Hypersonic Weapons: Vulnerability to Missile Defenses and Comparison to MaRVs

AbstractAssessing the utility of hypersonic boost glide vehicles (BGVs) requires comparing their capabilities to alternative systems that could carry out the same missions, particularly given the technical difficulties and additional costs of developing BGVs compared to more established technologies. This paper discusses the primary motivations given for BGVs—most notably countering missile defenses—and summarizes current hypersonic development programs. It finds that evading the most capable current endo-atmospheric defenses requires that BGVs maintain speeds significantly higher than Mach 5 throughout their glide phase, which has implications for their mass and range. The paper then compares BGVs to maneuverable reentry vehicles (MaRVs) carried on ballistic missiles flown on depressed trajectories and shows that MaRVs can offer significant advantages over BGVs in a wide range of cases. Finally, the paper shows that BGV maneuvering during its glide phase can result in substantial costs in range and glide speed. AcknowledgementsThe authors would like to thank Steve Fetter and Paul Zarchan for useful comments on parts of this work.Disclosure statementNo potential conflict of interest was reported by the author(s).Notes1 The speed of sound in the atmosphere varies by about 10% over the range of altitudes of interest for BGVs (10–50 km). We assume a speed of 300 m/s, which is roughly consistent with a standard engineering approximation that uses 1000 ft/s as sound speed at these altitudes. See “1976 Standard Atmosphere Calculator,” DigitalDutch, https://www.digitaldutch.com/atmoscalc/table.htm.2 Richard H. Speier, George Nacouzi, Carrie A. Lee, and Richard M. Moore, Hypersonic Missile Nonproliferation: Hindering the Spread of a New Class of Weapons (Santa Monica, CA: RAND Corporation, 2017), 53–93, https://rand.org/pubs/research_reports/RR2137.html.3 MaRVs were developed and tested during the Cold War and in the 2000s. See Matthew Bunn, “Technology of Ballistic Missile Reentry Vehicles,” in Review of U.S. Military Research and Development: 1984, eds. Kosta Tsipis and Penny Janeway (Mclean, VA: Pergamon, 1984), 87–107, https://scholar.harvard.edu/files/bunn_tech_of_ballastic_missle_reentry_vehicles.pdf. See also National Research Council, U.S. Conventional Prompt Global Strike: Issues for 2008 and Beyond, Committee on Conventional Prompt Global Strike Capability (2008), https://doi.org/10.17226/12061, and Amy Woolf, Conventional Prompt Global Strike and Long-Range Ballistic Missiles: Background and Issues (Washington, DC: Congressional Research Service, 2021), https://crsreports.congress.gov/product/pdf/R/R41464.4 James M. Acton, “Hypersonic Boost-Glide Weapons,” Science and Global Security 23 (2015): 191–219, http://scienceandglobalsecurity.org/archive/sgs23acton.pdf; David Wright, “Research Note to Hypersonic Boost-Glide Weapons by James M. Acton: Analysis of the Boost Phase of the HTV-2 Hypersonic Glider Tests,” Science and Global Security 23 (2015): 220–9, http://scienceandglobalsecurity.org/archive/sgs23wright.pdf.5 Cameron L. Tracy and David Wright, “Modelling the Performance of Hypersonic Boost-Glide Missiles,” Science and Global Security 28 (2021): 135–170, http://scienceandglobalsecurity.org/archive/sgs28tracy.pdf. This paper uses a different coordinate system for the equations of motion than is used in many papers. That system and the reasons behind it are described in Appendix A.6 “The First Missile Regiment of Avangard Took Up Combat Duty,” TASS, December 27, 2019, https://tass.ru/armiya-i-opk/7436431; “Deployment of