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| John Doe... |
 Posted: Wed Oct 28, 2009 3:03 pm |
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Derek Lyons wrote:
[quote]If you steer the tail away from the tower, you're steering the
midsection and nose *towards* the tower. Hence, it's better to steer
the tail towards in order to direct the flight path away and onto the
proper trajectory.
[/quote]
Where was the SRB in the Ares1X positioned relative to the 2 SRBs used
in shuttle ? Was it positioned at the same location as one of the
Shuttle SRBs, was it positioned where the shuttle SSMEs would have been ?
If the Shuttle SRBs had no problems clearing the tower without touching
it, why would this glorified firecracker have problems since it is much
smaller/thinner and thus should have far more clearance ? |
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| Derek Lyons... |
| Posted: Wed Oct 28, 2009 3:14 pm |
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John Doe <jdoe at (no spam) doe.org> wrote:
[quote]Derek Lyons wrote:
If you steer the tail away from the tower, you're steering the
midsection and nose *towards* the tower. Hence, it's better to steer
the tail towards in order to direct the flight path away and onto the
proper trajectory.
Where was the SRB in the Ares1X positioned relative to the 2 SRBs used
in shuttle ? Was it positioned at the same location as one of the
Shuttle SRBs, was it positioned where the shuttle SSMEs would have been ?
If the Shuttle SRBs had no problems clearing the tower without touching
it, why would this glorified firecracker have problems since it is much
smaller/thinner and thus should have far more clearance ?
[/quote]
It doesn't have more clearance - it has the same clearance as it was
mounted over the LH SRB hole.
D.
--
Touch-twice life. Eat. Drink. Laugh.
http://derekl1963.livejournal.com/
-Resolved: To be more temperate in my postings.
Oct 5th, 2004 JDL |
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| Jeff Findley... |
| Posted: Wed Oct 28, 2009 3:48 pm |
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"Derek Lyons" <fairwater at (no spam) gmail.com> wrote in message
news:4ae9a10c.2933711468 at (no spam) news.supernews.com...
[quote]"Greg D. Moore \(Strider\)" <mooregr_delet3th1s at (no spam) greenms.com> wrote:
"Derek Lyons" <fairwater at (no spam) gmail.com> wrote in message
news:4aeb8c0c.2928335000 at (no spam) news.supernews.com...
"Jeff Findley" <jeff.findley at (no spam) ugs.nojunk.com> wrote:
The press conference following is giving some indication that the first
stage did recontact the upper stage simulator after separation, but
they're not outright admitting it yet. This is a problem with SRB's.
It's not an insoluble one though. Polaris A1 had serious recontact
problems between the (thrust terminated) second stage and the warhead.
It's a matter of getting the timing right.
An interesting question will be how the timing and other factors change
with
a full 5-segment SRB.
Yep. And this is also exactly why you fly test flights.
[/quote]
And yet there was little sympathy by you for Falcon I's initial flight
failures even though they clearly learned from them and ultimately were
successful in achieving orbit.
I suppose you have more sympathy for NASA because they deliberately set the
"official goals" very low, allowing them to claim success even in the face
of an obvious failure? Obviously the PAO has been taking lessons from
Montgomery Scott. ;-)
Jeff
--
"Take heart amid the deepening gloom
that your dog is finally getting enough cheese" - Deteriorata - National
Lampoon |
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| Jeff Findley... |
| Posted: Wed Oct 28, 2009 4:17 pm |
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"John Doe" <jdoe at (no spam) doe.org> wrote in message
news:0096c30c$0$27961$c3e8da3 at (no spam) news.astraweb.com...
[quote]Jeff Findley wrote:
The thrust
doesn't stop cleanly like a liquid engine. It slowly tails off. And
with
the hammer head design of the vehicle, getting a clean separation will be
a
challenge.
Should they actually launch a real vehicle, wouldn't the second stage
ignite at the same time as separation to ensure it doesn't start to
thumble and lose its orientation and also to ensure it doesn't
collide/recontact with the first stage ?
[/quote]
Possibly, but US upper stages tend to be lit after a clean separation. On
top of that Ares I's SRB first stage is to be recovered and reused, so I'm
not sure firing the upper stage engine essentially on top of the SRB would
be advisable.
