Ranger Block Seismo capsules

The three Ranger Block 2 missions - Rangers 3, 4 and 5 - were the first, albeit unsuccessful attempts to soft land and return data from an extraterrestrial surface. Having separated from the upper stage of the launcher, the Ranger cruise stage would have delivered the landers to the lunar surface on a direct descent trajectory. The landers comprised a 63.5 cm diameter balsa wood capsule mounted on a solid retro motor for descent braking. The spherical capsule enclosed and protected a 27.5 cm diameter seismometer experiment. Lunar planetary protection requirements of the time were met by baking of components at 125 °C for 24 h, clean assembly and bathing of the assembled spacecraft in ethylene oxide (Figure 17.1).

Target Objectives

Prime contractor Launch site, vehicle

Launch date Arrival date

Landing site co-ordinates

End(s) of mission(s)


Payload experiments

The Moon

To achieve the first soft landing on the Moon and transmit lunar seismic data Aeronutronic Division, Ford Motor Company ETR, Atlas-Agena B

Ranger 3 Ranger 4 Ranger 5

26/01/1962 23/04/1962 18/10/1962

Missed by 37745 km Impacted on 28/01/1962 6/04/1962

Missed by 724 km on 21/10/1962

(lunar far side)

Seismo capsules had an expected lifetime of 30-60 days Rangers 3 and 5 were tracked until 31/01/1962 and 30/10/1962, respectively.

Lunar capsule system: 148.3 kg, incl. ^98 kg retro motor

• Capsule temperature & maximum deceleration measurement (Ewing)

The Project Scientist was Harold Washburn

Delivery architecture Thermal aspects

Power aspects

Communications architecture

EDL architecture

Landing speed(s)

Active operations (deployments, etc.)

Key references

Separation from cruise stage during approach at 21.4 km altitude

Insulation and 1.68 kg of water evaporating in an open-loop cooling system. 'Shower curtain' aluminized Mylar insulation surrounded the lander during cruise. Black 'saw-tooth' surface pattern added to white capsule for Rangers 4 and 5 to maintain a more even temperature during cruise

AgCd battery

One-way DTE phase-modulated analogue signal at 960 MHz, 50 mW

Spin-up to 300 rpm and firing of solid retro-rocket (Hercules BE-3). Separation of 63.5 cm diameter balsa wood capsule from retro upon burnout at 300 m altitude, then free-fall to surface

Intended: <56 ms-1; Ranger 4 impacted at 2.67 km s-1

Righting of seismometer achieved passively using freon liquid, which was then removed by means of a puncturing device

Hall, 1977; NASA, 1962, 1963; Wilson, 1982; Adamski, 1962

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