| Science Forum Index » Space Forum » Ares I-X flight stage separation successful???... |
|
Page 1 of 2 Goto page 1, 2 Next |
|
| Author |
Message |
| Jeff Findley... |
 Posted: Wed Oct 28, 2009 11:19 am |
|
|
|
Guest
|
The video of the Ares I-X flight was posted on NASA Watch. Is it me or does
the stage separation look like it wasn't clean. From the view of the ground
camera, it certainly looks like the SRB first stage is still ramming the
simulated upper stage *after* the separation motors (in the SRB skirt) fire.
In fact, what looks like a bad separation looks like it caused the simulated
upper stage to turn sideways quickly after separation.
On the shuttle, SRB separation happens when the SSME's are still firing, so
this sort of thing isn't an issue. The separation motors on the shuttle
push the SRB's away from the shuttle stack laterally. On Ares I-X, the
separation motors were designed to decelerate the first stage and pull it
away from the simulated upper stage.
Jeff
--
"Take heart amid the deepening gloom
that your dog is finally getting enough cheese" - Deteriorata - National
Lampoon |
|
|
| Back to top |
|
|
|
| Greg D. Moore (Strider)... |
| Posted: Wed Oct 28, 2009 11:30 am |
|
|
|
Guest
|
"Jeff Findley" <jeff.findley at (no spam) ugs.nojunk.com> wrote in message
news:82705$4ae87d39$927a2cda$17295 at (no spam) FUSE.NET...
[quote]The video of the Ares I-X flight was posted on NASA Watch. Is it me or
does the stage separation look like it wasn't clean. From the view of the
ground camera, it certainly looks like the SRB first stage is still
ramming the simulated upper stage *after* the separation motors (in the
SRB skirt) fire. In fact, what looks like a bad separation looks like it
caused the simulated upper stage to turn sideways quickly after
separation.
On the shuttle, SRB separation happens when the SSME's are still firing,
so this sort of thing isn't an issue. The separation motors on the
shuttle push the SRB's away from the shuttle stack laterally. On Ares
I-X, the separation motors were designed to decelerate the first stage and
pull it away from the simulated upper stage.
[/quote]
Well, given the upper stage had no RCS (that I'm aware of), the sudden 90
degree "turn" it made did seem wrong.
And thinking about it, you're right. I wonder if the SRB didn't decelerate
quickly enough.
It'll be interesting to see the post-flight data come in.
--
Greg Moore
Ask me about lily, an RPI based CMC. |
|
|
| Back to top |
|
|
|
| Jeff Findley... |
| Posted: Wed Oct 28, 2009 11:31 am |
|
|
|
Guest
|
"Jeff Findley" <jeff.findley at (no spam) ugs.nojunk.com> wrote in message
news:82705$4ae87d39$927a2cda$17295 at (no spam) FUSE.NET...
[quote]The video of the Ares I-X flight was posted on NASA Watch. Is it me or
does the stage separation look like it wasn't clean. From the view of the
ground camera, it certainly looks like the SRB first stage is still
ramming the simulated upper stage *after* the separation motors (in the
SRB skirt) fire. In fact, what looks like a bad separation looks like it
caused the simulated upper stage to turn sideways quickly after
separation.
On the shuttle, SRB separation happens when the SSME's are still firing,
so this sort of thing isn't an issue. The separation motors on the
shuttle push the SRB's away from the shuttle stack laterally. On Ares
I-X, the separation motors were designed to decelerate the first stage and
pull it away from the simulated upper stage.
[/quote]
NASA Spaceflight (dot com) also thinks the first stage recontacted the
simulated upper stage after separation.
http://www.nasaspaceflight.com/2009/10/live-ares-i-x-second-launch-attempt/
We'll have to wait and see if the other test objectives were met.
Jeff
--
"Take heart amid the deepening gloom
that your dog is finally getting enough cheese" - Deteriorata - National
Lampoon |
|
|
| Back to top |
|
|
|
| Fred J. McCall... |
| Posted: Wed Oct 28, 2009 12:02 pm |
|
|
|
Guest
|
"Jeff Findley" <jeff.findley at (no spam) ugs.nojunk.com> wrote:
:The video of the Ares I-X flight was posted on NASA Watch. Is it me or does
:the stage separation look like it wasn't clean. From the view of the ground
:camera, it certainly looks like the SRB first stage is still ramming the
:simulated upper stage *after* the separation motors (in the SRB skirt) fire.
