When a Russian Soyuz rocket on its way to resupply the International Space Station crashed last week, it brought down with it confidence in the continuity of the space station program. The next Soyuz launch was pushed back, and on Monday, NASA announced that it was considering abandoning the space station altogether until it was satisfied it had a reliable way to get astronauts there. That uncertainty has put pressure on the private U.S. companies currently developing the next U.S. space vehicles that will replace the retired space shuttle. It also gave rise to suggestions that other countries' vehicles could be used to supply the station, though none are officially being considered to ferry astronauts there. Below, we've compiled a list of the launch vehicles, capsules, and space planes being considered as alternatives to the Russian Soyuz rockets.

Launch Vehicle - Capsule Combinations:

  • SpaceX Falcon 9 / Dragon: Probably the best-known private U.S. space company, SpaceX is set to test-launch its Dragon space capsule on Nov. 30. The pressure is on for a successful flight, reported Florida Today, as that could lead to a contract with NASA as soon as next year. Dragon carries seven passengers and a total payload of 6,614 pounds. Last December, a Spacex capsule orbited the earth twice before splashing down into the Pacific Ocean. SpaceX wants to perform a "virtual docking" in the November test, as well as a "berthing" test, in which the space station would grab the capsule with its robotic arm. The Dragon is designed to be lifted into orbit by the Falcon 9 launch vehicle, a two-stage rocket that lifted the first Dragon test capsule.
  • United Launch Alliance Atlas V / CST 100: Initially developed by Lockheed Martin, the Atlas V now operates under a Lockheed-Boeing joint venture known as United Launch Alliance. On Aug. 4, Boeing announced that it would use the two-stage Atlas V to launch its CST-100 space capsule on a mission to the International Space Station by 2015. The CST 100 seats seven, but the total payload hasn't been determined yet. The Atlas 5 has already made 26 successful flights over five years, according to Reuters, and Boeing currently uses the rocket to launch "NASA science probes, commercial satellites and military payloads."

Launch Vehicles and Space Planes:

  • Japan Aerospace Exploration / Mitsubishi H-IIB: The two-stage H-IIB rocket uses liquid oxygen and hydrogen, as well as four strap-on solid-fuel boosters. It was designed to carry supplies to the International space station, and is designed to work with the HTV cargo unit, which has a payload of eight tons.
  • European Space Agency Ariene 5: This two-stage rocket uses a cryogenic main stage and a reusable second stage with storable propellant. It routinely launches satellites, and has been used to deliver supplies to the International Space Station. The Ariene 5 has a payload of more than 20 tons, according to the ESA website.
  • SpaceDev Dream Chaser: Designed to be launched on an Atlas 5 rocket, the Dream Chaser would land horizontally, like a space shuttle. It also carries seven passengers, though the total payload is not yet known. The vehicle is still in testing, and is slated for a full-scale subsonic drop test in mid 2012, according to parent company Sierra Nevada Corporation.