SPACECRAFT LM ADAPTER

 

Spacecraft - Lunar Module Adapter.

(P-76) Spacecraft - Lunar Module Adapter.

Dimensions

Function


The spacecraft-LM adapter is an aluminium structure which protects the LM during launch and provides the structural attachment of the spacecraft to the launch vehicle.

The spacecraft-LM adapter (SLA) is constructed of eight 1.7-inch thick aluminium honeycomb panels which are arranged in two sets of four of equal size: the upper or forward panels, about 21 feet long, and the lower or aft panels, about 7 feet long. The exterior surface of the SLA is covered completely by a layer of cork 30/1000 of an inch thick . The cork helps insulate the LM from the heat generated by the spacecraft pushing through the atmosphere during boost.

The lunar module is attached to the SLA at four places around the joint between the upper and lower SLA panels, Besides the lunar module, the SLA extends down to the top of the LM) and an umbilical which houses connecting circuits between the launch vehicle and the spacecraft,

Completed SLA in Tulsa before shipment.

(P-77) Completed SLA in Tulsa before shipment.

SLA-SM SEPARATION

The SLA and SM are joined by bolts through a flange that extends around the circumference of the two structures, The only other connection is an umbilical cable through which electrical power is supplied to the SLA. This power is used to trigger the separation devices.

Redundancy is provided in three areas to assure separation. The signals that initiate the ordinance are redundant; the detonators and cord trains are redundant, and the charges are ''sympathetic''- that is, detonation on one charge will set off another.

The SLA and SM and the four upper panels of the SLA are separated by an explosive train which cuts through the metal connecting the structures.

The explosive train consists of 28 charge holders, each of which contains two strands of detonating cord, either one of which will sever the joint. The charge holders (aluminium strips to which the detonating cord is bonded) are mounted on the flange connecting the SM and SLA and on the splice plates (metal strips) which join the forward panels, Boosters (larger charges) are used at the ends of each charge holder and at crossover points to assure that the entire explosive train fires.  

Although the explosive train fires like a fuse-that is, it travels from one point to another-it travels so fast that for practical purposes the entire train can be said to explode simultaneously. Two sets of thrusters-one pyrotechnic and one spring-are used in deploying and jettisoning the SLA's upper panels.

The four pyrotechnic thrusters are located at the top of the lower panels at the upper panel joints and are used to rotate the panels backwards, Each of these thrusters has two pistons, one acting on each panel, so that each panel has two pistons thrusting against it, one on each end. The explosive train which separates the panels is routed through two pressure cartridges In each thruster assembly, ignition of the pressure cartridge drives the pistons against the panels to begin deployment, Redundancy is provided because ignition of one pressure cartridge normally will sympathetically ignite the other.

The pyrotechnic thrusters apply only a small amount of impulse to the panels (for only 2 degrees of rotation), but this is enough to assure deployment, The speed (33 to 60 degrees per second of angular velocity) imparted by this thrust remains essentially constant. The panels are connected to the lower panels by two hinges. When the panels have rotated about 45 degrees, the hinges disengage and free the panels from the aft section of the SLA.

The spring thrusters are mounted on the outside of the upper panels, When the panel hinges disengage, the springs in the thruster push against the lower panels to propel the panels away from the vehicle. The opening speed and the spring thruster force are such that the panels will be pushed away from the vehicle at an angle of 110 degrees to the vehicle centerline and a speed of about 5-1/2 miles an hour. This assures that the panels will be headed away from the spacecraft.

How SLA panels are jettisoned.

(P-78) How SLA panels are jettisoned.

SLA-LM SEPARATION

Spring thrusters also are used to separate the LM from the SLA. After the CSM has docked with the LM, mild charge are fired to release the four connections which hold the LM to the SLA. Simultaneously, four spring thrusters mounted on the lower SLA panels push against the LM to separate the two vehicles.

SLA-LM separation system.

(P-79) SLA-LM separation system.

The separation is controlled by two lunar module separation sequence controllers located inside the SLA near the attachment point to the instrument unit. The redundant controllers send signals which fire the charges that sever the connections and also fire a detonator to cut the LM-instrument unit umbilical. The detonator impels a guillotine blade which severs the umbilical wires.

Technicians at Tulsa put the finishing touches on SLA forward panel.

(P-80) Technicians at Tulsa put the finishing touches on SLA forward panel.