Black Knight Flight Data

The information below is an edited version of a report entitled "A Summary of "Black Knight" Flight Data from 1958 to 1962", written by H.W.B. Gordon B.A. and L.W. Parkin MSc, which may be found in the Public Record Office, Kew [part of AVIA 6 17362]. The report was published in February 1964. It is incomplete in the sense that the Black Knight programme was not yet complete, but since it was declassified only in 1995, we may have to wait for the rest of the data.

From 1958 to 1962, fourteen "Black Knight" ballistic research vehicles were launched at Woomera. The first two were vehicle proving flights, being single stage rounds fitted with non-separating heads. Of the remaining twelve, six were single-stage and six two-stage rounds; separating heads were fitted on all twelve.

The Gamma engine, specially developed and built for Black Knight was used throughout as the first stage motor. The first version to be developed, the Gamma 201, was used for the first twelve firings and the Gamma 301, being a modification incorporating automatic mixture-ratio control, was used in the last two firings.

The second stage was added to provide greater re-entry velocity. In all such firings the Cuckoo Mk.I solid propellant motor was used, firing downwards after apogee.

The main purpose of the firings with the separating heads has been to obtain data on the behaviour of the head during re-entry into the atmosphere. In the two firings using the Gamma 301 engine, of equal importance was the proving of the vehicle, in particular the new engine and certain other new features on the second stage which would be required for the future DAZZLE programme of firings . The present Note gives a brief description of each vehicle fired, and summarises the results obtained. Only in certain cases have these results been discussed in any detail, viz. where they have led to important modifications.

SUMMARY OF FLIGHTS

BK.01 : The main objectives of this proving trial were achieved: ground handling techniques, trials procedures, launching, priming and monitoring equipment, all proved adequate. Propulsion, control, guidance and instrumentation, including telemetry, were satisfactory. The vehicle failed to reach the full estimated burn-out velocity due to an electrical fault in the destruct command system but 90% of the propellants were successfully burnt. The only major change made as a result of the trial was to eliminate that part of the guidance radar system which provided the "destruct command" facility, limiting the function of the system to guidance only. A second command link was fitted to provide the duplicate "destruct command" system required by WRE.

BK03, the second proving trial, was successful except for an engine malfunction late in flight resulting in a long period of "cold" thrusting (due to decomposition of H.T.P, in the absence of kerosene). The fault was subsequently traced to excessive heating of the propulsion bay, in which temperatures were measured during flight. Control of the vehicle was satisfactory both during "hot" burning and "cold" burning. In this trial, the guidance telescope tracking was made the primary source of information and radar tracking was retained as the stand-by; this proved very successful: very good tracking information with low noise was received until engine flameout, after which radar information was used during "cold" burning. Telemetry performance was generally satisfactory; most of the propulsion and control parameters were recorded and vibration environmental measurements were made.

BK04, the first re-entry experiment with a separating spin-stabilised head, was very successful. The main stage reached its designed burn-out velocity and both guidance and control of the vehicle were satisfactory. Telemetry on the main stage worked through flight over apogee to re-entry and valuable information on systems performance was obtained. The head separation, turnover and spin-stabilisation system was successful. The head re-entered (200,000 feet) at 11,740 ft/sec, telemetry worked throughout to impact, except for a short period during re-entry, and some information on re-entry dynamics and heating was obtained. Recovery of the head with the patches of materials under test attached to it yielded valuable information on ablation during re-entry.

BK05, a re-entry experiment using a double cone eroding head, was designed for greater penetration at high speed into the atmosphere with the object of obtaining much greater heating, particularly in the nose cone which was made of doorstops. A complicated parachute recovery system was built into the head in an attempt to prevent damage to the nose cone on impact.
Overheating in the propulsion bay, as in BK03 (unfortunately not confirmed until after BK05) again caused premature engine cut-out resulting in a reduced re-entry velocity.
A hitherto unsuspected long decay time of thrust at engine shut-down resulted in collision of body and head at separation. The body telemetry continued to function to re-enter but head telemetry ceased just after head separation; evidence suggests that during turnover the head aerial was broken by impact with the body. The head was recovered and it was found that the -parachute had torn out the inner core of the head and the base dome had been pulled off. Early deployment of the parachute would have resulted in excessive drag loads and it can only be assumed that this happened. Some supporting evidence is that the barometric switch used to deploy the parachute was found on recovery to operate at a pressure equivalent to 22,000 ft instead of the expected height of 10,000 ft.
However, the trial was not a complete failure. Recovery of the head yielded data on erosion, albeit at a lower re-entry speed than intended.