:In fact, what looks like a bad separation looks like it caused the simulated
:upper stage to turn sideways quickly after separation.
:
:On the shuttle, SRB separation happens when the SSME's are still firing, so
:this sort of thing isn't an issue. The separation motors on the shuttle
:push the SRB's away from the shuttle stack laterally. On Ares I-X, the
:separation motors were designed to decelerate the first stage and pull it
:away from the simulated upper stage.
:
The problem is that if the stage still has significant thrust (and
unlike liquids, you can't cleanly shut down thrust on a solid) you
need a fairly beefy separation motor to do the job.
--
"Insisting on perfect safety is for people who don't have the balls to
live in the real world."
-- Mary Shafer, NASA Dryden |
|
|
| Back to top |
|
|
|
| Jeff Findley... |
| Posted: Wed Oct 28, 2009 1:35 pm |
|
|
|
Guest
|
"Fred J. McCall" <fjmccall at (no spam) gmail.com> wrote in message
news:5n1he55tb1bhip6qdrrq7vsi85pcgsgpp4 at (no spam) 4ax.com...
[quote]"Jeff Findley" <jeff.findley at (no spam) ugs.nojunk.com> wrote:
:The video of the Ares I-X flight was posted on NASA Watch. Is it me or
does
:the stage separation look like it wasn't clean. From the view of the
ground
:camera, it certainly looks like the SRB first stage is still ramming the
:simulated upper stage *after* the separation motors (in the SRB skirt)
fire.
:In fact, what looks like a bad separation looks like it caused the
simulated
:upper stage to turn sideways quickly after separation.
:
:On the shuttle, SRB separation happens when the SSME's are still firing,
so
:this sort of thing isn't an issue. The separation motors on the shuttle
:push the SRB's away from the shuttle stack laterally. On Ares I-X, the
:separation motors were designed to decelerate the first stage and pull it
:away from the simulated upper stage.
:
The problem is that if the stage still has significant thrust (and
unlike liquids, you can't cleanly shut down thrust on a solid) you
need a fairly beefy separation motor to do the job.
[/quote]
True. I believe Ares I-X had eight separation motors in the base of the SRB
skirt. Making them bigger and/or more numerous would surely impact payload
negatively. Perhaps the solution is to make sure the thrust has dropped to
some acceptable level before firing the separation motors. From what I
read, it sounded like Ares I-X was triggering the separation pyros and
motors based on time after ignition, not on acceleration.
Jeff
--
"Take heart amid the deepening gloom
that your dog is finally getting enough cheese" - Deteriorata - National
Lampoon |
|
|
| Back to top |
|
|
|
| Jeff Findley... |
| Posted: Wed Oct 28, 2009 4:46 pm |
|
|
|
Guest
|
"Pat Flannery" <flanner at (no spam) daktel.com> wrote in message
news:sbadnZtbcLdQWHXXnZ2dnUVZ_gKdnZ2d at (no spam) posted.northdakotatelephone...
[quote]Jeff Findley wrote:
The video of the Ares I-X flight was posted on NASA Watch. Is it me or
does the stage separation look like it wasn't clean. From the view of
the ground camera, it certainly looks like the SRB first stage is still
ramming the simulated upper stage *after* the separation motors (in the
SRB skirt) fire. In fact, what looks like a bad separation looks like it
caused the simulated upper stage to turn sideways quickly after
separation.
To me it looked like either:
1.) the base mounted SRB separation motors fired before the connection
between the two stages was severed.
2.) Air drag on the upper stage caused it to slide right back into the SRB
as it tried to fall away.
NASA is saying they don't think there was any recontact between the two
halves after separation, but it sure looked like they came into contact to
me.
[/quote]
Air drag should have been low at that altitude. I'm betting residual
pressure in the SRB casing causing enough thrust to overcome the separation
motors. SRB thrust doesn't terminate very cleanly unless you do something
fairly drastic to the casing, which has never been done with a shuttle SRB,
except on Challenger's last flight.
Jeff
--
"Take heart amid the deepening gloom
that your dog is finally getting enough cheese" - Deteriorata - National
Lampoon |
|
|
| Back to top |
|
|
|
| Jeff Findley... |
| Posted: Wed Oct 28, 2009 4:49 pm |
|
|
|
Guest
|
"Pat Flannery" <flanner at (no spam) daktel.com> wrote in message
news:HvmdnQMcTsvAVXXXnZ2dnUVZ_gudnZ2d at (no spam) posted.northdakotatelephone...
