Author Topic: Orbital ATK ready for Antares’ second life  (Read 2318 times)

Online Chris Bergin

http://www.nasaspaceflight.com/2016/01/orbital-atk-antares-second-life/ - really good article by Philip Sloss. Lots of interesting quotes in this one.

Offline Lee Jay

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Re: Orbital ATK ready for Antares’ second life
« Reply #1 on: 01/21/2016 03:13 PM »
Great article.  But I don't get something.

"We were going to take the sub-cooler out, but then we started looking back at the data for cross-country LOX temperature rise from the storage tank across an uninsulated line to the launch mount and we scared ourselves that on a worst-case day we could be too warm."

If it's boiling-point LOX, I would think its temperature would have only to do with pressure, and nothing to do with heat influx from outside.  Heat influx would influence only how much boiloff you get, but the final temperature is still the boiling point at whatever the pressure is.  What am I missing here?
« Last Edit: 01/21/2016 03:14 PM by Lee Jay »

Offline robertross

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Re: Orbital ATK ready for Antares’ second life
« Reply #2 on: 01/21/2016 03:28 PM »
That was a great article Philip, thanks!

So many excellent details on the new configuration for Antares.
Remembering those who made the ultimate sacrifice for our rights & freedoms, and for those injured, visible or otherwise, in that fight.

Online abaddon

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Re: Orbital ATK ready for Antares’ second life
« Reply #3 on: 01/21/2016 03:48 PM »
Honest question, how much of a new vehicle should we consider this to be?  It is a little sobering to hear the number of changes made, but I don't have a lot of context.  Is this comparable to F9 1.0->1.1 (arguably a new vehicle), or more like F91.1->F9FT (more of a major upgrade)?  Any other examples that might fit here?

Offline edkyle99

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Re: Orbital ATK ready for Antares’ second life
« Reply #4 on: 01/21/2016 04:09 PM »
Honest question, how much of a new vehicle should we consider this to be?  It is a little sobering to hear the number of changes made, but I don't have a lot of context.  Is this comparable to F9 1.0->1.1 (arguably a new vehicle), or more like F91.1->F9FT (more of a major upgrade)?  Any other examples that might fit here?
I think that the Falcon 9 v1.0 to v1.1 comparison is the best analogy.  Antares is getting new first stage engines, which require changes to the propulsion section.  Falcon 9 v1.1 also got new engines, but in addition it featured a heavily redesigned propulsion section.  I believe that Antares will likely be stretched in the future (like v1.1) to better exploit RD-181 capabilities.

The jump from Atlas II to Atlas III might be another apt comparison.

 - Ed Kyle
« Last Edit: 01/21/2016 04:11 PM by edkyle99 »

Offline sdsds

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Re: Orbital ATK ready for Antares’ second life
« Reply #5 on: 01/21/2016 05:16 PM »
Great article. Thanks!

how much of a new vehicle should we consider this to be?  It is a little sobering to hear the number of changes made

I wonder if it is worthwhile assigning two different "newness" metrics. One would reflect how likely it is that the newness would lead to a loss of mission; the other how likely it is the newness would lead to delay of mission?

From the article it sounds like they're able to do some amount of new software testing in Chandler with hardware in the loop, which is great. But if they're not doing testing integrated with the actual vehicle until the effort shifts to Wallops, then that newness seems to me very likely to create delay(s).
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Offline pippin

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Re: Orbital ATK ready for Antares’ second life
« Reply #6 on: 01/21/2016 10:35 PM »
Do we have any information about the weight changes of the first stage due to the new engines?
If I look at Wikipedia (I know... that's why I'm asking...) the RD181 is about twice as heavy as the AJ26 but then it might not be apples-to-apples because different structure on the rocket side of things might be affected (AJ26 had to be gimbaled as a whole while R181 gimbals the nozzle) so this might or might not offset some of the weight gain.

As a result of all this: do we know how the performance changes for the 200-series? More thrust means lower gravity losses, RD181 has a slightly higher ISP but then there is the weight gain and the loss of subcooled LOX.... Is performance getting better or worse without the stretched tanks?

Offline sdsds

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Re: Orbital ATK ready for Antares’ second life
« Reply #7 on: 01/21/2016 11:23 PM »
do we know how the performance changes for the 200-series? [...]  Is performance getting better or worse without the stretched tanks?

My launch dynamics foo is poor but the long coast between stage 1 and stage 2 burns implies to me they are still managing to retain plenty of contingency margin for the second stage.

So I would be a bit shocked if what the vehicle overall can achieve has gotten any worse!
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Offline arachnitect

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Re: Orbital ATK ready for Antares’ second life
« Reply #8 on: 01/21/2016 11:33 PM »
do we know how the performance changes for the 200-series? [...]  Is performance getting better or worse without the stretched tanks?

My launch dynamics foo is poor but the long coast between stage 1 and stage 2 burns implies to me they are still managing to retain plenty of contingency margin for the second stage.

So I would be a bit shocked if what the vehicle overall can achieve has gotten any worse!

I've seen 15-20% improvement thrown around.

Offline WindnWar

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Re: Orbital ATK ready for Antares’ second life
« Reply #9 on: 01/22/2016 02:05 AM »
Since it lacks the subcooled lox that means less weight which probably offsets any weight gain in the engines, combined with the increased thrust. Given the higher thrust, I wonder how much more stress this places on the structure during max q? Will they have to throttle down at that point and then throttle up or is there enough margin in the structure to not need too? With the upgrade you end up with a first stage with almost the same thrust as the Atlas V first stage, but about a 40 second shorter burn time. Definitely sounds like a future upgrade to a bigger tank would be a nice improvement.

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