Editors Note: This description of the recovery of Surveyor V originally appeared in a special edition of the Hughes News on September 15, 1967. It is believed that Jim Cloud provided the technical details herein.
A telephone call from a JPL man located at El Segundo, buckets collecting simulated spacecraft fuel at a remote spot in Placerita Canyon, a word that probably no more than one in a thousand had heard, and a tremendous effort sparked by HAC’s Jim Cloud all figured heavily in Surveyor V’s successful soft landing on the moon Sunday evening.
Mr. Cloud, husky, brown-haired 15-year Hughesite who has been with the Surveyor Program since its inception and is the assistant program manager for Engineering/ Manufacturing, was credited by NASA and JPL officials with leading the sterling effort that saved the mission after a problem in the high pressure regulator made success appear only remotely possible.
And while the rest of the world waited breathlessly right up to the touchdown at 5:46:45 pm (PDT) Sunday for the moment of ultimate success, Mr. Cloud was convinced as early as Friday evening that Surveyor V was a good bird and would make it all the way.
He was specific in his interpretation of why Surveyor V succeeded as he recounted with uncanny detail the hair-raising 48 hours between the time the trouble developed and touchdown.
“People and the flexibility of the spacecraft, “ he said, “but primarily people. We had a great team and nothing asked wasn’t done. Everyone worked long, hard hours to get the job done. The whole effort was just tremendous.”
He didn’t say it (NASA and JPL officials said it for him), but he was there the entire time leading the effort, making and assessing critical calculations all the way, and coming up with the right decisions at the right time.
It all began just before the scheduled midcourse correction, a mere 1 degree change in trajectory to put the spacecraft right on target in the moon’s Sea of Tranquility. The Atlas Centaur booster had been extremely accurate, the best yet in a Surveyor launch. But that 1 degree change was required to put Surveyor at the exact spot NASA wanted to explore as a potential landing site for the Apollo astronauts.
Midcourse correction and the final phases of terminal descent involve three vernier engines aboard the Surveyor spacecraft. The vernier system includes three thrust chambers and a propellant feed system composed of three fuel tanks, three oxidizer tanks, and high pressure helium tanks, propellant lines, and valves for arming, operating, and deactivating the system.
Each vernier engine has a pair of fuel and oxidizer tanks. The tanks contain Teflon expulsion bladders to permit complete and positive expulsion of their contents. These bladders are deflated by injecting pressurized helium into the tanks, forcing fuel and oxidizer into the feed lines. The fuel and oxidizer ignite immediately when they mix in the thrust chambers.
The midcourse correction was executed successfully with a 14-second vernier engine burn. Then, propulsion specialists reported a possible anomaly in the helium pressure.
“Within a couple of minutes we were assessing data and in 5 minutes confirmed that we were losing pressure through the high pressure regulator,” Mr. Cloud said.
Particle or Damage?
Ed Ellion, manager of the Propulsion Department in Space Systems Division, and Bob Breshears, head of the Propulsion System Analysis group for Surveyor (and also cited by NASA and JPL of outstanding work), were called in and hypothesized two failure modes.
The first was that a particle, barely visible to the naked eye, had become stuck in the valve seat. The second, the valve seat may have been damaged during final testing on earth.
At any rate, the propellant tank pressure increased to the point that it opened the relief valve and vented helium into space.
They quickly calculated the burning time required to establish a pressure differential to keep the valve open long enough to dislodge the particle, if that were the case.
Flight path and trajectory people preferred to turn the spacecraft around 180 degrees before firing the engines to maintain the trajectory, but with the pressure dropping so rapidly it was decided to fire the engines and thrust the spacecraft off the trajectory with a sun line maneuver, or toward the sun, one of the standard reference points (along with the star Canopus).
That first non-standard burn was for 10.05 seconds. John Ribarich did the maneuver analysis, as he did for all the maneuvers up to the terminal descent.
It immediately became clear that the pressure decay had not diminished and a second non-standard vernier engine burn was ordered, this time away from the sun to compensate for the sun line maneuver. The firing went 23 seconds.
The problem persisted. Thirty-five of the 180 pounds of fuel on board had been used, the standard allowance for midcourse correction. NASA, JPL, and HAC officials huddled to discuss the problem, the mission, and possible alternatives, including the much publicized high earth orbit.
Mal Meredith, manager of the Guidance and Trajectory Department in Space Systems Division, who worked with Mr. Cloud on the trajectory and terminal analysis, joined with JPL’s Bill O’Neil to calculate the possible earth orbit. Mr. Breshears was convinced that the spacecraft could be put into earth orbit at any time until the helium pressure registered 1900 psi.
Then came the call from the JPL man assigned to Surveyor work at El Segundo. Editor’s note: The consensus is that Don Pedretti, who later became a Hughes employee, placed this telephone call from his assigned location at KSC in Florida.
Don Pedretti asked if the ullage factor had been taken into account.
Ullage, the word so little known, is the amount of space a container lacks of being full. If the ullage in the fuel tanks and high pressure helium tank could be filled with trapped gas resulting from engine firings, that gas would serve as a pressure against the fuel and force it into the feed lines, just as the escaping helium would do.
At this time, Mr. Breshears determined that the ullage pressure would be great enough at any time almost up to the moment of impact to allow firing of the main retro and perhaps a little more. If so a landing might be possible.
“This was the turning point,” declared Mr. Cloud. “Now the odds were down to about a 1000 to 1 for a successful landing even though the minimum fuel requirements permitted only a few hundred feet of error at touchdown.
