Ukraine: The missiles used in the big attack are a surprise

Russia's biggest airstrike in weeks struck targets across Ukraine on Thursday, using a

of weapons. 

The Ukrainian Air Force said among them were six of Russia's air-launched hypersonic missiles, known as

, or Daggers - the most used in a single wave since the war began a year ago.

Here are the main questions raised by the use of the new missiles.

A Russian MiG-31 fighter carrying a Kinzhal missile takes off from the Hemeimeem airbase in Syria on June 25, 2021. (Russian Defense Ministry Press Service via AP, File)

First of all, what are hypersonic missiles?

Hypersonic missiles are long-range, highly maneuverable munitions capable of reaching speeds of at least

- five times the speed of sound, or more than 1 mile per second.

That speed renders traditional air defense systems virtually

, because by the time they are detected by ground-based radar, they are almost on target.

China and the United States

are competing to develop and deploy hypersonic missiles.

Other countries are also working on this technology:

.

How does Kinzhal work?

The typical hypersonic vehicle brings its warhead to the lower limit of space on top of a traditional long-range missile.

After separating, it uses gravity to gain enormous speed on its descent back to Earth.

The vehicle can be an unpowered

or a cruise missile that uses gravitational acceleration to ignite a special

engine that takes it hundreds of miles further.

The Kinzhal is a bit different.

It is a

of the Russian army's Iskander short-range ballistic missile, designed to be fired from truck-mounted launchers on the ground.

Launching the missile from a high-altitude warplane, rather than from the ground, leaves it with more fuel to reach higher speeds.

Aside from its ability to reach hypersonic speeds upon airdrop, the Kinzhal is believed to behave like a ground-launched Iskander, meaning it is capable of maneuvering to make it difficult to intercept.

Some Iskanders can also launch pre-impact

, designed to further confuse air defense radars.

The conventionally armed Iskanders are believed to be carrying around

What else is known about the Kinzhal?

Russia originally developed the Kinzhal to breach US missile defense systems and claims it reaches speeds of Mach 10 and above.

The Pentagon has said that it is launched by

Moscow first said it had deployed the Kinzhal to Ukraine nearly a year ago in an attack on an underground weapons depot, and has since regularly claimed responsibility for its use.

There is another hypersonic missile that Russia claims to have in its arsenal:

the

a cruise missile that can be launched from ships.

However, Russia has not reported carrying out test launches of the Zircon during exercises announced by President

in January, and it is not known to have ever been used in combat.

Why are the Kinzhals so worrying for Ukraine?

Ukraine

capable of shooting down the Kinzhals, according to Yuriy Ihnat, a spokesman for the Ukrainian air force.

And their use on Thursday significantly increased the proportion of Russian missiles hitting targets.

Of the 81 missiles fired by Russia overnight and in the morning, Ukraine stated that

, a higher proportion than usual.

Ukraine noted that Russia had also fired more ballistic missiles and fewer cruise missiles than usual, a possible factor in the increase in successful strikes.

What are the limitations of the Kinzhal?

Target coordinates are loaded into the missile's operating system prior to launch, and due to the enormous speed it achieves in flight, any small deviation—for example, a wing control surface moving too much or too little—can cause a

That may explain why a Kinzhal appears to have hit a car in kyiv on Thursday, rather than a more military-significant target.

And like any hypersonic missile, the Kinzhal's flight path reaches the highest regions of Earth's atmosphere before returning to Earth for finer maneuvering.

It can be detected by space sensors, although US defense officials say such systems are

against hypersonics.

Why would Russia use so much of its hypersonic arsenal in a single wave?

Ukraine's military intelligence agency has estimated that Russia had, before the barrage fired on Thursday, no more than

Ihnat said.

It is not clear why Russia decided to fire

, potentially more than a tenth of its total arsenal.

"For one reason or another, they needed a result" this time, Ihnat said.

But it is possible that Russia will be able to replenish the Kinzhals relatively easily.

Since the Kinzhal is simply a modified version of an already existing missile, it might be easier to produce than, say, creating more

, which have to be built from scratch.

Will the war change the use of Kinzhals?

Not necessarily, although Russia can produce more Kinzhals relatively quickly.

Although more Russian missiles than usual passed through on Thursday, the air war alone

.

By comparison, Russia causes much more destruction with the thousands of artillery shells it fires into the Ukraine.

And the ground war remains in a stalemate.

Many analysts say Russia's long-awaited spring offensive is already underway, but is having

because its troops and arsenals are so depleted.

c.2023 The New York Times Company

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