That was fun to write.
Since a solid 2nd stage is less precise in placing a payload into orbit than a Liquid
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?
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.
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.
Quote from: Jim on 03/06/2013 03:52 pmThe 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.
Does "a submerged design" mean the nozzle throat is actually touching/within the grain of the prop?
Quote from: Chris Bergin on 03/06/2013 03:05 amThat was fun to write.That was fun to read!
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 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.
So, if the Navy is satisfied that using HMX is OK for SLBMs (and there haven't been any incidents, right?), then why isn't it used for launch vehicles? Especially for solid upper stages (like Castor 30) where the higher Isp would make a lot of difference.
Is more thrust the primary reason? (Military missiles being in a bigger hurry to get there than orbital launchers.) - Ed Kyle
Quote from: Kabloona on 03/14/2013 01:05 amQuote from: edkyle99 on 03/14/2013 12:22 amIs more thrust the primary reason? (Military missiles being in a bigger hurry to get there than orbital launchers.) No, it's all about highest Isp for max performance (impulse) per unit mass, and the highest Isp solids are Class 1.1 because their ingredients are "high energy" to put it euphemistically. And as you know from the rocket equation, for a given payload, using a higher Isp propellant means the booster can be lighter and smaller, all other things being equal. And this is a priority for ICBMs that have to fit into silos and submarines.I've seen references to a new miracle propellant called CL-20 that seems like a game-changer. More energy but safer, etc.. But much harder to say: Hexanitrohexaazaisowurtzitane [hexa-nitro-hexa-aza-iso-wurtzi-tane] - Ed Kyle
Quote from: edkyle99 on 03/14/2013 12:22 amIs more thrust the primary reason? (Military missiles being in a bigger hurry to get there than orbital launchers.) No, it's all about highest Isp for max performance (impulse) per unit mass, and the highest Isp solids are Class 1.1 because their ingredients are "high energy" to put it euphemistically. And as you know from the rocket equation, for a given payload, using a higher Isp propellant means the booster can be lighter and smaller, all other things being equal. And this is a priority for ICBMs that have to fit into silos and submarines.
Is more thrust the primary reason? (Military missiles being in a bigger hurry to get there than orbital launchers.)
CL-20 could be a significant advance for military propellants if it can be stabilized long-term in propellant formulations, but again, that'll be a Class 1.1 propellant, so it'll never see use in launch vehicles.Aside from its higher energy, it produces less of a smoke signature than HMX-based propellants, and reduced/minimum smoke propellants are especially attractive to Air Force and Navy for use in air-launched and ship-based missiles because low-visibility smoke trails mean it's harder for the enemy to see where the missile came from. So that's its most likely future application.
Isn't the China Lake formulation limited by it's natural degradation rate?
Wouldn't a Class 1.1 Propellant simplify FTS?
Yes, that was quite an interesting way to dispose of the stages. Are they using the same method for the first stages, or something less jarring, like burning them?
Quote from: Kabloona on 03/14/2013 01:42 pmCL-20 could be a significant advance for military propellants if it can be stabilized long-term in propellant formulations, but again, that'll be a Class 1.1 propellant, so it'll never see use in launch vehicles.This paper says there is a chance that propellant formulations using CL-20 have the potential to be Class 1.3. https://docs.google.com/viewer?a=v&q=cache:CSWrlJkujGgJ:publications.drdo.gov.in/ojs/index.php/dsj/article/download/2158/1139+&hl=en&gl=us&pid=bl&srcid=ADGEEShlrLum9IA9koHKNeq34PE7qVdjzLy5bxzHWkiTD9Pp8fIbcqKDQvbt_JgSMdVA8lwhug5XCvCVJ_mxDa21P264bCHM1VJYd9ePo96FP0vpJ0mXveS_zD5Ad_db0MVI9MTZ8cGC&sig=AHIEtbT5oNI557sxHOHACAhwofTbl-P_NQATK apparently makes the stuff, though only as a military grade. There were stories about it being used for ABM R&D work I think.https://www.fbo.gov/index?s=opportunity&mode=form&id=048e8c26275ed38540513fdea33a66e2&tab=core&_cview=0 - Ed Kyle
CL-20 could be a significant advance for military propellants if it can be stabilized long-term in propellant formulations, but again, that'll be a Class 1.1 propellant, so it'll never see use in launch vehicles.
Chris, can we keep him?
Quote from: edkyle99 on 03/10/2013 12:47 amQuote 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.Correction and retraction: I stated earlier that the Pegasus (Orion) motors were derived from Trident II (D5) technology, based on what I now realize was a faulty memory bank. (I did once work on Pegasus, but it was a long time ago, and clearly my memory had an SEU on this issue.) In pondering that statement further, I realize it was incorrect, and that the correct derivation of Orion motors was from the strap-on graphite epoxy motors (GEMs) developed for the Delta II. Somehow I forgot that and then misremembered Trident II instead of Delta II...arghh...getting old...Anyway, anyone who's interested can Google "atk propulsion product catalog" and see their whole lineup of motors and see the close correspondence between the GEM and Orion diameters...something I should have done before promulgating incorrect information. Apologies to all.(You can also see from the catalog that the Orion motors use the same QDL-1 propellant formulation as the GEM-40, so I'm fairly confident that my "correction" here is, ummm, correct).
As for the Orion 50 motors, I do not know the full history of the series, but I believe that they were clean sheet for Orbital in support of the Pegasus program. I guess I'll have to do some digging to confirm.
The motor diameters, lengths, etc were probably optimized for Pegasus, but Hercules already had the low-cost GEM case technology and propellant forumulation from the strap-ons they had already developed for Delta II, so they applied what they could from GEM to the Orion 50 series.
Quote from: Kabloona on 03/23/2013 11:56 pm The motor diameters, lengths, etc were probably optimized for Pegasus, but Hercules already had the low-cost GEM case technology and propellant forumulation from the strap-ons they had already developed for Delta II, so they applied what they could from GEM to the Orion 50 series.Pegasus flew before the first GEM.
I saw a inert Pegasus perform B-52 fitchecks in 8/89 at EAFB
MLV contract was awarded 1987