Avangard continues in Dombarovskiy,” Russian Strategic Nuclear Forces, December 16, 2020, https://russianforces.org/blog/2020/12/deployment_of_avangard_continu.shtml.7 “Avangard,” Center for Strategic and International Studies, July 31, 2021, https://missilethreat.csis.org/missile/avangard/.8 An additional motivation appears to be a desire to match work on hypersonic weapons by Russia and China. See, for example, Oren Liebermann, “US is Increasing Pace of Hypersonic Weapons Development to Chase China and Russia, Senior Admiral Says,” CNN, November 20, 2022, https://www.cnn.com/2022/11/20/politics/us-hypersonic-china-russia-competition/index.html.9 Ivett A. Leyva, “The Relentless Pursuit of Hypersonic Flight,” Physics Today, 70 (2017): 30–6, https://doi.org/10.1063/PT.3.3762.10 See, for example, Joseph Trevithick, “Here's How Hypersonic Weapons Could Completely Change the Face of Warfare,” The War Zone, June 6, 2017, https://www.thedrive.com/the-war-zone/11177/heres-how-hypersonic-weapons-could-completely-change-the-face-of-warfare; Benjamin Knudsen, “An Examination of U.S. Hypersonic Weapon Systems,” Technical Report, George Washington University, June 2017, DOI:10.13140/RG.2.2.14375.96164; “Hypersonic Strike and Defense: A Conversation with Mike White,” Center for Strategic and International Studies, June 10, 2021, https://www.csis.org/analysis/hypersonic-strike-and-defense-conversation-mike-white. Another possible motivation, reducing warning of an attack by avoiding detection, does not appear to be as central. Ground-based radars will not see a BGV during glide until it is within about 500 km, but this may not be particularly relevant. This range should still provide time to launch short-range interceptors against it. For high-value targets, forward-basing radars would provide additional warning time. Moreover, U.S. and Russian space-based infrared (IR) sensors (which China is developing) can provide early warning of the launch of the boosters carrying BGVs and can also detect IR emissions from BGVs gliding at sufficiently high speeds, providing warning and cuing information even if this data is not sufficient to guide interceptors (see Paper 1).11 This paper focuses on terminal defenses for several reasons, discussed in detail below. BGVs can underfly midcourse (exo-atmospheric) defenses, which appears to be a motivation for Russia’s development of the Avangard HGV, but this paper focuses on shorter range BGVs used for conventional conflict.12 Congressional Budget Office (CBO), “U.S. Hypersonic Weapons and Alternatives,” January 2023, https://www.cbo.gov/publication/58255.13 See Paper 1 and analysis below.14 CBO, “U.S. Hypersonic Weapons.”15 Acton, “Hypersonic Boost-Glide Weapons.”16 “Minimum-energy trajectories” give the maximum range for a given burnout speed and altitude.17 Lisbeth Gronlund and David Wright “Depressed-Trajectory SLBMs: A Technical Assessment and Arms Control Possibilities,” Science and Global Security 3 (1992): 101–59, http://scienceandglobalsecurity.org/archive/sgs03gronlund.pdf.18 Press reports also reflect this ambiguity. Russia’s Kinzhal system used against Ukraine is a maneuvering air-launched ballistic missile rather than a BGV (Kelley Sayler, Hypersonic Weapons: Background and Issues for Congress (Washington, DC: Congressional Research Service, 2023), https://crsreports.congress.gov/product/pdf/R/R45811)). The “hypersonic weapon” North Korea has reportedly tested is also described this way (Iain Marlow and Jon Herskovitz, “Kim Jong Un’s Hypersonic Missiles Show He Can Hit U.S. Back,” Bloomberg, January 12, 2022, https://www.bloomberg.com/news/articles/2022-01-12/kim-jong-un-s-new-hypersonic-missiles-show-he-can-hit-u-s-back).19 