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#280
by
Fuji
on 23 Mar, 2016 13:30
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Twenty Doves Take Flight on Successful OA-6 Launchhttps://www.planet.com/pulse/twenty-doves-take-flight-on-successful-oa-6-launch/Tonight (March 22, 2016) at 11:07pm EDT 20 of our Flock 2e Prime satellites successfully launched into Low Earth Orbit.
Flock 2e Prime will increase our on-orbit collection capacity in both true-color(RGB) and near-infrared bands. Two special Flock 2e Prime Doves are tech demos of our next-generation Dove satellite, never before tested in orbit.
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#281
by
edkyle99
on 23 Mar, 2016 13:36
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[...] Combined with the 1+minute Centaur burn difference from the pre-launch "press kit", it seems that the information provided by launch companies is becoming absurdly less precise.
The burn times will vary considerably for the 5 launch opportunities within the window. Given the low acceleration of the Centaur with the heavy payload, the plane change could account for all the differences.
So what should the Mission Overview say? For the tech folks, it would be best if there were 5 columns, showing the estimated times for each of the 5 trajectories. But I can understand why they think that's too much detail. Perhaps just a note at the bottom saying "These are the times for a center of window launch. Non-center launches may require up to XX seconds of additional second stage burn."
An explanatory note would do the trick, I think.
- Ed Kyle
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#282
by
the_other_Doug
on 23 Mar, 2016 15:05
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The NASA/ULA visualization people were aware that the Centaur burn ran long, even though PAO didn't say much about it. When the burn had run about 40 seconds longer than PAO had announced as the anticipated cutoff time, a little message flashed up over the animation saying that the real-time, based-on-telemetry display could run from 2 to 4 seconds late. This was at a point where the burn was already a good 40 seconds longer than announced. That could only have been done as a response to the over-long Centaur burn.
I'm not all that convinced about the visualization being completely accurate this time, though. BECO was called out and a good three to five seconds passed before the animation showed the booster cutting off. Also, it seemed that the attitude of the Centaur in the animation was pitched up in relation to the flight path a lot more than I've seen in past animations. Perhaps there was some kind of attitude issue, but if so, the orbit ended up being close to nominal.
I kept thinking, when the perigee display in the animation was still hundreds of miles negative until just a few seconds prior to SECO, that there was either something wrong with the numbers or that they were a lot farther away from injection at 18:09 than they ought to be. They weren't even close at 18:16, if you believe that number as the projected SECO time.
Also, at one point the numbers display changed significantly, we lost speed information, and the miles display changed to a nautical miles display. It seemed to me that either the altitude or the projected apogee of the vehicle at that point changed from showing something in the 180's in statute miles to something in the low 120's in nautical miles. And there is not that big of a disparity in statute and nautical miles at that height; 120 nm is about 140 mi, not 180.
And speaking of units of measurement, the animation gave speed (when it was displayed) in miles per hour, when traditionally NASA has used feet per second, and has more recently been transitioning to meters per second. I don't recall seeing displays in mph on earlier Atlas launches, though I could be mis-remembering and they've been doing it all along. I just think I would have noticed it, since it's unusual in this day and age.
There were just a lot of little funnies in the animation display this time, it seemed to me. Anyone else notice any others?
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#283
by
refsmmat
on 23 Mar, 2016 15:17
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The burn times will vary considerably for the 5 launch opportunities within the window. Given the low acceleration of the Centaur with the heavy payload, the plane change could account for all the differences.
You're not kidding about the payload mass vs. acceleration. It seemed odd to me that between 643s and 930s not only was altitude declining from 213 to 175.1 miles, but during this time the 8 ball appeared to be pointing well above the horizon. The most efficient direction of thrusting is aligned with the prograde direction, but there was a lot of compromising to keep out of the upper atmosphere.
The Antares lv paired with the smaller solid 2nd stage and smaller Cygnus was much more powerful, affording a 47-second coast between 1st and 2nd stages, and orbital insertion after 447 seconds instead of 1150.
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#284
by
Jim
on 23 Mar, 2016 15:22
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I kept thinking, when the perigee display in the animation was still hundreds of miles negative until just a few seconds prior to SECO, that there was either something wrong with the numbers ....
That is exactly what happens as a vehicle "climbs" orbit. Until it reaches orbital velocity, the perigee is going to be negative (when it is referenced from the earth's surface). Which mean if the engine shuts down early, the vehicle is going to hit the ground before it reaches its perigee.
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#285
by
Jim
on 23 Mar, 2016 15:27
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The Antares lv paired with the smaller solid 2nd stage and smaller Cygnus was much more powerful,
No, it isn't "more" much less "much more" powerful. The Atlas has more lift capability, hence "more" powerful. Atlas has more total impulse.
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#286
by
Jim
on 23 Mar, 2016 15:27
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The NASA/ULA visualization people
ULA, no NASA involvement.
