Why Hypersonics? Why Now?

With the recent push for hypersonics, and the associated “breakthroughs” in their development, one could be forgiven for thinking hypersonics is something new.  It isn’t.  The United States had boost-glide hypersonic aircraft in the mid-60s. The USAF made a conscious decision to NOT field hypersonic aircraft decades ago.  So why bring it back now? What is different about today’s world that makes hypersonics necessary?

The back-and-forth of offense and defense in airpower has been going on ever since the first airplane appeared over a battlefield. Initial air defenses were inadequate to deal with even the wood and fabric biplanes of the Great War. Caliber, range, rate, and fusing were all problems with anti-aircraft guns, and none of these problems were solved by war’s end. During the entirety of the war, the advantage lay with aircraft. Anti-Aircraft Artillery (AAA) made significant strides in the interwar years and during the Second World War. Inadequacies were overcome with ‘volume of fire.’  The fusing of shells to permit airbursts and a higher volume and rate of fire brought aircraft and AAA capabilities to near parity. Aircraft went higher and faster to outmaneuver the guns. Aircraft regained the advantage. Despite the guns receiving radar guidance and larger calibers, by 1960 the ‘high-fast flyer’ would never be truly at risk from ground-based AAA.[1]

Enter the Surface-to-Air Missile (SAM).  As the world watched the USAF deploy the B-52 Stratofortress and fly the U-2 and SR-71 with impunity, the Soviet Union needed a way to close the gap. The Soviets developed the S‑75 Dvina (NATO: SA-2 Guideline) specifically to defeat the high, fast flyer. The downing of Gary Powers’ U‑2 vindicated SAM technology and forced the USAF to radically change its battle doctrine.[2]

In the 1967 Arab-Israeli War, Egypt had 18 S‑75 battalions at 35 known sites. The Israelis went full offense with their airpower, employing low-altitude tactics, effectively nullifying the Egyptian defense. The Egyptians launched only 22 missiles, downing only 2 Israeli aircraft while losing 8 of their 18 battalions to Israeli air attacks.[3] This indicated that the advantage still lay with the offense, so long as the offense spent considerable energy and resources degrading SAMs. When the offense did not seriously degrade air defense, the advantage disappeared. This was clearly demonstrated in the classic confrontation of the early SAM era: LINEBACKER II (1972).  B-52 strikes did not actively engage air defenses, and Wild Weasel tactics were employed on a fairly limited basis. While the B‑52 and the S‑75 have proponents on both sides, evidence suggests this matchup was a draw.[4]

 

This pattern of ‘cat-and-mouse’ between offensive aircraft development and defensive anti-aircraft technology continues. Aircraft will gain the advantage with some critical capability, be it electronic warfare or stealth, and anti-air defenses respond in a similar way to combat those advantages.  The S‑300 missile system (NATO: SA-10 Grumble) introduced a rapid advance in SAM capability; and, by the fall of the Soviet Union, the digitally flown, precision equipped F-15s and F-16s had been nullified by the S‑300P series. When it comes to pure capability, 4th Generation aircraft, like the F-15, F-16, F-18, cannot defeat the S‑300.[5]

Stealth and Low Observable technologies shifted the balance back in the favor of the offense and increased the capability gap.  While S-300 upgrades and proliferation threatened to close the gap, advances in Electronic Warfare have slowed the rate of closure.  But they could not stop SAM technology from catching up and closing the gap yet again.  Today, stealth aircraft are facing missile and radar systems that are potentially capable of detecting and engaging them.[6] The balance between air and ground has returned.

Today’s comparison between the F-35 and S-400 could best be described as a draw.  Similarly, the latest version of the S-400 claims to be capable of detecting, tracking, and engaging cruise missiles, aircraft, and ballistic missiles simultaneously.  These capabilities are threatening to give an advantage to air defenses for the first time in history.  Since its inception, defense against the aircraft has lagged behind the aircraft itself.  It has caught up.

Question: What can Air Power do to regain the advantage?

Answer: Hypersonics.

There are two ways to defeat any defense in any domain: (1) defeat it directly with a weapon it cannot defend against, or (2) overwhelm it with more than it can handle. When the S-300 hit the battlefield, the US fielded a weapon to defeat it directly: The Cruise Missile (CM).  Early S-300 systems could marginally detect CMs some of the time.  When they were detectable, CMs were too fleeting to engage effectively.  CMs were small, with matching small radar cross-sections, resulting in less time for the CM to be engaged.  The S-300 simply couldn’t catch up. The CM was immune to this new air defense, i.e.,  the CM could directly overcome the S‑300, either to engage the air defense directly or bypass it and attack any number of targets. This is the main reason the United States never pursued supersonic or hypersonic CMs in the 1970s, 80s or 90s; it never needed to do so. The subsonic CM was good enough. The opposite was true of the Soviet’s decision to field a supersonic CM; their subsonic CM was not good enough to engage American Carrier Battle Groups.^[7] By the time radars and SAMs got better and faster, making them capable of detecting and destroying CMs, the US had a significant number of CMs and again did not need to pursue faster CMs.  It was easier to overwhelm the defense with more CMs than the S‑300 could handle.