[quote]For this prototype test flight, was it normal that the fake second stage
immediatly lost its attitude and started to thumble at separation
(aka: was there still enough air resistance to cause that) ?
Once there is a real second stage, would its mass be significantly
higher than the fake one and give it more time in the proper attitude
before air resistance would start to cause it to thumble ?
[/quote]
The simulated upper stage had similar mass and inertia properties similar to
a fueled upper stage, so the deceleration caused by air drag would be
similar to a real stage. Plus, separation was pretty high up, so air drag
wouldn't be that high to begin with. I'd imagine the big problem here is
the thrust of the SRB didn't fall off as quickly as NASA's "worst case"
prediction, which is what was used to set the timing of the separation
events.
Jeff
--
"Take heart amid the deepening gloom
that your dog is finally getting enough cheese" - Deteriorata - National
Lampoon |
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| Derek Lyons... |
| Posted: Wed Oct 28, 2009 4:40 pm |
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"Jeff Findley" <jeff.findley at (no spam) ugs.nojunk.com> wrote:
[quote]
"Derek Lyons" <fairwater at (no spam) gmail.com> wrote in message
news:4ae9a10c.2933711468 at (no spam) news.supernews.com...
"Greg D. Moore \(Strider\)" <mooregr_delet3th1s at (no spam) greenms.com> wrote:
"Derek Lyons" <fairwater at (no spam) gmail.com> wrote in message
news:4aeb8c0c.2928335000 at (no spam) news.supernews.com...
"Jeff Findley" <jeff.findley at (no spam) ugs.nojunk.com> wrote:
The press conference following is giving some indication that the first
stage did recontact the upper stage simulator after separation, but
they're not outright admitting it yet. This is a problem with SRB's.
It's not an insoluble one though. Polaris A1 had serious recontact
problems between the (thrust terminated) second stage and the warhead.
It's a matter of getting the timing right.
An interesting question will be how the timing and other factors change
with a full 5-segment SRB.
Yep. And this is also exactly why you fly test flights.
And yet there was little sympathy by you for Falcon I's initial flight
failures even though they clearly learned from them and ultimately were
successful in achieving orbit.
[/quote]
I had little sympathy for the first failure because it was a stupid
dipshit failure. The later failures I didn't mention sympathy one way
or another - I only seemed unsympathetic by comparison because I
wasn't cheering my head off at accomplishing nothing like pretty much
everyone else. Pointing out the plain fact that a vehicle designed to
reach orbit didn't actually do so, regardless of whatever else it
achieved, places you firmly in the detractor camp around these parts.
[quote]I suppose you have more sympathy for NASA because they deliberately set the
"official goals" very low, allowing them to claim success even in the face
of an obvious failure? Obviously the PAO has been taking lessons from
Montgomery Scott. 
[/quote]
I don't have any particular sympathy for NASA. It's the same
situation as the Falcon I test series - pointing out facts like liquid
engines not tailing off cleanly and that solid rocket recontact is a
solvable problem is neither sympathetic or unsympathetic. It's merely
unflinching willingness to address facts as facts without spin. I
don't always suceed, but intellectual honesty and integrity is a goal
I strive mightily towards.
D.
--
Touch-twice life. Eat. Drink. Laugh.
http://derekl1963.livejournal.com/
-Resolved: To be more temperate in my postings.
Oct 5th, 2004 JDL |
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| Derek Lyons... |
| Posted: Wed Oct 28, 2009 5:24 pm |
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"Jeff Findley" <jeff.findley at (no spam) ugs.nojunk.com> wrote:
[quote]I'd imagine the big problem here is the thrust of the SRB didn't fall
off as quickly as NASA's "worst case" prediction, which is what was
used to set the timing of the separation events.
[/quote]
Myself, I'd assume that NASA used acceleration and chamber pressure
data to determine timing of BDM firing. That's how they monitor SRB
performance on the Shuttle, and I see no reason to assume a priori
that the Ares solid motor would be different. (The solid fueled
missiles with which I am familiar use acceleration to time non thrust
terminated separation events.)
