Author Topic: Antares A-One General Discussion Thread (2)  (Read 63116 times)

Online Chris Bergin

Re: Antares A-One General Discussion Thread (2)
« Reply #120 on: 04/21/2013 07:00 pm »
Since there has been some confusion about how the winds affected our launch attempts and who has authority to wave what, I'd like to offer the following (admittedly a bit pedestrian) explanation:

Surface winds AT THE PAD affect the clearance during lift-off.  Orbital has established a basic 15kts limit for ANY DIRECTION, waivable to 20kts by LD (Eberly).  Eberly has a "pocket reserve" of a few kts if the wind direction is "away from the TEL."  The range helps LD with the go/nogo decision (including computing its effect on POV) but this is not a range decision - it's Orbital's.

Wind SHEAR during ascent induces an angle of attack that changes the aerodynamic load on the vehicle.  This being a first flight, we (Orbital) have rather strict limits on this, which can be alleviated by the choice of trajectory (out of about 5 pre-loaded in the Flight Computer) which can be made as late as L-45m.  Range sends us (Paul Baumgartner and Tracy Chisholm) the balloon data and they (Paul and Tracy) compute the resulting aero loads right at their consoles in the RCC.  Again, an Orbital call - no "single" wind speed limit value.  Not counted on the Weather Officer's POV forecast.

Wind magnitude and direction affect the ground track of trajectory which could bring the vehicle closer to a destruct line than we would be comfortable with.  The trajectories (out of the five mentioned above) that relief aerodynamic loads tend also to be "looser" in terms of lateral position tightness... so, for example, yesterday, only ONE of the trajectories met the aero load criteria (again, yesterday was a 4-sigma day as far as altitude winds were concerned) and that trajectory "grazed" the north destruct line close to the pad.  Again, this is an Orbital call, and Saturday we were ready to fly with that trajectory and those winds (having discussed the trajectory with the FSO who was OK with the grazing.)  Not in the POV.

Now for the part which is NOT under Orbital's discretion: winds and clouds affect three "Public Safety" criteria: Distance Focusing Overpressure (DFO), Toxicity, and Debris.  I don't know a lot about DFO - I believe it is associated with being indoors and a blast breaking the windows and the glass injuring the public.  Toxicity is associated with things such as nitrogen tetroxide, hydrazine and - gulp - plutonium.  We don't have any of these nasty items on THIS flight (Cygnus WILL carry Hydrazine and N2O4.)  Debris is simply pieces of a (supposedly destroyed) rocket falling on undesirable places and is affected by, among other things, population density.

Both the ranges AND the FAA have a "probability of casualty (E sub C)" calculation protocol that is driven by the size and characteristics of the vehicle, the geography of the trajectory, and the atmosphere (winds, clouds, temperature profile, etc.)  The range recalculates these probabilities whenever they launch a balloon.

All U.S. ranges agreed to add up the E sub C of each effect and use a composite criterion (100 per million) as a range go/no go criterion.  FAA on the other hand (I will not comment on why) requires each of the three to be under 30 ppm.  Therefore, you could be OK with the range E sub C but not with the FAA's, as happened on Wednesday (DFO was higher than 30 ppm, toxicity is zero for this vehicle, debris was under 30 ppm) - the composite was well below 100 ppm, so the range was OK, but the DFO was above 30 ppm, so FAA was NOT OK.

In addition, the range can - and does - impose a "no debris expected to fall" area in the VICINITY OF THE RANGE - and the FAA automatically "imposes" the same rule.  There are no "probabilities" in this calculation: it is a "binary" criterion.  Balloon data also drives this calculation.

THIS ONE is what stopped us yesterday: Wallops was willing to do a real-time redraw of the affected area (the souther tip of Assateague Island) that the strong mid-altitude winds created, with the necessary evacuation of the public (some 40 people according to the Fish and Wildlife people that control that area), but FAA was unable to concur in real time.

None of these criteria can be part of the POV since they depend on the complex atmospheric profile that is much, much harder to forecast than, say, surface winds or cloud bases.

I hope this clarifies a bit what is admittedly a very complex situation.

As others have noted, that's really informative. Thanks for taking the time to write that up!
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Offline mtakala24

Re: Antares A-One General Discussion Thread (2)
« Reply #121 on: 04/21/2013 07:01 pm »
What kind of tracking cameras does the range have? Do we get to see footage on NasaTV?

Or will it be similar to Soyuz launches, where the tracking footage is only rarely seen and NASATV only shows normal tv camera footage.

Offline antonioe

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Re: Antares A-One General Discussion Thread (2)
« Reply #122 on: 04/21/2013 07:08 pm »
The range has an amazing range (no pun intended) of cameras, including some high-speed devices on loan from JSC (yes, JSC)  Obviously, there is a much more limited choice for real-time casting.  I don't know what the public availability of the other material will be, it will not belong to Orbital.
« Last Edit: 04/21/2013 07:09 pm by antonioe »
ARS LONGA, VITA BREVIS...

Offline deltaV

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Re: Antares A-One General Discussion Thread (2)
« Reply #123 on: 04/21/2013 07:17 pm »
That, too.  But Antares' stage 1 is also larger in total percentage than S-V's stage 1 so it gets "depleted" slower w.r.t. the total mass of the rocket (stage 1 provides more of the total DV in Antares' case than S-V)

To tell you the thruth, I haven't run the numbers, so I don't know which effect is greater...

IANARS but I don't think that number of stages affects acceleration before staging occurs. Assuming that two rockets have the same specific impulse and same initial thrust to weight ratio it follows that they have the same acceleration vs. time curve (before staging).