BK06 was a repeat of BK05 with a similar head but using a tape recorder to record separation and re-entry data. Vehicle performance was good, a re-entry velocity of' 11,220 ft/sec being achieved at 200,000 ft. There was some thrust even after the eight seconds allowed between burn-out and head separation; this caused collision between main stage and head, initiated the ejection of the pyrotechnic flashes and deployed the parachute on the ascent instead of later, as intended, during descent. The tape recorder in the head was switched on correctly and covered the separation phase and later part of the re-entry. The tape cassette, with recordings intact, was recovered together with the eroded durestos nose cone. Further data on erosion was obtained.

BK08, the first two-stage vehicle to be fired, was intended to-obtain re-entry of the head at a higher speed. Main stage performance was good but the second stage did not separate from the main stage and so was not ignited. The failure of explosive bolts or inertia switch circuitry was the probable cause. The trial, however, proved the aerodynamics of a new configuration, the control stability with the heavier vehicle, the stressing with greatly increased forward weight and the necessarily modified guidance arrangements.

BK09, the second two-stage vehicle, was most successful. Separation of the second stage, initiation of the second stage boost (by Phillips ionisation gauge) and separation of the head from the second stage boost was satisfactory. The second stage boost "lit up" at the correct height on the downward trajectory prior to re-entry and a re-entry velocity of 15,000 ft/sec was achieved at 200,000 f t. The tape recorder in the head recorded data during re-entry down to 80,000 ft. Just prior to this an abnormal and completely unexpected increase in head oscillation occurred. The head broke up shortly after this and unfortunately the last inch or so of tape which had passed through the tape head was lost. This corresponded to the period immediately prior to head break-up. The break-up of the head at a low height during re-entry indicated that either the plank construction of the head was unsatisfactory or abnormally high loading was applied during re-entry, may be resulting from an unstable oscillation. A single upper-atmosphere experiment, measurement of Sporadic E, worked satisfactorily. The "Gaslight" ground instrumentation (Photometers, Radiometers and Spectral ballistic cameras) obtained some re-entry information. The head conical surface durestos planks were recovered and peak temperature during re-entry estimated.

BK07 was a single stage vehicle with a high drag heat shield head equipped to give separation details, heat transfer data and re-entry dynamics, using telemetry. Extensive instrumentation was put in the motor bay to investigate base heating and pressure distribution. In addition lightly loaded spring flaps were fitted to the pressure bleed holes in the propulsion bay to check the direction of flow through these holes. Their movement was monitored by telemetry.
Changes in position of H.T.P. tank baffles were made to check on "H.T.P. slosh" and a kerosene level sensor was included to enable kerosene consumption to be measured.
Propulsion was satisfactory except that towards the end of the burning phase one of the four motors reverted to "cold" thrusting and this resulted in a reduced re-entry velocity. This motor fault was subsequently attributed to a failure of a kerosene feed pipe.
The head was separated from the main body but the additional thrust units in the head, provided to give increased separation, did not operate; nor did the turn over and spin thrust units. However, the head did re-enter nose first, but at large initial incidence; the recovered head shows that impact was on the nose and that there was no re-entry burning on the afterbody. Head telemetry was extremely good and re-entry data was obtained. Complete dynamic analysis of the re-entry head was possible and head temperatures during re-entry were obtained.
Temperatures and pressures in the motor bay were measured. The flaps over the base bleed hole in the motor bay opened at engine light-up and shut (two at 83 seconds and two at 89 seconds) without significant changes in motor bay pressures. There was no significant effect of the new arrangement of baffles in the H.T.P, tank on slosh damping.
The kerosene level sensor worked and the kerosene flow rate was determined. The upper atmosphere experiments, Geiger and scintillation counters and Sporadic E, were switched on correctly just after engine burn-out. The tracking lamps which were fitted for the first time to this vehicle were seen clearly by the guidance telescope operator and the kinetheodolitc operators after engine flame-out until about 200 seconds. The electronic flash unit failed to function.

