Author Topic: CASTOR 30XL prepares for static fire ahead of providing Antares boost  (Read 28511 times)


Offline Lee Jay

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Can't wait to follow its flights on NSF!

Online Galactic Penguin SST

I am pretty sure that this will surely get the tin can swan a huge kick in the, um, bottom! (not unlike the many other small solid upper stages, except we should get live rocketcam this time!  8))
Chinese spaceflight is a cosmic riddle wrapped in a galactic mystery inside an orbital enigma... - (not) Winston Churchill

Offline Todd Martin

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Since a solid 2nd stage is less precise in placing a payload into orbit than a Liquid, I wonder how Cygnus compares to Dragon in delta V.  It seems reasonable to expect that Cygnus will need more flexibility to reach ISS.  The lack of precision in orbital insertion could also mean that the target "drop off" point for Antares is further from ISS than what Falcon 9 is permitted?


Offline sdsds

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That was fun to write.

That was fun to read! Two quick questions for those of us not totally familiar with this stuff:
1. What does the phrase, " dual density exit cone" mean?
2. Is the " Large Class Stage program" the USAF effort that led to the Castor 30 initially, before Orbital became involved with it?

Since a solid 2nd stage is less precise in placing a payload into orbit than a Liquid

It isn't totally obvious that's true. Clever thrust vectoring algorithms can control the velocity at motor cut-off even without the ability to terminate thrust early or otherwise alter the total impulse provided by the motor.
-- sdsds --

Offline AnimatorRob

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Since a solid 2nd stage is less precise in placing a payload into orbit than a Liquid, I wonder how Cygnus compares to Dragon in delta V.  It seems reasonable to expect that Cygnus will need more flexibility to reach ISS.  The lack of precision in orbital insertion could also mean that the target "drop off" point for Antares is further from ISS than what Falcon 9 is permitted?



It has been explained to me in the past that the total impulse of a solid is actually very well known and that any mid-course corrections can either be made by altering the first stage burn or the trajectory on the the second stage.

Online DavidH

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Work is being done for Solar Probe Plus:
http://solarprobe.jhuapl.edu/mission/docs/SolarProbeME.pdf
which adds TVC to the Star 48B to make a Star 48BV.

Is there any reason to think Cygnus would need TVC and the Star 48BV?

Section 3.1.7
Quote
The ATK STAR-48BV stage is a thrust-vector-controlled motor offering a simple control system and higher performance than the spinning STAR-48B, which has been used in programs such as New Horizons. The STAR-48BV uses a loaded motor case from the flight-proven STAR-48B, with nozzle design qualified for the Conestoga program and a newly developed thrust vector actuator (TVA) control system currently being qualified to support vectorable nozzles across the STAR product line. The nozzle and thrust vector control system will be used on a STAR-37FMV in mid-2008, and the STAR-48BV upper stage currently is under contract and scheduled for a first flight as part of the Minotaur IV launch vehicle.
TL;DR
Keep your posts short if you want them to be read.

Offline Todd Martin

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It has been explained to me in the past that the total impulse of a solid is actually very well known and that any mid-course corrections can either be made by altering the first stage burn or the trajectory on the the second stage.
[/quote]

Total impulse does not fully determine payload insertion height, since launch performance is affected by atmospheric pressure, temperature, and cross-winds.  I'm sure alterations to the 1st stage burn helps and the trajectory on the 2nd could help as well to some extant.  I am less convinced that thrust vector control will be significantly helpful since the CASTOR 30XL has only 1 nozzle.

Offline Jim

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The Cygnus will act as a third stage and trim out any dispersions.  It has an SM based on the STAR spacecraft bus. There will be a third stage or trim stage for other missions or the payload will have to handle the dispersions.

But what does have one nozzle have to do with TVC not being helpful. 
« Last Edit: 03/06/2013 03:53 PM by Jim »

Offline Todd Martin

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The Cygnus will act as a third stage and trim out any dispersions.  It has an SM based on the STAR spacecraft bus. There will be a third stage or trim stage for other missions or the payload will have to handle the dispersions.

But what does have one nozzle have to do with TVC not being helpful. 

Thanks for clarifying about the 3rd stage SM.  TVC with 1 nozzle is perfectly capable of keeping a rocket pointed in the right direction.  TVC with 2 or more nozzles could use Cosine losses to reduce effective thrust and hence orbital height.  With just 1 nozzle, the only way I can see to use TVC as a means to adjust orbital insertion height is to "Tack" the entire rocket back and forth.  IMHO, that sounds challenging to guidance, slow and cumbersome. 

Offline strangequark

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The Cygnus will act as a third stage and trim out any dispersions.  It has an SM based on the STAR spacecraft bus. There will be a third stage or trim stage for other missions or the payload will have to handle the dispersions.

