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词条 RS-68
释义

  1. Design and development

     Proposed uses  Human-rating 

  2. Variants

  3. See also

  4. References

  5. External links

{{Infobox rocket engine
| image= RS-68 rocket engine test.jpg
| image_size= 300
| caption= An RS-68 engine undergoing hot-fire testing at NASA's Stennis Space Center during its developmental phase.
| name= RS-68
| purpose= First stage engine for the Delta IV rocket
| first_flight= 2002
| last_flight=
| successor=
| country_of_origin= United States
| manufacturer= Rocketdyne
Pratt & Whitney Rocketdyne
Aerojet Rocketdyne
| designer=
| type=Liquid
| status= Active
| fuel= Liquid hydrogen
| oxidiser= Liquid oxygen
| cycle=Gas-generator cycle
| nozzle_ratio= 21.5
| description=
| thrust(SL)= RS-68: {{convert|2,950|kN|lbf|abbr=on|order=flip}}
RS-68A: {{convert|3137|kN|lbf|abbr=on|order=flip}}[1]
| thrust_to_weight=RS-68: 45.3
RS-68A: 47.4
| specific_impulse_vacuum= RS-68: {{convert|410|isp|abbr=on}}
RS-68A: {{convert|412|isp|abbr=on}}[2]
| chamber_pressure= {{convert|1,488|psi|MPa|abbr=on}}
| burn_time=
| dry_weight= RS-68: {{convert|14560|lb|abbr=on}}
RS-68A: {{convert|14870|lb|abbr=on}}[1]
| length= {{convert|5.20|m|abbr=on|order=flip}}
| diameter= {{convert|2.43|m|abbr=on|order=flip}}
| used_in= Delta IV
}}

The Aerojet Rocketdyne RS-68 (Rocket System 68) is a liquid-fuel rocket engine that uses liquid hydrogen (LH2) and liquid oxygen (LOX) as propellants in a gas-generator power cycle. It is the largest hydrogen-fueled rocket engine ever flown.[3]

Its development started in the 1990s with the goal of producing a simpler, less-costly, heavy-lift engine for the Delta IV launch system. Two versions of the engine have been produced: the original RS-68 and the improved RS-68A. A third version, the RS-68B, was planned for the National Aeronautics and Space Administration's (NASA) Ares V rocket that was later canceled.

Design and development

A leading goal of the RS-68 program was to produce a simple engine that would be cost-effective when used for a single launch. To achieve this, the RS-68 has 80 percent fewer parts than the multi-launch Space Shuttle main engine (SSME).[4] The adverse consequences of this simplicity were the RS-68's having a significantly lower thrust-to-weight ratio and a 10 percent lower specific impulse compared to the SSME. The benefit of this simplicity is the RS-68's reduced construction cost.[4]

{{citation needed span|The RS-68 was developed at Rocketdyne Propulsion and Power, located in Canoga Park, Los Angeles, California, where the SSME is manufactured. It was designed to power the Delta IV Evolved Expendable Launch Vehicle (EELV). The initial development engines were assembled at the nearby Santa Susana Field Laboratory where the Saturn V's Rocketdyne F-1 engines were developed and tested for the Apollo missions to the Moon. The initial testing of the RS-68 occurred at the Air Force Research Laboratory (AFRL), Edwards Air Force Base, California, and later at NASA's Stennis Space Center.|date=August 2018}} The RS-68 was certified in December 2001 for use on Delta IV rockets.[5]

The RS-68 is part of the Common Booster Core (CBC) used to create the five variants of the Delta IV family of launch vehicles. The largest of the launch vehicles, the "Heavy", uses three CBCs mounted together.[6]

At its maximum 102 percent thrust, the engine produces {{convert|758000|lbf|kN|sigfig=3|lk=on}} in a vacuum and {{convert|663000|lbf|kN|sigfig=3}} at sea level. The engine's mass is {{convert|14560|lb|kg}}. With this thrust, the engine has a thrust-to-weight ratio of 51.2 and a specific impulse of {{convert|410|isp}} in a vacuum and {{convert|365|isp}} at sea level.[7] The RS-68 is gimbaled hydraulically and is capable of throttling between 58 and 102 percent thrust.[8]

