Exos

Sounding rocket. Country: USA. Status: Retired 1965. Department of Defence Designation: PWN-4.

Three stage vehicle consisting of 1 x M-6 + 1 x Nike + 1 x Recruit

Historical Essay © Andreas Parsch

University of Michigan RM-86/PWN-4 Exos

The Exos sounding rocket was developed by the University of Michigan with the assistance of NACA under a contract from the Air Force Cambridge Research Center (AFCRC). It was a three-stage rocket combining an M6 Honest John (see M31/MGR-1A) first stage, an M5 Nike Ajax (see SAM-A-7/MIM-3) second stage and a Thiokol XM19 Recruit as third stage. The three fins of the Nike booster had to be replaced by four new clipped-delta fins. The Exos is very similar, but not identical to the Aerolab Co. Argo C-1, which used the same combination of rockets, but a slightly different aerodynamic design. The first flight test of an all-up Exos rocket occurred in June 1958.

After zero-launch from a specially built rail launcher, the first stage burned for about 4.4 seconds, after which it was separated from the vehicle by aerodynamic drag. After 25 seconds of coasting, the second stage fired for about 3 seconds, followed by separation and almost immediate firing of the third stage for further 1.6 seconds. The third stage and payload nose cone then continued to coast to an apogee of about 480 km (300 miles) (for a 23 kg (50 lb) payload).

In April 1959, the USAF allocated the formal research missile designation XRM-86 to the Exos at the request of the AFCRC, and in June 1963 this designation was changed to PWN-4A. At least eight research flights of XRM-86/PWN-4A vehicles were launched from Eglin AFB between February 1960 and November 1965, mostly with ionosphere research experiments as payload.

Note: Data given by several sources show slight variations. Figures given below may therefore be inaccurate!

Data for PWN-4A:

[1] Frederick I. Ordway III, Ronald C. Wakeford: "International Missile and Spacecraft Guide", McGraw-Hill, 1960
[2] Norman J. Bowman: "The Handbook of Rockets and Guided Missiles", Perastadion Press, 1963
[3] Department of Defense Missile Nomenclature Records
[4] "Sounding Rocket Study of Eighteen Vehicles, Summary Report", NASA, 1961

Manufacturer: Michigan. Launches: 10. Failures: 1. Success Rate: 90.00%. First Launch Date: 1958-06-26. Last Launch Date: 1965-11-02. Launch data is: complete. Apogee: 600 km (370 mi). Liftoff Thrust: 365.000 kN (82,055 lbf). Total Mass: 2,600 kg (5,700 lb). Core Diameter: 0.58 m (1.90 ft). Total Length: 12.90 m (42.30 ft).

• Stage1: 1 x HJ Nike-1. Gross Mass: 1,900 kg (4,100 lb). Empty Mass: 954 kg (2,103 lb). Motor: 1 x M-6. Thrust (vac): 365.000 kN (82,055 lbf). Burn time: 5.00 sec. Length: 4.90 m (16.00 ft). Diameter: 0.58 m (1.90 ft). Propellants: Solid.

• Stage2: 1 x HJ Nike Nike-3. Gross Mass: 599 kg (1,320 lb). Empty Mass: 256 kg (564 lb). Motor: 1 x M5E1. Thrust (vac): 195.600 kN (43,973 lbf). Burn time: 3.40 sec. Length: 3.60 m (11.80 ft). Diameter: 0.42 m (1.37 ft). Propellants: Solid.

• Stage3: 1 x Nike Yardbird-2. Gross Mass: 200 kg (440 lb). Empty Mass: 29 kg (63 lb). Motor: 1 x Yardbird. Thrust (vac): 75.000 kN (16,860 lbf). Burn time: 3.40 sec. Length: 2.50 m (8.20 ft). Diameter: 0.23 m (0.75 ft). Propellants: Solid.

1958 June 26 - Wallops Island -. Model 1 test Agency: NACA/AFCRL. Apogee: 370 km (220 mi).

1958 September 25 - Wallops Island -. Model 2 test Agency: NACA/AFCRL. Apogee: 460 km (280 mi).

1960 February 19 - 17:18 GMT - Eglin -. Exos CRL AA13.320C FAILURE: Failure. Chemical release mission Agency: USAF. Apogee: 37 km (22 mi).

1961 August 11 - 14:30 GMT - Eglin -. Exos CRL AA13.194 Ion density Test / ionosphere mission Agency: USAF. Apogee: 114 km (70 mi).

1962 August 3 - 17:46 GMT - Eglin -. Bipolar Probe Ionosphere mission Agency: USAF. Apogee: 365 km (226 mi).

1962 October 25 - 06:00 GMT - Eglin -. Exos CRL AA13.195 Ionosphere mission Agency: USAF. Apogee: 669 km (415 mi).

1963 July 25 - 22:38 GMT - Eglin -. Exos CRL AC13.831 Refractive Index Ionosphere mission Agency: USAF. Apogee: 623 km (387 mi).

1965 May 25 - 23:20 GMT - Eglin -. Exos CRL AD13.815 EM Absorption Ionosphere mission Agency: USAF. Apogee: 488 km (303 mi).

1965 May 26 - 23:20 GMT - Eglin -. Exos CRL AD13.812 EM Absorption Ionosphere mission Agency: USAF. Apogee: 488 km (303 mi).

1965 November 2 - 20:00 GMT - Eglin -. Exos CRL AE13.559 IQSY 30-kg Sphere Aeronomy mission Agency: USAF. Apogee: 686 km (426 mi).