Richard Hallion, “The History of Hypersonics: or, ‘Back to the Future—Again and Again’,” American Institute of Aeronautics and Astronautics, AIAA-2005-329 (2005), 43rd AIAA Aerospace Sciences Meeting and Exhibit, 10–13 January 2005, Reno, NV, https://doi.org/10.2514/6.2005-329.20 Woolf, Conventional Prompt Global Strike.21 Acton, “Hypersonic Boost-Glide Weapons.”22 “An Historical Overview of Waverider Evolution,” Staar Research, https://www.gbnet.net/orgs/staar/wavehist.html.23 Research is being done on BGVs designed to optimize lift at more than one velocity; see, e.g., Zhen-tao Zhao, Wei Huang, Li Yan, Yan-guang Yang, “Overview of Wide-speed Range Waveriders,” Progress in Aerospace Sciences (2020) 113: 1–14, https://doi.org/10.1016/j.paerosci.2020.100606.24 Acton, “Hypersonic Boost-Glide Weapons.” Plans called for the HTV-2 to have L/D of 3.5 to 4 and the HTV-3 to have L/D of 4 to 5. The program was terminated before HTV-3 was produced.25 Woolf, Conventional Prompt Global Strike.26 Kenneth W. lliff and Mary F. Shafer, “A Comparison of Hypersonic Flight and Prediction Results,” American Institute of Aeronautics and Astronautics, AIAA-93-0311 (1993), 31st Aerospace Sciences Meeting and Exhibit, 11–14 January 1993, Reno, NV, https://doi.org/10.2514/6.1993-311.27 Woolf, Conventional Prompt Global Strike, 17.28 “Advanced Hypersonic Weapon,” Army Technology, April 10, 2012, https://www.army-technology.com/projects/advanced-hypersonic-weapon-ahw/ The Army reportedly tested a “downscaled version” in October 2017 (Sydney J. Freedberg, Jr., “Army Warhead Is Key to Joint Hypersonics,” Breaking Defense, August 22, 2018, https://breakingdefense.com/2018/08/army-warhead-is-key-to-joint-hypersonics/).29 Acton, “Hypersonic Boost-Glide Weapons.”30 Joseph Trevithick, “USAF, Army, and Navy Join Forces to Field America’s First Operational Hypersonic Weapon,” The Drive, October 11, 2018, https://www.thedrive.com/the-war-zone/24181/usaf-army-and-navy-join-forces-to-field-americas-first-operational-hypersonic-weapon.31 John A. Tirpak, “Air Force Cancels HCSW Hypersonic Missile in Favor of ARRW,” Air Force Magazine, February 10, 2020, https://www.airforcemag.com/air-force-cancels-hcsw-hypersonic-missile-in-favor-of-arrw/.32 CBO, “U.S. Hypersonic Weapons.”33 Yi Feng, Shenshen Liu, Wei Tang, Yewei Gui, “Aerodynamic Configuration Design and Optimization for Hypersonic Vehicles, American Institute of Aeronautics and Astronautics (2017), 21st AIAA International Space Planes and Hypersonics Technologies Conference, 6–9 March 2017, Xiamen, China, https://doi.org/10.2514/6.2017-2173; The analysis in Appendix G of National Research Council, U.S. Conventional Prompt Global Strike, 206–215, assumes L/D = 2.2 for its calculations.34 Joseph Trevithick, “The Army and Navy Have Conducted the First Joint Test of Their New Hypersonic Weapon,” The Drive, March 20, 2020, https://www.thedrive.com/the-war-zone/32667/the-army-and-navy-have-conducted-the-first-joint-test-of-their-new-hypersonic-weapon, Caleb Larson, “This U.S. Missile Can Kill Any Target on the Planet (In Less Than an Hour),” National Interest, June 23, 2020, https://nationalinterest.org/blog/buzz/us-missile-can-kill-any-target-planet-less-hour-163303.35 Sayler, Hypersonic Weapons.36 John A. Tirpak, “Roper: The ARRW Hypersonic Missile Better Option for USAF,” Air Force Magazine, March 2, 2020, https://www.airforcemag.com/arrw-beat-hcsw-because-its-smaller-better-for-usaf/.37 Stephen Losey, “US Air Force drops Lockheed hypersonic missile after failed tests,” Defense News, March 30, 