Spaceship One - a partial sucess.

First returns; the 100km mark was broken, ascent phase control
problems remain.

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

Derek Lyons wrote:
First returns; the 100km mark was broken, ascent phase control
problems remain.

This time the control problems were at the end of the burn,
but it looked pretty exciting for a bit there...

I hope there's a straightforwards answer so they can fly
the next flight on time.


-george william herbert

In article ,
(Derek Lyons) wrote:

First returns; the 100km mark was broken, ascent phase control
problems remain.

And always will, with that design. Once it gets out of the atmosphere
it simply doesn't have enough authority on the attitide control jets to
compensate for the variations in thrust vector you're always going to
get from a rocket with solid fuel.

The higher a flight is aiming for, the worse the problem will be.

-- Bruce

(George William Herbert) wrote:

Derek Lyons wrote:
First returns; the 100km mark was broken, ascent phase control
problems remain.

This time the control problems were at the end of the burn,
but it looked pretty exciting for a bit there...

20 odd rolls according to Miles O'Brien on CNN, somewhat more severe
than last time.

I hope there's a straightforwards answer so they can fly
the next flight on time.

Agreed.

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

On 9/29/04 8:30 AM, in article
, "Bruce Hoult"
wrote:

In article ,
(Derek Lyons) wrote:

First returns; the 100km mark was broken, ascent phase control
problems remain.

And always will, with that design. Once it gets out of the atmosphere
it simply doesn't have enough authority on the attitide control jets to
compensate for the variations in thrust vector you're always going to
get from a rocket with solid fuel.

Just from my observation, the problem appeared to be a coupling from yaw
to roll - definitely had a significant yaw angle, and the effective dihedral
is extraordinarily high with this design - a lot like the lifting bodies
that had similar control issues. Maybe that resulted from a yaw thrust
vector misalignment, maybe just plain old roll/yaw coupling issues at high
speeds. But it seems very unlikely to be something that can easily be fixed.

Brett

In article ,
(Derek Lyons) wrote:

(George William Herbert) wrote:

Derek Lyons wrote:
First returns; the 100km mark was broken, ascent phase control
problems remain.

This time the control problems were at the end of the burn,
but it looked pretty exciting for a bit there...

20 odd rolls according to Miles O'Brien on CNN, somewhat more severe
than last time.

Was it the same direction?

My crazy wild-eyed theory: there's a swirl in the N2O entering the
combustion chamber, or there is a spiral pattern in the way the solid
fuel is cast or something like that.

-- Bruce

On 9/29/04 8:46 AM, in article
, "Bruce Hoult"
wrote:

In article ,
(Derek Lyons) wrote:

(George William Herbert) wrote:

Derek Lyons wrote:
First returns; the 100km mark was broken, ascent phase control
problems remain.

This time the control problems were at the end of the burn,
but it looked pretty exciting for a bit there...

20 odd rolls according to Miles O'Brien on CNN, somewhat more severe
than last time.

Was it the same direction?

My crazy wild-eyed theory: there's a swirl in the N2O entering the
combustion chamber, or there is a spiral pattern in the way the solid
fuel is cast or something like that.

-- Bruce

That's possible, but the "swirl" as a direct source of roll torque would
seem to be insufficient. Much more likely, to me, is a thrust vector
misalignment in yaw, driving it to a static yaw angle of attack, and then
the dihedral effect rolls it. That could be a powerful effect, far more
powerful than the swirl.

I don't have any direct professional experience with hybrids, but I would
be amazed if it's worse in "swirl" than your average liquid engine. And
that's always proven to be small to the point of negligible.

But he thrust vector misalignment could very easily be a few degrees,
and is very often just ignored (!) (I have a few stories that have to wait
40 something years to tell) and that could be more than enough.

Brett

On Thu, 30 Sep 2004 03:46:39 +1200, Bruce Hoult wrote:

In article ,
(Derek Lyons) wrote:


My crazy wild-eyed theory: there's a swirl in the N2O entering the
combustion chamber, or there is a spiral pattern in the way the solid
fuel is cast or something like that.


Exciting flight.

Sounds possible, swirl in the combustion chamber with rapidly decreasing
aerodynamic roll control.

Maybe.

Craig Fink

On Wed, 29 Sep 2004 16:00:02 +0000, Brett Buck wrote:

On 9/29/04 8:46 AM, in article
, "Bruce Hoult"
wrote:


That's possible, but the "swirl" as a direct source of roll torque would
seem to be insufficient. Much more likely, to me, is a thrust vector
misalignment in yaw, driving it to a static yaw angle of attack, and then
the dihedral effect rolls it. That could be a powerful effect, far more
powerful than the swirl.

I don't have any direct professional experience with hybrids, but I would
be amazed if it's worse in "swirl" than your average liquid engine. And
that's always proven to be small to the point of negligible.

But he thrust vector misalignment could very easily be a few degrees,
and is very often just ignored (!) (I have a few stories that have to wait
40 something years to tell) and that could be more than enough.


The pilot hung in there with increasing roll rate to get the altitude
target. He said he shut the engine down 11 seconds early and used much of
the RCS propellent to take out most of the roll on the way to apogee. So
he could have gone higher.

Craig Fink

Brett Buck wrote:


That's possible, but the "swirl" as a direct source of roll torque
would
seem to be insufficient. Much more likely, to me, is a thrust vector
misalignment in yaw, driving it to a static yaw angle of attack, and
then
the dihedral effect rolls it. That could be a powerful effect, far
more
powerful than the swirl.

I don't have any direct professional experience with hybrids, but
I would
be amazed if it's worse in "swirl" than your average liquid engine.
And
that's always proven to be small to the point of negligible.

Is it true that this effect is negligable? The second Ariane flight
developed excessive roll from this problem. True, the torque is small
compared to the thrust, but just like today it exceeded the control
authority and forced a premature shutdown (though because the fuel was
spun to the outside of the tank, not deliberate shutdown.)

From: http://www.esa.int/export/esaCP/Pr_14_1998_p_EN.html

"The most significant anomaly, namely excessive roll torque during
cryogenic main stage flight, has now been explained. It will be
remembered that the possible causes of the 900 Nm (Newton metre) roll
torque registered in flight were narrowed down to two :

* roughness of the internal surface of the Vulcain engine divergent
causing the boundary layer of the main jet to spiral;

* snapping of one of the rods attaching the Vulcain engine turbine
exhaust lines to the aft end of the divergent.

Three test firings of the Vulcain engine were performed on a teststand
equipped with a roll torque measurement device. Throughout engine
running time on all three tests, roll values very similar to those
encountered in flight 502 were recorded. The first of the above
explanations is therefore confirmed. The excess roll torque phenomenon
will now be countered by repositioning the turbine exhausts.

[...]

The studies and tests conducted since flight 502 have also shown that
the premature main stage shutdown that occurred during that flight was
caused by the excessive roll torque. Action to overcome the torque
problem will therefore also prevent a recurrence of the premature
shutdown."