The RS-68A is an updated version of the RS-68, with increased specific impulse and thrust (to over {{convert|700000|lbf|kN|sigfig=2}} at sea level).[9] The first launch on June 29, 2012, from the Cape Canaveral Air Force Station used three RS-68A engines mounted in a Delta IV Heavy rocket.[10]

Proposed uses

In 2006, NASA announced that five RS-68 engines would be used instead of SSMEs on the planned Ares V. NASA chose the RS-68 because of its lower cost, about $20 million per engine including the cost of NASA's upgrades. The upgrades included a different ablative nozzle to accommodate a longer burn, a shorter start sequence, hardware changes to limit free hydrogen at ignition, and a reduction in the amount of helium used during countdown and flight. Thrust and specific impulse increases would occur under a separate upgrade program for the Delta IV rocket.[11] Later, the Ares V was changed to use six RS-68 engines, designated the RS-68B.[12]

Human-rating

It has been reported that the RS-68 needs over 200 changes to receive a human-rating certification.[13] NASA has stated that those changes include health monitoring, removal of the fuel-rich environment at liftoff, and improving the robustness of its subsystems.[14][15]

Variants

  • RS-68 is the original version. It produces {{convert|663000|lbf|kN|lk=on|sigfig=3}} thrust at sea level.[16]
  • RS-68A is an improved version. It produces {{convert|705000|lbf|kN|abbr=on|sigfig=3}} thrust at sea level and {{convert|800000|lbf|kN|abbr=on|sigfig=3}} thrust in a vacuum.[17] {{citation needed span|Its specific impulse in a vacuum is {{convert|414|isp}}. Certification testing was completed in November 2010.|date=July 2018}}
  • RS-68B was a proposed upgrade to be used in the Ares V launch vehicle for NASA's Constellation program.[12] The Ares V was to use six RS-68B engines on a {{convert|10|m}} core stage, along with two 5.5-segment solid rocket boosters. It was later determined that the ablative nozzle of the RS-68 was poorly suited to this multi-engine environment, causing reduced engine efficiency and extreme heating at the base of the vehicle.[18]

See also

  • Comparison of orbital rocket engines
  • M-1 (rocket engine)
  • National Launch System
  • Rocketdyne J-2
  • RS-83
  • Space Launch Initiative
  • TR-106

