Author Topic: Orbital's Antares Development Update Thread  (Read 1065249 times)

Offline Antares

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Re: Taurus II Development News
« Reply #200 on: 01/02/2010 03:04 pm »
Thanks for the links.  How is that a "switch"?  Do we know what the previous plans were?  How do we know there was a switch?
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Offline kevin-rf

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Re: Taurus II Development News
« Reply #201 on: 01/02/2010 05:29 pm »
Purely speculative, but has Orbital mentioned any possibility of a development path for Taurus-II to lead to heavier payload capacities? Perhaps outrigger SRMs or multi-core configurations?

The only thing they have hinted at to date is to replace the solid upper stage with a liquid upper stage.
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Offline Freddie

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Re: Taurus II Development News
« Reply #202 on: 01/06/2010 02:17 pm »
The Taurus II User's manual publicly appeared on-line on or about December 28, 2009.  It can be reviewed at http://www.orbital.com/NewsInfo/Publications/Taurus_II_UG.pdf .

Offline sdsds

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Re: Taurus II Development News
« Reply #203 on: 01/06/2010 03:01 pm »
The Taurus II User's manual publicly appeared on-line on or about December 28, 2009.  It can be reviewed at http://www.orbital.com/NewsInfo/Publications/Taurus_II_UG.pdf .

It's interesting to note the User's Guide mentions "payloads weighing up to 6500 kg."  The Orbital website still says, "payloads weighing up to 5750 kg."  Has something allowed Orbital to reduce vehicle margins?
« Last Edit: 01/06/2010 03:01 pm by sdsds »
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Offline ugordan

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Re: Taurus II Development News
« Reply #204 on: 01/06/2010 03:54 pm »
That's some "interesting" velocity behavior at different milestones in the flight in "Figure 3.2-2. Taurus II Typical 3-Stage Mission Profile to LEO". Jumping up and down until payload separation at 2490 m/s? I should hope not!  ;D

Offline Patchouli

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Re: Taurus II Development News
« Reply #205 on: 01/06/2010 04:03 pm »
Looking the users guide it seems the Castor 30 is not an issue to making this a crew vehicle.
It's max acceleration is only 3.7g with in the limits of acceptable which I believe is 4 - 4.5g.
Instead the problem is in the first stage acceleration profile with a max acceleration of of 6g well outside NASA limits.
Not fatal but would not pleasant for the crew.
I wonder how difficult this would be to fix and would it impact the payload too badly?
« Last Edit: 01/06/2010 04:05 pm by Patchouli »

Offline ugordan

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Re: Taurus II Development News
« Reply #206 on: 01/06/2010 04:09 pm »
I wonder how difficult this would be to fix and would it impact the payload too badly?

The AJ26 engines can be throttled down. With which comes a slight decrease in payload performance.
« Last Edit: 01/06/2010 04:10 pm by ugordan »

Offline Jim

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Re: Taurus II Development News
« Reply #207 on: 01/06/2010 05:19 pm »
Looking the users guide it seems the Castor 30 is not an issue to making this a crew vehicle.
It's max acceleration is only 3.7g with in the limits of acceptable which I believe is 4 - 4.5g.
Instead the problem is in the first stage acceleration profile with a max acceleration of of 6g well outside NASA limits.


What NASA limits?

Offline Patchouli

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Re: Taurus II Development News
« Reply #208 on: 01/06/2010 05:38 pm »
Looking the users guide it seems the Castor 30 is not an issue to making this a crew vehicle.
It's max acceleration is only 3.7g with in the limits of acceptable which I believe is 4 - 4.5g.
Instead the problem is in the first stage acceleration profile with a max acceleration of of 6g well outside NASA limits.


What NASA limits?


The Saturn vehicles limited acceleration to no more then 4g the Shuttle to just above three.
I also remember some OSP stuff I read about changing the flight profiles of the EELVs slightly to get rid of a 5.7g acceleration.
A Boeing representative refereed to it as an easy fix.
It seems NASA does prefer a crew LV to pull no more then 4g under nominal operation.
I figure any new crew transport vehicle must meet the requirements set by the Saturn LV and the Shuttle.
These same rules also apply to amusement park rides so it's a reasonable and logical requirement.
I wouldn't question it if I was an LV manufacture.
Though Virgin believes 6g for a short time during reentry should not be a serious issue for most people who do not have any serious heart trouble so long as they are in a reclined position.
I guess the rules likely are more complex then a simple g limit but also likely include duration.
« Last Edit: 01/06/2010 05:51 pm by Patchouli »

Offline Jim

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Re: Taurus II Development News
« Reply #209 on: 01/06/2010 05:55 pm »

I figure any new crew transport vehicle must meet the requirements set by the Saturn LV and the Shuttle.
These same rules also apply to amusement park rides so it's a perfectly reasonable and logical requirement.


There are no requirements that apply to the shuttle, saturn or current vehicles.  Do some research before making such statement.   NASA has no 4 g limit.


Offline sdsds

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Re: Taurus II Development News
« Reply #210 on: 01/06/2010 06:34 pm »
That's some "interesting" velocity behavior at different milestones in the flight in "Figure 3.2-2. Taurus II Typical 3-Stage Mission Profile to LEO". Jumping up and down until payload separation at 2490 m/s? I should hope not!  ;D

Yes, something's definitely fishy there.  At 600x600 km, isn't orbital speed  something like 7500 m/s?  Also in the same table it's "interesting" that payload separation takes place 6 minutes after stage 3 burnout, but they occur at exactly the same latitude and longitude!

