NASA Apollo project Lunar Roving Vehicle(LRV)

• length:122inches (310cm)
• width:6ft (183cm)
• wheel base:90inches (230cm)
• weight:on the Earth:462pounds(209kg) on the Moon:77pounds(35kg)
• ground clearance:14inches (35.5cm)
• turning radius:10ft (305cm)
• maximum speed:8.7mph (14km/h)
• power supply:36V primary silver-zinc batteries x 2, DC motor x 4
• range:about57miles (92km)
• manufacturer:BOEING Company Space Center Seattle, Washington. General Mortors Delco Electronics Division's Santa Barbara Operation California. (navigation system:BOEING Company Aerospace Group Electronics Organization)

Development

LRV was built by Boeing Company and their subsidiary : General Mortors Delco Electronics Division under a contract from NASA Marshall Space Flight Center. In 1969 when Apollo 11 succeeded to reach the Moon, Moon bike for one man ride was researched. Before release of LRV-1 for Apollo 15, following eight test vehicles were made for development.

• Full scale mock-up : for design verification.
• LM-LRV : for examine influence to LM structure while load on LM.
• two One sixth weight units : for develop Deployment System mechanism
• Mobility test unit : to prove the drive system.
• Nnormal Earth-gravity unit : for astronaut training o the Earth made by Delco Electronics.
• Vibration unit : to uncover any potential weakness in structual design.
• Qualification unit : tested under the conditions expected on the Moon surface.

And three LRVs from LRV-1(APOLLO15) to LRV-3(APOLLO17) was made and used on the Moon. Seat belt design was changed at LRV-2, and fender design was changed at LRV-3.
LRV-1 was released to NASA at 14.Mar.1971. It was only 17 month after Boeing start to develop LRV. It is said that this was phenomenal speed, considering that all Apollo units (from CSM to spacesuits) took 50-60 months from start of development to shipment.

Performance

LRV will carry total about 1140 pounds (517kg), include two astronauts and their life support system(PLSS), scientific experimentation materials about 340 pounds, lunar samples, This is over twice its own weight, In comparison, the average family automobile can carry only about half its weight. And the operational lifetime of the LRV on the Moon was about 78 hours during the lunar day.
The LRV can climb over obstacle one-foot high from standing start, and cross 28-inch crevasses. The fully loaded vehicle will be able to climb and descend slopes as steep as 25 degrees. A parking brake will hold the LRV on slopesup to 35 degrees. The LRV can run on the slope of 45 degree in pitch and roll with full load.
It's maximum speed reach 14km/h in Apollo 15 mission, and 17km/h in Apollo 16.

Structure

Floor panels of the chassis were beaded aluminum panels. Ground clearance was kept from 17inch(empty) to 14inch(full load) by dumper. Two seats are tubular aluminum frames spanned by nylon. They are folded flat onto the center chassis and unfolded somewhat like a lawn chair by the astronauts.

Control and display console was installed at the ceter of the chassis. On the console, there is a hand controller, navigation system to show the distance and direction from LM. And arm rest made by fiberglass was provided in front of hand controller.
The wheels are an open wire mesh design with a chevron tread covering 50 percent of the surface contact area. Each wheel is driven by its own separate traction drive assembly consisting of a harmonic drive reduction unit, drive motor, and blake assembly. And fiberglass fender was attached at each wheel. the part of the fender is furnished by astronauts on the moon.
The drive motor were direct-current series, brush-type 36VDC, 1/4 horsepower motor. Each motor is instrumented for thermal monitoring. A thermal switch at each motor will close when its upper operating temperature is approached. The harmonic drive reduction unit reduces the motor speed at the rate of 80:1 and allows continuous application of power to the wheels at all speeds without requiring gear shifting. Brake was mechanical, and controlled from hand controller by wire.
The front and rear steering assemblies are mechanically independent of each other. Provision is made to steer with either set of wheels (or both sets). In the event of a steering malfunction, one set of wheels may be disconnected mechanically, and the misson can continue using the active steering system. Maximum travel of the steering linkage results in an outer wheel angle of 22 degrees and an inner wheel angle of 50 degrees.

Two batterys are installed on front chassis. Each batteryis designed for a capacity of 115 ampere hours and contains 23 cells. Each battery weighs 59 pounds. Re-charge of these battery is impossible.
DGU:DIRECTIONAL GYRO UNIT and SPU:SIGNAL PROCESSING UNIT were installed on on front chassis too. DGU was used to know LRV heading direction and the north direction of the Moon. And SPU carries out digital and analog computer functions. These equipments are coverd with multilayered aluminized mylar and nylon netting insulation blanket with a white beta cloth. Aluminum thermal straps connected to the SPU and DGU transfer heat away from the electronic components and store it in the batteries and fusible mass heat sinks. At the end of the lunar sortie, astronauts open fiberglass dust covers to expose fused silica thermal mirrors mounted on top of the batteries. When the batteries reach their lower limit operating temperature of approximately 45 degrees Fahrenheit.

How to drive

LRV was controlled with T-shaped hand controller on the console. You can handle LRV with one hand, and can run to front and rear with various speed. Tilting the controller left or right of the neutral position initiates steering commands in the direction the controller moves. Tilting the controller forward of the neutral position proportionally increases forward speed.

Reverse power is applied when the controller is tilted backwards past the neutral position and a reverse inhibit switch on the hand controller is thrown by the driver. Braking is initiated when the controller is pulled backward. At approximately three inches backward, a spring-loaded catch will engage the handle to lock it in the "park" position. A "turn left" command releases the parking brake.

