Apollo 5

Apollo 5
COSPAR ID	1968-007A
SATCAT no.	03106
End of mission
	File:LM1 embr original.jpg

Apollo 5 was the first unmanned flight of the Apollo Lunar Module, which would later carry astronauts to the lunar surface.

Objectives

The Apollo 5 mission was intended to test the Lunar Module in a space environment, in particular its descent and ascent engine systems, and its ability to separate the ascent and descent stages. The descent engine would become the first throttleable rocket engine fired in space.

The mission was also intended to perform a "fire in the hole" test - as depicted in the mission's insignia - whereby the engine of the ascent stage would be fired whilst still attached to the descent stage. This would simulate the conditions experienced in an abort during descent to the lunar surface.

Delays

As with Apollo 4, this flight experienced long delays. The primary cause of this was the Lunar Module. It was well behind schedule. Some of the delay could be attributed to lack of experience scheduling to build a manned spacecraft to land on the Moon.

It had been planned to launch Apollo 5 in April 1967 and so delivery at the Cape was hoped for around September 1966. But delays kept occurring. Although the lunar module was fully designed, there was trouble fabricating the custom made parts. The all important engines were also having problems. The descent engine was not burning smoothly and the ascent engine was having fabrication and welding difficulties.

In the end these problems were overcome but it took several months and it wasn't until 23 June 1967 that the Lunar Module arrived at the Cape onboard Aero Spacelines' Super Guppy. After four months of tests and repair the Lunar Module was mated to the launch vehicle on 19 November.

On 17 December 1967, a LM test failed in the Grumman ascent stage manufacturing plant. A window in LM-5 (Apollo 11's LM "Eagle") shattered during its initial cabin pressurization test, designed to pressurize the cabin to 39 kilopascals (5.7 lbf/in²). Both inner and outer windows and the acrylic glass cover of the right-hand window shattered when the pressure reached 35 kPa (5.1 lbf/in²).

On 28 December 1967 a decision was made to replace the glass windows in LM-1 with aluminum windows, as a precaution against a failure in flight similar to the one that occurred on LM-5 in testing.

Flight

The launch vehicle for Apollo 5 was the Saturn IB, a smaller rocket than the Saturn V but capable of launching an Apollo spacecraft into Earth orbit. The Saturn IB AS-204 that was used on Apollo 5 was the one originally intended for Apollo 1. It had been undamaged in the fire at Launch Complex 34 and was reassembled at Launch Complex 37B for the Apollo 5 launch.

The windows of LM-1 were replaced before the flight with solid aluminum plates. To shorten delivery time for the Lunar Module, it was decided to do without the module's legs. Without a crew, there was no need for the launch escape system rocket which usually sat on the very tip of the Saturn. As a consequence the assembled rocket was only 55 meters tall.

On January 22, 1968, eight months after the planned launch date, Apollo 5 lifted off just before sunset. The Saturn IB worked perfectly, inserting the second stage and LM into a 163 x 222 km orbit. The Lunar Module separated 45 minutes later, and after two orbits started a planned 39 second burn of its descent engine. This was curtailed after four seconds by the onboard guidance computer, which detected that the engine's thrust was not building up rapidly enough. This was due to a software bug; the propellant tanks were only partially pressurised, and it took longer than the programmed four seconds to reach full acceleration.

The ground controllers moved to an alternate plan. They turned off the guidance computer and started an automatic sequence programmed into the onboard computer. This fired the descent engine two more times. It then performed the "fire in the hole" test and another ascent engine burn.

After four orbits the mission was over, and the two stages were left to decay into the Pacific several hundred kilometers southwest of Guam on 12 February.

The Apollo 5 LM ascent stage (1968-007A) decayed 24 January 1968. The LM descent stage (1968-007B) decayed 12 February 1968.

Insignia

This patch was not designed by NASA but by the engineers at Grumman Aircraft who designed and built the Lunar Module. It portrays the fire-in-the-hole test. It also shows the LM without landing gear and with the Moon in the top right.

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