| A multistage (or multi-stage) rocket is, like any | | | | itself. The thrust of the future stages is able to |
| rocket, propelled by the recoil pressure of the gases | | | | provide more acceleration than if the earlier stages |
| it emits as it burns fuel. What characterizes it as | | | | were still attached, or than a single, large rocket |
| "multi-stage" is that it successively jettisons one or | | | | would be capable of. When a stage drops off, the |
| more stages as they become empty. It is effectively | | | | rest of the rocket is still travelling near to the speed |
| one or more rockets (stages) stacked on top of or | | | | that the whole assembly reached at burn-out time. |
| attached next to each other ("parallel staging"); in | | | | This means that it needs less total fuel to reach a |
| order to reduce the total amount of mass which | | | | given velocity and/or altitude. |
| needs to be accelerated to the final speed/height. | | | | A further advantage is that each stage can use a |
| Generally each stage consists of one or more | | | | different type of rocket motor, with each stage |
| motors, plus fuel and oxidiser tanks for a liquid rocket | | | | motor tuned for the conditions in which it will operate. |
| or the casing for a solid rocket. In rocketry, this | | | | Thus the lower stage motors are designed for use at |
| concept is known as staging. | | | | atmospheric pressure, while the upper stages can use |
| Solid or liquid rocket Boosters are often used for | | | | motors suited to near vacuum conditions. Lower |
| parallel staging schemes and all motors are ignited at | | | | stages tend to require more structure than upper as |
| launch. These are sometimes referred to as 'stage 0'. | | | | they need to bear their own weight plus that of the |
| The first stage is at the bottom and is usually the | | | | stages above them, optimizing the structure of each |
| largest, the second stage above it and is usually the | | | | stage decreases the weight of the total vehicle and |
| next largest, etc. In the typical case, the first stage's | | | | provides further advantage. |
| motor(s) fire and then any fitted boosters, and the | | | | Disadvantages |
| entire rocket is propelled upwards. When the | | | | On the downside, staging requires the vehicle to lift |
| boosters run out of fuel, they detached from the | | | | motors which are not being used until later, as well as |
| rest of the rocket (usually with some kind of small | | | | making the entire rocket more complex and harder |
| explosive charge) and fall away. The first stage then | | | | to build. Nevertheless the savings are so great that |
| burns to completion and falls off. This leaves a | | | | every rocket currently used to deliver a payload into |
| smaller rocket, with the second stage on the bottom, | | | | orbit uses staging. |
| which then fires. This process is repeated until the | | | | In more recent times the usefulness of the technique |
| final stage's motor burns out. | | | | has come into question due to developments in |
| The Space shuttle has two large boosters and is not | | | | technology. In the case of the Space Shuttle the |
| Single-stage-to-orbit (SSTO). | | | | costs of space launches appear to mostly composed |
| Advantages | | | | of the operational costs of the people involved (as |
| The main reason for multi-stage rockets and | | | | opposed to fuel or equipment), reducing these costs |
| boosters is that once the fuel is burnt, the space and | | | | appears to be the best way to lower the overall |
| structure which contained it and the motors | | | | launch costs. New technology that is mainly in the |
| themselves (in the case of liquid-fuelled rockets) are | | | | theoretical and developmental stages is being looked |
| useless and only add weight to the vehicle which | | | | at to lower the costs of launch vehicles. More |
| slows down its future acceleration. By dropping the | | | | information can be found on single stage to orbit |
| stages which are no longer useful, the rocket lightens | | | | designs that do not have separate stages. |