Crown Copyright. From PRO file AVIA 65/1568
Notes on a proposal for a liquid hydrogen/liquid oxygen Second Stage Black Knight.
1. Work is in progress in Satellite Launcher Division, GW Department, on a design of a
second stage Black Knight, using liquid hydrogen/liquid oxygen as a propellant. This work is
related to Westcott work on LH2/LO2 combustion chambers and design studies in
conjunction with Saunders Roe on an advanced B.S.S.L.V. third stage.
2. Initial design considerations
Design studies work started with the following major objectives:-
2.1 The design of the second stage using the most promising propellant combination to gain experience of liquid Hydrogen/liquid Oxygen problems in: -
(a) engine design and associated propellant supply problems.
(b) structural design with special problems of obtaining good structural weight factors with low density propellants and the need for thermal insulation.
(c) light-up, separation problems, re-light, free-fall, transition to low thrust, and other related systems problems.
2.2 Maximum flexibility in design for the addition of more complex systems as research proceeds, i.e., alternative methods of propellant supply. Relating to this desired flexibility a tentative requirement was established for the ability to ground-launch the stage alone.
2.3 It was considered important that engines, component and structural techniques developed should have in all cases direct application to any related launching vehicle, specifically B.S.S.L.V.
2.4 The design shall demand the minimum of modifications to Black Knight or its associated facilities.
2.5 The design shall permit all design of guidance techniques.
2.6 The capability to launch a payload into the earth orbits shall be aimed at.
2.7 Last, but more important, development and manufacturing costs should be kept to a minimum.
3. Design details
Work so far has indicated that most of these objectives can be met. However, without fairly extensive modification, Black Knight with a second stage cannot launch a payload into orbit with any degree of confidence. Performance calculations and scantling weight estimates show that the stage alone without an additional third stage, may attain a 300 miles orbit. But a very small pay-load, sensitive to structure and ancillary systems weight growth, would almost disappear. The configuration consisting of Black Knight with Gamma 301 engines working at a Take Off thrust of 25,000 lb. (the limit of its present design) a 2,200 lb. LH2/LO2 stage and a third stage propellant motor of about 450 lb. weight with performance and charge/total weight ratio similar to that of the Scout "Altair" motor may project a 150 lb payload into a 300 mile orbit making fairly pessimistic performance assumptions.
These factors indicate that design aims may be followed in stages as follows:-
1. The development of a "basic" second stage with perhaps first launching from the ground using Black Knight range facilities.
2 Launchings from Black Knight with sub-orbital performance testing of advanced systems in flight as necessary.
3. The addition of the third stage for orbital launching.
4. Design of the "basic" second stage
R.P.E., Westcott and ourselves considered the best design for the "basic" second stage should employ pressure fed chambers using helium gas bottles. Thrust and stage weight optimisation calculations are not yet complete (1.12.61), but present figures are:
|Chamber Pressure||120 p.s.i.|
|Vacuum S.I.||400 secs|
Engine of four chambers each chamber 1,000 lb. thrust.
S.I. dependent expansion ratio with four chamber design
expansion ratios of 1,000 to 5,000 are possible adding considerable SI bonus.
|Stage weight||2,000 to 2500 lb.|
|Total burning time||circa of 160 secs|
The main design problem is that of the combustion chamber. This would be based upon current R.P.E, injection chamber design and would need an extension of the work to the
cooling of the expansion nozzle. This would be partially cooled by propellants and partially by radiation (c.f. Agena expansion cone). Each chamber would be developed with a
vacuum thrust of 1,000 lb. and mounted with a complete engine as a four chamber assembly similar to B.K.
Helium pressure feed to the chamber as an initial approach would minimise development work in this area. Ignition system end control valves would need development and/or adaptation together with expansion of LH2 handling techniques.
Low temperature structural strength thermal insulation and other cryogenic problems will need a fair amount of supporting research. The stage, if 3 ft. in diameter will be 14 ft. long. Structural material under consideration would include:
1. light alloys
3. Stainless steel.
4. Fibre glass
5. Multi-reflector super-insulation
Scheme investigations in connection with third stage designs indicated that as in BK the use of chamber pairs for pitch and yaw and all chambers for roll should be satisfactory. Autopilot electronics except for modified shaping networks may be borrowed from from the transistorised BK design. Auto-gyros will depend upon the time of flight. For second stage firings, say of 150 lb, to a probe height of 4,000 miles, a standard BK package would be adequate. For orbital flights using a third stage version the Reid & Sigrist gyro wander rate is excessive for accurate third stage injection. Orthodox integrating rate gyros with wide angle degree of freedom may be necessary.
