1. A multistage rocket uses two or more stages, each with their own engines and propellant. Stages are discarded completely after their propellant is consumed. 2. There are two types of multistage rockets: series staging where the second stage fires after the first is finished, and parallel staging where upper stage engines are used during lower stage operation by arranging stages alongside each other. 3. Stage separation can occur within the atmosphere using techniques like firing holes or ullage rockets, or out of the atmosphere in space using springs or solid propellant rockets. Selection of separation systems considers factors like joint rotation, reliability, and debris confinement.

1. UNIT IV
STAGING OF
ROCKETS AND
MISSILES
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2. REASONS FOR MULTISTAGING:
1. To improve performance by eliminating dead weight during powered flight.
2. To maintain acceleration within reasonable limits by reducing thrust in mid
flight.
A multistage (or multi-stage) rocket is a rocket that uses two or more
stages, each of which contains its own engines and propellant.
A tandem or serial stage is mounted on top of another stage; a parallel
stage is attached alongside another stage
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3. NOMENCLATURE OF A
MULTISTAGE ROCKET
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STAGE:
A stage (which is also known as a step), is a complete propulsion unit with motor,
propellant feed system, tanks, propellant together with control equipment, which is
discarded completely when all the propellant of that stage is consumed.
SUB ROCKET:
A sub rocket is a complete rocket vehicle, consisting of one or more stages together
with a payload and the guidance and control system

4. TYPES OF MUTISTAGE ROCKETS:
There are two fundamental types of rocket staging. They are,
1. Series staging
2. Parallel staging
1.SERIES STAGING:
Series staging is also known as vertical staging. In a series staged rocket, the second stage
fires after the first stage is finished. The series staging is also known as tandem staging.
Some of the best examples of series rockets are, Explorer I and Saturn V.
2.PARALLEL STAGING:
Parallel staging is defined as staging a vehicle such that the upper stage engines are also
used during lower stage operation. This is usually accomplished by arranging the stages
alongside one another, hence the name parallel staging. The perfect example of parallel
staging is Titan III C
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5. ADVANTAGES:
1. Reduction of gravitational losses.
2. In a gravitational field, the parallel staging is always advantageous to consume the
propellant as fast as possible.
DISADVANTAGES:
1. The disadvantage of parallel staging is that the rocket is likely to be bulky and for the
flight through the atmosphere the drag penalty may be large.
2. The second disadvantage of parallel staging is the reduction in nozzle efficiency
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6. STAGE SEPARATION TECHNIQUES:
In multistage launch vehicles the stage separation process is broadly
classified into two
categories. They are,
1. SEPARATION OCCURING WITHIN THE
ATMOSPHERE.
2. SEPARATION OCCURING OUT OF ATMOSPHERE.
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7. 1. SEPARATION OCCURING WITHIN
THE ATMOSPHERE:
.Separation within the atmosphere is otherwise known as booster
separation/lower stage separation/strap on separation
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8. -The burn out of the first stage generally occurs within the upper regions of the
atmosphere (i.e) 45km to 60km, to minimize the energy lost due to the
aerodynamic forces
a. FIRING IN THE HOLE TECHNIQUE
hot separation through the holes
b. ULLAGE ROCKET TECHNIQUE
short duration solid propellant rocket motor placed between
the stages to push the lower stage.
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11. 2. SEPARATION OUT OF
ATMOSPHERE (IN SPACE):
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12. Separation occurring out of atmosphere is also known as
vacuum/space/upper stage separation. The separation of
subsequent stages takes place either at extreme high altitudes in
space
The problem of separation is relatively simplified when occurs in
space because of absence of aerodynamic forces
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13. This separation technique involves two methods.
a. HELICAL COMPRESSION SPRING
TECHNOLOGY
b. SHORT DURATION SOLID PROPELLANT
TECHNOLOGY
ADVANTAGES:
1. No separate command is needed for actuation
2. Highly reliable
DRAW BACK:
1. Much heavier when compared to other jettisoning system.
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14. STAGE SEPARATION SYSTEMS:
Selection of stage separation system of launch vehicle is an extensive and
exhaustive process.
The critical criterions are,
1. Joint rotation
2. Simultaneity
3. Reliability
4. Confinement of debris
5. Low shock levels
6. Weight
7. Cost.
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