Further, given the dangers of asymmetrical thrust tailoff on a Shuttle
flight it's reasonable to assume that NASA and ATK are quite familiar
with the formulation, mixing. and casting procedures needed to closely
control thrust tailoff. (And asymmetrical or unexpected tailoff
performance has never to my knowledge been experienced inflight.) In
addition, with the large number of SRM's and RSRM's ground tested or
flown in the Shuttle program, it's equally reasonable to assume that
NASA is well familiar with the thrust termination characteristics of
these motors and that the Ares flight software and hardware would be
designed with this performance in mind.
That's not to say that a level of tailoff that is out of family is
impossible - only that it seems improbable at first glance. I'd be
very, very, careful about jumping to that conclusion.
I've been reviewing some NASA videos on the web, and they all show
seperation/BDM firing preceding BTM firing and stage starting to
tumble by a second or two. This is confirmed in the press kit which
shows BDM firing at T+124 and BTM firing at T+127. (The launch
timeline linked below shows different absolute times by a second or
so, but the same three second delay.) Also shown in those videos, the
first stage tumbles on a plane at 90 degrees to the BDM packages,
confirmed by the diagram in the flight test plan linked below.
But the flight video shows something very different... it shows
seperation and BDM firing almost simultaneously with what appears to
be BTM firing and the initiation of tumbling. (Assuming A: BTM firing
is visible, and B: the BTM's fired in the first place.) It also
seems, but it's hard to tell, that the booster was tumbling in the
wrong plane.
I'm starting to suspect there's something more going on here than just
a timing issue with thrust tailoff.
Press kit:
http://spaceflightnow.com/ares1x/presskit.pdf
Launch Timeline:
http://spaceflightnow.com/ares1x/091022launchtimeline.html
Flight Test Plan:
http://www.scribd.com/doc/17213945/NASA-Ares-IX-Flight-Test-plans
D.
--
Touch-twice life. Eat. Drink. Laugh.
http://derekl1963.livejournal.com/
-Resolved: To be more temperate in my postings.
Oct 5th, 2004 JDL |
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| Brian Thorn... |
| Posted: Wed Oct 28, 2009 7:20 pm |
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On Wed, 28 Oct 2009 13:32:21 -0400, "Greg D. Moore \(Strider\)"
<mooregr_delet3th1s at (no spam) greenms.com> wrote:
[quote]AIUI: The actual Ares-I will not be as constrained - the
vulnerability to tribo can be vastly mitigated but NASA elected not to
spend the money to do so for this unique one-off launch. You have to
specially certify the coatings used on the vehicle and the electrical
bonding between stages and components (to prevent currents flowing
along the skin and arcing amongst vehicle components).
That makes a bit more sense. For a test vehicle, I can see not spending the
money on that.
[/quote]
And even then, it was only an issue because the USAF got the willies
about the thing, and thought it would shake itself to pieces, crash
into Patrick AFB's Officers Club, spiral out toward Disney World, or
some such disastrous turn of events. So they definitely demanded that
the destruct signal could get through, and therefore enforced the
little-known, seldom-used "triboelectrification clause".
I'm not Ares I's biggest fan, but the detractors were starting to spew
so much bullshit ("it's so long and skinny it will be
uncontrollable!", "it will shake itself to pieces and even the Range
Safety command system will be toast!", "the wind will blow it into the
tower!" "It's Satan Incarnate!") about it that hip-high boots were
needed.
And that, um, exciting seperation? So much for that ever-popular "This
test flight is useless!" argument.
Brian |
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| Brian Thorn... |
| Posted: Wed Oct 28, 2009 7:28 pm |
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On Wed, 28 Oct 2009 17:03:23 -0400, John Doe <jdoe at (no spam) doe.org> wrote:
[quote]If you steer the tail away from the tower, you're steering the
midsection and nose *towards* the tower. Hence, it's better to steer
the tail towards in order to direct the flight path away and onto the
proper trajectory.
Where was the SRB in the Ares1X positioned relative to the 2 SRBs used
in shuttle ? Was it positioned at the same location as one of the
Shuttle SRBs, was it positioned where the shuttle SSMEs would have been ?
[/quote]
It was on the inboard SRB mount of the MLP, closest to the tower.