References

1. ^1 {{cite web | url=http://www.ulalaunch.com/products_deltaiv.aspx | title=DELTA IV | publisher=United Launch Alliance | accessdate=July 13, 2014 | deadurl=no | archiveurl=https://web.archive.org/web/20140720073154/http://www.ulalaunch.com/Products_DeltaIV.aspx| archivedate=July 20, 2014}}
2. ^{{cite web | url=http://www.ulalaunch.com/uploads/docs/Launch_Vehicles/Delta_IV_Users_Guide_June_2013.pdf | title=Delta IV User's Guide | date=June 2013 | accessdate=July 13, 2014 | publisher=United Launch Alliance | deadurl=no | archiveurl=https://web.archive.org/web/20140710005717/http://www.ulalaunch.com/uploads/docs/Launch_Vehicles/Delta_IV_Users_Guide_June_2013.pdf | archivedate=July 10, 2014}}
3. ^{{cite press | url=http://atk.mediaroom.com/index.php?s=25280&item=57973 | title=ATK Propulsion and Composite Technologies Help Launch National Reconnaissance Office Satellite | publisher=Alliant Techsystems | date=January 19, 2009 | deadurl=no | archiveurl=https://web.archive.org/web/20140222134317/http://atk.mediaroom.com/index.php?s=25280&item=57973 | archivedate=February 22, 2014}}
4. ^1 "AIAA 2002-4324, Propulsion for the 21st Century—RS-68" {{webarchive | url=https://web.archive.org/web/20090319075127/http://www.pwrengineering.com/dataresources/PropulsionForThe21stCentury-RS-68.doc | date=March 19, 2009}}. AIAA, July 8–10, 2002.
5. ^{{cite press | url=http://www.boeing.com/news/releases/2001/q4/nr_011219s.html | title=Rocketdyne RS-68 Engine Certified for Boeing Delta IV | date=December 19, 2001 | publisher=Boeing | deadurl=yes | archiveurl=https://web.archive.org/web/20121010153432/http://www.boeing.com/news/releases/2001/q4/nr_011219s.html | archivedate=October 10, 2012}}
6. ^{{cite web | url=https://www.ulalaunch.com/docs/default-source/rockets/atlas-v-and-delta-iv-technical-summary.pdf | title=Atlas V and Delta IV Technical Summary}}
7. ^{{cite web | url=https://www.ulalaunch.com/rockets/delta-iv | title=United Launch Alliance Delta IV Heavy}}
8. ^Boeing white paper on RS-68 development {{webarchive | url=https://web.archive.org/web/20070415124430/http://www.engineeringatboeing.com/dataresources/PropulsionForThe21stCentury-RS-68.doc | date=April 15, 2007}}
9. ^{{cite press release | publisher=United Launch Alliance | date=September 25, 2008 | title=United Launch Alliance First RS-68A Hot-Fire Engine Test a Success | url=http://www.ulalaunch.com/news_RS68A.html | quote=Currently, the RS-68 engine can deliver more than 660,000 pounds of sea level thrust and the upgraded RS-68A will increase this to more than 700,000 pounds. The RS-68A also improves on the specific impulse, or fuel efficiency, of the RS-68. | accessdate=September 30, 2008}}{{dead link | date=November 2017 | bot=InternetArchiveBot | fix-attempted=yes}}
10. ^{{cite press release | publisher=United Launch Alliance | date=June 29, 2012 | title=United Launch Alliance Upgraded Delta IV Heavy rocket successfully Launches Second Payload in Nine Days for the National Reconnaissance Office | url=http://www.ulalaunch.com/united-launch-alliance-upgraded-delta-iv.aspx?title=United+Launch+Alliance+Upgraded+Delta+IV+Heavy+Rocket++Successfully+Launches+Second+Payload+in+Nine+Days+for+the++National+Reconnaissance+Office&archived=True&Category=all&Page=22 | deadurl=no | archiveurl=https://web.archive.org/web/20160820020437/http://www.ulalaunch.com/united-launch-alliance-upgraded-delta-iv.aspx?title=United+Launch+Alliance+Upgraded+Delta+IV+Heavy+Rocket++Successfully+Launches+Second+Payload+in+Nine+Days+for+the++National+Reconnaissance+Office&archived=true&category=all&page=22 | archivedate=August 20, 2016}}
11. ^{{cite press release | publisher=National Aeronautics and Space Administration | date=May 18, 2006 | title=NASA's Exploration Systems Progress Report | url=http://www.nasa.gov/home/hqnews/2006/may/HQ_06226_RS-68_ENGINE.html | accessdate=May 30, 2006 | deadurl=no | archiveurl=https://www.webcitation.org/66Vmj3FML?url=http://www.nasa.gov/home/hqnews/2006/may/HQ_06226_RS-68_ENGINE.html | archivedate=March 28, 2012}}
