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Aviation History
1942
1942 - 0342.PDF
FLIGHT FEBRUARY 12TH, 194* LUNAR SPACE/VESSEL Possibilities of a Rocket Flight to the Moonp: Release Velocity Question : Stability and\Coimol : Landing Gear By R. A. SMITH, Organising Sfc, j^itish Interplanetary Society The Fuel EVER since it was realised that the propulsive effect of a rocket is the result of the reaction upon it of the acceleration imparted to the emitted gases, it has been ob vious that in this reaction lay the possibility of producing tractive effect independent of the surrounding medium. Granted that the tractive effect is there, the next question to arise is whether it is of sufficient magnitude to make possible a flight to the moon and back. Those who have considered such a flight think of it in the following terms: — (i) Acceleration in the shortest pos sible time to " Release Velocity," with jets at full blast. This velocity hav ing been attained, sufficient momen tum would have been built up to carry the ship, at steadily decreasing velo city, to the lunar orbit. The force of gravitation acting on the ship would decelerate it, but its momentum would prevent its being brought to rest. "Release Velocity" «nay be defined as that velocity which a body will have attained at any point in a gravitational field as the result of hav ing been permitted to fall freely under the influence of that field from in finity to that pomt, by this formula: V = Release Velocity = V 2g — where g — gravitational acceleration at surface of body, whose radius is r, x being the distance from the centre of the body to the point at which it is desired to calculate '' Release Velo city." (2) Having reached the point at which the gravitational attraction of the Earth and Moon are balanced, the ship will begin to accelerate, increas ing its speed until, at the appropriate moment, rockets are discharged to wards the Moon, decelerating the ship to rest on the lunar surface. (3) On return, the ship would be accelerated; bji^rocket discharge to lunar "Release Velocity," and then be permitted to coast under momen tum. (4) Re-passing fta^hce point, the ship would accel«j^e in free fall to wards the Earth, until, at the appro priate moment, rockets were again discharged, decelerating the ship to a velocity at which it would be safe to' re-enter the Earth's atmosphere. From this point the ship would com plete its descent by parachute, or other air-braking device. it will be seen from the foregoing that the project consists of two periods of acceleration and two of decelera tion, under power. The total effort will be the same ^s if these had been four successive periods of acceleration to a fictitious velocity, Vt, known as total Velocity. Corrections would have to be ap plied to the value Vt, thus obtained, to allow for various factors, such as, loss of time in attaining '' Release Velocity," power reserve for approach and correction manoeuvres, and allqrfj ance for atmospheric drag. FurthS corrections will be required to com pensate for any change in weight, not directly connected with fuel con sumption. Exhaust Velocity An equation can be derived, consis tent with the conservation of energy and observed experimental results, as follows: — v ' 1 M° v,= ;vlogt where Vt = total verity, at time t, v = exhaust velocity, M<,= original mass, and Mt = mass at time t_ This equation in the form V, Log, M„_ ''Wt relates exhaust velocity to payload ratio, which is the reason for the prominence given to exhaust velocities by " Astronautical " experimenters. Directly it is announced that ex haust velocities of the order of 3.9 kms./sec. have been obtained in prac tical experiment (after correction t*v^ vacuum performance) it will be tim^"' to consider the details of a practical space-ship, providing the fuel is suffi ciently compact. Compactness is essential to reduce both container weight and the overall dimensions of* the ship • to reasonable figures. The reason advanced by some ex perimenters for the use of liquid fuels is that by valving and throttling the Fig. 1. Ship complete as at departure from earth's surface :—(1) Overhang of pressure cabin ; (2) Rocket tube (large size); (3) Outer shell (jettisoned after leaving atmosphere) ; (4) Inner shell of pressure cabin ; (5) Handrail and supports ; (6) Walkway; (7) Firing control; (8) Operator's couch; (9) Airlock; (10) Smaller tubes; (n) Larger tubes (side view); (12) Cage ; (13) Thrust web ; (14) Radial observation port ; (15) Forward axial observation port ; (16) Instrument,panel and parachute locker ; (17) Food and tool lockers ; (18) Firing current power pack ; (19) Torque jets ; (20) Axial liquid fuel control rockets ; (21) Space for air, water, and liquid fuel tanks ; (22) Cable duct.
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