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#287
by
the_other_Doug
on 23 Mar, 2016 15:31
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The NASA/ULA visualization people
ULA, no NASA involvement.
Ah, good to note. The little "brand sigil" in the corner was both the ULA logo and the NASA logo, so it was unclear who was generating the visualization.
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#288
by
ugordan
on 23 Mar, 2016 15:33
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The NASA/ULA visualization people were aware that the Centaur burn ran long, even though PAO didn't say much about it. When the burn had run about 40 seconds longer than PAO had announced as the anticipated cutoff time, a little message flashed up over the animation saying that the real-time, based-on-telemetry display could run from 2 to 4 seconds late. This was at a point where the burn was already a good 40 seconds longer than announced. That could only have been done as a response to the over-long Centaur burn.
This is nothing unusual about this launch, they post that comment about telemetry delay virtually on every launch.
I'm not all that convinced about the visualization being completely accurate this time, though. BECO was called out and a good three to five seconds passed before the animation showed the booster cutting off.
Yes, because as the above point states, the animation *is* delayed from what the immediate telemetry shows. Nothing unusual again. No "damage control" reaction to the (apparent) longer Centaur burn.
Also, it seemed that the attitude of the Centaur in the animation was pitched up in relation to the flight path a lot more than I've seen in past animations. Perhaps there was some kind of attitude issue, but if so, the orbit ended up being close to nominal.
Because it was the heaviest payload Atlas V carried to LEO and the (relatively underpowered) RL-10 would suffer higher gravitational losses otherwise. The vehicle would probably have dropped down like a rock during the 13 or so minute Centaur burn if the thrust vector was more toward the horizontal. It needed to keep altitude while attempting to gain speed.
Remember that Atlas is optimized for high energy missions, not heavy LEO insertions.
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#289
by
the_other_Doug
on 23 Mar, 2016 15:35
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I kept thinking, when the perigee display in the animation was still hundreds of miles negative until just a few seconds prior to SECO, that there was either something wrong with the numbers ....
That is exactly what happens as a vehicle "climbs" orbit. Until it reaches orbital velocity, the perigee is going to be negative (when it is referenced from the earth's surface). Which mean if the engine shuts down early, the vehicle is going to hit the ground before it reaches its perigee.
Yep -- that I understood. It was NASA PAO announcing that they should see SECO momentarily, while projected perigee was sitting at minus 780 miles, that said to me "no, we better not see SECO until that perigee turns into a nice, healthy, positive number." And that took a while.
Again, just a set of funnies around the timing of this launch's events. Hmm -- a thought just struck me. If Cygnus was significantly overweight, wouldn't that result in the numbers we saw?
Someone sneaking another several gorilla suits up on this one...?
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#290
by
Prober
on 23 Mar, 2016 16:29
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on the ground pre-flight.
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#291
by
Chris Bergin
on 23 Mar, 2016 16:42
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I'm not sure about the potential sensitivity of several posts that followed those above, so I've moved them into moderation, not least to protect the person posting - until we know they are clear to be posted. I'll be asking ULA based on the specific nature anyway.
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#292
by
NovaSilisko
on 23 Mar, 2016 16:44
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Because it was the heaviest payload Atlas V carried to LEO and the (relatively underpowered) RL-10 would suffer higher gravitational losses otherwise. The vehicle would probably have dropped down like a rock during the 13 or so minute Centaur burn if the thrust vector was more toward the horizontal. It needed to keep altitude while attempting to gain speed.
Remember that Atlas is optimized for high energy missions, not heavy LEO insertions.
As I pointed out during the live updates, Centaur was accelerating at a mere 0.65g, which neccessitated a high angle of attack relative to the horizon. Cygnus is a big bird.
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#293
by
edkyle99
on 23 Mar, 2016 17:57
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After looking at the videos one more time, it is apparent that both the NASA announcer and the ULA data guy were both expecting Centaur cutoff around T+18 min 9 sec or thereabouts. Both gave "one minute" calls about one minute before that time. The explanation given in the press conference about some variation being expected doesn't explain a full 1+ minute extra burn time to me. Perhaps RL10 underperformed, or maybe that new boattail misbehaved at fairing separation, etc.. The good news is that Space Track doesn't show a Centaur still in orbit, so whatever happened doesn't appear to have prevented the deorbit burn, and, of course, Cygnus separated into its planned orbit.
- Ed Kyle
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#294
by
woods170
on 23 Mar, 2016 17:59
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Chris, what exactly changed in the boattail design/material to make it an upgraded boattail??
The PLF boattail uses an improved isogrid structure. Also the the pyro controllers and batteries that used to be installed in the boattail for executing PLF jettison have been removed and replaced with a simpler ordnance system. Savings in weight, complexity and cost.
Nice improvements. Thanks for the info.
