Editing Solid-propellant rocket (section)

==Performance==
[[File:STS-130 exhaust cloud engulfs Launch Pad 39A.jpg|thumb|right|An [[exhaust gas|exhaust]] cloud engulfs [[Launch Pad 39A]] at [[NASA|NASA's]] [[Kennedy Space Center]] as the {{OV|105}} lifts off.]]
A typical, well-designed [[ammonium perchlorate composite propellant]] (APCP) first-stage motor may have a vacuum [[specific impulse]] (''I''{{sub|sp}}) as high as {{convert|285.6|isp}} (Titan IVB SRMU).<ref>{{cite web
 |url=http://www.ltas-vis.ulg.ac.be/cmsms/uploads/File/DataSheetSolidATK.pdf
 |title=ATK Space Propulsion Products Catalog, p.30
 |date=May 2008
 |publisher=Alliant Techsystems (ATK)
 |access-date=8 Dec 2015
 |archive-url=https://web.archive.org/web/20180730082316/http://www.ltas-vis.ulg.ac.be/cmsms/uploads/File/DataSheetSolidATK.pdf
 |archive-date=30 July 2018
 |url-status=dead
}}</ref> This compares to {{cvt|339.3|isp}} for RP1/LOX (RD-180)<ref>http://www.pw.utc.com/Products/Pratt+%26+Whitney+Rocketdyne/Propulsion+Solutions/Space{{dead link|date=November 2017 |bot=InternetArchiveBot |fix-attempted=yes }}</ref> and {{cvt|452.3|isp}} for LH<sub>2</sub>/LOX (Block II [[RS-25]])<ref>{{cite web |url=http://www.pw.utc.com/Products/Pratt+%26+Whitney+Rocketdyne |title=Pratt & Whitney Rocketdyne |access-date=2014-01-07 |url-status=dead |archive-url=https://web.archive.org/web/20110426223005/http://www.pw.utc.com/Products/Pratt+%2526+Whitney+Rocketdyne |archive-date=2011-04-26 }}</ref> bipropellant engines. Upper stage specific impulses are somewhat greater: as much as {{cvt|303.8|isp}} for APCP (Orbus 6E),<ref name="spaceandtech.com">{{cite web |url=http://www.spaceandtech.com/spacedata/elvs/titan4b_specs.shtml |title=Titan IVB - Specifications |access-date=2014-02-09 |url-status=usurped |archive-url=https://web.archive.org/web/20130719221015/http://www.spaceandtech.com/spacedata/elvs/titan4b_specs.shtml |archive-date=2013-07-19 }}</ref> {{cvt|359|isp}} for RP1/LOX (RD-0124)<ref>http://www.russianspaceweb.com/engines/rd0124.htm {{Dead link|date=February 2022}}</ref> and {{cvt|465.5|isp}} for LH<sub>2</sub>/LOX (RL10B-2).<ref>{{cite web |url=http://www.pw.utc.com/StaticFiles/Pratt%20.../Products/.../pwr_rl10b-2.pdf |title=RL10B-2 brochure|publisher=Pratt & Whitney Rocketdyne|year=2009 |access-date=2018-08-25 |url-status=dead |archive-url=https://web.archive.org/web/20120326211303/http://www.pw.utc.com/products/pwr/assets/pwr_rl10b-2.pdf |archive-date=2012-03-26 }}</ref> 

Propellant fractions are usually somewhat higher for (non-segmented) solid propellant first stages than for upper stages. The {{convert|117,000|lb|kg|order=flip|adj=on}} Castor 120 first stage has a propellant mass fraction of 92.23% while the {{convert|31,000|lb|kg|order=flip|adj=on}} Castor 30 upper stage developed for Orbital Science's Taurus II COTS (Commercial Off The Shelf) (International Space Station resupply) launch vehicle has a 91.3% propellant fraction with 2.9% graphite epoxy motor casing, 2.4% nozzle, igniter and thrust vector actuator, and 3.4% non-motor hardware including such things as payload mount, interstage adapter, cable raceway, instrumentation, etc. Castor 120 and Castor 30 are {{convert|93|and|92|in|m|2|order=flip|sp=us}} in diameter, respectively, and serve as stages on the Athena IC and IIC commercial launch vehicles. A four-stage Athena II using Castor 120s as both first and second stages became the first commercially developed launch vehicle to launch a lunar probe (''[[Lunar Prospector]]'') in 1998.