BK13 was a single stage vehicle with a double cone eroding head similar to BK.05 and BK.06 except for
(1) the substitution of a low-power telemetry beacon plus a tape recorder in place of the normal telemetry sender (BK05) or tape recorder (BK06),
(2) the use of a cine camera for filming the head wake during re-entry and,
(3) the deletion of the recovery parachute system.
As in BK07, further measurements were made in the motor bay to investigate base heating and pressures.
A kerosene level sensor and H,T.P. level probes were used to provide information on mixture ratio during flight. Two upper atmosphere research experiments were carried - Ionic composition and Galactic radio noise. Propulsion was good and a re-entry velocity of 10,870 ft/sec was achieved at 200,000 ft. Motor bay temperatures and pressures were successfully recorded. The flaps over the base bleed holes opened before take-off and closed later as in BK07. The kerosene level sensor and H.T.P. probes worked and propellant usage in flight was determined. The head separation, turnover and spin systems were faultless, as were the pyrotechnic flashes on re-entry. Unfortunately, due to an incorrect setting of the switch, the tape recorder in the head started too soon and the tape had run out before re-entry; for the same reason the camera in the head did not record the re-entry wake. The durestos nose cone and materials specimens were recovered and erosion measurements were made. The electronic flashes were observed clearly but the tracking lamps were not seen.

BK14 was another two-stage vehicle with second stage and head similar to that of BK08. The initiation of the second stage light-up was to be by means of a Phillips ionisation gauge as on BK09. Upper atmosphere experiments carried were a cosmic ray scintillation counter and electron temperature measurement. Premature "run-out" of kerosene occurred at 128 seconds followed by fourteen seconds "cold" burning; the final shutdown occurred at the correct time. Subsequent analysis of records indicated that a leak had developed in the kerosene supply system which accounted for the excessive kerosine flow rate. Initiation of second stage srparation was dependent on the operation of an inertia switch. Due to a drop in first stage performance, associated with cold burning, the acceleration was not high enough to operate the switch. Because of this, events following burnout, such as second stage separation, spin, ignition, head separation and and recording did not take place. Had the second stage operated, the resultant re-entry velocity would have been adequate for a satisfactory experiment. In view of this, alternative methods for arming second stage separation, not dependent on first stage perforfmance, were subsequently employed. Because the second stage did not separate, there was no change-over of selected telemetry channels to upper atmosphere measurements. The tracking lamps were seen and aided tracking until 200 seconds.

BK17 was another two-stage vehicle but with a lighter low-drag eroding head to give higher re-entry speed. The first stage performance was very good. The kerosene level sensor and H,T.P. probes worked well and propellent usage in flight was determined. Visual observation and camera records of re-entry were confusing but it soon became clear that the second stage had not functioned correctly. The head and tape recorder were recovered. Subsequent analysis of head tape record and body telemetry indicated that second stage separation occurred at re-entry and not at the end of first stage burning. It was possible to deduce from the records that the failure of second stage separation at first stage burn-out was due to failure of one of the two explosive bolts. (In subsequent vehicles explosive bolts and associated circuits were duplicated.) Subsequently at re-entry the second stage was torn off, followed by second stage burning. Body telemetry was satisfactory until re-entry: good records were obtained of motor pressures, control data and propellant levels. After burn-out telemetry channel change-over switch No.1 operated so electron temperature was recorded and the "Faraday" propagation experiment was successful but, because switch No.2 failed to operate, the galactic radio noise was not recorded.
In subsequent vehicles change-over of telemetry channels was time-operated and independent of second stage operation. The head was separated from the second stage but remained in the separation bay of the body until at re-entry physical separation of body, second stage and head took place.
The tape of the recorder in the head ran out before re-entry. In subsequent heads, the speeds of the tape in the tape recorder was reduced so as to run for a longer period and ensure recording re-entry.