Overall control of multi-stage vehicle during the first stage of the ascent through the atmosphere is under investigation. Aero-elasticity effects of 20/1 fineness ratio vehicle of similar geometry to Scout and Vanguard must be closely investigated.
Radio command guidance is advocated. Initial take off turn over be handled by the Black Knight visual and SCR 584 installation. FSP.16 tracking and WREBUS command guidance now that facilities exist should be inexpensive since optical tracking range extends to Black Knight "all burnt" range it may be possible to eliminate the SCR.584 phase and use FPS.16 tracking with first and second stage above, say, 10 miles. Closed loop guidance for sub-orbital - and elliptical orbit flights - can be eliminated using programmed auto-pilot. This topic is under investigation.
All electronic equipment for the second stage:-
1. Auto-pilot and electronics, space datum and programme.
2. Power supplies
3. Small FPS.16 beacon.
5. WREBUS receiver.
would be located in a forward pressurised bay as in Black Knight.
Propulsion bay equipment would consist of :-
2. Pressurised bottles.
3. Spark ignition coil and battery
4. Chamber actuator (electric actuators appear very satisfactory here, but single shot pneumatic and hydraulic systems are being looked into.)
Electronic bay equipment weight is assumed as 230 lb. This is conservative.
5. Possible third stage designs.
Two types of design are being considered.
1. An orthodox solid stage orientated by the second stage attitude at cut-off into the correct injection direction and spun-stabilised by lateral spin rockets, as originally planned for the Black Knight re-entry second stage.
Cuckoo motor as it exists is about the right size but its case weight is excessive compared with comparable U.S. motors such as Altair used in Scout of the same size. Tho specific impulse of 240 seconds in Vacuo assumed in performance calculations is no problem. Case weight reduction to U.S. standards will need development of the type now under was at R.P.E. (Cuckoo II).
2. Again eliminating the need for equipment in the third stage other than pay-load a spun third stage is considered but using LH2/LO2. A design using a single 1,000lb fixed chamber of the type required for the second stage and spherically wound fibre LH2 and LO2 resevoir, helium pressure feed and spinning at, say, 20 rads/sec. is being looked at. Performance bonuses ...
6. Ground Facilities.
The use of Black Knight facilities eliminates considerable cost. Main additions will be :
1. Monitoring consul in E.C.5 for second stage function (in quiescence)
2. Addition to the Servicing tower to take the increased height of the configuration. Since the towers each cost 10,000 each modifications should not be a large item in the total budget.
3. An extension to the cable mast.
4. LH2 and LO2 bowser facilities
5. LH2 plant. A 320 lb/week is suggested
An 'off the shelf' price of £20,000 has been suggested.
7. Time Scale.
Based on the Black Knight exercises, three years from go-ahead to first launching appears feasible, (B.K. contract June 1955, first launching September, 1958.)
In view of the need far no new capital facilities, Westcott have stated two years as development for the engine unit briefly described produced by them with contractor assistance. This is compatible in terms of time scale.
8. Cost and mode of development.
Cost estimates are based on the following mode of development.
1. R.A.E. have overall authority for the vehicle design as in B.K.
R.P.E. have prime authority for engine development and design. Basically chamber and some aspects of the feed system. The 1,000 lb. engine can be developed in the present facilities. LH2 will be derived from a plant now being installed by Westcott producing 320 lb. a week at a cost of 30s. a lb..
3. Structure and some aspects of feed system.
This will be under R.A.E. authority, Space Department, Structures Department Met./Phys. Department, Chemistry Department and a Prime Contractor say, Saunders-Roe. Overall assembly may be possible in R.A.E.
This will be jointly designed, developed and produced with Space Department and contractors.
5. Static firing tests of complete second stage vehicles. R.P.E. are looking into the possibility of using the P.1 site.
There [sic, These?] estimates are initial ones and should need further close examination. The scale of work is estimated at two launchings a year. Large modifications costs for Black Knight are not included.
... back to the liquid hydrogen page ...