Blue Origin has a reusable space rocket. SpaceX does, too. (And SpaceX's rocket can land on a boat). But what about United Launch Alliance, the one-time "monopolist" in American spaceflight owned by Boeing (NYSE:BA) and Lockheed Martin (NYSE:LMT)? Will ULA ever figure out how to build a reusable rocketship of its own?

As a matter of fact, yes.

As a matter of fact... they may already have figured out how to do it.

Improving on the improvements

Much has been written already about United Launch Alliance's new Vulcan rocket, designed to replace Lockheed Martin's Atlas V -- and more importantly, replace the Russian RD-180 engine that powers the Atlas, with something made closer to home.

Vulcan is expected to be cheaper than Atlas, and should help close the price gap between ULA's high-cost space launches, and what SpaceX charges for a similar service. One thing that Vulcan cannot do, however, is launch a rocket into space, then return to land on Earth under its own power.

But as DefenseNews.com reported last week, Boeing and Lockheed Martin are already hard at work making their rockets reusable... just in a slightly different way.

If you can't beat 'em, leapfrog 'em

Boeing and Lockheed Martin have clearly lost the "race to reusable" in Stage 1 booster rockets. That's just a fact. Their plan for recovering first-stage rockets -- parachuting them into the atmosphere, then snagging the parachute with a helicopter, is so complex as to be laughable. (Besides which, it's unproven).

But that doesn't mean Boeing and Lockheed Martin have run clean out of ideas. Skipping merrily past the idea of landing first stage rockets on Earth for later reuse, Boeing and Lockheed are focusing their efforts on making second stage rockets reusable.

Recall: Most satellite launches these days utilize a two-stage rocket approach. Stage 1 -- the core booster -- generally burns for about three minutes before it's out of gas. At that point, it drops into the sea (or in the case of the SpaceX Falcon 9, descends to land under its own power), while Stage 2 ignites to carry the satellite the rest of the way into orbit. Then Stage 2, too, runs out of gas, falls, and burns up in the atmosphere.

At United Launch Alliance, Boeing and Lockheed's new plan is to upgrade their Centaur Stage 2 rocket into a new version dubbed "ACES" (Advanced Cryogenic Evolved Stage). Bigger than Centaur, ACES will hold more fuel, and will be capable of reaching orbit itself (and remaining there). Thus, ACES could be reused in space -- refueled, and perhaps even mated with other ACES rockets to form larger spaceships or space stations in orbit, where it could be tasked with new missions in space. Given enough fuel, United Launch Alliance CEO Tory Bruno says an orbiting ACES rocket could conceivably be used "forever."

Seeing the future

All of these plans are still in the formative stage, mind you. ACES doesn't actually exist yet, except in the mind of ULA. But the Centaur second stage will be part of Vulcan when it begins operations in 2019, and Bruno believes that ULA can have its first ACES rocket ready for work by about 2024.

It still remains to be seen what missions ACES might perform once it's ready. But the refueling and reassembly capabilities envisioned for ACES would jibe quite nicely with Boeing's plans to assemble a Mars mission spacecraft in space. With Boeing targeting a Mars departure date of 2033 or thereabouts, that will give the company nearly a decade to work out the kinks on its new tech.