[quote]Greg D. Moore (Strider) wrote:
Well, given the upper stage had no RCS (that I'm aware of), the sudden 90
degree "turn" it made did seem wrong.
And thinking about it, you're right. I wonder if the SRB didn't
decelerate quickly enough.
It'll be interesting to see the post-flight data come in.
There was supposed to be some sort of "tumble motor" on the upper stage to
get it to go aerodynamically unstable after seperation and cause it to
quickly decelerate, but it would have to be gawdawful powerful to cause it
to swing around that fast.
[/quote]
There were eight separation motors and four tumble motors on the base of the
SRB. As far as I know, the upper stage didn't have tumble motors, only roll
control motors (which performed well). The intent was to tumble the SRB
*after* a clean separation so it would encounter more air drag. The
ultimate goal was to insure that it did *not* recontact the upper stage.
Obviously something went wrong with that on this flight.
Jeff
--
"Take heart amid the deepening gloom
that your dog is finally getting enough cheese" - Deteriorata - National
Lampoon |
|
|
| Back to top |
|
|
|
| hallerb at (no spam) aol.com... |
| Posted: Wed Oct 28, 2009 4:55 pm |
|
|
|
Guest
|
[quote]
I mean, really, what did they prove with this other than that they can
mock up something that looks sort of like an Ares and that they still
know how to ignite an SRB to launch it?
[/quote]
nasa proved it can wastefully spend boatloads of money:( |
|
|
| Back to top |
|
|
|
| Pat Flannery... |
| Posted: Wed Oct 28, 2009 5:28 pm |
|
|
|
Guest
|
Jeff Findley wrote:
[quote]The video of the Ares I-X flight was posted on NASA Watch. Is it me or does
the stage separation look like it wasn't clean. From the view of the ground
camera, it certainly looks like the SRB first stage is still ramming the
simulated upper stage *after* the separation motors (in the SRB skirt) fire.
In fact, what looks like a bad separation looks like it caused the simulated
upper stage to turn sideways quickly after separation.
[/quote]
To me it looked like either:
1.) the base mounted SRB separation motors fired before the connection
between the two stages was severed.
2.) Air drag on the upper stage caused it to slide right back into the
SRB as it tried to fall away.
NASA is saying they don't think there was any recontact between the two
halves after separation, but it sure looked like they came into contact
to me. |
|
|
| Back to top |
|
|
|
| Pat Flannery... |
| Posted: Wed Oct 28, 2009 5:39 pm |
|
|
|
Guest
|
Greg D. Moore (Strider) wrote:
[quote]Well, given the upper stage had no RCS (that I'm aware of), the sudden 90
degree "turn" it made did seem wrong.
And thinking about it, you're right. I wonder if the SRB didn't decelerate
quickly enough.
It'll be interesting to see the post-flight data come in.
[/quote]
There was supposed to be some sort of "tumble motor" on the upper stage
to get it to go aerodynamically unstable after seperation and cause it
to quickly decelerate, but it would have to be gawdawful powerful to
cause it to swing around that fast.
Pat |
|
|
| Back to top |
|
|
|
| Derek Lyons... |
| Posted: Wed Oct 28, 2009 6:09 pm |
|
|
|
Guest
|
Pat Flannery <flanner at (no spam) daktel.com> wrote:
[quote]Jeff Findley wrote:
There were eight separation motors and four tumble motors on the base of the
SRB. As far as I know, the upper stage didn't have tumble motors, only roll
control motors (which performed well). The intent was to tumble the SRB
*after* a clean separation so it would encounter more air drag. The
ultimate goal was to insure that it did *not* recontact the upper stage.
Obviously something went wrong with that on this flight.
Wouldn't tumbling the SRB make parachute deployment more difficult?
What if it ended up nose-down when the drogues deployed, and they
wrapped around the front end?
[/quote]
Shuttle SRB's tumble too Pat. It stablizes when it gets down into
dense atmosphere.
D.
--
Touch-twice life. Eat. Drink. Laugh.
http://derekl1963.livejournal.com/
-Resolved: To be more temperate in my postings.
Oct 5th, 2004 JDL |
|
|
| Back to top |
|
|
|
| Pat Flannery... |
| Posted: Wed Oct 28, 2009 6:56 pm |
|
|
|
Guest
|
Jeff Findley wrote:
[quote]There were eight separation motors and four tumble motors on the base of the
SRB. As far as I know, the upper stage didn't have tumble motors, only roll
control motors (which performed well). The intent was to tumble the SRB
*after* a clean separation so it would encounter more air drag. The
ultimate goal was to insure that it did *not* recontact the upper stage.
