Spacecraft and Instruments

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Launch Vehicle Summary
launch vehicle The launch vehicle supplies almost all the energy that the spacecraft needs in order to get from Earth to Mars.

Read more about the launch vehicle here, or find out what will happen during launch in the Mission Timeline.

Orbiter Will Launch on an Atlas V-401

Mars Reconnaissance Orbiter will use an Atlas V-401 launch vehicle, the smallest of the Atlas V family. It is 57 meters (188 feet) tall. This launch vehicle was selected because it provides the performance needed to fly a large spacecraft to Mars in the 2005 launch period.

Although the geometry of Earth and Mars permit missions to be launched every two years, the 2005 mission requires more performance than for 2003 and 2007 launch dates given the position of the planets in their orbits. In addition, this spacecraft is heavier than previous Mars missions.

Details About the Launch Vehicle

The Atlas V was developed by Lockheed Martin Commercial Launch Services as part of the US Air Force Evolved Expendable Launch Vehicle (EELV) program. The term "expendable launch vehicle" means it is only used once.

The Mars Reconnaissance Orbiter version of the vehicle is a two-stage launch vehicle that does not use solid rocket boosters. The two-stage rocket is simpler than previous three-stage rockets and has better performance.

The total vehicle weight at liftoff is about 333,000 kilograms (733,000 pounds). Of this total, about 305,000 kg (672,000 lb) is fuel. To launch the orbiter and set it on its course to Mars, the Atlas V will accelerate the spacecraft to about 11,000 meters per second (25,000 miles per hour).

The main components of the launch vehicle are the:

Drawing of Payload Adapter Payload Adapter: The payload adapter is the physical structure used to connect the orbiter to the launch vehicle.

The spacecraft is mounted on top of the Centaur using an 1194-millimeter-diameter (47 inch) Payload Adapter. A clamp band is used to secure the spacecraft to the launch vehicle. When the launch vehicle mission is complete, the Centaur releases the clamp band and the spacecraft separates from the launch vehicle using "push-off" springs.

The payload interface provides the electrical interface between the orbiter and the launch vehicle.

During pre-launch and launch, the spacecraft communicates to the launch vehicle and to the ground through wiring that disconnects when the spacecraft separates. This wiring permits final checkout of the spacecraft before launch and provides telemetry data and other signals to the launch vehicle. The launch vehicle transmits this information to the engineers all across the country who are monitoring the launch.

Drawing of Stage I Atlas Booster Stage I Atlas Booster: The Atlas first stage is powered by liquid Oxygen and RP-1 (similar to kerosene) and uses a RD-180 engine supplied by Russia. The Stage 1 Booster's total weight is approximately 305,000 kilograms (672,000 pounds) at launch.

The first stage operates for about four minutes. The booster provides about 4 million Newtons* (900,000 pounds) of thrust. During this phase the spacecraft accelerates to supersonic speeds of about 4500 meters per second (10,000 miles per hour).

(*A Newton is a unit of force required to accelerate a mass of one kilogram, one meter per second...every second!).

After the first stage burn is done (called Booster Engine Cutoff, or BECO), the first stage falls back to Earth in the Atlantic Ocean. At that time, the spacecraft is about 112 kilometers (370,000 feet) above the Earth.

Drawing of Payload Fairing Payload Fairing: Mars Reconnaissance Orbiter uses a payload fairing (nose cone) that is 4 meters (13 feet) in diameter and weighs about the same as the spacecraft.

The fairing protects the spacecraft from the weather on the ground as well as from the atmosphere during flight. When the launch vehicle is on the launch pad, the spacecraft is supplied with air conditioning in order to control temperature and to protect it from dust and dirt.

Shortly after Centaur ignition, the fairing is no longer needed, so it is separated into its two halves by explosive bolts and jettisoned. This operation is automatically controlled by timers in the Centaur. The two fairing halves swing away to either side of the spacecraft and fall back to Earth, landing in the ocean.

Stage II Centaur Upper Stage Booster Stage II Centaur Upper Stage Booster: The Centaur upper stage is powered by liquid Oxygen and liquid Hydrogen, which provides the remaining energy necessary to send the spacecraft on its trajectory to Mars.

Keeping the spacecraft in the Right Position

The Centaur is a very sophisticated upper stage and can control its orientation very precisely. This ability is important both to control the direction of thrust during the burns, as well as to prevent sunlight from shining directly into spacecraft cameras and sensors which would be damaged by high intensity light.

The Centaur always knows its position relative to the sun and has computer programs on board that automatically control the orientation of the spacecraft relative to the sun. Because the position of the sun relative to the spacecraft is different for each day of the launch period, these computer programs have to be updated in case launch doesn't occur on the first day of the launch period.

+ How Stage II Works