The Tower Avoidance Maneuver didn't push the nozzle-end toward the
tower, it just leaned the entire rocket several degrees away from the
tower, which made the expanding plume appear to move toward the tower
more rapidly than had it gone straight up. Very exciting, to say the
least. But look at Saturn V launch footage some time... the avoidance
maneuver is very visible there, too.
Here's Apollo 15. Compare the Saturn to the Tower.
http://www.hq.nasa.gov/office/pao/History/alsj/a15/ap15-liftoff2-noID.jpg
Brian |
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| Jorge R. Frank... |
| Posted: Wed Oct 28, 2009 8:47 pm |
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Jeff Findley wrote:
[quote]"John Doe" <jdoe at (no spam) doe.org> wrote in message
news:0096c30c$0$27961$c3e8da3 at (no spam) news.astraweb.com...
Jeff Findley wrote:
The thrust
doesn't stop cleanly like a liquid engine. It slowly tails off. And
with
the hammer head design of the vehicle, getting a clean separation will be
a
challenge.
Should they actually launch a real vehicle, wouldn't the second stage
ignite at the same time as separation to ensure it doesn't start to
thumble and lose its orientation and also to ensure it doesn't
collide/recontact with the first stage ?
Possibly, but US upper stages tend to be lit after a clean separation. On
top of that Ares I's SRB first stage is to be recovered and reused, so I'm
not sure firing the upper stage engine essentially on top of the SRB would
be advisable.
[/quote]
Probably would not result in more damage than the SRB does to its own
bottom end due to plume recirculation.
The real upper stage will also have ullage motors firing before the J-2X
to settle the propellants and, not coincidentally, to increase the
separation rate.
[quote]For this prototype test flight, was it normal that the fake second stage
immediatly lost its attitude and started to thumble at separation
(aka: was there still enough air resistance to cause that) ?
Once there is a real second stage, would its mass be significantly
higher than the fake one and give it more time in the proper attitude
before air resistance would start to cause it to thumble ?
The simulated upper stage had similar mass and inertia properties similar to
a fueled upper stage, so the deceleration caused by air drag would be
similar to a real stage.
[/quote]
No, the real stage will separate at a higher altitude due to Ares I
having a five-segment SRB vs the four-segment SRB of Ares I-X. The air
density, and therefore the drag, will be far lower even though the upper
stage mass properties are similar. |
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| Greg D. Moore (Strider)... |
| Posted: Wed Oct 28, 2009 9:33 pm |
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"Brian Thorn" <bthorn64 at (no spam) suddenlink.net> wrote in message
news:1vqhe559b36cfoaq46esaac8bpfki366jq at (no spam) 4ax.com...
[quote]
And even then, it was only an issue because the USAF got the willies
about the thing, and thought it would shake itself to pieces, crash
into Patrick AFB's Officers Club, spiral out toward Disney World, or
some such disastrous turn of events. So they definitely demanded that
the destruct signal could get through, and therefore enforced the
little-known, seldom-used "triboelectrification clause".
I'm not Ares I's biggest fan, but the detractors were starting to spew
so much bullshit ("it's so long and skinny it will be
uncontrollable!", "it will shake itself to pieces and even the Range
Safety command system will be toast!",
[/quote]
Well that one was from the Range Safety folks themselves.
[quote]"the wind will blow it into the
tower!" "It's Satan Incarnate!") about it that hip-high boots were
needed.
And that, um, exciting seperation? So much for that ever-popular "This
test flight is useless!" argument.
[/quote]
Umm, I'm not sure it belays that argument. I mean we have a system that
doesn't fully model the actual thing and very likely wouldn't happen in the
real system.
So it might be a case of a problem being found that isn't really a problem.
So, I'm still not sold on the usefulness of this test.
[quote]
Brian
[/quote]
--
Greg Moore
Ask me about lily, an RPI based CMC. |
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| John Doe... |
| Posted: Wed Oct 28, 2009 10:20 pm |
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Is Ares1X the first rocket where the main engine consists only of an SRB ?
Shuttle, Arianne have SRBs that are side mounted and can detach while a
main engine can push the rest of the vehicle ahead (reducing separation
issues). Soyuz also sheds its side mounted liquid engines while the main
engines can continue to push the stack ahead.