2023, https://www.defensenews.com/air/2023/03/30/us-air-force-drops-lockheed-hypersonic-missile-after-failed-tests/.38 Guy Norris, “High-Speed Strike Weapon to Build on X-51 Flight,” Aviation Week & Space Technology, May 20, 2013, https://web.archive.org/web/20140104023933/http://www.aviationweek.com/Article/PrintArticle.aspx?id=/article-xml/AW_05_20_2013_p24-579062.xml&p=1&printView=true.39 “X-51A Waverider,” U.S. Air Force Factsheet, May 3, 2013, https://web.archive.org/web/20130619105330/http:/www.af.mil/information/factsheets/factsheet.asp?fsID=17986; “Hyper-X Program,” NASA Factsheet, February 28, 2014, https://www.nasa.gov/centers/armstrong/news/FactSheets/FS-040-DFRC.html.40 Kristen N. Roberts, Analysis and Design of a Hypersonic Scramjet Engine with a Starting Mach Number of 4.00, Master’s thesis in Aerospace Engineering, University of Texas at Arlington, 2008, http://hdl.handle.net/10106/1073.41 Sydney J. Freedberg, Jr., “Hypersonics: DoD Wants ‘Hundreds of Weapons’ ASAP,” Breaking Defense, April 24, 2020, https://breakingdefense.com/2020/04/hypersonics-dod-wants-hundreds-of-weapons-asap/.42 Sayler, Hypersonic Weapons.43 “Kh-47M2 Kinzhal,” Missile Threat, 19 March 2022, https://missilethreat.csis.org/missile/kinzhal/#easy-footnote-bottom-10-3801. The Kinzhal mass is estimated as 3,800 kg (Vladimir Karnozov, “Putin Unveils Kinzhal Hypersonic Missile,” AIN Online, March 2, 2018, https://www.ainonline.com/aviation-news/defense/2018-03-02/putin-unveils-kinzhal-hypersonic-missile).44 Franz-Stefan Gady, “China Tests New Weapon Capable of Breaching US Missile Defense Systems,” The Diplomat, April 28, 2016, https://thediplomat.com/2016/04/china-tests-new-weapon-capable-of-breaching-u-s-missile-defense-systems/; Sayler, “Hypersonic Weapons.”45 Mike Yeo, “China unveils drones, missiles and hypersonic glide vehicle at military parade, Defense News, October 1, 2019, https://www.defensenews.com/global/asia-pacific/2019/10/01/china-unveils-drones-missiles-and-hypersonic-glide-vehicle-at-military-parade/.46 Zhao Lei, “Superfast aircraft test a ‘success’,” China Daily, August 6, 2018, http://usa.chinadaily.com.cn/a/201808/06/WS5b6787b4a3100d951b8c8ae6.html.47 Sayler, Hypersonic Weapons.48 These values vary slowly with L/D and β. For L/D = 6, they would be 34 km at Mach 5 and 44 km at Mach 10.49 Thomas Newdick, “This Is Our First View of Russia’s New S-500 Air Defense System In Action,” The Drive, July 20, 2021, https://www.thedrive.com/the-war-zone/41627/this-is-our-first-view-of-russias-new-s-500-air-defense-system-in-action.50 Andrew M. Sessler, John M. Cornwall, Bob Dietz, Steve Fetter, Sherman Frankel, Richard L. Garwin, Kurt Gottfried, Lisbeth Gronlund, George N. Lewis, Theodore A. Postol, et al., Countermeasures: The Operational Effectiveness of the Planned US National Missile Defense System (Cambridge, MA: Union of Concerned Scientists and MIT Security Studies Program, April 2000), 28, https://www.ucsusa.org/sites/default/files/2019-09/countermeasures.pdf.51 Ibid.52 Theodore A. Postol and George N. Lewis, “The Illusion of Missile Defense: Why THAAD Will Not Protect South Korea,” Global Asia 11, no. 3 (2016): 80–5, https://www.globalasia.org/data/file/articles/78a89c3da89bc3fae2f1e8249871c58e.pdf.53 “Theater High Altitude Area Defense (THAAD),” Aerojet Rocketdyne, March 13, 2019, https://rocket.com/defense/missile-defense/thaad.54 For a discussion of acceleration saturation effects for various types of guidance, with and without lags, see Paul Zarchan, Tactical and Strategic Missile Guidance - An Introduction, 7th ed. (Reston, VA: American Institute of Aeronautics and Astronautics, Inc., 2019), Vol.1: 157–60, 206–11, 216–23, 254; Vol. 2: 165–7, 