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#295
by
russianhalo117
on 23 Mar, 2016 18:12
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After looking at the videos one more time, it is apparent that both the NASA announcer and the ULA data guy were both expecting Centaur cutoff around T+18 min 9 sec or thereabouts. Both gave "one minute" calls about one minute before that time. The explanation given in the press conference about some variation being expected doesn't explain a full 1+ minute extra burn time to me. Perhaps RL10 underperformed, or maybe that new boattail misbehaved at fairing separation, etc.. The good news is that Space Track doesn't show a Centaur still in orbit, so whatever happened doesn't appear to have prevented the deorbit burn, and, of course, Cygnus separated into its planned orbit.
- Ed Kyle
there was some unofficial talk that Centaur and its debris did not land in the NOTAMed area and that time delays appeared to had a knock on exponential effect starting with Centaur Sep from the CCB. Chris will let us know the verdict(s) as soon as he can tell us.
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#296
by
edkyle99
on 23 Mar, 2016 18:14
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After looking at the videos one more time, it is apparent that both the NASA announcer and the ULA data guy were both expecting Centaur cutoff around T+18 min 9 sec or thereabouts. Both gave "one minute" calls about one minute before that time. The explanation given in the press conference about some variation being expected doesn't explain a full 1+ minute extra burn time to me. Perhaps RL10 underperformed, or maybe that new boattail misbehaved at fairing separation, etc.. The good news is that Space Track doesn't show a Centaur still in orbit, so whatever happened doesn't appear to have prevented the deorbit burn, and, of course, Cygnus separated into its planned orbit.
- Ed Kyle
there was some unofficial talk that Centaur and its debris did not land in the NOTAMed area and that time delays appeared to had a knock on exponential effect starting with Centaur Sep from the CCB. Chris will let us know the verdict(s) as soon as he can tell us.
I now see another site (not sure if OK to give a link) presenting a good argument for an early first stage cutoff (5.4 seconds early is the claim) being the root cause. The argument derives from a close analysis of the publicly broadcast information, especially around the time of BECO.
- Ed Kyle
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#297
by
russianhalo117
on 23 Mar, 2016 18:19
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After looking at the videos one more time, it is apparent that both the NASA announcer and the ULA data guy were both expecting Centaur cutoff around T+18 min 9 sec or thereabouts. Both gave "one minute" calls about one minute before that time. The explanation given in the press conference about some variation being expected doesn't explain a full 1+ minute extra burn time to me. Perhaps RL10 underperformed, or maybe that new boattail misbehaved at fairing separation, etc.. The good news is that Space Track doesn't show a Centaur still in orbit, so whatever happened doesn't appear to have prevented the deorbit burn, and, of course, Cygnus separated into its planned orbit.
- Ed Kyle
there was some unofficial talk that Centaur and its debris did not land in the NOTAMed area and that time delays appeared to had a knock on exponential effect starting with Centaur Sep from the CCB. Chris will let us know the verdict(s) as soon as he can tell us.
I now see another site (not sure if OK to give a link) presenting a good argument for an early first stage cutoff (5.4 seconds early is the claim) being the root cause. The argument derives from a close analysis of the publicly broadcast information, especially around the time of BECO.
- Ed Kyle
Ask Chris as he moved such talk to the Moderation threads
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#298
by
Lee Jay
on 23 Mar, 2016 18:25
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I now see another site (not sure if OK to give a link) presenting a good argument for an early first stage cutoff (5.4 seconds early is the claim) being the root cause. The argument derives from a close analysis of the publicly broadcast information, especially around the time of BECO.
- Ed Kyle
Even with Centaur's modest acceleration, I can't see how 5 or 6 seconds of first stage early cutoff would need 70 or 80 seconds of RL-10 burn to make up. I also can't see how Centaur would have that much extra prop left at nominal cutoff time with a heavy payload, even if it is to a low energy orbit.
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#299
by
the_other_Doug
on 23 Mar, 2016 18:35
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Not bringing in another site or items currently in moderation, my feeling at the time while watching it was that BECO seemed early. A few seconds early or late never seems to be a huge deal, so I didn't pay it a lot of mind at the time. But if it was as early as some are saying, up to five or more seconds, I can surely see why the Centaur burn was lengthened. I'd love to see estimates of velocity at staging, planned vs. actual. That would tell the tale in re the required extra Centaur-delivered velocity, and if the 80 extra seconds are in the right range for making it up.
One question -- was guidance closed-loop, internal only? Or did ground control determine the trajectory and burn length adjustments and radio these up to the Centaur? From the way everyone reacted last night, I'd guess the rocket itself decided how much more it needed out of the Centaur, and us on the ground mostly just stood by and watched while it did its thing.
There was no tracking video through the NASA/ULA coverage at staging. I wonder if anyone else got any video from up along the coast. It might be instructive to see if there were any unusual visual cues at BECO...
