Author Topic: CASTOR 30XL prepares for static fire ahead of providing Antares boost  (Read 28504 times)

Offline spectre9

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Excellent article.

ATK has done a good job.

Nozzle almost looks like a straight cone.

So the motor pictured is the one they're going to static fire?

Offline kevin-rf

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The submerged nozzle is used primarily to reduce motor length. It introduces some issues, but it is commonly used on modern motors.
Doesn't it also reduce the length of the interstate, reducing vehicle weight?
If you're happy and you know it,
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Offline Antares

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Doesn't it also reduce the length of the interstate, reducing vehicle weight?

That's the most drastic sequester move yet.
If I like something on NSF, it's probably because I know it to be accurate.  Every once in a while, it's just something I agree with.  Facts generally receive the former.

Offline kevin-rf

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Doh, Interstage!!!

As long as they don't take out MARS LP-0A on-ramp to space we should be good ;)
If you're happy and you know it,
It's your med's!

Online Chris Bergin

Excellent article.

ATK has done a good job.

Nozzle almost looks like a straight cone.

So the motor pictured is the one they're going to static fire?

Thanks! And yep - this is the static fire motor, which will be followed by six production motors that will fly with Antares.

Offline PahTo

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Thanks for all the info/links--NSF rocks as usual.  Best to the OSC/ATK/Antares team!
« Last Edit: 03/07/2013 02:41 PM by PahTo »

Offline baldusi

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The submerged nozzle is used primarily to reduce motor length. It introduces some issues, but it is commonly used on modern motors.
Doesn't it also reduce the length of the interstate, reducing vehicle weight?
Antares doesn't have an interstage per se, it encloses the payload and second stage in the 3.9m fairing. Having said that, it does allows for more volume for the payload and reduces the second stage support structure.

Offline renclod

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...
The submerged nozzle ... introduces some issues, ...


Such as slag accumulation in the volume between the casing and the submerged part of the nozzle, right ?

On the plus side, a submerged nozzle design is more "quiet", correct ?


Offline Kabloona

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The submerged nozzle is used primarily to reduce motor length. It introduces some issues, but it is commonly used on modern motors.
Doesn't it also reduce the length of the interstate, reducing vehicle weight?

Yes, the purpose of the submerged nozzle is to reduce overall length. The Castor 30XL is a derivative of the Castor 120 (MX Stage 1 derivative), and the MX was designed to be as compact as possible, no expense spared. The submerged nozzle design for the Castor 120 got carried over into the Castor 30.

Coincidentally, the solids for Pegasus were adapted from the Trident DII (D-5) sub-based ICBMs, for which compact design was even more essential. I don't recall off the top of my head, but those are likely submerged nozzle designs as well.

Submerged nozzle design is especially useful in upper stages where expansion ratios are larger and nozzles are longer and interstages are involved.
« Last Edit: 03/09/2013 02:26 PM by Kabloona »

Offline Kabloona

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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 grain is designed such that max nozzle deflection leaves adequate clearance for the hot combustion gases to "turn the corner" and flow into the nozzle throat. The main concern in that area is "erosive" burning, in which high velocity hot combustion gases flowing over the grain surface cause the grain to burn too fast in a localized area. So the clearances there are carefully designed to avoid erosive burning.

As for propellant chemistry, the propellant doesn't know the difference between sea level and altitude, so there's no point in varying the chemistry for altitude. Upper stages with the same chemistry as lower stages will deliver higher Isp simply because vacuum conditions allow higher expansion ratios, which improve Isp.

The MX (Peacekeeper) ICBM did have different propellants on each stage, but that was mainly because each stage was developed by a different contractor.
« Last Edit: 03/09/2013 02:19 PM by Kabloona »

Offline Kabloona

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Coincidentally, the solids for Pegasus were adapted from the Trident DII (D-5) sub-based ICBMs, for which compact design was even more essential. I don't recall off the top of my head, but those are likely submerged nozzle designs as well.
I've always thought that the Orion motor series was more closely related to the Small ICBM ("Midgetman") development effort, though they don't seem to be direct copies of anything in particular.  SICBM was 46 inches in diameter.  Trident D2 is 83 inches diameter.  The Orion 50 motors are 50.5 inches diameter.  What these all shared were innovative carbon carbon composite motor cases, along with high expansion ratio nozzles and advanced propellant formulations.


No, Hercules leveraged their Trident II (D5) case technology to develop the Pegasus motors. The diameters were different, but they used the same graphite/epoxy case winding materials and methods.

Propellants are completely different, though, for safety reasons. D5 uses a high energy propellant containing HMX, which is too detonable for use in boosters. For the Orion motors, they switched to a safer AP/HTPB formulation.
« Last Edit: 03/10/2013 02:46 AM by Kabloona »

Offline simonbp

D5 uses a high energy propellant containing HMX, which is too detonable for use in boosters.