552–3. See also N. F. Palumbo, R. A. Blauwkamp, and J. M. Lloyd, “Modern Homing Missile Guidance Theory and Techniques,” Johns Hopkins APL Technical Digest, 29 (2010): 42–59, https://www.jhuapl.edu/Content/techdigest/pdf/V29-N01/29-01-Palumbo_Homing.pdf.55 Zarchan, Tactical and Strategic Missile Guidance, 1: 152; 2: 147, 307, 439.56 Angle-of-attack can be created using fins or small thrusters on the missile or interceptor body.57 Zarchan, Tactical and Strategic Missile Guidance, 1: 157.58 Lockheed Martin, “PAC-3 MSE Overview,” January 5, 2022, https://www.lockheedmartin.com/content/dam/lockheed-martin/mfc/documents/pac-3/2022-01-05_LM_PAC-3_MSE_Overview.pdf.59 Terry H. Phillips, “A Common Aero Vehicle (CAV) Model, Description, and Employment Guide,” Schafer Corporation (January 27, 2003).60 Jon Hawkes “Patriot games: Raytheon’s Air-Defence System Continues to Proliferate,” Jane’s International Defence Review 52 (2019): 1–6, https://web.archive.org/web/20190601000000; https://www.raytheon.com/sites/default/files/2018-12/Raytheon_article%20reprint_IDR%201901.pdf.61 Office of the Director, Operational Test and Evaluation, “DOT&E FY 2016 Annual Report: Patriot Advanced Capability-3 (PAC-3),” December 2016, 175–7, https://www.dote.osd.mil/Portals/97/pub/reports/FY2016/army/2016patriot.pdf?ver=2019-08-22-105407-280; Isaac Maw, “Patriot Missile to Receive $133M in Upgrades Over Next Five Years,” engineering.com, July 9, 2018, https://www.engineering.com/story/patriot-missile-to-receive-133m-in-upgrades-over-next-five-years.62 Patrick O’Reilly, Ed Waters, “The Patriot PAC-3 Missile Program—An Affordable Integration Approach,” https://apps.dtic.mil/sti/pdfs/ADA319957.pdf; Missile Defense Project, "Patriot," Missile Threat, Center for Strategic and International Studies, June 14, 2018, https://missilethreat.csis.org/system/patriot/ (last modified March 24, 2022).63 Missile Defense Advocacy Alliance (MDAA), “Patriot Advanced Capability-3 Missile,” August 18, 2020, https://missiledefenseadvocacy.org/defense-systems/patriot-advanced-capability-3-missile/. This speed is consistent with a recent article giving a maximum speed of existing interceptors as “about 1.7 km/s” (“Japan set to develop railguns to counter hypersonic missiles,” NIKKEI Asia, January 4, 2022, https://asia.nikkei.com/Politics/Japan-set-to-develop-railguns-to-counter-hypersonic-missiles).64 North Atlantic Treaty Organization (NATO), “Patriot,” Fact Sheet, December 2012, https://www.nato.int/nato_static/assets/pdf/pdf_2012_12/20121204_121204-factsheet-patriot-en.pdf; MDAA, “Patriot.”65 Leland H. Jorgensen, “Prediction of Static Aerodynamic Characteristics for Space-Shuttle-Like and Other Bodies at Angles of Attack from 0o to 180o,” NASA Report TN D-6996 (1973), https://ntrs.nasa.gov/api/citations/19730006261/downloads/19730006261.pdf.66 Jorgensen, “Prediction of Static Aerodynamic Characteristics.”67 Leland H. Jorgensen, “A Method for Estimating Static Aerodynamic Characteristics for Slender Bodies of Circular and Noncircular Cross Sections,” NASA Report TN 0-7228 (1973), https://ntrs.nasa.gov/api/citations/19730012271/downloads/19730012271.pdf.68 Acton, “Hypersonic Boost-Glide Weapons;” “X-41 CAV (USAF/DARPA Falcon Program),” Directory of U.S. Military Rockets and Missiles, Appendix 4: Undesignated Vehicles (2009), http://www.designation-systems.net/dusrm/app4/x-41.html; this is similar to the result in Wright, “Research Note to Hypersonic Boost-Glide Weapons.”69 Phillips, “A Common Aero Vehicle.”70 Qinglin Niu, Zhichao Yuan, Biao Chen, and Shikui Dong, “Infrared Radiation Characteristics of a Hypersonic Vehicle Under Time-Varying Angles of Attack,” Chinese