GB2106221A - Rockets - Google Patents

Abstract

The stabiliser fins (8) of a rocket are movable along the longitudinal axis of the rocket from the usual flight position to the rear of the centre of gravity (9) of the rocket to a position (10) forward of the centre of gravity when thrust ceases; this renders the rocket aerodynamically unstable to reduce the distance of travel and the impact velocity. <IMAGE>

Description

SPECIFICATION Rockets This invention relates to rockets.

According to the present invention a rocket comprises stabiliser fins which are movable along the longitudinal axis of the rocket from a position to the rear of the centre of gravity of the rocket to a position forward of the centre of gravity of the rocket. It is preferred that the fins are arranged to move forward under the influence of inertia when thrust from the rocket's motor is terminated. This can be achieved by the drag/weight ratio of the fins and supports movable therewith being less than that of the body. Preferably there is a lock to secure the fins in the forward position and this may take the form of a wedge.

The invention may be carried into practice in various ways and one rocket embodying the invention will be described by way of example with reference to the drawing which is a diagrammatic side view of the rocket.

The rocket comprises a body 1 with a nose portion 2, a transponder and power pack 3 and a rocket motor with an outlet 4 for the propulsion gas. There is a stabiliser fin assembly 5 comprising a collar or sleeve 6 which is slidable along the body of the rocket and carries supports 7 to which are fixed four fins 8. The fin assembly 5 is slidably movable from a position at the rear of the rocket to a position 10 forward of the centre of gravity 9.

Shaped stops or wedges 12 are provided to secure the fins in the forward position.

In use the sliding fins 8 remain at the rear of the body of the rocket while the rocket is thrusting and accelerating under the presence of the take off thrust. The take off thrust lasts approximately 3 seconds and terminates at an altitude of about 1000 feet (300 metres). The drag/weight ratio of the fin assembly 5 is less than that of the body 1 which has a high drag. When the thrust is terminated, the setback acceleration causes the fin assembly to move forward to the position 10 forward of the centre of gravity 9 under the influence of the inertia of the assembly. This renders the rocket unstable aerodynamically and gives it a high drag and the rocket thus has a low apogee trajectory. At the desired forward point of the fins' movement the shaped wedges 1 2 stop further forward movement and secure the fins in place.

Such a rocket takes off quickly but does not climb to a great height. In the last part of the climb, after burnout the rocket will be tumbling.

During the descent, the rocket will either be tumbling or falling on its side and hits the ground with a low velocity of about 100 feet/second (30 metres/second).

A rocket as described therefore has a low apogee trajectory and a low impact velocity. This means that damage to the area on which the rocket iands, damage to any payload and damage to the rocket itself is minimized. Important and expensive parts of the rocket can therefore be recovered and reused.

In an alternative embodiment there may be some form of payload other than a transponder.

The payload may for example be data collecting equipment.

1. A rocket with stabiliser fins which are movable along the longitudinal axis of the rocket from a position to the rear of the centre of gravity of the rocket to a position forward of the centre of gravity of the rocket.

2. A rocket as claimed in Claim 1 in which the fins are arranged to move forward under the influence of inertia when thrust is terminated.

3. A rocket as claimed in Claim 1 in which the drag/weight ratio of the fins and supports movable therewith is less than that of the remainder of the rocket.

4. A rocket as claimed in Claim 1, Claim 2 or Claim 3 in which there is a lock to secure the fins in the forward position.

5. A rocket substantially as specifically described herein with reference to the accompanying drawing.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (5)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Rockets This invention relates to rockets. According to the present invention a rocket comprises stabiliser fins which are movable along the longitudinal axis of the rocket from a position to the rear of the centre of gravity of the rocket to a position forward of the centre of gravity of the rocket. It is preferred that the fins are arranged to move forward under the influence of inertia when thrust from the rocket's motor is terminated. This can be achieved by the drag/weight ratio of the fins and supports movable therewith being less than that of the body. Preferably there is a lock to secure the fins in the forward position and this may take the form of a wedge. The invention may be carried into practice in various ways and one rocket embodying the invention will be described by way of example with reference to the drawing which is a diagrammatic side view of the rocket. The rocket comprises a body 1 with a nose portion 2, a transponder and power pack 3 and a rocket motor with an outlet 4 for the propulsion gas. There is a stabiliser fin assembly 5 comprising a collar or sleeve 6 which is slidable along the body of the rocket and carries supports 7 to which are fixed four fins 8. The fin assembly 5 is slidably movable from a position at the rear of the rocket to a position 10 forward of the centre of gravity 9. Shaped stops or wedges 12 are provided to secure the fins in the forward position. In use the sliding fins 8 remain at the rear of the body of the rocket while the rocket is thrusting and accelerating under the presence of the take off thrust. The take off thrust lasts approximately 3 seconds and terminates at an altitude of about 1000 feet (300 metres). The drag/weight ratio of the fin assembly 5 is less than that of the body 1 which has a high drag. When the thrust is terminated, the setback acceleration causes the fin assembly to move forward to the position 10 forward of the centre of gravity 9 under the influence of the inertia of the assembly. This renders the rocket unstable aerodynamically and gives it a high drag and the rocket thus has a low apogee trajectory. At the desired forward point of the fins' movement the shaped wedges 1 2 stop further forward movement and secure the fins in place. Such a rocket takes off quickly but does not climb to a great height. In the last part of the climb, after burnout the rocket will be tumbling. During the descent, the rocket will either be tumbling or falling on its side and hits the ground with a low velocity of about 100 feet/second (30 metres/second). A rocket as described therefore has a low apogee trajectory and a low impact velocity. This means that damage to the area on which the rocket iands, damage to any payload and damage to the rocket itself is minimized. Important and expensive parts of the rocket can therefore be recovered and reused. In an alternative embodiment there may be some form of payload other than a transponder. The payload may for example be data collecting equipment. CLAIMS

1. A rocket with stabiliser fins which are movable along the longitudinal axis of the rocket from a position to the rear of the centre of gravity of the rocket to a position forward of the centre of gravity of the rocket.

2. A rocket as claimed in Claim 1 in which the fins are arranged to move forward under the influence of inertia when thrust is terminated.

3. A rocket as claimed in Claim 1 in which the drag/weight ratio of the fins and supports movable therewith is less than that of the remainder of the rocket.

4. A rocket as claimed in Claim 1, Claim 2 or Claim 3 in which there is a lock to secure the fins in the forward position.

5. A rocket substantially as specifically described herein with reference to the accompanying drawing.