Wait, it's too detonable to be used for boosters, but apparently safe enough to put on a submarine next to a nuclear reactor?!?

Offline Jim

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Weapon systems have different design requirements

Offline R7

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Wait, it's too detonable to be used for boosters, but apparently safe enough to put on a submarine next to a nuclear reactor?!?

Yeah, and not just Tridents, the torpedoes are full of explosives too. HMX is insensitive. There's also nice safety clearance during launch. The submarine is ~50ft below surface while missile is catapulted way above surface before booster ignites. I'm dubious the whole grain could even detonate without some colossal casting error with all HMX clumped into one big chunk.
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Offline Kabloona

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D5 uses a high energy propellant containing HMX, which is too detonable for use in boosters.

Wait, it's too detonable to be used for boosters, but apparently safe enough to put on a submarine next to a nuclear reactor?!?

Well, this is a whole 'nother subject, but DoD wants the highest possible performance from their ICBMs, so they're willing to accept the risk of using propellants that contain high explosives like HMX, etc. These high-energy propellants (Class 1.1) are more hazardous than safer (Class 1.3) AP/HTPB propellants, but that doesn't mean you can detonate a D5 motor by just hitting it with a hammer. DoD has funded extensive research on the safety of high energy propellants, so they know exactly how to handle them.

If I were on a sub, I'd be more worried about the reactor than the D5.


« Last Edit: 03/11/2013 12:28 PM by Kabloona »

Offline Calphor

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D5 uses a high energy propellant containing HMX, which is too detonable for use in boosters.

Wait, it's too detonable to be used for boosters, but apparently safe enough to put on a submarine next to a nuclear reactor?!?

Well, this is a whole 'nother subject, but DoD wants the highest possible performance from their ICBMs, so they're willing to accept the risk of using propellants that contain high explosives like HMX, etc. These high-energy propellants (Class 1.1) are more hazardous than safer (Class 1.3) AP/HTPB propellants, but that doesn't mean you can detonate a D5 motor by just hitting it with a hammer. DoD has funded extensive research on the safety of high energy propellants, so they know exactly how to handle them.

If I were on a sub, I'd be more worried about the reactor than the D5.



You have to be careful with the generalization that 1.1 propellants are the only ones that are formulated with explosives. The split between 1.1 and 1.3 is relatively arbitrary based on a few specific tests. Some of the newer propellant formulations are blurring the line between the two by incorporating explosives into the mix to increase performance. I don't foresee a formulation come into play for 1.3 application that incorporates some of the more sensitive explosives (nitroglycerin, CL-20, etc.), but HMX and RDX have been used in 1.3 formulations.

Somewhat off topic, but maybe informative...

Offline Kabloona

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You have to be careful with the generalization that 1.1 propellants are the only ones that are formulated with explosives. The split between 1.1 and 1.3 is relatively arbitrary based on a few specific tests. Some of the newer propellant formulations are blurring the line between the two by incorporating explosives into the mix to increase performance. I don't foresee a formulation come into play for 1.3 application that incorporates some of the more sensitive explosives (nitroglycerin, CL-20, etc.), but HMX and RDX have been used in 1.3 formulations.

Somewhat off topic, but maybe informative...

True, I was simplifying for the sake of brevity.
« Last Edit: 03/12/2013 03:29 PM by Kabloona »

Offline strangequark

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Wait, it's too detonable to be used for boosters, but apparently safe enough to put on a submarine next to a nuclear reactor?!?

I'd also like to add that "detonable" is not the same thing as "sensitive".

Offline Kabloona

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Wait, it's too detonable to be used for boosters, but apparently safe enough to put on a submarine next to a nuclear reactor?!?

I'd also like to add that "detonable" is not the same thing as "sensitive".

Which is why D5's really don't mind hammers or nuclear reactors.  ;)

Anyhow, good luck strangequark to your Antares teammates on the 30XL test. Is there a target date yet? I didn't see one mentioned in Chris' article.
« Last Edit: 03/12/2013 06:53 PM by Kabloona »

Offline Calphor

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Wait, it's too detonable to be used for boosters, but apparently safe enough to put on a submarine next to a nuclear reactor?!?

I'd also like to add that "detonable" is not the same thing as "sensitive".

Which is why D5's really don't mind hammers or nuclear reactors.  ;)

Anyhow, good luck strangequark to your Antares teammates on the 30XL test. Is there a target date yet? I didn't see one mentioned in Chris' article.

I'm not sure if strange quark has a better estimate, but the last estimated test date I have heard was 27 March. I'm not sure how good that date is, so take it for what it is worth.

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