Hajile facts for kids

Hajile was a secret project developed by the British Admiralty during the final years of World War II. Its goal was to create a way to drop supplies and heavy equipment from airplanes without using parachutes. Instead, it used special retrorockets to slow down the items just before they hit the ground, making sure they landed safely.

Developing Hajile

The British Army needed a way to drop heavy gear and vehicles from planes flying at high speeds. They wanted the items to fall quickly to avoid being hit by enemy anti-aircraft guns. But, the items also needed to land without much damage and be ready to use right away.

Regular parachutes wouldn't work because they slowed things down too much, making them drift and easy targets. So, the team came up with a clever idea: put the supplies on a platform surrounded by cordite rockets. These rockets would fire at the very last moment to slow the platform down for a soft landing.

The project got its unusual name during an early test. As the rockets fired, a huge cloud of smoke and fire surrounded the equipment. An officer watching exclaimed, "Look at it! It's Elijah in reverse!" He was thinking of the biblical story where the prophet Elijah went to heaven in a "chariot of fire."

Testing the System

Early Trials

When testing began, some big problems quickly showed up. The hardest part was getting the rockets to fire at the exact right moment. If they fired too early, the platform would speed up again and crash. If they fired too late, they wouldn't slow down the load enough.

The solution they found was a "plumb-bob." This was a weighted line that dangled below the platform. When it touched the ground, it would trigger the rockets. However, they had to be very careful with the plumb-bob's weight. It needed to be heavy enough not to be blown back up by the strong winds during the fall. But it also had to be light enough to react instantly when it hit soft ground like grass.

The first tests were simple. They dropped a concrete block from a tall crane. In the first two tries, they didn't use enough rocket fuel. The concrete block crashed hard and dug itself deep into the ground. On the third try, they used too much fuel. This time, the block shot up several dozen feet into the air before crashing back down!

They then built a prototype for testing over water. Water was a good test surface because it was flat and smooth, and the rig might not get damaged. After figuring out the right plumb-bob weight, full-scale tests began. A large concrete block was attached to the Hajile platform and loaded into a Lancaster bomber.

After a few attempts where the device landed too far from shore, the bomber crew was told to aim as close to the testing facility as possible from about 2,000 ft (610 m) (610 meters) high. A team member, Gerald Pawle, later remembered what happened:

• The Hajile came screaming through the air.
• The people watching on the pier were amazed.
• Then, they realized it was going to hit their building directly!
• Everyone started running away as fast as they could.
• The concrete "bomb" landed right on the roof of the engineering shop.
• It smashed through a huge steel beam and destroyed a covered walkway.
• Luckily, no one was hurt, but the cooks nearby thought it was the end of the world!

Further tests showed that the first design with four rockets wasn't quite enough. Adding four more rockets around the platform helped a lot. With eight rockets, the block slowed down completely a few feet above the water. Instead of crashing, Hajile quietly sank below the surface.

Making it Better

The team tried to get jeeps to test Hajile over land. But it was hard to convince the Royal Navy to give them working vehicles to drop from 2,000 ft (610 m) (610 meters) with an experimental, possibly explosive, device. Eventually, the United States Navy provided two jeeps, and serious trials began.

The first jeep test was a big failure. Snow that day made the rocket fuses wet. The rockets didn't fire, and the whole setup crashed to the ground, only slightly slowed by a small pilot parachute. It hit the ground at about 40 ft/s (12 m/s) (12 meters per second), causing a lot of damage to the jeep.

Hajile was worked on for two more weeks before another test. This time, the rockets fired correctly. When the smoke cleared, the jeep was mostly in one piece. But it had landed upside-down, with the platform's rockets pointing to the sky!

More testing showed Hajile was very unreliable. Sometimes, rockets misfired, sending the platform spinning. Other times, the weight of the load was misjudged, and the platform shot back into the air before crashing down with enough force to break it apart.

One of the last times the rockets fired by accident was on the morning of the Normandy landings (D-Day). Hajile was on the ground with its crew around it. An electrician, who didn't know the device was "live" (turned on), started testing the wires. He accidentally connected the firing circuit. All eight rockets immediately fired! The platform shot forty feet into the air, then lurched sideways and crashed back to earth. Several crew members were injured, and one was blinded for several days.

What Happened Next

Testing of Hajile went on for so long that the device was still not working reliably when the war ended. Since there was no chance to use the project in action, it was put aside. The group that developed it, the DMWD, was closed down after the war, so Hajile was permanently shelved. Like many secret research projects, the details of Hajile were kept hidden for many years. Very few people showed interest once the documents about the project became public.

See also

• Retrorocket
• Soviet air drop technique similar to Hajile
• Curiosity descent stage