These Are The 3 Commercial Space Capsules Competing For A NASA Contract Worth Billions

At 4 p.m. ET today, NASA will announce the winner of the contract for its Commercial Crew program.

Worth billions, the contract is not only lucrative but historic, as whoever receives it will play a pivotal role in the future of manned space travel, by establishing what will essentially be a taxi service to and from low-Earth orbit and eliminating America's reliance on Russian Soyuz rockets. This last factor is especially important in light of escalating tensions between the US and Russia over the power struggle in the Ukraine.

The winner will not only provide transportation for astronauts to and from the International Space Station, but will, in principle, be free to sell a ride to low-Earth orbit to anyone willing to pay for it.

The award is the culmination of a race that began in 2010, when NASA began awarding funding to private companies to develop a capsule capable of carrying astronauts into orbit and back. Unlike previous NASA programs, in which NASA handled all of the work and the funding, the Commercial Crew program entails a partnership between government and industry, in which NASA set the final safety and functionality requirements for the transportation system, but left it to the companies themselves to figure out the best way to meet those requirements.

Here are the three contenders for the Commercial Crew contract, along with what they have to offer:

1. Boeing: CST-100

Seen by many - including the Wall Street Journal - as the safe choice, Boeing's seven-seater CST-100 capsule offers a weld-less design that reduces structural risks and shaves off mass and production time. That same sleekness extends to the interior of the craft, which swaps cluttered instrumental gear for tablet-based control interfaces, and bulky metal chairs for slim plastic seating.

2. SpaceX: Dragon V2

The rapid rise of Elon Musk's SpaceX as a serious contender in manned spaceflight makes the Dragon V2 an exciting choice for the contract. The Dragon V2 has already proved itself capable of performing the task, having successfully delivered food and supplies to the ISS three times since 2012. Like the CST-100, the Dragon V2 seats seven and boasts a sleek interior. And SpaceX may have an advantage, in that it already won a cargo contract with NASA for the original Dragon.

3. Sierra Nevada Corporation: Dream Chaser

Designed in partnership with Lockheed Martin, the Dream Chaser is easily the most enigmatic of the three choices, but that reflects more on its marketing than the advantages it could provide. The winged, seven-seater craft features a "lifting body design," which essentially means that the craft itself functions like one giant wing to provide lift.

While the winged body makes the Dream Chaser more complicated to manufacture, maintain, and maneuver, it also offers more pilot control and the option of deviating slightly from the flight path in case of emergencies.

And although Sierra Nevada Corporation is the least-known brand among the three, it does the distinction of having developed the engine for the SpaceShipTwo for Virgin Galactic - definitely a household name, and one that has its own separate deal with NASA for transporting cargo.

The winner?

In the bigger picture, all three companies are offering reusable, seven-seater shuttles that could help revive the American space program and open the gates to commercial space travel. In light of these high stakes, it's possible that NASA may hedge its bets and offer contracts to more than one company, as some have predicted.

Watch the announcement live here at 4pm EST: Broadcast live streaming video on Ustream