BK15 was a re-entry physics experiment but limited by the availability of' ground instrumentation on the range at the time, i.e. the "Gaslight" project equipment and not the more sophisticated "Dazzle" project equipment.
A single stage vehicle was fitted with a separating uninstrumented 36 inch diameter copper sphere (the first pure metal head used). The object was to achieve re-entry of the sphere in advance of and well separated from the main body, to provide spatial resolution for ground instruments. This was to be done by turning the vehicle over in the yaw plane after engine burn-out and separating and pushing the head vertically downwards away from the body when it had turned through 180o.
A sabot containing thrust units was used to push the head away; the sabot itself was to have remained attached to the body by a lanyard. Subsidiary upper atmosphere experiments were also carried out and further data obtained on Gamma 201 engine performance and propellant usage. It was also intended to test for the first time an "automatic pilot" in the ground guidance system. The vehicle was loaded correctly, the utilisation of propellant was efficient and the performance of the motor was excellent. A head re-entry velocity of 11,600 ft/sec was achieved at 200,000 feet.
Due to guidance telescope tracking difficulties the "automatic pilot" was not introduced during flight as intended. Telemetry was very good and measurements were made in the upper atmosphere by the Cerenkov scintillation counter, the Sporadic E probe and in the Faraday Rotation experiment. The vehicle turnover and head separation devices worked but the timing of the latter was incorrect; the head was separated before the vehicle had turned through 180o.
The lanyard failed to hold the sabot to the body and the sabot therefore accompanied the head. The re-entry of the body and sabot was recorded by the Baker Nunn camera. The re-entry of the head was not recorded by any ground instrument nor was it seen by any observer. This in itself is a significant result since it confirms the prediction that, because of the absence of ablation products and other contaminants in its wake, the re-entry into the atmosphere of a puce copper head should be a target difficult to detect by optical means. The sphere was recovered and, as expected, there was no heat discolourisation of the surface; the maximum surface temperature did not exceed 350C during re-entry.

BK16 was the proving trial of the Black Knight vehicle for re-entry physics experiments (Project Dazzle). It was a two-stage vehicle powered for the first time by a Gamma 301 engine. A transistor control system was also tested for the first time. To meet the requirements for the re-entry physics experiments, ignition of the second stage was timed to occur at about one million feet and the head was separated from the second stage at an increased velocity in order to achieve re-entry of the head well separated (15,000 feet) from the rest of the vehicle at re-entry. To ensure acquisition of the re-entry of the head by ground instruments, a "C" band transponder was flown in the second stage and tracked by AN/FPS.16 radars at the range. The head was a 15o semi-angle copper cone, shape G.W.20, a type to be flown later in the Dazzle programme. As with BK15, limited ground instrumentation was available to obtain some re-entry data. Dynamics and head temperature measurements during re-entry were also included in this trial. Some upper atmosphere experiments: proportional counter, electron temperature and Faraday rotation, were also carried out.
Propulsion was very good, a re-entry velocity of 14,600 ft/sec was achieved at 200,000 feet.
Telemetry was successful: all engine pressures, control system parameters and guidance data were successfully recorded. Motor bay temperatures were measured on the ascent.
Once again, as with BK15, difficulties with guidance telescope tracking necessitated a change back to radar information for guidance until telescope tracking was resumed. All the aims of the trial were achieved. The Gamma 301 engine and the transistor control system were both proved in flight. Separation and ignition of the second stage and separation of the head were achieved according to plan. The FPS.16 radars successfully tracked the "C" band transponder and excellent records were obtained from which the trajectory and all events (second stage separation, spin and ignition and head separation) were determined. The range at Woomera was provided with an excellent opportunity of rehearsing for the "Re-entry Physics" experiments to follow. The head tape recorder was recovered and data on re-entry dynamics and temperatures was obtained. The trial confirmed expected re-entry characteristics of an uncontaminated low-drag head.

BK18 was the second proving vehicle for the Gamma 301 engine and the transistor control system. The head was a 12.5o semi-angle doorstops cone, 2 inch nose radius (as on head H2/04) and with a seem-elliptical base (as on head H2/03) and was fitted with accelerometers and rate gyroscopes for investigation of re-entry dynamics.
No provision was made to measure re-entry heating. No attempt was made, either, to meet the requirements for radiation measurements by ground instruments, by separating the re-entry of the head from that of the second stage as was done in. Ignition of the second stage was planned (as in and) to be initiated by the Phillips ionisation gauge at about 350,000 feet altitude on the descent.
Instead of a "C" band transponder, a pyrotechnic flare was fitted to the second stage to be ignited with the second stage, to aid acquisition by ground instruments. Propulsion was once again excellent; a re-entry velocity of 15,750 ft/sec was attained at 200,000 feet. The transistor control system was proved for the second time. The guidance telescope tracking problem was again evident, and the guidance radar information was used throughout flight for guidance and proved most satisfactory. All the vehicle systems were successful. The second stage flare was ignited in vacuo and proved to be a useful acquisition aid for sighting ground instruments. Ground instrumentation was successfully operated and re-entry instruments data was obtained. The head tape recorder was recovered and all the data was successfully recorded, from which the dynamic behaviour of the head during re-entry was determined.

H.W.B. Gordon B.A. and L.W. Parkin MSc.

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