Control and Display Console

The Control and Display Console is divided into two main parts. navigaion on the upper section of the panel and controls for switching and monitoring of electrical loads on the lower section.

INTEGRATED POSITION INDICATOR(IPI) / HEADING INDICATOR

displays the LRV heading with respect to lunar north.

BEARING INDICATOR

shows bearing to the LM.

DISTANCE INDICATOR

reports distance traveled by the LRV in increments of 0.1 kilometer. This dispaly is driven from the navigation signal processing unit which, in turn, receives its inputs from the third-fastest traction drive odometer to compensate for wheel slipping.

RANGE INDICATOR

shows the distance to the LM.

ATTITUDE INDICATOR

provides indications of LRV pitch and roll. To read roll angles, the indicator is rotated forward, which exposes the ROLL scale to the left crewman. This indication is read by the crew and reported to the Mission Control Center.

SUN SHADOW DEVICE

determines the LRV heading with respect to the sun. This heading can be compared with the gyro heading at regular intervals as a check against gyro drift. When lifted into position, the device casts a shadow on a graduated scale.

SPEED INDICATOR

shows LRV velocity from 0 to 20 km/h. This display is driven by the odometer pulses from the right rear wheel.

GYRO TORQUING SWITCH

adjusts the navigation gyro to correct the HEADING indication. Moving the switch RIGHT moves the heading scale counterclockwise; with the switch in LEFT, the scale rotetes clockwise.

NAV POWER CIRCUIT BREAKER

used to route power from the main busses to the navigation subsystem.

SYSTEM RESET SWITCH

used to reset the BEARING/DISTANCE/RANGE digital displays to zero.

POWER SECTION

contains the circuit breakers that connect the batteries with the main power busses, the auxiliary outlet circuit breaker, and the circuit breakers and controlling switch for the +-15 VDC power to the pulse-width modulators. With four main power busses, any principal load, sch as a drive motor, steering motor, etc., may be connected to any battery.

STEERING SECTION

circuit breaker and switch for each of the two steering motors.

DRIVE POWER SECTION

circuit breaker and switch for each of the four drive motors.

DRIVE ENABLE SECTION

contains a switch for each drive motor which permits the driver to select either pulse-width modulator(PWM) 1 or 2.

POWER/TEMPERATURE MONITOR

provides a status of the vehicle's electrical system and the temperatures of the batteries and motors. Battery voltage and current flow are displayed on the same meter. The position of the "volts-amps" switch determines whitch of the two is being displayed.

CAUTION AND WARNING SYSTEM

gives the astronauts a visual warning that one of the batteries or traction drive motors is overheating. A spring-loaded, hinged "Alarm" panel, located on top of the console, is held down by a magnet.

Deployment System

The LRV is stowed in a "nose down" position and is attached to the LM 'quadrant one' at three points. Deployment is accomplished by the astronaut sequentially pulling two nylon operating tapes. A D-handle is pulled by the astronaut while standing on the LM access ladder. This retracts three pins holding the LRV for deployment. A spring-loaded pushoff rod will begin to move the folded vehicle away about 4 degrees.

Pulling the tape on right side of quadrant causes a cable strage drum to rotate, which releases cable. Gravity will cause the vehicle to rotate outbord after the pushoff rod has extended. At 40 to 50 degrees of deployment motion, a cable will pull pins which unlock the forward and aft chassis sections so they can unfold. From about 50 degrees of deployment, the aft chassis section, which is under spring pressure, unfolds and latches into position. Meanwhile, the forward chassis section has been held at about a 45-degree position. Unfold of forward section begins when the center and aft sections have rotated 73 degrees. Finally, the astronaut pulls the second operating tape (on the left side of the LM quadrant) allowing the forward end of the LRV to be lowered to the surface. The astronauts must then disconnect the deployment hardware from the vehicle by pulling a series of release pins.

Deployment of the LRV is possible with the LM tilted at any angle up to 14.5 degrees in any direction and with the bottom of the descent stage 14 to 62 inches above the lunar surface. The deployment time will take no more than 15 minutes under the "worst case" situation, and about five minutes with the LM nearly level.

Post Deployment Activities

After the LRV is on the surface, the vehicle will be visually inspected. The crew will erect the seats and place other crew station systems in operation order. One crewman will board and power-up the vehicle. He will back it away from the LM and drive it to a designated area for payload loading while the second crewman monitors and provides direction for the back-away operation. A lunar communications relay unit(LCRU), a high-gain antenna for TV transmission and a television camera will be mounted on the front of the chassis. Then astronauts will confirm communications equipment operation using both self contained and auxiliary LRV power system. Low-gain antenna for voice comminications will be mounted in the inbord handholds on console. Finally, the tools and experimentswill be loaded on the pallet behind the seats.
In driving, the high-gain antenna will be locked. So TV transmission is only possible when the vehicle has stopped. However, the low-gain antenna can be oriented while driving and voice communications are possible at all times.
At the conclusion of each EVA, the crew will park the LRV so it can be viewed from LM and power down all LRV systems. Battery dust covers will be raised to permit accumulated system heat rejection to the space environment.

LRV scale model

Photos of the LRV scale model posted on this site, is a 1/32 scale resin assembly kit made of EVA model. It is a realistic precision model with a total of 120 parts. Unfortunately, however, the shop was closed with the death of the owner. It is a kit that can not be obtained now.

Drawings

Related document download

A Brief History of the Lunar Roving Vehicle(PDF)(NASA)

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Applying Thermal Control Experiences On Apollo Lunar Rover(PDF)(NASA)

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