Battle Gets Hot
The battle to land on the moon was now joined in earnest.
Late Friday, Merle Guenther headed a JPL crew that began testing actual engine flow rates as a function of feed pressure at Edwards AFB. This data was used to confirm prior calculations of engine capability to control the vernier descent with a decreasing pressure system. Later, they took the engines to the Hughes test site in Placerita Canyon to check the ullage theory on the S-6 test vehicle, outfitted with a fuel system.
Dr. Ellion, Phil Donatelli, head of Surveyor Vernier Propulsion Section; Frank Danis, and several other Hughesites, working in conjunction with JPL counterparts at Placerita, filled the propellant tanks on 820 psi to simulate the predicted ullage pressure on the vernier engine tanks on Surveyor V at terminal descent, using alcohol and Freon.
Buckets were placed under each of the thrust chambers and the engines were fired. When the engines stopped firing at 500 ps1 (below that figure the engines won’t operate), the alcohol-freon expelled into the buckets weighed 68 pounds.
That was Sunday morning…and the odds for success improved vastly, between 1 in 4 and 1 in 10.
Between the completion of the tests at Pacerita and the actual terminal descent phase, three thrusting maneuvers, all analyzed by Mr. Ribarich, were executed to lighten the vehicle, to attempt to trap more ullage gas, and to pinpoint the spacecraft on the landing site. The final 5-second tweak burned off 4.3 pounds of fuel and put the spacecraft back on the original trajectory despite the zigzag flight from earth and left a helium-ullage pressure of about 850 psi, sufficient for the landing.
Also late Saturday, the men involved in determining the non-standard terminal descent began the horrendous task of dovetailing seemingly infinite numbers of calculations in order to put Surveyor V in the right place, at the right time, at the right speed.
Men worked furiously computing, calculating, checking, performing in minutes and hours functions that normally take days and weeks.
But Restrictions Tough
All they had to do was come up with an entirely new terminal descent sequence to override the pre-programmed sequence data already onboard the spacecraft. Only now, the restrictions were twice as severe as for a normal landing.
All functions in the terminal descent phase normally accomplished in a three minute period now had to be performed in about half the time.
New and precise times for igniting the vernier engines and main retro rocket, commanding the jettison of the main retro rocket, as well as turning the thrusters to high power thrusting, had to be determined.
Jettisoning of the main retro rocket, normally accomplished at about 35,000 feet, would have to be done at slightly more than 4000 feet, with the possibility that it would remain trapped in the descending spacecraft. And additional steering time was desired so that the radar altimeter doppler velocity sensor would be effective.
Time, on earth and at the moon, was a critical factor.
Key figure in solving the timing problem was Neal Hertzmann, manager of Flight Control Subsystems. In a simulation study, conducted Saturday night, he determined that it would be impossible to initiate steering before main retro burnout as proposed. The simulation showed that with the acceleration loop saturated steering would not be effective and a significant limit cycle was possible.
Based on this information, for main retro jettison and vernier engine high power thrusting, plus further data on retro engine “tail-off” supplied by Larry Spicer of HAC and Rich Haserot of JPL, HAC’s Len Davids came up with a new terminal descent analysis.
Mr. Davids, of the Guidance and Trajectory Department, manually calculated the proposed descent on plotting paper, put the data into a 7094 computer at JPL, used the time-shared GE 265 computer in Bldg. 105 at the Airport Site via tie line, and modified the information on the spot in Space Flight Operations Facility at JPL. (In Bldg. 105, Chief Switchboard Operator Elsie Grob spent virtually all of Saturday and Sunday handling tie lines which had problems of their own.)
The new non-standard terminal descent sequence was confirmed late Saturday in a closed-loop simulation designed by Jan Sikola at Space Flight Operations Facility and conducted on Surveyor SC-6 at Cape Kennedy being prepared for launch.
All data that would override the on-board data was put on the final tape a couple of hours before the scheduled landing.
To pre-plan such a landing with its extensive maneuvers would normally require 4 to 6 weeks. The 20 to 30 men who lived with the mission accomplished the virtually impossible in 40 hours.
The name Surveyor V will be long remembered, but it never would have made the headlines without names like Neal Hertzmann, Arnold Neil, Len Davids, Mal Meredith, Ed Ellion, John Ribarich, Bob Breshears, Frank Danis, Larry Spicer, Rich Haserot, Merle Guenther. Paul Sterba, who computed the new center of gravity on the vehicle after the loss of helium to see that the capability for attitude control during main retro burn hadn’t been upset.
Also Dick Dibos and Frank Rickman, who determined the final roll angle for optimum operation of the radar altimeter doppler velocity sensor at low velocities; George Kerster, who contributed to the terminal sequence timing and retro tailoff work; Jack Stockey and Jeff Leising of JPL who determined that retro would have to follow burnout by more than 5 seconds or it might bump the spacecraft.
Without Ed Pfund, HAC’s director of Spacecraft Performance Analysis Command and Bud Wrather, head of Mission Control, and Ray Cress at Goldstone, who performed coolly throughout the mission. Without Ed Hawthorne, spacecraft manager, who put together a bird that through its flexibility met every challenge.
And certainly without Jim Cloud, directing, calculating, making the critical recommendations to the JPL project office for the final decisions.
Editor’s note: Several months later Hughes published a report with the technical details of the Surveyor V mission.