moving fast enough horizontally to
be in orbit, reentry heating would have needed a *lot* more attention.
--
"Think outside the box -- the box isn't our friend." | Henry Spencer
-- George Herbert |

On 21 Jun 2004, LRW wrote:

[snip]
But it's my uneducated understanding that returning space craft, like
all objects entering our atmosphere, super-heat from the friction of
falling through our atmosphere.

[snip]
Now, correct me if I'm wrong, but didn't the commercial SpaceShipOne
reach the very edge of the atmosphere? Doesn't it also need the
observe the same careful considerations for reentry?

Airplanes don't superheat.

Baseballs and Skydivers don't either.

It's all about air friction.

If you are moving through the air, you have to push it aside to get
through. The faster and more energetically you do this the more you will
heat it (and it will heat you).

Spacecraft in orbit superheat on return because they are moving VERY fast
as they enter the upper atmosphere.

Spaceship one is using a trajactory that just barely rises above the
atmosphere... and has no "ground speed" at all.

So instead of smashing into the upper atmosphere at 5 or 6 miles per
second (22,000 miles per hour) like a space-shuttle, Spaceship One hits
the upper atmosphere at around 1,200 miles per hour. The energy that it's
hull must absorb/shed is therefore only about 5% as much. This is easy to
handle with normal aircraft materials.

The numbers I've just given are really rough. But they're not completely
wrong.

I hope this helps.

Gene Pharr
New Orleans, LA

--
Alcore Nilth - The Mad Alchemist of Gevbeck