Imagine a blimp that works like a submarine.

To go up, the pilot releases compressed helium, filling the hull and making the craft lighter than air. To go down, the skipper takes on air as ballast, making the ship heavy enough to land.

Airships may sound like a pipe dream, a fanciful vision from a bygone era.

But a real-life submarine of the sky is taking shape right now at one of the World War II-era blimp hangars in Tustin.

The Aeroscraft may be a forerunner of hybrid airships that will fill the skies in the future. Developers see the crafts ferrying supplies to troops on the front lines, aiding refugees in disaster zones and shuttling cargo from ship to shore at a fraction of the cost of moving freight today.

These airships can go where there are no roads or airfields, landing and taking off vertically.

“We’re building this to revolutionize cargo transportation,” said Fred Edworthy, vice president of Worldwide Aeros Corp., the Montebello airship firm behind Aeroscraft. “This is a new dimension of flight.”

The Aeroscraft project – partially funded by about $35 million in Pentagon and NASA contracts – is part of a wider effort to develop the next generation of airships for military and private use. Southern California is a major hub of this new industry.

“Southern California is the Silicon Valley of aerospace development,” said Igor Pasternak, who founded Worldwide Aeros in Ukraine, then moved the firm to California in 1994.

One of his competitors is Lockheed Martin, which has been developing a family of cargo airships at its Skunk Works facility in Palmdale for more than six years. The Sky Tug is a hybrid vehicle that will be able to carry 20 tons of cargo, using both helium and its aerodynamic design to create lift. Unlike the Tustin-built model, the Sky Tug can’t take off or land without ground facilities.

Another major player is Northrop Grumman, which is behind the U.S. Army’s Long Endurance Multi-Intelligence Vehicle. The hybrid airship is being developed with help from Northrop’s Southern California facilities. The ship will provide long-term surveillance, staying airborne for up to 16 days.

The U.S. military is behind the push for increased use of airships, with efforts dating to 1978, according to a U.S. Government Accountability Office report released last month.

The Defense Department has invested $7 billion over the past six years in airship research, about 80 percent of that in “aerostats” – tethered balloons or blimps – used for surveillance in Afghanistan and on the Mexican border, the GAO report said.

Several of the programs, however, have been plagued by cost overruns, accidents, delays or technical problems resulting in program reductions or cancellations, according to the GAO. Northrop’s airship is at least 10 months behind schedule, raising questions about whether it will be available for deployment in Afghanistan, the report said.

This new generation of airship remains a fledgling industry, with most commercial production still in the early stages.

The resurgence seems like a throwback to an era when zeppelin’s ferried passengers across the Atlantic and Navy blimps scoured the seas for enemy subs.

Pasternak, who has been building traditional blimps for decades, decided about eight years ago that existing technology made airships impractical because they are unable to carry cargo. That led to his firm’s involvement in designing modern airships and, ultimately, to developing a new “buoyancy management system” for the Aeroscraft.

“It’s this buoyancy management system that sets us apart,” Edworthy said. “It’s a little bit like a submarine where you’re using water for buoyancy. Here, you’re using air.”

The system works like this: Compressed helium is released from nine vessels on the craft, filling the hull and making it lighter than air.

To descend, the helium is pumped back into the vessels, creating a vacuum that draws air into cylindrical tubes inside the craft. That increases the ship’s weight so it can land like a helicopter.

The airship, being built at the former Tustin Marine air base, is 254 feet long, 97 feet wide and 47 feet high. Unlike the traditional blimp, which gets its shape from the gas that fills it, the Aeroscraft has a skeleton made from strong, but ultralight, aluminum and carbon fiber materials.

It has three propellers – one on each side and one aft – to help stabilize the craft while hovering and during takeoffs and landings. The side-mounted props can tilt upward for takeoff and landing stability, then to the front for forward motion.

The Aeroscraft is expected to have a range of nearly 3,600 miles and a top speed of almost 140 mph.

But the prototype is just a baby. Edworthy said the production model will be 500 feet long and 160 feet wide and have the capacity to carry 66 tons of cargo – roughly three times that of C-130 cargo planes and almost as much as the top payload of a C-17. But it will use about one-third the fuel.

Ultimately, the developer wants to build an airship that can haul 500 tons of cargo, but that project won’t begin for another 10 to 15 years, Pasternak said.

Since the Aeroscraft can take off and land vertically, it can go almost anywhere – either to a combat zone or into a disaster zone, with a payload far surpassing that of helicopters.

As envisioned, the craft will fly out to sea, unload cargo ships outside the ports of Los Angeles and Long Beach and ferry goods to the Inland Empire, bypassing clogged roadways.

“You don’t need any ground infrastructure whatsoever,” said Munir Jojo-Verge, the engineer who designed steering and other control systems for the craft. “You can use it where trucks can’t go. If you have issues with the roads, you can get in.”

Contact the writer: 714-796-7734 or jcollins@ocregister.com