Solid rockets can provide high thrust for relatively low cost. For this reason, solids have been used as initial stages in rockets (for example the [[Space Shuttle]]), while reserving high specific impulse engines, especially less massive hydrogen-fueled engines, for higher stages. In addition, solid rockets have a long history as the final boost stage for satellites due to their simplicity, reliability, compactness and reasonably high [[Propellant mass fraction|mass fraction]].<ref>[http://www.astronautix.com/props/solid.htm Solid<!-- Bot generated title -->] {{webarchive|url=https://web.archive.org/web/20020105224630/http://www.astronautix.com/props/solid.htm |date=2002-01-05 }}</ref> A spin-stabilized solid rocket motor is sometimes added when extra velocity is required, such as for a mission to a comet or the outer solar system, because a spinner does not require a guidance system (on the newly added stage). Thiokol's extensive family of mostly titanium-cased ''Star'' space motors has been widely used, especially on Delta launch vehicles and as spin-stabilized upper stages to launch satellites from the cargo bay of the Space Shuttle. ''Star'' motors have propellant fractions as high as 94.6% but add-on structures and equipment reduce the operating mass fraction by 2% or more.

Higher performing solid rocket propellants are used in large strategic missiles (as opposed to commercial launch vehicles). [[HMX]], C<sub>4</sub>H<sub>8</sub>N<sub>4</sub>(NO<sub>2</sub>)<sub>4</sub>, a nitramine with greater energy than ammonium perchlorate, was used in the propellant of the Peacekeeper ICBM and is the main ingredient in NEPE-75 propellant used in the Trident II D-5 Fleet Ballistic Missile.<ref>{{cite web|url=http://www.globalsecurity.org/wmd/systems/d-5-features.htm|title=Trident II D-5 Fleet Ballistic Missile FBM / SLBM - United States|first=John|last=Pike|website=www.globalsecurity.org}}</ref> It is because of explosive hazard that the higher energy military solid propellants containing HMX are not used in commercial launch vehicles except when the LV is an adapted ballistic missile already containing HMX propellant (Minotaur IV and V based on the retired Peacekeeper ICBMs).<ref>''Minotaur IV User's Guide, Release 1.0'', Orbital Sciences Corp., January 2005, p. 4</ref> The Naval Air Weapons Station at China Lake, California, developed a new compound, C<sub>6</sub>H<sub>6</sub>N<sub>6</sub>(NO<sub>2</sub>)<sub>6</sub>, called simply [[CL-20]] (China Lake compound <sup>#</sup>20). Compared to HMX, CL-20 has 14% more energy per mass, 20% more energy per volume, and a higher oxygen-to-fuel ratio.<ref name="navair.navy.mil">[http://www.navair.navy.mil/techTrans/index.cfm?map=local.ccms.view.aB&doc=crada.13 navy.mil]{{dead link|date=April 2025|bot=medic}}{{cbignore|bot=medic}}</ref> One of the motivations for development of these very high [[energy density]] military solid propellants is to achieve mid-course exo-atmospheric ABM capability from missiles small enough to fit in existing ship-based below-deck vertical launch tubes and air-mobile truck-mounted launch tubes. CL-20 propellant compliant with Congress' 2004 insensitive munitions (IM) law has been demonstrated and may, as its cost comes down, be suitable for use in commercial launch vehicles, with a very significant increase in performance compared with the currently favored APCP solid propellants. With a specific impulse of 309 s already demonstrated by Peacekeeper's second stage using HMX propellant, the higher energy of CL-20 propellant can be expected to increase specific impulse to around 320 s in similar ICBM or launch vehicle upper stage applications, without the explosive hazard of HMX.<ref>M. D. Black, ''The Evolution of ROCKET TECHNOLOGY'', pp. 92-94, Native Planter, SLC, 2012, payloadz.com under ''ebook/History''</ref>

An attractive attribute for military use is the ability for solid rocket propellant to remain loaded in the rocket for long durations and then be reliably launched at a moment's notice.