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?
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?
Quote from: Calphor on 03/07/2013 03:41 amThe 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?
...The submerged nozzle ... introduces some issues, ...
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?
Quote from: Kabloona on 03/09/2013 02:08 pmCoincidentally, 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.
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.
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?!?
Quote from: Kabloona on 03/10/2013 02:19 amD5 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?!?
Quote from: simonbp on 03/10/2013 06:23 pmQuote from: Kabloona on 03/10/2013 02:19 amD5 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...
Quote from: simonbp on 03/10/2013 06:23 pmWait, 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".
Quote from: strangequark on 03/12/2013 06:21 pmQuote from: simonbp on 03/10/2013 06:23 pmWait, 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.