Although the space shuttle is still a technical marvel, the fleet is aging and has become increasingly expensive to operate. Recent problems with foam insulation have exposed crews to danger, rendered it unsafe to fly, and caused NASA to ground the entire fleet. NASA needs a vehicle that is capable of carrying crew and payloads to Earth orbit, the moon and Mars. With future exploration in mind, NASA is designing a new vehicle.
NASA's new spaceship, the Orion Crew Exploration Vehicle, will actually consist of two ships:
- The Crew Exploration Vehicle (CEV) will transport four to six astronauts.
- The Cargo Launch Vehicle (CLV) will lift heavy payloads and astronauts when necessary.
The Orion will use proven technologies from the Apollo and space shuttle programs. They will also be safer and more versatile for long-term space exploration.
In this article, we'll examine the concept and technology behind the Orion and learn how it will help us explore the moon and beyond.
NASA has selected Lockheed Martin to design and build the Orion. Main systems (such as power, navigation, life support, communications, and computers) will be more advanced versions of those on the Apollo and the space shuttle.
The CEV will consist of three basic parts:
- A capsule to hold the crew.
- A service module to hold the main propulsion system, power systems, and attitude controls. Attitude refers to how the spacecraft is oriented in space (x, y, and z directions or pitch, roll, yaw axes). Apollo used four units of four thrusters mounted on the service module for this task, while the shuttle uses reaction control thrusters located on the nose and aft sections.
- A booster to lift the CEV into Earth orbit.
For lunar landing missions, there will be a special module.
The capsule will be cone-shaped like the Apollo command module, because it is more aerodynamic than the shuttle. Instead of re-entering the atmosphere of Earth orbit at 8 kilometers per second (like the shuttle), the CEV will re-enter the atmosphere from the higher velocities of lunar travel, at 11 kilometers per second.
Besides shape, the CEV crew capsule has several other things in common with the Apollo, along with a few differences:
- The larger diameter (16.5 feet, or 5 meters, instead of 3.9 feet) will hold more crew and cargo.
- The CEV aft heat shield will be ablative, meaning that it will boil away. Apollo used a single, multi-layered aft heat shield made of aluminum and epoxy resin that ablated as it absorbed the heat of re-entry. (It was designed to be used only once, just like the rest of the command module.) The shuttle uses ceramic thermal tiles, thermal blankets, and reinforced carbon resins to absorb the heat. However, this concept has proven to be more difficult to service than its theoretical design. The CEV heat shield will be replaceable up to 10 times and last the design life of the vehicle.
- Air bags on the CEV will enable both land recoveries and sea recoveries. All of the Apollo's recoveries were ocean splashdowns.
- The CEV's position atop the launch booster puts it out of the way of falling debris like pieces of foam or ice.
- An escape tower -- a small rocket that lifts the command module off the booster in the event of a launch failure -- is one of the CEV's unique features. This mechanism is safer than the shuttle's abort procedures.
In the next section, we'll explore the service module and the booster.
CEV Service Module, Boosters and CLV
The CEV service module will also be cylindrical. It will cover and protect the heat shield of the CEV capsule while in flight and provide power, propulsion, and attitude control. The service module will be jettisoned prior to re-entry.
Some features of the service module include:
- A single engine propulsion, which will use slightly more efficient methane/oxygen fuel rather than the hypergolic mixture of Apollo SM (hydrazine/nitrogen tetroxide). Methane/oxygen fuel has a greater specific impulse than hydrazine/nitrogen tetroxide, which means a longer burn time for the same mass of propellant and greater velocities. In the future, it may be possible to make methane fuel from components on the moon and Mars to fuel this type of vehicle.
- A larger fuel capacity to make different lunar orbits and landing sites possible.
- Solar panels to generate electricity to supplement the energy from the fuel cells.
- Conduits containing liquid ammonia or water/glycol mixtures to transfer heat to radiators so it can escape into space. In outer space, the difference in temperature between sunlight and shade is about 400 degrees Fahrenheit. This uneven heating causes thermal stress on the metals in the spacecraft's structure. To counter this effect, the Apollo spacecraft rotated on its axis when going to the moon to allow solar radiation to heat the spacecraft evenly (the "barbecue roll maneuver"). The CEV will probably do the same.
- Attitude control with thrusters similar to the Apollo.
The Apollo required a massive launch vehicle (Saturn V) to lift both crew and payload. The shuttle's main engines needed to supply large amounts of thrust to the vehicle for the same reasons. The CEV launch booster, will only lift the crew, not heavy payloads. Because of this, the CEV booster can be smaller than the Apollo and space shuttle boosters.
The first stage of the CEV booster will be a solid rocket booster (SRB) named Ares I, which will be similar to the one on the space shuttle. The second stage will consist of a single space shuttle engine fueled by liquid hydrogen and oxygen tanks. Neither stage will be recovered or re-used (the shuttle SRBs were both recovered and re-used).
Manned space exploration requires placing both astronauts and payloads into orbit. Past vehicles have combined humans and payloads on the same rocket, but the CEV concept has separated these functions. The CLV will lift heavy payloads, like lunar landers, moon transfer stages and space station components. If necessary, the CLV can also be configured to launch humans.
The CLV will consist of two stages:
- The firs t stage will have five main engines fueled by liquid hydrogen and liquid oxygen (named Ares V)
- The second will have either a shuttle main engine or an Apollo J-2 engine, also fueled by liquid hydrogen and liquid oxygen.
Next, we'll look at the future of space exploration.
The Future of Space Exploration
NASA wants the Orion CEV to be versatile for future space exploration. They project that it will be able to transport crews to the International Space Station by 2014, the moon by 2020. Mars will be the next goal.
The main objective of the CEV is a return to the moon. During the design stage of the Apollo, there were two proposals to put man on the moon:
- The Earth Orbit Rendezvous (EOR) - pieces of a large moon rocket would be assembled in Earth orbit and launched to the moon
- The Lunar Orbit Rendezvous (LOR) - two smaller spacecraft (command/service module and lunar module) would meet in lunar orbit
Scientists eventually agreed that the LOR approach would save more weight and achieve President John F. Kennedy's goal of landing a man on the moon within 10 years. The flight plan for the CEV return to the moon incorporates elements of both the EOR and the LOR.
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The CEV lunar missions will establish a lunar base to explore the moon and search for water at the moon's South Pole (necessary for surviving on the moon and a potential source of material to make rocket fuel). They will also allow astronauts to test equipment and techniques for future missions to Mars. Since the moon is only three days away, it is safer and less expensive to launch missions to Mars from there. A rescue mission would also be easier for a lunar mission than a Mars mission. The CEV will serve as a model for designing other deep space, manned spacecraft.
With the CEV, NASA hopes to return astronauts to the moon and make real the dream of sending humans to explore Mars and the rest of the solar system.
For lots more information on space flight, the Orion Crew Exploration Vehicle and related topics, check out the links on the next page.
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More Great Links
- Allday, Jonathan. Apollo in Perspective Institute of Physics Publishing, Bristol, 2000.ISBN 0-7503-0645-9
- "Crew Exploration Vehicle Ensures Safe, Reliable Travel to Space Station, Moon, Mars." Nothrup Grumman Corporation, Oct. 12, 2005 http://www.irconnect.com/noc/press/pages/news_releases.mhtml?d=87722
- Introducing NASA's New Spaceship. NASA. http://www.nasa.gov/missions/solarsystem/explore_main.html
- How We'll Get Back to the Moon, NASA. http://www.nasa.gov/missions/solarsystem/cev.html
- NASA Exploration Systems Directorate. http://www.nasa.gov/missions/solarsystem/explore_main.html