RM-90 Blue Scout II

The RM-90 Blue Scout II was an American sounding rocket and expendable launch system which was flown three times during 1961.^[1][2][3] It was a member of the Scout family of rockets.^[4] Blue Scout II was a military version of the NASA-operated Scout X-1, with adjustments to the payload fairings, engine nozzles and fins.^[1][3]

Blue Scout II rocket
Function	Expendable launch system Sounding rocket
Manufacturer	Vought
Country of origin	United States
Size
Height	24 metres (79 ft)
Diameter	1.02 metres (3 ft 4 in)
Mass	16,874 kilograms (37,201 lb)
Stages	Four
Capacity
Payload to LEO
Mass	30 kilograms (66 lb)
Associated rockets
Family	Scout
Launch history
Status	Retired
Launch sites	Canaveral LC-18B
Total launches	3
Success(es)	2
Failure(s)	1
First flight	1961-03-03
Last flight	1961-11-01
First stage – Algol 1B
Powered by	1 solid
Maximum thrust	471 kilonewtons (106,000 lbf)
Specific impulse	236 sec
Burn time	40 seconds
Propellant	Solid
Second stage – Castor 2
Powered by	1 TX-354-3
Maximum thrust	286 kilonewtons (64,000 lbf)
Specific impulse	247 sec
Burn time	27 seconds
Propellant	Solid
Third stage – Antares 1A
Powered by	1 X-254
Maximum thrust	60 kilonewtons (13,000 lbf)
Specific impulse	256 sec
Burn time	39 seconds
Propellant	Solid
Fourth stage – Altair 1A
Powered by	1 X-248A
Maximum thrust	14 kilonewtons (3,100 lbf)
Specific impulse	255 sec
Burn time	40 seconds
Propellant	Solid

Blue Scout II had a total length of 21.65 m and a finspan of 2.84 m.

It was capable of sending a 30 kg payload to a 300 km orbit at 28.00 degrees.^[1] It was a four stage vehicle, with the following engines:^[1][2][3][5]

• Stage 1: Algol 1B, solid propellant;

• Stage 2: Castor 2 (TX-354-3), solid propellant;

• Stage 3: Antares 1A (Star 31/X-254), solid propellant;

• Stage 4: Altair 1A (X-248), solid propellant.

Blue Scout II was used for two HETS test flights, and the launch of the Mercury-Scout 1 satellite for NASA.^[1][2][6] This rocket and RM-89 Blue Scout I were replaced by Blue Scout Junior.^[3]

Blue Scout II parameters

Parameter	1st Stage	2nd Stage	3rd Stage	4th Stage
Gross Mass	10,705 kg	4,424 kg	1,225 kg	238 kg
Empty Mass	1,900 kg	695 kg	294 kg	30 kg
Thrust	470 kN	259 kN	60.5 kN	12.4 kN
Isp	214 s (2.10 kNs/kg)	262 s (2.57 kNs/kg)	256 s (2.51 kNs/kg)	256 s (2.51 kNs/kg)
Burn time	40 s	37 s	39 s	38 s
Length	9.12 m	6.04 m	3.38 m	1.83 m
Diameter	1.01 m	0.79 m	0.78 m	0.46 m
Engine:	Aerojet General Algol 1	Thiokol XM33 (TX-354-3) Castor 2	Allegany Ballistics Lab X-254 Antares 1A	Allegany Ballistics Lab X-248 Altair 1
Propellant	Solid	Solid	Solid	Solid

Launches

All three Blue Scout II launches occurred from Launch Complex 18B at the Cape Canaveral Air Force Station, the same launch pad used for the Blue Scout I.^[1][2]

The first two launches were successfully conducted on 3 March and 12 April 1961 respectively, using vehicles D-4 and D-5.^[1][2][7] They both carried HETS A2 plasma research experiments on suborbital trajectories.

The third launch was conducted on 1 November, using vehicle D-8, with the Mercury-Scout 1 satellite for NASA, which was intended to reach low Earth orbit.^[6] The launch failed after the rocket went out of control, and was destroyed by the range safety officer 43 seconds after liftoff.^[1][2]

Date	Serial	Agency	Orbit	Mission Description
1961 March 3	D-4	USAF	Suborbital, 2540 km apogee[7]	HETS A2-1 plasma mission
1961 April 12	D-5	USAF	Suborbital, 1931 km apogee[7]	HETS A2-2 plasma mission
1961 November 1	D-8	USAF	373 km × 643 km, 32.5° (planned)[6]	Mercury-Scout 1 (failure)