Journal of Aeronautics 32 (2019): 867, https://doi.org/10.1016/j.cja.2019.01.003.71 Using values for the CAV-L model gives somewhat lower lift but does not significantly change the results.72 Candler and Leyva, “Computational Fluid Dynamics Analysis.”73 U.S. Government Accountability Office, “Hypersonic Weapons: DOD Should Clarify Roles and Responsibilities to Ensure Coordination across Development Efforts,” GAO-21-378 (March 22, 2021): 13, https://www.gao.gov/products/gao-21-378; Steve Trimble, “Document Likely Shows SM-6 Hypersonic Speed, Anti-Surface Role,” Aviation Week, March 12, 2020, https://aviationweek.com/defense-space/missile-defense-weapons/document-likely-shows-sm-6-hypersonic-speed-anti-surface-role; Tyler Rogoway, “Navy To Supersize Its Ultra Versatile SM-6 Missile For Even Longer Range And Higher Speed,” The Drive, March 20, 2019, https://www.thedrive.com/the-war-zone/27068/navy-to-supersize-its-ultra-versatile-sm-6-missile-for-even-longer-range-and-higher-speed.74 Tracy and Wright, “Modelling the Performance.”75 David Wright, Laura Grego, and Lisbeth Gronlund, The Physics of Space Security (Cambridge, MA: American Academy of Arts and Sciences, 2005), https://www.ucsusa.org/resources/physics-space-security. This equation assumes a single stage booster.76 U.S. Air Force, “AGM-86B/C/D Missiles,” Factsheet (August 2019), https://www.af.mil/About-Us/Fact-Sheets/Display/Article/104612/agm-86bcd-missiles/; U.S. Air Force, “AGM-129A Advanced Cruise Missile, Factsheet (n.d.), https://www.af.mil/About-Us/Fact-Sheets/Display/Article/104543/agm-129a-advanced-cruise-missile/; “AGM-158 JASSM,” Airforce Technology, July 5, 2013, https://www.airforce-technology.com/projects/agm-158-jassm-standoff-missile/; Sydney J. Freeberg, “Navy Warships Get New Heavy Missile: 2,500-Lb LRASM,” Breaking Defense, July 26, 2017, https://breakingdefense.com/2017/07/navy-warships-get-new-heavy-missile-2500-lb-lrasm/.77 Steve Trimble, “More ARRW Details Emerge as Congress, White House Add New Hurdles,” Aviation Week and Space Technology, July 14, 2021, https://aviationweek.com/defense-space/missile-defense-weapons/more-arrw-details-emerge-congress-white-house-add-new-hurdles.78 U.S. Air Force, “B-52H Stratofortress,” Factsheet (June 2019), https://www.af.mil/About-Us/Fact-Sheets/Display/Article/104465/b-52h-stratofortress/; U.S. Air Force, “B-1B Lancer,” Factsheet (September 2016), https://www.af.mil/About-Us/Fact-Sheets/Display/Article/104500/b-1b-lancer/; John A. Tirpak, “AFGSC Eyes Hypersonic Weapons for B-1, Conventional LRSO,” Air Force Magazine, April 7, 2020, https://www.airforcemag.com/afgsc-eyes-hypersonic-weapons-for-b-1-conventional-lrso/ reports the B1 may be able to carry up to 31 ARRWs, which would appear to give a total mass of 60,000–7,000 kg.79 “X-41 CAV (USAF/DARPA Falcon Program),” Directory of U.S. Military Rockets and Missiles, Appendix 4: Undesignated Vehicles (2009), http://www.designation-systems.net/dusrm/app4/x-41.html; Wright, “Research Note to Hypersonic Boost-Glide Weapons.”80 Woolf, Conventional Prompt Global Strike, and National Research Council, U.S. Conventional Prompt Global Strike.81 See Table 4.1 in National Research Council, U.S. Conventional Prompt Global Strike, 102–3.82 S. Fetter, “A Ballistic Missile Primer” (1990), https://fetter.it-prod-webhosting.aws.umd.edu/sites/default/files/fetter/files/1990-MissilePrimer.pdf. Note that we define the factor f differently than this reference.83 This value is somewhat lower than that of modern strategic reentry vehicles, since the MaRV is assumed to have fins and a nonzero angle-of-attack during reentry, although it need needs to generate