China and Russia have developed cruise missiles that theoretically can travel up to nine times the speed of sound (Mach 9) while at a low altitude, that are almost impossible to detect and stop, and that can do enormous damage without the use of explosives or nuclear warheads.

In 2018, Russian President Vladimir Putin claimed that Russia has a hypersonic glide vehicle (HGV) in its arsenal, the Avangard system, which he called “practically invulnerable” to Western air defenses.

In a recent talk sponsored by ORION, an amateur science and astronomy club based in Oak Ridge, Douglas J. Elder, an expert in hypersonic aerodynamics, said the U.S. Department of Defense “is fast tracking Russian and Chinese hypersonic missile development to improve U.S. defenses against such threats. DARPA (Defense Advanced Research Projects Agency) and the U.S. Air Force are emphasizing their own concept development of hypersonic weapons to counter the Chinese and Russian threats.”

These government agencies, Elder said, are working on two concepts with Lockheed Martin and the Raytheon Technologies-Northrup Grumman partnership.

Elder, who worked for Rockwell International when it was building the space shuttle first launched in 1981, said Russia had already destroyed buildings in Ukraine with its hypersonic Kinzhal missiles. He suggested that one concern is that China, in its effort to control the South China Sea, might launch a DZ-ZF hypersonic weapon from an island to destroy a U.S. Navy aircraft carrier in the vicinity.

“We don’t need to push the panic button,” Elder said, after acknowledging that news about Russian and Chinese hypersonic missiles hit the Defense Department “like a shock wave.” While the United States has hypersonic intercontinental ballistic missiles that soar above the atmosphere and fire multiple reentry vehicles toward the earth’s surface, it lacks new hypersonic cruise missiles or HGVs that head for their targets at a lower level within earth’s atmosphere, not from a high altitude.

He noted that the development and deployment of hypersonic cruise missiles and hypersonic glide vehicles face two problems: high cost and heating challenges from traveling at more than five times the speed of sound (Mach 5) through the earth’s atmosphere.

The Pentagon estimates the cost of a single hypersonic weapon can range from $40 million to more than $100 million.

Elder talked about how the space shuttle, which had been traveling at 25 times the speed of sound, experienced temperatures around 3,000 degrees Fahrenheit as it re-entered the earth’s atmosphere. It also compressed the air ahead of it while experiencing friction and the retarding force of drag.

The nose tip of high-performance missiles and rockets, he said, is usually made of carbon-carbon materials designed to absorb large quantities of heat without increasing the vehicle’s temperature very much. These materials, which consist of carbon matrices reinforced with high-strength carbon fibers, “ablate,” or vaporize, when entering the atmosphere, protecting the reentry vehicles from heat damage. Even tungsten nose tips on spacecraft turn into gas upon reentry.

On May 10, according to CNN, a Russian jet bomber fired three Kinzhal hypersonic missiles — projectiles flying at least five times the speed of sound — at the southern Ukrainian port city of Odesa, helping to destroy hotels, a shopping mall and other civilian targets.

Russia, a CNN reporter remarked, claimed it had used this missile to destroy an underground warehouse storing missiles and aviation ammunition in Ukraine in mid-March, the first known use of a hypersonic weapon in combat.

But the Kinzhal missile, CNN reported, is not a hypersonic glide vehicle, a highly maneuverable payload that can theoretically fly at hypersonic speed while altering its direction and altitude to evade radar detection. Theoretically, the HGV, which Russia claims to have, will be nearly impossible for missile defenses to intercept — that is, prevent this weapon from destroying its intended target.

According to weapons experts quoted on the U.S. website Military.com, “the air pressure in front of the (hypersonic) weapon forms a plasma cloud as it moves, absorbing radio waves.”

As a result, new hypersonic weapons are extremely difficult to detect on radar systems. Because they are zeroing in on a target from a low altitude at very high speed, it is theoretically too late to intercept them.

These weapons can be launched from airplanes, ships and submarines. Many of these missiles will not have explosives or warheads because the projectile’s high speed, mass and kinetic energy are expected to inflict maximum damage.

Noting that the Kinzal missiles traveled a short distance from Russia into neighboring Ukraine, Elder said he and his colleagues have done experiments shooting small hypersonic missiles into nearby Army tanks.

“At hypersonic speed, a tungsten projectile can penetrate the armor like it’s butter,” he noted. “As the projectile penetrates the armor, the tungsten penetrator and armor turn to liquid in a very small region. When we fired a 12-inch-long projectile at 2.5 kilometers per second into the side of a tank, we observed that the interior and three simulated crew members were destroyed.”

The U.S. Navy, he added, is investigating the use of electromagnetic railguns (EMRG) aboard long ships to launch a scramjet, which could then fire a hypersonic cruise missile for a long distance. The EMRG uses an electric current to create a magnetic field that imparts a much higher kinetic energy to an object made of conductive materials than can be achieved using conventional propellants, say, in a rocket.

A scramjet is a supersonic-combustion ramjet, a type of jet engine in which the air drawn in for combustion is compressed solely by the aircraft’s forward motion. A scramjet, which has no rotating parts like a conventional jet engine, operates by burning hydrogen fuel in a stream of supersonic air compressed by the aircraft’s forward speed. The ignited hydrogen gas expands in the nozzle to propel the vehicle to supersonic velocities as high as Mach 6. Scramjets launched by EMRGs may someday be used to put satellites into orbit or to send a manned spacecraft to the moon.

“I don’t think that scramjets have yet been designed to go long distances,” Elder said. “Now the U.S. Air Force drops the scramjet from an airplane. The scramjet needs a system like the EMRG to get it up to the desired high velocity. At a certain altitude the faster the scramjet goes, the hotter it gets. If the material on the nose tip vaporizes too much, you either slow down the vehicle or go to another altitude. Heat can be bad for the projectile.”

Elder said that DARPA and the Defense Department have established the Hypersonic Air-Breathing Weapons (HAWC) program that will conduct flight demonstrations of hypersonic systems of different designs and configurations to determine if they are feasible, efficient and affordable as air vehicles and if they can survive the thermal stresses of a high-temperature cruise. HAWC will also examine whether hydrocarbon scramjet-powered propulsion can enable a sustained hypersonic cruise and whether affordable manufacturing techniques can be developed.

Now writing a book for undergraduate students on building model rockets, Elder worked as program manager and chief engineer for NASA, Lockheed Missile & Space, McDonnell-Douglas, Rockwell International, Kaman Sciences and Boeing.

A Russian Air Force MiG-31K jet carries a high-precision, hypersonic, aero-ballistic Kinzhal missile during the Victory Day military parade in Moscow, Russia, on May 9, 2018. This missile has been fired on targets in Ukraine this year.

Lockheed Martin’s hypersonic Air-launched Rapid Response Weapon (ARRW) is intended to travel 500 miles in just 10 minutes once fired from a B-52 bomber. (Mike Tsukamoto/staff; Lockheed Martin; USAF)

An artist’s rendering of a hypersonic glide vehicle (left) and a scramjet-powered hypersonic cruise missile.

Schematic showing a ballistic missile, hypersonic glide vehicle and scramjet-powered hypersonic cruise missile. The latter two fly mainly at low altitudes within the earth’s atmosphere.