Here is the original Operational Requirement for the project as issued by the Air Ministry:
1. Current day interceptor projects are expected to be adequate in performance to match the enemy threat in normal circumstances, but may be unable to destroy enemy aircraft carrying out special operations at exceptional heights.
2. An aircraft to fulfil this requirement must have a outstanding ceiling and altitude performance. So far as is known at present, the characteristics can only be provided by rocket propulsion, and, although aware of the probable operating limitations of this method, the Air Staff consider that the promise of tactical advantage more than outweighs other considerations.
3. The Air Staff require a single rocket propelled interceptor built to satisfy the broad requirement that follows.
General design considerations.
4. In order to facilitate ease and speed of production, the aircraft and its equipment are to be as simple as possible.
5. In the first instance, operation in temperate climates only is envisaged. Should world wide operation be required later, a separate requirement will be stated.
6. Although the Air Staff would consider any proposal for unconventional methods of take off if great advantages were gained thereby, conventional operation with a normal undercarriage would be preferred, since this would not only reduce the amount of auxiliary equipment required but was facilitate ground handling and assist turnaround.
7. Should unconventional take offs have to be accepted in order to get the necessary performance, any specialist equipment involved, such as catapults, launching ramps or trolleys must be designed concurrently with the aircraft and must feature ease of transport and assembly.
8. For conventional operation the aircraft will normally be used from 2000 yd standard fighter runways , but it is desirable that it should be able to operate from runways or prepared strips 1500yds or less.
9. Because it is not intended to land the aircraft under rocket power, and because all available rocket fuel is likely to be consumed in climb and flight at altitude, a small auxiliary turbine engine is to be provided which will enable the aircraft to return to base and land under its own power. The maximum thrust of the auxiliary engine is to be sufficient to recover from a baulked landing by climbing away with wheels and flaps down, with armament fitted, but with all rocket fuel consumed.
10. Neither the aircraft nor its rocket motor are to be regarded as expendable in any way.
11. Justification for this project depends mainly on this aircraft's ability to reach an exceptionally high altitude very quickly and there develop sufficient speed for long enough to intercept and destroy a fast flying enemy. Height, rate of climb, speed (and acceleration) are therefore of prime importance, and it is essential that the first should be considerably better than that expected in contemporary conventional fighter projects.
12. A subsonic ceiling of at least 75 000 ft is required.
Rate of Climb.
13. The aircraft should be able to reach 60 000 ft from rest at sea level in 2 to 3 minutes using maximum power.
14. Because this aircraft is required for high altitude interception, and all possible weight saving is essential, the Air Staff is prepared to accept a design limitation of M=0.95 below 20 000 ft. Above 20 000 ft, however, the design limitation is to increase progressively so that at 42 000 ft the limitation has risen to M=2.0 and remains constant at M=2.0 above 42 000 ft. The aim is that an aircraft of this type should be capable of supersonic speed at all heights above 30 000 ft while carrying its armament. The greatest practicable degree of thrust control by throttling is required.
15. The endurance should be sufficient to provide a sortie as follows:
(a) take off and climb to 60 000 ft
(b) 7 minutes cruise at 60 000 ft at not less than M=0.8 in steady level flight.
(c)2 minutes combat at 60 000 ft at M=0.95 in steady level flight.
(d) Descent from altitude followed by cruise on the auxiliary power at for 10 minutes.
(e) Approach and landing followed by recovery from a baulked landing and a second circuit and landing.
16. Provision should be made for extra fuel to increase the cruise time of paragraph 15(b) above by 3 minutes.
17. It s accepted that if maximum thrust is used in obtaining supersonic flight for combat, or if the aircraft is used above 60 000 ft, the above endurance figures will be reduced.
18. A high degree of manoeuvrability is required at all heights, particularly above 50,000ft. A rate of roll of 200 degrees a second is to be the aim.
19. If conventional take off methods are employed, the distance to under I.CA.N. conditions at maximum A.U.W. is not to exceed 2000yds. The aim is to have the shortest take-off run compatible with the other characteristics required.