less lift force during dive than a BGV, which dives from horizontal flight. At any point, the velocity angle is measured with respect to the local horizontal.84 Assuming β = 7,500 kg/m2 with L/D = 2.6 during glide and L/D = −1 to −2 during dive gives, for the Mach 5 case, 28.3 km altitude at the end of glide at and a dive range and time of 70 km and 62 s; for the Mach 9 case, the altitude at the end of glide is 36.4 km and the dive range and time are 143 km and 65 s.85 Acton, “Hypersonic Boost-Glide Weapons.”86 National Research Council, U.S. Conventional Prompt Global Strike, Appendix G; Acton, “Hypersonic Boost-Glide Weapons.”87 Daniel Patrascu, “F-22 Raptor Pulls High Gs, Looks Cool Doing It,” Autoevolution, April 24, 2022, https://www.autoevolution.com/news/f-22-raptor-pulls-high-gs-looks-cool-doing-it-186903.html; U.S. Air Force, “F-16 Fighting Falcon,” Factsheet (September 2021), https://www.af.mil/About-Us/Fact-Sheets/Display/Article/104505/f-16-fighting-falcon/, states the F-16 can withstand nine g’s with a full load of fuel, but the body is larger than that of a BGV. National Research Council, U.S. Conventional Prompt Global Strike notes that new technologies can “withstand the effects of maneuvers up to 40 g’s.”88 This insensitivity is in part because a longer ballistic phase at a given burnout speed will decrease the time the vehicle spends in glide and thus the duration of drag but will also result in a larger reentry angle and therefore require a sharper pull-up maneuver. This gives a larger velocity loss during pull-up, mitigating the effects of the shorter glide phase.89 The MaRV typically requires a smaller L/D to put it on a steep dive since it begins reentry at a larger angle than the BGV. It could be designed to create higher lift if the goal was to increase the amount of maneuvering it could achieve during reentry.90 Joseph Trivithick, “Army Delivers First Canisters to Its New Hypersonic Missile Battery but Won’t Say Where It’s Based,” The Warzone, May 19, 2021, https://www.thedrive.com/the-war-zone/39851/army-delivers-first-canisters-to-its-new-hypersonic-missile-battery-but-wont-say-where-its-based.91 See for example, National Academies of Sciences, Engineering, and Medicine, High-Speed, Maneuvering Weapons: Unclassified Summary (Washington, DC: The National Academies Press, 2016), https://doi.org/10.17226/23667; Center for Strategic and International Studies, “Complex Air Defense: Countering the Hypersonic Missile Threat,” Transcript, February 9, 2022, https://www.csis.org/analysis/complex-air-defense-countering-hypersonic-missile-threat-0; Missile Defense Agency, “MDA Hypersonic Concept.”92 Ivan Oelrich, “Cool Your Jets: Some Perspective on to Hyping of Hypersonic Weapons,” Bulletin of the Atomic Scientists 76 (2020): 37–45, https://doi.org/10.1080/00963402.2019.1701283.93 Zarchan, Tactical and Strategic Missile Guidance, 1: 272. This model works well for altitudes between 10 and 50 km.94 Assuming instantaneous changes in glide altitude is a simplification that ignores the complicated dynamics of these maneuvers and the additional drag they would create. We assume these maneuvers are short compared to the time the vehicle spends gliding at the lower altitude, and that our estimate of the increased drag will be a reasonable lower bound, which shows the significant range reduction that can result from such a turn.95 Since the vehicle is assumed to have enough vertical force to glide, this requires cosθ ≠ 0.Additional informationFundingDW was supported in part by the Laboratory of Nuclear Security and Policy at MIT and the Program on Science and Global Security at Princeton University.