WASHINGTON — When you send an e-mail message, it gets broken into tiny packets of information, tossed into the world’s data stream and reassembled at its destination.

Thanks to the world-standard Internet Protocol (IP), packets that somehow vanish en route are replaced so quickly you rarely notice the delay.

But every bit counts when you’re watching a firefight unfold in live video sent via satellite from a Predator unmanned aerial vehicle. Lose one packet, and you can lose your live feed — and possibly your soldiers as well.

That’s why the routers — the devices that handle packets — in the Pentagon’s next communications satellites will have to be the orbital equivalent of Federal Express: what to use when it absolutely, positively has to be delivered at the speed of light.

“Encrypted video over IP via satellite — that’s the most difficult thing to do,” said Brad Wurtz, the president and chief executive officer of Caspian Networks. “Normally, if you lost a packet, you’d resend the packet, but you can’t do that in live video in wartime conditions.”

Founded in 1999, Caspian invented routers that guarantee the arrival of an entire stream of data, not just individual packets. By keeping track of information streams, these flow-state routers can direct packets like a smart traffic cop, letting urgent ones through first while making sure the others don’t wander off.

The privately held San Jose, Calif.-based firm is still working to sell terrestrial network service providers on the benefits of flow-state routers. But the Air Force believes the idea may be key to the service’s Transformational Satellite Communications System (T-Sat), which is meant to deliver about two orders of magnitude more bandwidth than today’s Milstar constellation.

After T-Sat spacecraft start going up in 2013, it will provide the wireless links in the Pentagon’s Global Information Grid, the ber-network intended to connect every U.S. war fighter on the planet.

Funded by a two-year Air Force contract, Caspian is working with veteran payload builder Northrop Grumman to ready its products for space. The routers must be shielded from cosmic radiation, and their transistors redesigned to withstand the onslaught of atomic particles.

“With regular electronics, you get particles zinging through, which can cause shorts,” said Stuart Linsky, who manages Northrop’s transformation communications program.

Moreover, space-bound components must be far more reliable than the regular chips — a bad chip can hardly be replaced in orbit. Northrop will use “a plethora of techniques” to meet the need, many developed for the multibillion-dollar Advanced Extremely High Frequency Communications military satellite system, Linsky said.

Caspian’s challenge is to make the space-hardened components do the same job as their earthbound cousins. The firm’s engineers are fine-tuning the algorithms for the new chips, Wurtz said.

A typical Caspian flow-state router installation can handle 120 gigabits per second, but a full rack of gear weighs roughly 300 pounds, too heavy for the planned satellites, Wurtz said. The smaller router cards prepared for orbit will likely handle a few gigabits per second, with a total capacity of around 10 gigabits per satellite, Linsky said.

The Air Force contract calls for a demonstration of a space-capable flow-state router in mid-2006, followed by a production proposal later that year. If the Caspian-Northrop plan is approved, production would start in early 2007, Linsky said.

The next contract phase, commonly referred to as the Acquisition and Operations Support phase, begins in 2007, said Tonya Racasner, a spokeswoman for the Air Force’s Space and Missile Systems Center in Los Angeles. Neither the Air Force nor Northrop officials would say how much the initial phase would cost, citing competitive sensitivity.

Caspian hopes eventually to sell the space-router technology to other satellite builders. “I think we’ll see commercial satellite applications coming along, and that’s part of our long-term strategy,” Wurtz said.

Linsky sees the router as the breakthrough that will allow communications satellites, civilian as well as military, to use the ubiquitous data standards of the Internet.

“I think we’ll look back in 10 years and say, ‘This program is really what opened up IP to space,’” the Northrop manager said.