The specific impulse effect is real. Another reason for the Saturn V to pull ahead during the later part of the first stage burn is that the F1 has more back-pressure losses at sea level than the RD-180 so its thrust increases more as its ascends than RD-180 does.
« Last Edit: 04/21/2013 07:28 pm by deltaV »

Offline antonioe

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Re: Antares A-One General Discussion Thread (2)
« Reply #124 on: 04/21/2013 07:38 pm »
Right now, my brain is too fried to think...
ARS LONGA, VITA BREVIS...

Offline Space Pete

Re: Antares A-One General Discussion Thread (2)
« Reply #125 on: 04/21/2013 07:56 pm »
Still lots of aircraft in the vicinity of Wallops - I assume airspace will be closed for launch?

http://flightaware.com/live/airport/KWAL
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Offline antonioe

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Re: Antares A-One General Discussion Thread (2)
« Reply #126 on: 04/21/2013 08:09 pm »
Those are probably mission aircraft
ARS LONGA, VITA BREVIS...

Offline antonioe

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Re: Antares A-One General Discussion Thread (2)
« Reply #127 on: 04/21/2013 08:12 pm »
No, they are not... I don't know when the NOTAMS activate ...
ARS LONGA, VITA BREVIS...

Offline sdsds

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Re: Antares A-One General Discussion Thread (2)
« Reply #128 on: 04/21/2013 08:38 pm »
Is it simply an effect of shadowing or is the upper part of the yellow duct now a darker color than the rest?
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Online ugordan

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Re: Antares A-One General Discussion Thread (2)
« Reply #129 on: 04/21/2013 08:39 pm »
Shadow.

Offline mtakala24

Re: Antares A-One General Discussion Thread (2)
« Reply #130 on: 04/21/2013 08:40 pm »
Shadow of the water tower.

Offline ClaytonBirchenough

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Re: Antares A-One General Discussion Thread (2)
« Reply #131 on: 04/21/2013 08:49 pm »
Dumb question, but I'm curious... What's the orbital decay on the mass simulator?
Clayton Birchenough

Offline Kaputnik

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Re: Antares A-One General Discussion Thread (2)
« Reply #132 on: 04/21/2013 08:50 pm »
Dumb question, but I'm curious... What's the orbital decay on the mass simulator?

About 2 weeks.
And please don't post questions on the live update thread, Chris is busy enough as it is  :)
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Offline yg1968

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Re: Antares A-One General Discussion Thread (2)
« Reply #133 on: 04/21/2013 08:54 pm »
Next poll for final count is at L-12 mins.

We missed it because NASA TV decided to show a video instead. Grrr... They should start their webcast 30 minutes earlier in order to show their videos.
« Last Edit: 04/22/2013 12:36 pm by yg1968 »

Offline Kabloona

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Re: Antares A-One General Discussion Thread (2)
« Reply #134 on: 04/21/2013 09:52 pm »
Dumb question, but I'm curious... What's the orbital decay on the mass simulator?

They said about 2 weeks on the NASA TV broadcast.

Offline mtakala24

Re: Antares A-One General Discussion Thread (2)
« Reply #135 on: 04/21/2013 11:37 pm »
having watched the liftoff replay a few times, it seems that the stage really did not move too much towards the TEL, but right after that, seemed to move quite a way to the opposite side, which makes it look like it did move towards the TEL. And I have a strong feeling that this movement away from it was by design.

Of course, I'm just an amateur.

Offline antonioe

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Re: Antares A-One General Discussion Thread (2)
« Reply #136 on: 04/22/2013 04:32 am »
What you saw MIGHT be the "Baumgartner Maneuver" - an initial pitch AWAY from the TEL makes the TAIL of the rocket actually get CLOSER to the TEL ... but then the resulting (small) lateral acceleration carries the rocket AWAY from it ... this maneuver had to be very carefully designed, a trade between the initial tail movement towards the obstacle which is the inevitable result of the pitch, and the desired effect...

I was told (by Paul B. himself) that the pitch-away and the resulting tail-towards-TEL motion would be so small that they would not be perceptible ... maybe he was not counting on telephoto lenses and HD video (and sharp NASASpaceflight subscribers...)  ;D
ARS LONGA, VITA BREVIS...

Offline Retired Downrange

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Re: Antares A-One General Discussion Thread (2)
« Reply #137 on: 04/22/2013 04:38 am »
...and I think they could use some more of that high velocity tape to hold the umbilical segments to the TEL :)

edit-spelling
« Last Edit: 04/22/2013 04:42 am by Retired Downrange »

Offline Kabloona

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Re: Antares A-One General Discussion Thread (2)
« Reply #138 on: 04/22/2013 04:42 am »
What you saw MIGHT be the "Baumgartner Maneuver" - an initial pitch AWAY from the TEL makes the TAIL of the rocket actually get CLOSER to the TEL ... but then the resulting (small) lateral acceleration carries the rocket AWAY from it ... this maneuver had to be very carefully designed, a trade between the initial tail movement towards the obstacle which is the inevitable result of the pitch, and the desired effect...


You might want to consider replacing the Baumgartner Maneuver with the Fly Straight Up Maneuver... ;)

Online aameise9

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Re: Antares A-One General Discussion Thread (2)
« Reply #139 on: 04/22/2013 07:47 am »
The Economist (typically lukewarm on space) covers Antares launch:

http://www.economist.com/blogs/babbage/2013/04/private-spaceflight

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