I'm even a little concerned about the timeline itself.  Could they really be planning a 59 second coast between stage 1 MECO and stage 2 ignition?  What's that about?

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Offline ugordan

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Re: Taurus II Development News
« Reply #211 on: 01/06/2010 06:39 pm »
I'm even a little concerned about the timeline itself.  Could they really be planning a 59 second coast between stage 1 MECO and stage 2 ignition? 

Note the table above the erroneous one has numbers that appear correct and it says 1st stage burns out at 4600 m/s. The coast costs them "only" 50 m/s.

Offline sdsds

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Re: Taurus II Development News
« Reply #212 on: 01/06/2010 07:31 pm »
I'm even a little concerned about the timeline itself.  Could they really be planning a 59 second coast between stage 1 MECO and stage 2 ignition? 

Note the table above the erroneous one has numbers that appear correct and it says 1st stage burns out at 4600 m/s. The coast costs them "only" 50 m/s.

It seems likely the interval between MECO and S2 ignition is only 3 or 4 seconds, but those are the intervals they show between fairing sep and S2 ignition.  Maybe the formula for the cell showing the S2 ignition time references the cell above, and somehow fairing sep got inserted in between the other two events without reworking the spreadsheet to compensate for that.

If Orbital would just publish the formulas used to generate these values, maybe we could "fix it for them"! <grin>
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Offline ugordan

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Re: Taurus II Development News
« Reply #213 on: 01/06/2010 07:37 pm »
I'm even a little concerned about the timeline itself.  Could they really be planning a 59 second coast between stage 1 MECO and stage 2 ignition? 

Note the table above the erroneous one has numbers that appear correct and it says 1st stage burns out at 4600 m/s. The coast costs them "only" 50 m/s.

It seems likely the interval between MECO and S2 ignition is only 3 or 4 seconds,

Page 19:

Quote
The Taurus II lifts off the pad approximately 2 seconds after Stage 1 ignition. Stage 1 burns for approximately 223 seconds, and separates after a brief post-burn coast. The upper stage stack continues to coast for approximately 50 seconds before the fairing is jettisoned. After fairing jettison, Stage 2 is ignited and boosts the upper stack to an altitude of approximately 153 km x 100 km before Stage 2 burnout and separation occurs, at 427 seconds into the flight.

Offline sdsds

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Re: Taurus II Development News
« Reply #214 on: 01/06/2010 08:09 pm »
Page 19: [...]

Ah yes, thank you.  I really should learn to read the text, rather than just looking at the pictures.
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Offline yinzer

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Re: Taurus II Development News
« Reply #215 on: 01/07/2010 12:46 am »
The coast between stage 1 and 2 is almost certainly from limits on maximum burn time of the solid stage.  Pegasus and Taurus do the same thing - you need to let the upper stage coast up high enough so that it burns out at orbital altitude.
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Offline Comga

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Re: Taurus II Development News
« Reply #216 on: 01/07/2010 03:19 am »
Quote
The Taurus II lifts off the pad approximately 2 seconds after Stage 1 ignition. Stage 1 burns for approximately 223 seconds, and separates after a brief post-burn coast. The upper stage stack continues to coast for approximately 50 seconds before the fairing is jettisoned. After fairing jettison, Stage 2 is ignited and boosts the upper stack to an altitude of approximately 153 km x 100 km before Stage 2 burnout and separation occurs, at 427 seconds into the flight.

I would think that this is the last place they would want to get innovative. Orbital just had a failure to jettison the fairing while under thrust.

Would opening the fairings in free-fall make it harder to move them out of the way or would it be easier without significant forces?

Which other rockets have jettisoned their fairings before second stage ignition?

And what advantage is there for the very long coast?

(SpaceX tried one second, so they have to do the opposite and try one minute? :P)

Quote
The Taurus II ACS provides three-axis attitude control throughout boosted flight and coast phases. The ACS uses the two main engine configuration to provide yaw, pitch and roll control during Stage 1 flight. Stage 2 flight is controlled by the combination of the Stage 2 TVC and the onboard ACS system located on the avionics ring. The Stage 2 ACS employs a cold gas nitrogen system with heritage from all of Orbital’s space launch vehicles.

Does that mean that the second stage, cold gas, ACS has to keep the first stage oriented for the entire 50+ seconds until second stage ignition?
« Last Edit: 01/07/2010 03:53 am by Comga »
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Offline Antares

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Re: Taurus II Development News
« Reply #217 on: 01/07/2010 04:14 am »
The remaining stack has a much higher ballistic number than the shed pieces of fairing.  No concern for recontact.

Coast duration: It acts the same as the Pegasus and Taurus stages yinzer mentioned: There's a well-known amount of impulse from the solid stage, so the flight computer would calculate the duration of the coast needed to hit the 2nd stage burnout target.  Rather than tailoring stage burn duration to hit a target orbit, it tailors the coast duration.  Kinda cool, eh?

Other rockets have jettisoned the fairing during first stage burn.  Can't think of, and too lazy to look for, any that have jettisoned during coast, especially a long one.
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Offline Art LeBrun

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Re: Taurus II Development News
« Reply #218 on: 01/07/2010 04:23 am »
Earlier Atlas-Centaurs jettisoned insulation panels and shroud during first stage burn. Made a spectacular sight on launches just after sunset.
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Offline WHAP

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Re: Taurus II Development News
« Reply #219 on: 01/07/2010 05:07 am »
Atlas I's and II's jettisoned their fairings during first stage burn, as do the 5 meter Atlas V's. 
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