'Fire in the Hole': 50 Years Since Apollo 5, First Lunar Module Test-Flight

An unusual sight greeted Cape Kennedy spectators at sunset on 22 January 1968, as the “stubby” Saturn IB, bearing only Lunar Module (LM)-1, rose to orbit. Photo Credit: NASA

By a strange quirk of fate, NASA’s Apollo 5 mission—which launched 50 years ago, this week—used the same booster as should have been ridden by the ill-fated Apollo 1 crew of Virgil “Gus” Grissom, Ed White and Roger Chaffee. The three astronauts were intended to fly in early 1967, atop a Saturn IB booster, to put the “Block I” variant of the Apollo Command and Service Module (CSM) through its paces in low-Earth orbit. However, all three men died when a flash-fire swept through their spacecraft during a ground test. The Saturn IB itself was unharmed and was reassigned to carry Apollo 5, the first flight of the Grumman-built Lunar Module (LM), which would someday transport humans to the surface of the Moon. It was one of many legacies of the bravery of the Apollo 1 crew.

Video Credit: NASA

Many of us can point to our “favorite” rockets, but in the annals of “unusual”, the Saturn IB which lofted Apollo 5 on 22 January 1968 must rank highly. It was the eighth and final launch of a Saturn-class booster to originate from Launch Complex (LC)-37 at what is now Cape Canaveral Air Force Station, Fla., but its appearance was quite distinct. Unlike later Saturn IB missions—which incorporated an S-IB first stage and S-IVB second stage, topped-off by the Apollo CSM—Apollo 5 carried only the 37,000-pound (16,800 kg) LM, covered by the protective panels of the 28-foot-tall (8.5-meter) Spacecraft/Lunar Module Adapter (SLA) and capped by a bullet-like payload shroud, some 11.3 feet (3.4 meters) tall. Since the mission was unmanned, no launch escape system was necessary and the “stubby” vehicle stood a mere 180 feet (55 meters) tall, some 20 percent shorter than the “nominal” Saturn IB.

After the tragedy of Apollo 1, the Saturn IB for Grissom’s unrealized mission was destacked from LC-34 at Cape Kennedy, checked for corrosion or damage and finally restacked on LC-37 on 12 April 1967. The plan was to test the ascent and descent stages of the LM, including an evaluation of the effectiveness of the descent and ascent engines, which would respectively deliver future astronauts down to the surface of the Moon and back into lunar orbit. “LM-1”, as it was known, had an incomplete environmental control system, no landing legs and its distinctive triangular forward-facing windows had been replaced with aluminum covers. When its job was done in low-Earth orbit, it was intended that the spacecraft would burn up in the atmosphere. Apollo 5 was a true “test” mission.

Lunar Module (LM)-1 is mated to the Spacecraft/Lunar Module Adapter (SLA) in November 1967, ahead of integration with the Saturn IB booster. Photo Credit: NASA

LM-1 was delivered to Cape Kennedy aboard a Super Guppy transport aircraft on 23 June 1967 and its descent and ascent engines were installed a few weeks later. Trouble was brewing, however, and in mid-August the two stages were de-mated in order to repair a leak in the ascent engine. By early September, testing had resumed, but a further de-mate became necessary, in order to accommodate a leak modification in the propulsion feed system. The two stages were re-mated on 29 October and LM-1 was installed atop the Saturn IB on 19 November. However, a few weeks later, another lunar module—LM-5, then under test at Grumman’s facility in Bethpage, N.Y.—sustained a shattered window during a pressurization test. It was decided to replace LM-1’s windows with solid aluminum panels as a precaution against failure. As circumstances transpired, LM-5 turned out to be the very lunar module which would carry Neil Armstrong and Buzz Aldrin to the Moon’s surface in July 1969.

Propellant loading aboard the Saturn IB was troubled, mainly due to procedural issues and niggling glitches, pertaining to clogged filters and ground support equipment. Nevertheless, a simulated demonstration test of the launch took place on 19 January 1968. Three days later, the final steps to launch were being watched intently, with future Apollo astronauts Frank Borman, Bill Anders, Jim McDivitt and Rusty Schweickart observing from the Mission Operations Control Room (MOCR) at the Manned Spacecraft Center (MSC) in Houston, Texas. “Okay, all flight controllers, let’s play it cool,” came the typically calm remarks of Flight Director Gene Kranz in the final minutes before liftoff.