20. It must be possible to use normal powered approach and landing technique under auxiliary power. Under I.C.A.N. conditions, and with all rocket fuel consumed, but with full weapon load, the landing distance over 50ft is not to exceed 1500yds. The aim is to have the shortest landing run compatible with the other characteristics required.
21 Air brakes are required. As they will be used as an aid to combat, it must be possible to use them through the entire speed range of the aircraft without affecting stability or otherwise impairing its aiming and weapon firing qualities.
Particular Design Features.
22. A pressure cabin is required. The pressure differential should not be more than 4 psi and not less than 3psi. This will provide adequate cockpit pressure whilst avoiding the dangers of explosive decompression.
23. Because there may be many new operating hazards to be faced for the first time in this aircraft, particular attention must be paid to ensure the best possible emergency escape facilities for the pilot. A dinghy and personal survival pack are required.
24. The best possible view is required particularly in the forward hemisphere. Special attention is to be paid to de-icing and demisting the windscreen and canopy, using a method which imposes no restriction on the pilot's view through the transparency.
Hood and Windscreen strength
25. Particular attention is to be paid to the strength of the hood and windscreen in order to reduce the risk of failure under the extreme operating conditions of temperature and pressure.
26. The armament is to consist of at least two Blue Jay air to air missiles.
27 Although adequate range information is necessary for the use of Blue Jay, the present radar ranging equipment is likely to impose an intolerable weight and performance penalty on the aircraft. Radar ranging is not therefore to be fitted. The possibilities of obtaining the necessary range information by other lighter and less complicated means are to be examined.
28. The normal reflector gunsight is required when BlueJay weapons are carried.
29. A G45 camera installation is required.
30. Because of the limited range and endurance, and also to preserve the essential requirement for ease and speed of prediction, there is no intention an elaborate standard of equipment for this aircraft or of regarding it as in any way capable of all weather operation. The standard to be aimed at is that n the hands of a pilot of average wartime skill and experience the aircraft should be capable of taking off, climbing, and of delivering its attack, and returning safely to base by day in weather conditions down to 8/8th cloud, with base about 2000ft, and visibility about 3 miles. Operation in conditions somewhat worse than this is expected to be practicable but it is accepted that it may involve an appreciable problem due to numbers of aircraft landing away from their own bases.
For Information Only.
Guidance to target.
31. It was originally intended to develop concurrently with the aircraft some special system of radio or radar guidance. However, after closer examination of the guidance system, it has now been decided to operate the aircraft under normal close control.
32. Flight instruments are required to supply all the information at present provided by the standard panel, in all conditions of flight of which the aircraft is capable. In particular, a means of presenting the pilot with information and pitch attitude and heading during near vertical climb.
Radio and Communications.
33. The following equipment is required:-
(a)VHF providing 10 channels.
(b) single channel stand by VHF
(d) IFF Mark 10
34. Connections are required for a pressure suit, an anti-g suit, and an air ventilated suit. If available the Universal coupling now being developed will be required. It should be possible to operate the aircraft whilst wearing an inflated pressure suit.
35. Oxygen is required for a climb to 60 000 ft., 15 minutes at this altitude, including 5 minutes after a cabin pressure failure and with the pressure suit inflated and a descent to below 10 000 ft in these conditions.
36. A source of electrical power is required which will provide electricity for the operation of essential equipment during the descent with the rocket motor off.
37. It is essential that every effort is made to design this aircraft to facilitate servicing. Accessibility of components is to be adequate to allow servicing by change of major components in the field by squadron personnel. The aircraft is to have a reliable performance with a minimum requirement for servicing and inspection, other than the need to replenish consumable stores, over any period of 100 hours flying or four moths elapsed time, which ever is the less. Provision is to be made for simple and rapid refuelling, re-arming and replenishment servicing to facilitate turn-round of the aircraft within the shortest possible time.
38. It will be necessary for adequate lifting or supporting points to be provided to facilitate transportation of aircraft if necessary, such as after a forced landing.
39. The Air Staff require this aircraft in service by 1957.
Air Ministry 18th August 1953.
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