Obviously something went wrong with that on this flight.
[/quote]
Wouldn't tumbling the SRB make parachute deployment more difficult?
What if it ended up nose-down when the drogues deployed, and they
wrapped around the front end?
BTW, did this thing stage where the actual Ares 1 would?
The operational one will stage at the top of the interstage, to reveal
the bell of the upper stage engine; this one appeared to separate at the
base of the interstage where it joined the SRB.
If that's the case, then the staging aerodynamics are not representative
of the actual booster.
Pat |
|
|
| Back to top |
|
|
|
| Fred J. McCall... |
| Posted: Wed Oct 28, 2009 7:43 pm |
|
|
|
Guest
|
Pat Flannery <flanner at (no spam) daktel.com> wrote:
:Jeff Findley wrote:
:> There were eight separation motors and four tumble motors on the base of the
:> SRB. As far as I know, the upper stage didn't have tumble motors, only roll
:> control motors (which performed well). The intent was to tumble the SRB
:> *after* a clean separation so it would encounter more air drag. The
:> ultimate goal was to insure that it did *not* recontact the upper stage.
:> Obviously something went wrong with that on this flight.
:
:Wouldn't tumbling the SRB make parachute deployment more difficult?
:What if it ended up nose-down when the drogues deployed, and they
:wrapped around the front end?
:BTW, did this thing stage where the actual Ares 1 would?
:The operational one will stage at the top of the interstage, to reveal
:the bell of the upper stage engine; this one appeared to separate at the
:base of the interstage where it joined the SRB.
:If that's the case, then the staging aerodynamics are not representative
 f the actual booster.
:
Pretty much nothing else was, so why should that be?
I mean, really, what did they prove with this other than that they can
mock up something that looks sort of like an Ares and that they still
know how to ignite an SRB to launch it?
--
"The reasonable man adapts himself to the world; the unreasonable
man persists in trying to adapt the world to himself. Therefore,
all progress depends on the unreasonable man."
--George Bernard Shaw |
|
|
| Back to top |
|
|
|
| Dave... |
| Posted: Sat Oct 31, 2009 7:49 am |
|
|
|
Guest
|
On Oct 31, 11:40 am, David Spain <nos... at (no spam) 127.0.0.1> wrote:
[quote]
FWIW, NASA animations for this flight don't show the upper stage tumbling
after separation, which makes me think that was not an expected outcome.
Dave
[/quote]
I wouldn't read too much into those animations. Those animations are
released for PR purposes. Needless to say, they aren't based on CFD
analysis.
Bob Ess stated:
"We went back and looked at all the flight models and dispersion cases
that we ran, and we found thousands of them that matched what we saw"
http://www.spaceflightnow.com/ares1x/091030recovery/
"Ess described the upper stage simulator as "inherently unstable"
because its center-of-gravity is located near the back end of the
vehicle."
Dave |
|
|
| Back to top |
|
|
|
| Dave... |
| Posted: Sat Oct 31, 2009 9:01 am |
|
|
|
Guest
|
On Oct 31, 2:22 pm, kT <cos... at (no spam) lifeform.org> wrote:
[quote]
All upper stages are like that. It has to do with wanting to locate your
center of pressure on the stack behind the center of gravity of the
entire stack while in the atmosphere (i.e. - at launch) in order to
increase aerodynamic stability and control authority (which also affects
fuel efficiency) and wanting to keep the center of gravity behind the
center of pressure at high altitudes nearing vacuum, and in vacuum
itself, in order to increase the control authority and the reduce fuel
consumption via the reduced control forces necessary to control the
vehicle, which more or less in the end reduces to cosine losses by
thrust vector control. Less deviation means better fuel efficiency.
[/quote]
I doubt that. Upper stages are driven by mass consideration rather
than aerodynamic stability considerations. With the full stack, you
may have aerodynamic stability considerations. But once separation
occurs and the upper stage is off, you're generally well over 100kft,
well past Max-Q, and aero forces are becoming minimal...
And control forces don't significantly affect fuel efficiency. Drag
is a small part of a LV's delta-V budget anyway, and any off-nominal
AOA is a small part of THAT small part. Gravity drag is a more
significant loss by comparison.
Dave |
|
|
| Back to top |
|
|
|
|
