ROCKET STAGING
ROCKET STAGING
All rockets use the thrust generated by a propulsion system to overcome the weight of the rocket. For full scale satellite launchers, the weight of the payload is only a small portion of the lift-off weight. Most of the weight of the rocket is the weight of the propellants. As the propellants are burned off during powered ascent, a larger proportion of the weight of the vehicle becomes the near-empty tankage and structure that was required when the vehicle was fully loaded. In order to lighten the weight of the vehicle to achieve orbital velocity, most launchers discard a portion of the vehicle in a process called staging.
Types of Staging-
There are two types of rocket staging-
1. Serial Staging
2. Parallel Staging.
1. Serial Staging
In serial staging (sometimes identified as tandem or vertical staging), the first
stage is at the bottom and is usually the largest; the second stage and subsequent
upper stages are above it, usually decreasing in size. The first-stage engines are
every time electronically ignited. As this stage runs out of propellant, the upper
retaining cap splits, sending hot gas onto the next stage, burning it, and throwing the
lower stage back to the Earth. This leaves a smaller rocket, with the second stage on
the bottom, which then fires. It operates at high altitude and thus under very
minimal atmospheric pressure. This process is repeated until the final stage’s
motor burns to completion.
Example- Saturn V and Explorer I.
2. Parallel Staging
In parallel staging, solid or liquid rocket boosters are used
to assist with liftoff. These are sometimes referred to as “stage 0.” In the typical
case, the first-stage and booster engines fire to propel the entire rocket upwards.
When the boosters run out of fuel, they are detached from the rest of the rocket and
fall away. The first stage then burns to completion and falls off.
Example- Atlas
Advantages of Staging
For a multistage rockets and boosters once the fuel is exhausted, the space and structure which contained it and the motors themselves are dropped being no longer useful. Thus the rocket lightens itself. The thrust of next stages is able to provide more acceleration than if the earlier stage were still attached or a single, large rocket. Thus, rocket performance is improved by eliminating dead weights.
Disadvantages of Staging
Staging requires the vehicle to lift motors which are not yet being used; this means
that the first stages must produce higher thrusts than they supposed to do.
Staging also makes the entire rocket more complex and harder to build.
In addition, each staging event is a significant point of failure during a launch,
with the possibility of separation failure, ignition failure, and stage collision.
Theory of Jet Propulsion & Efficiency
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