Before the CM, the only viable method of destroying targets protected by S-300 systems was the ICBM.  It is not the nuclear warhead of the ICBM makes it so extraordinary, rather it is the speed of the ICBM.  ICBMs are hypersonic weapons and boast terminal speeds of 5-7 kilometers per second, equating to Mach 14 to Mach 20.  The defenses simply cannot catch it.

When it comes to hypersonic weapons, we already have them.  So why take the trouble to field a hypersonic cruise missile when we already have hypersonic ballistic missiles?

Modern Cruise Missiles trump Ballistic Missiles in accuracy by a factor of ten; they are cheaper by a factor of two, easier to operate and maintain, afford greater mobility and survivability, are less susceptible to counterforce strikes, and do not possess any ‘nuclear’ stigma.  The CM gave the United States nuclear and non-nuclear methods of defeating early S-300 systems easily.^[8]  The penetrating bomber could have accomplished the same thing; however, bombers are quantum leaps more expensive than CMs, with a much longer development time, an exponentially larger logistical tail, and risk to both bomber and crew.

Hypersonic CMs are necessary because the S-400 system got better in a hurry, while typical air-, submarine-, and surface-ship-launched CMs have reached their limit in effectiveness.  Today’s CMs (ALCM, Tomahawk, Harpoon, et al.) are no longer good enough. Their success is no longer guaranteed. Modern integrated air defenses are a direct challenge to the US concept of Global Strike.  The entirety of the United States, NATO, and allied 4th generation aircraft are at risk, representing the bulk of the Western air fleets, including all fielded CMs. Defense experts claim a 4th-Generation strike package could experience a 20‑30 percent attrition rate.^[9]  While 5th-Generation low-observable aircraft retain advantages against these systems, they are no longer totally immune and exist only in limited numbers.[10]

A hypersonic CM (HCM) is the solution to re-creating that capability gap and reinstituting the dominance of Global Strike.  HCMs could attack the newest S‑400 systems directly, with impunity.  Air defenses will not be able to engage this weapon with anything resembling consistency, whether the systems detect the missiles or not.^[11]  HCMs could re-assert the dominance of US forward presence in the face of continued A2/AD proliferation.  It is a not a lasting solution, however, it simply repeats previous solutions for the same problem.  The HCM will attack the SAM directly, until the day the SAM is good enough to engage the HCM, and then the HCM will overwhelm the system.

It is not a new idea; it is just a faster old idea.

 

 

NOTES:

[1] “Anti-Air Defenses,” Jane’s IHS 360, https://janes.ihs.com/artilleryairdefense/display/1494641

[2] This was the point where the US made a conscious decision to go low.

[3] “S-75 Family,” Jane’s IHS 360, https://janes.ihs.com/artilleryairdefense/display/1494641

[4] Marshall L. Michel, The Eleven Days of Christmas: America’s Last Vietnam Battle (San Francisco: Encounter Books, 2002), 11.

[5] While the claim is certainly debatable, this speaks only to the science.  The S-300 can detect, engage, and destroy all 4^th generation aircraft.  Tactics, such as electronic warfare and deception practices, make it harder for the S‑300 but when judged on pure physics, the S‑300 defeats the aircraft before the aircraft defeat the S-300.  See “S-300 Family,” Jane’s IHS 360, https://janes.ihs.com/artilleryairdefense/display/1494641.

[6] Jeremy Bender, “Russia and China are Developing Drones that could make Stealth Aircraft Obsolete,” Business Insider: Military & Defense, August 27, 2015.  http://www.businessinsider.com/russia-and-china-trying-to-make-stealth-obsolete-2015-8

[7] The Raduga P-270 Moskit (NATO: SS-N-22 Sunburn) had a top speed of Mach 3 and was fielded in the early 1970s.  Previous Soviet sub-sonic cruise missiles were inadequate to penetrate USN Carrier defenses.  This missile showed promise in evading F-14 screens and Standard Missile/CIWS engagements.  It was too fast for all those defenses.  The Soviets later scrapped supersonic CMs when they made a quality-vs-quantity decision.  They decided to go with a much larger number of cheap subsonic CMs over the more- expensive and harder-to-employ-and-maintain supersonic CMs. Reference Betts, Cruise Missiles, 360.

[8] David W. Kearn, “Facing the Missile Challenge: US Strategy and the Future of the INF Treaty,” RAND Corporation, 2012, 29-30.

[9] 4th generation strike package includes F-15s, F-16s F/A-18s, GR1s, Eurofighters, and CMs; McCarthy, “Anti-Access/Area-Denial.”

[10] 5th generation low observable aircraft are the stealth F-22A Raptor and B-2A Spirit.

[11] “Hypersonic Missiles: Speed is the New Stealth,” The Economist, June 1, 2013.  http://www.economist.com/news/technology-quarterly/21578522-hypersonic-weapons-building-vehicles-fly-five-times-speed-sound