Apollo 7 crewmen Wally Schirra (left) and Walt Cunningham confer on 22 January 1968, as the Saturn IB for the unmanned Apollo 5 waits in the background on LC-37. Photo Credit: NASA

Without further ado, at 5:48 p.m. EST on 22 January 1968, the eight H-1 engines of the S-IB first stage roared to life, turning night into day across the steadily darkening Cape Kennedy. Generating an impressive 1.6 million pounds (725,000 kg) of propulsive yield, the booster lumbered away from LC-37 and began a picture-perfect ride to orbit. The laborious nature of a Saturn IB launch was unsurprising, for the booster weighed 1.3 million pounds (590,000 kg), only a little less than the 1.6-million-pound (725,750 kg) thrust of its eight H-1 first-stage engines. Two and a half minutes into ascent, the S-IB burned out and separated, allowing the S-IVB second stage and its single J-2 engine—burning with more than 200,000 pounds (90,000 kg) of propulsive yield—to pick up the thrust and deliver Apollo 5 into low-Earth orbit.

Just under an hour after liftoff, LM-1’s Reaction Control System (RCS) thrusters gently pushed it away from the spent S-IVB and a lengthy, two-orbit systems checkout entered high gear, ahead of two discrete burns by the descent and ascent engines. By this time, the spacecraft occupied an orbit of approximately 138 x 107 miles (222 x 172 km). This set up the proper conditions for the firing of TRW’s descent engine. The plan was for the engine to ignite and burn for 26 seconds at the 10-percent level of its 10,000 pounds (4,500 kg) of thrust, before ramping up to 92.5 percent for an additional 12 seconds. This would serve to adjust LM-1’s orbital parameters to 205 x 134 miles (330 x 215 km).

Manned Spacecraft Center (MSC) Director Bob Gilruth (right) and Director of Flight Crew Operations Chris Kraft watch the pre-flight preparations for the Apollo 5 mission on 22 January 1968. Photo Credit: NASA

Thirty-six minutes later, a second descent engine burn would be initiated, simulating the thrust levels expected during the Powered Descent phase of a “real” lunar landing mission. This second burn would be far longer than the first, running for 12.5 minutes, including 10 seconds each at 10-percent, 50-percent, 30-percent, 40-percent and 20-percent thrust levels of the engine. Finally, the engine would be ramped up to 92.5 percent rated performance, placing LM-1 into an orbit of 198 x 190 miles (318.5 x 307 km).

Next would be a critical ignition of the ascent engine, whilst still affixed to the descent stage. Known as “fire-in-the-hole”, this was in response to the possibility that future Apollo crews might need to boost themselves to safety in the event of an abort during Powered Descent. “The ascent propulsion system engine operation will begin simultaneously with the termination of the second descent burn,” NASA noted in its Apollo 5 pre-flight press kit. LM-1’s ascent engine would burn for 5.25 seconds, pushing the upper part of the lunar module into a slightly lower orbit. One revolution later, a test of the RCS drawing propellants from the ascent engine tanks would be performed and a second burn of 7.5 minutes in duration would position LM-1 into an orbit of 506 x 196 miles (815 x 315 km). At the termination of the second ascent engine burn, some 6.5 hours would have elapsed and the primary mission of Apollo 5 would be over.

Unofficial Grumman patch for Apollo 5, highlighting the “fire-in-the-hole” test of the lunar module’s ascent engine. Image Credit: Wikipedia, via Northrop Grumman

That, of course, was the pre-launch plan. The reality did not go well at first. The initial burn got underway, but was terminated by the guidance computer after only four seconds. Shortly before Apollo 5 launched, a suspected fuel leak had been detected and NASA decided to delay arming the engine until the time of ignition. This change increased the time needed for the propellant tanks to fully pressurize and for the engine’s thrust to build up to the required level. The change was not communicated to the computer programmers, which led to LM-1’s overly conservative “brain” not measuring any thrust within the pre-defined, 1.5-second timeframe and aborting the maneuver. “The computer made the only decision it could,” NASA noted in a post-flight film, “and it was the wrong one!”

In the MOCR, Gene Kranz’s team reached consensus to cut the duration of the longer, second burn of the descent engine and perform it whilst over U.S. tracking stations, before ramping it up to full power, ahead of the fire-in-the-hole burn. Eleven hours after leaving Cape Kennedy, the test was over and control of the now-separated descent and ascent stages was terminated. Both components were in sufficiently low orbits that their destruction in Earth’s upper atmosphere could be guaranteed in a relatively short time period. Indeed, the ascent stage re-entered two days later, on 24 January, with the descent stage following to its own demise on 12 February.

In spite of the difficulties, NASA was satisfied with the results of Apollo 5 and canceled its original plan to fly the LM-2 vehicle on a second unmanned test flight. Today, the unflown LM-2 sits in the National Air & Space Museum in Washington, D.C. It was decided to proceed directly to the first manned mission of the lunar module, using LM-3, which eventually took place on Apollo 9 in March 1969. Today, five decades since the troubled, but successful voyage of Apollo 5, it is remarkable to reflect that merely 18 months elapsed between the lunar module’s inaugural test and its successful planting of humans on the surface of the Moon.

 

 

FOLLOW AmericaSpace on Facebook!

2 comments to ‘Fire in the Hole’: 50 Years Since Apollo 5, First Lunar Module Test-Flight