[video] UKRJET In a field in central Ukraine, an experimental drone zoomed into the sky as engineers demonstrated its potential to intercept Russia’s jet-powered attack drones, which are tormenting the country.

The prototype, called a Zirka, reached a top speed of 280 miles an hour as its propellers whirred frantically. Not fast enough, the testers acknowledged.

“We still need to find a counter-jet solution,” said Lika Volovych, a manager at the Zirka’s manufacturer Noctis, as she watched it buzz high above. On the horizon, black smoke rose from a Russian drone strike on a nearby city.

Ukraine is rushing to find an answer to Russia’s new generation of jet-powered drones and cheap cruise missiles. Moscow is using them, together with ballistic and cruise missiles, to pummel Ukrainian cities in an aerial campaign that is threatening to change the balance of the war.

Disruptions to the SpaceX Starlink network could add an extra complication for some interceptors. On Wednesday, Ukraine said SpaceX had capped the speed of drone connections, disabling certain missions. Some high-speed interceptors that shoot down Russian jet drones were unable to function, Ukrainian President Volodymyr Zelensky said in Brussels on Friday. “It was very painful and very unpleasant,” he said. Still, most interceptors, including upcoming models, don’t use the network, their manufacturers said.

While Russia’s army is struggling on the front lines, Moscow is trying to bring Ukraine to its knees by battering its economy, energy infrastructure and civilian morale. For months, Ukraine has been desperately short of Patriot interceptors to shoot down ballistic missiles.

Now it is also short of defenses against jet-powered drones that can fly faster and higher than previous models. Ukraine has been caught flat-footed by their emergence, despite knowing that Russia had been working on them for over a year, and it is rushing to catch up.

Noctis has increased the Zirka’s speed by nearly 30%. That gives it a chance of downing the jet-powered Geran-4 drone, an advanced version of the Iranian Shahed, which can reach speeds of 310 mph but slows when maneuvering.

But it has little chance of catching the Geran-5 or the Banderol, a cheap cruise missile, which can reach speeds of 370 and 385 mph, respectively. Interceptors will also need better radars.

“They need very early detection, around 18 miles away, to get to the altitude and necessary target area,” said Kusti Salm, chief executive of Frankenburg Technologies, an Estonian company whose small, low-cost missiles are being sent to Ukraine.

In September, Russia launched 3,520 jet-powered Geran drones, only 54% of which were intercepted, according to Yurii Ihnat, a Ukrainian air-force spokesman. Russia also launched about 4,900 propeller-powered drones, roughly 90% of which were intercepted, according to Ihnat.

Russia launched 343 Banderols in September. Very few were intercepted, according to a person familiar with the matter.

If Ukraine can produce enough fast interceptors this fall, while European allies send other kinds of air-defense supplies, the country will have a difficult but manageable situation, said Tom Røseth, an associate professor at the Norwegian Defence University College in Oslo.

“Without this, the country faces a severe social situation, and mass strikes can affect its defense-industrial production, potentially changing the direction of the war this winter,” he said.

Ukraine might need to produce more than 1,000 high-speed interceptors a week to counter Russia’s rising production, industry executives say.

Ukraine’s domestic security service, known as the SBU, has released footage of a new jet-powered interceptor, which one defense analyst said could reach speeds of 435 mph.

Perennial Autonomy, a U.S.-based defense-technology company founded by former Google CEO Eric Schmidt, is testing a jet-powered interceptor drone with a top speed of 1,000 mph, a spokeswoman said. The company, which makes some of its drones in Ukraine, didn’t say when large-scale production would begin.

Ukrainian defense-tech company General Cherry said it plans to test a new jet-powered interceptor together with the military in early November, and hopes to produce hundreds a month by the end of this year.

A big hurdle is getting enough jet engines, said Eveline Buchatskiy, managing partner of D3, one of Ukraine’s largest defense investors. Few jet-engine makers in Europe and Ukraine can meet the demand, she said.

Ukraine currently produces up to 500 jet engines a month and can import a few thousand more, either directly or by purchasing engine components, according to one industry executive.

Downing a single Russian attack drone can require at least two interceptor drones. Ukraine also needs jet engines for its own missiles and strike drones.

Yevhenii Khmara, the country’s defense minister, told journalists Saturday that developing jet engines is a priority for Ukraine’s defense industry, with about 20 companies now working in the field.

One of them is Ukraine-based Culver Aerospace, which is building jet engines domestically for its own and other companies’ drones and missiles. The first ones with enough thrust to catch the new Gerans won’t be available until December.

Russia’s jet engines have mostly come from China so far—although it is now producing them at home too, according to Ukraine’s military intelligence service, HUR. Beijing has curbed the sale of such jet engines to Ukraine, according to Culver’s owner, Oleg Krot.

Ukraine needs to localize production so it isn’t reliant on other countries that can cut off supply, he said.

Meanwhile, Ukraine is relying on other ways of defending against jet drones, from electronic warfare to shoulder-launched missiles such as the U.S.-made Stinger.

Above all, it has been using jet fighters such as F-16s. With air-to-air missiles in short supply, Ukrainian pilots often use their cannons.

But a jet fighter can cost about $15,000 an hour to operate, without factoring in its missiles, ammunition and maintenance costs. Russia now launches its drones in smaller batches to keep the planes in the air all day and wear out their engines, said Valery Romanenko, a former Ukrainian air-defense officer and a researcher at Kyiv’s National Aviation University.

Large-calibre machine guns such as Brownings are also being fitted with computerized targeting to hit fast-moving objects. But the new Russian drones often fly at altitudes beyond machine-gun range, according to air-defense officers. “We fight back with what we have,” said Ihnat, the air-force spokesman.

Write to Alistair MacDonald at Alistair. Macdonald@wsj.com