But what does have one nozzle have to do with TVC not being helpful. 

Thanks for clarifying about the 3rd stage SM.  TVC with 1 nozzle is perfectly capable of keeping a rocket pointed in the right direction.  TVC with 2 or more nozzles could use Cosine losses to reduce effective thrust and hence orbital height.  With just 1 nozzle, the only way I can see to use TVC as a means to adjust orbital insertion height is to "Tack" the entire rocket back and forth.  IMHO, that sounds challenging to guidance, slow and cumbersome. 

It's called an energy scrub maneuver, and it is done routinely.

Offline Jim

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Also, there is the IUS method.  The SRM's were sized smaller than what was required, so that a overperformance would not result in a problem.  The RCS tanks were sized to make up the shortfall in case of a under or nominal motor performance.

Online PahTo

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Good article and thread! 

What improvements are there from the 30/30A to the 30B? 

Does "a submerged design" mean the nozzle throat is actually touching/within the grain of the prop?

Curious about the "dual density exit cone" as well.  Perhaps the ablative material of the cone wall is thicker to stand up to the higher thrust?

As I'm not sure of the specs for 30A/30B, the reference to "stretched" indicates the XL is a higher thrust, but not a longer burn-time, motor.

Offline simonbp

They'll be using the (new) solid test stand at AEDC, right? I remember climbing all over that at an open house back before it had even been used for a test. The old solid test stand was destroyed in the 90s when a Minuteman stage detonated during a late-night test. They really put a lot of effort into making the new stand much more durable (and put it out at the edge of the facility).

Offline Jim

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Does "a submerged design" mean the nozzle throat is actually touching/within the grain of the prop?


It means the nozzle entrance extends to inside the motor case

Online PahTo

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Thanks Jim.  I'm not sure why submerging the nozzle helps--perhaps makes TVC that much easier (both the physics of steering, as well as housing the TVC hardware).
I think it's safe to say the stretched casing carries more propellant as well as room for the nozzle (that is, they didn't just stretch to house the nozzle).

I realize how silly it sounds to ask if the nozzle was up at the grain of the prop. Then again, it does cause me to ponder the interface between the top of the nozzle and the bottom of the prop on any srm.

Speaking of prop, is there a dramatic difference between the chemical components of a solid used at sea level, and that used in vacuum?  On a simplistic level, is it still PBAN?  HTPB?  Some significantly different variation?

Online Chris Bergin

That was fun to write.

That was fun to read!

Thanks very much to both you and PahTo! :)

Online robertross

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Adding my vote on that great read Chris. Bravo.

Sounds like ATK really pulled out the stops to make that Castor a reality. Can't wait to see it in action!
Remembering those who made the ultimate sacrifice for our rights & freedoms, and for those injured, visible or otherwise, in that fight.

Offline Zed_Noir

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Thanks Jim.  I'm not sure why submerging the nozzle helps--perhaps makes TVC that much easier (both the physics of steering, as well as housing the TVC hardware).
I think it's safe to say the stretched casing carries more propellant as well as room for the nozzle (that is, they didn't just stretch to house the nozzle).

I realize how silly it sounds to ask if the nozzle was up at the grain of the prop. Then again, it does cause me to ponder the interface between the top of the nozzle and the bottom of the prop on any srm.

Speaking of prop, is there a dramatic difference between the chemical components of a solid used at sea level, and that used in vacuum?  On a simplistic level, is it still PBAN?  HTPB?  Some significantly different variation?

Check out pg 26 & pg 27 of the current ATK Motors PDF catalog for more info on the Castor 30A & Castor 30B. There's a cutaway diagram of the Castor 30B internal layout.

http://www.atk.com/wp-content/uploads/2013/02/ATK-Motor-Catalog-2012.pdf

By the way on pg 6 of the PDF is size comparison chart of current ATK rocket motors.

note - page number is what's on the page not the PDF page count

Online Calphor

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Thanks Jim.  I'm not sure why submerging the nozzle helps--perhaps makes TVC that much easier (both the physics of steering, as well as housing the TVC hardware).
I think it's safe to say the stretched casing carries more propellant as well as room for the nozzle (that is, they didn't just stretch to house the nozzle).

I realize how silly it sounds to ask if the nozzle was up at the grain of the prop. Then again, it does cause me to ponder the interface between the top of the nozzle and the bottom of the prop on any srm.

Speaking of prop, is there a dramatic difference between the chemical components of a solid used at sea level, and that used in vacuum?  On a simplistic level, is it still PBAN?  HTPB?  Some significantly different variation?
The propellant is essentially the same whether the motor is used at sea level or in vacuum. IIRC, the propellant in this case is HTPB.

The submerged nozzle is used primarily to reduce motor length. It introduces some issues, but it is commonly used on modern motors.

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