12. ^1 {{cite web | url=http://www.nasa.gov/mission_pages/constellation/ares/aresV/index.html | title=Overview: Ares V Cargo Launch Vehicle | publisher=National Aeronautics and Space Administration | accessdate=September 30, 2008 | archiveurl=https://web.archive.org/web/20080926214451/http://www.nasa.gov/mission_pages/constellation/ares/aresV/index.html | archivedate=September 26, 2008}}
13. ^{{cite web | website=NASAspaceflight.com | url=http://forum.nasaspaceflight.com/index.php?topic=14446.msg318877#msg318877 | title=United Launch Alliance First RS-68A Hot-Fire Engine Test a Success | date=September 27, 2008 | deadurl=no | archiveurl=https://web.archive.org/web/20180328171435/http://forum.nasaspaceflight.com/index.php?topic=14446.msg318877#msg318877 | archivedate=March 28, 2018}}
14. ^{{cite web | url=http://www.nasa.gov/exploration/about/faq.html#3 | title=Frequently Asked Questions, question 3 | publisher=National Aeronautics and Space Administration ESMD | deadurl=no | archiveurl=https://web.archive.org/web/20100112151132/http://www.nasa.gov/exploration/about/faq.html#3 | archivedate=January 12, 2010}}
15. ^{{cite web | url=http://www.nasa.gov/pdf/377875main_081109%20Human%20Rated%20Delta%20IV.pdf | title=Human Rated Delta IV Heavy Study Constellation Impacts | first1=David A. | last1=Bearden | first2=John P. | last2=Skratt | first3=Matthew J. | last3=Hart | format=PDF | date=June 1, 2009 | publisher=National Aeronautics and Space Administration | page=8 | deadurl=no | archiveurl=https://web.archive.org/web/20170228145012/https://www.nasa.gov/pdf/377875main_081109%20Human%20Rated%20Delta%20IV.pdf | archivedate=February 28, 2017}}
16. ^{{cite web | publisher=Pratt & Whitney Rocketdyne | date=October 2005 | title=RS-68 Propulsion System | url=http://www.pw.utc.com/StaticFiles/Pratt%20&%20Whitney%20New/Media%20Center/Assets/1%20Static%20Files/Docs/pwr_RS-68.pdf | archive-url=https://web.archive.org/web/20180714135306/http://www.pw.utc.com/StaticFiles/Pratt%20&%20Whitney%20New/Media%20Center/Assets/1%20Static%20Files/Docs/pwr_RS-68.pdf | dead-url=yes | archive-date=2018-07-14 | format=PDF }}
17. ^{{cite web | url=http://www.asdnews.com/news/32037/P&W_Successfully_Completes_Hot-Fire_Test_on_2nd_RS-68A_Certification_Engine.htm | title=P&W Successfully Completes Hot-Fire Test on 2nd RS-68A Certi| website=asdnews.com | accessdate=April 25, 2018 | deadurl=no | archiveurl=https://web.archive.org/web/20110725014233/http://www.asdnews.com/news/32037/P%26W_Successfully_Completes_Hot-Fire_Test_on_2nd_RS-68A_Certification_Engine.htm | archivedate=July 25, 2011}}
18. ^{{cite web | website=nasaspaceflight.com | date=June 2013 | title=The engines that refused to retire – RS-25s prepare for SLS testing | url=http://www.nasaspaceflight.com/2013/06/engines-refused-retire-rs-25s-prepare-sls-testing/ | deadurl=no | archiveurl=https://web.archive.org/web/20170830160316/https://www.nasaspaceflight.com/2013/06/engines-refused-retire-rs-25s-prepare-sls-testing/ | archivedate=August 30, 2017}}

External links

{{commons category|RS-68 (rocket engine)}}
  • Aerojet Rocketdyne's RS-68 page
  • RS-68 page on Astronautix.com
  • {{cite conference |url=http://www.pwrengineering.com/dataresources/PropulsionForThe21stCentury-RS-68.doc |format=doc |title=Propulsion for the 21st Century—RS-68 |year=2002 |conference=38th Joint Liquid Propulsion Conference |location=Indianapolis, Indiana |publisher=AIAA |first=B.K. |last=Wood |deadurl=yes |archiveurl=https://web.archive.org/web/20090319075127/http://www.pwrengineering.com/dataresources/PropulsionForThe21stCentury-RS-68.doc |archivedate=2009-03-19 |df= }}
{{Rocket engines}}{{Project Constellation}}

5 : Rocket engines using hydrogen propellant|Rocketdyne engines|Boeing spacecraft and space launch systems|Rocket engines using the gas-generator cycle|Rocket engines of the United States
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