In the case of other "payload on a stick" rockets such as Saturn5, did
the main engine bring the upper stages to higher altitude where air
resistance was not an issue ? (compared to what is planned for Ares1) |
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| Derek Lyons... |
| Posted: Wed Oct 28, 2009 10:26 pm |
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Brian Thorn <bthorn64 at (no spam) suddenlink.net> wrote:
[quote]And that, um, exciting seperation? So much for that ever-popular "This
test flight is useless!" argument.
[/quote]
Other than the seperation being almost nothing like the seperation in
an actual Ares I, this was a valuable discovery.
Or not.
D.
--
Touch-twice life. Eat. Drink. Laugh.
http://derekl1963.livejournal.com/
-Resolved: To be more temperate in my postings.
Oct 5th, 2004 JDL |
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| Cyberia... |
| Posted: Wed Oct 28, 2009 10:33 pm |
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"Brian Thorn" <bthorn64 at (no spam) suddenlink.net> wrote in message
news:4hrhe5thjsefgt1g8ftqjfvtehcvtfr72v at (no spam) 4ax.com...
[quote]The Tower Avoidance Maneuver didn't push the nozzle-end toward the
tower, it just leaned the entire rocket several degrees away from the
tower, which made the expanding plume appear to move toward the tower
more rapidly than had it gone straight up. Very exciting, to say the
least.
[/quote]
Surely you don't think it possible to gimbal the RSRM nozzle and cause the
nose to yaw immediately away from the tower while the aft end comes no
closer to it? If so you need to watch the replays more closely. Look at (for
example) the DLTR-3 view. This view is nearly perfect for observing the
distance between the tower and any part of the airframe as it ascends.
Before ignition, the skirt of the RSRM is just visible peeking around the
right edge of the port-side tail service mast of the MLP. The entire top
third of the rocket (more than a third, it seems) is already clear of the
tower even before launch.
By the time the skirt is midway up the tower it has moved well to the left
of this point. I've watched this view many times, and the motion of the
rocket's tail towards the tower is quite pronounced and unquaetionable.
There is probably plenty of clearance despite this motion, given that the
various service arms are rotated out to the sides. It still looks to me,
however, that gimballing the RSRM motor so that the aft end of the rocket
moves *away* from the tower rather than toward would give much more
clearance. The rocket could end up flying over the tower but all parts of
its airframe would have more clearance from that structure on the way up.
Perhaps doing so would cause more plume damage to be imposed as the rocket
overflies the tower. I had not considered this before, surely this must
figure into the decision to "fly away". |
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| Brian Thorn... |
| Posted: Wed Oct 28, 2009 11:26 pm |
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On Thu, 29 Oct 2009 00:20:33 -0400, John Doe <jdoe at (no spam) doe.org> wrote:
[quote]Is Ares1X the first rocket where the main engine consists only of an SRB ?
[/quote]
Nope. Scout, Pegasus, Taurus, Athena...
Brian |
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| John Doe... |
| Posted: Thu Oct 29, 2009 12:17 am |
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Ok, am watching the launch replay from "DLTR 3" location.
The rocket has an immediate slant (aft towards tower, tip towards the
water tank in that view) as soon as it was let go from the launch
platform. That slant was maintained until well above the structures, at
which point, the rocket initiated its ascent attitude with a greater slant.
Shouldn't the rocket have gone straight up until well clear of the
tower, at which point it begins to steer to the attitude needed to go
up/east ?
From my armchair point of view, it looks like a catastrophic failure
that didn't result in a catastrophy. Obviously NASA isn't going to
discuss this publically.
Is there a valid reason to actually program that slant as soon as the
bolts keeping the SRB on the launch platform have fired ?
Also, I have a feeling that conspiracy theorists will question why the
on-board cameras blanked out at launch (not showing the immediate slant
of the vehicle) and during separation (not showing the not-so-clean
separation).
During the original video, they spent a fair about of time showing some
telemetry guy in front of a rack, relating various data he was seeing on
a console. Didn't he , at one point, indicate he had lost a telemetry
feed ?
Has there been any information on the vibration nevironment and whether
it might have been responsible for such losses ? |
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