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Previous chapter: Soviet unmanned missions to Mars
Above: M-69 spacecraft. Credit: NPO Lavochkin
Proton's forgotten deja vu
Although the spectacular crash of the Proton rocket in 2013 was the first when the famed booster made a suicidal dive to the ground in front of multiple cameras of the Internet age, a very similar accident took place during Proton's adolescent years. On April 2, 1969, another Proton crashed to the ground just 30 seconds after its liftoff. Then, consequences were much more severe for the Soviet space program.
Mars 69 project
In mid-summer 1967, after sending away their latest probes to Venus, Soviet engineers at NPO Lavochkin design bureau took short vacations before switching their attention to an even more elusive goal -- Mars. This time, they hoped to take advantage of a more powerful Proton rocket, which was just coming of age, instead of a veteran Molniya booster, the carrier of all past Soviet planetary missions. With Proton's capabilities, the USSR could conceivably outshine NASA's Mariner probes scheduled to fly by the Red Planet during the upcoming launch window of 1969.
Obviously, the landing on the surface of Mars would be the most prized achievement both scientifically and politically. However with all the technical challenges to such a mission and just 20 months left until the opening of the launch window, Soviet planners limited their ambitions to a hard landing. Crushable atmospheric probes could still make measurements of the Martian atmosphere during their fast descent for the benefit of successive missions in 1971.
To save time, engineers at NPO Lavochkin eyed a yet-to-be-tested E-8 landing stage of an unmanned lunar rover, in the hope of converting it into a Mars probe. Instead of the rover, the stage would now carry a small capsule with a descent probe.
The E-8 stage would consume big part of its propellant in the effort to escape the Earth orbit, following the initial boost from a low parking orbit provided by Block-D stage of Proton. With the precise orbit of Mars still a mystery to the Soviet astronomers, navigating the mission involved considerable guesswork. According to the flight scenario, the landing capsule would separate from the cruise stage during its approach to Mars and would fire its own solid-propellant motor to enter the atmosphere. The entry angle would vary from 10 to 20 degrees. The aerodynamic braking would decrease a speed of the vehicle to Mach 3.5, enabling a parachute deployment at an altitude as high as 31.7 kilometers or as low as 2.2 kilometers. As a result, scientific measurements, starting at the parachute deployment could last from 900 to just 30 seconds.
In the meantime, the cruise stage would fire its engine again reducing its velocity by 1,750 meters per second, enough to ease the vehicle into orbit around Mars with an inclination from 35 to 55 degrees toward the planet's equator and bringing it to as close as 2,000 kilometers to the surface. Again, due to uncertainty of planning, an apogee of the Martian orbit could vary from 13,000 to 120,000 kilometers, requiring from 8.5 to 12 hours for a single revolution around the planet. (633)
Chief designer at NPO Lavochkin Georgy Babakin approved the preliminary design of the M-69 mission in November 1967. However in the next phase of development, engineers started realizing that the E-8 stage had been ill-suited for the Mars mission. It transpired that shifting center of gravity in the course of propellant consumption onboard the spacecraft made it very difficult to predict its moment of inertia at various points in the mission and, thus, to conduct accurate trajectory corrections for the approach to Mars. Developers also struggled to develop an effective thermal control system to cool sensitive avionics tacked into three different cylindrical sections. Finally, endurance tests revealed that elastic membranes used to push propellant out of the spacecraft's tanks could leak during a prolonged journey to Mars.
To tackle the problem, the project managers turned to a team of engineers proposing an alternative spacecraft design. It sported a lenticular-shape propellant tank with a metal membrane that was guaranteed to survive a journey to Mars. To enable a reliable ignition of the propulsion system in weightlessness of space, a cluster of smaller tanks would carry vacuumized bubble-free propellant. It would be used for the initial firing of the engine during 6-8 seconds to create enough acceleration forcing the rest of propellant toward the supply lines. Since these features could not be integrated into the existing design of the M-69 spacecraft, Babakin made a controversial decision to trash the old architecture and build a brand-new spacecraft just 13 months before launch!
According to the new flight profile, the spacecraft would conduct two trajectory corrections -- one 40 days after launch and another 10-15 days before reaching Mars, -- enabling an initial orbit around the planet passing as close as 1,000 kilometers from the surface. The highest point of the orbit would be 70,000 kilometers from the planet.
It was decided to bring the lander into the orbit of Mars along with its "mother ship" and only then release it to the surface, rather than trying to separate two vehicles on the approach to the planet. However, as the whole spacecraft gained weight and engineers run out of time for required drop tests of the Martian capsule from a high-altitude balloon, the mission management had no choice but to abandon the landing part of the mission. Leaders of the Russian space industry still hoped to beat Americans to the Martian orbit, since NASA had planned such an attempt only in 1971.
The Soviet M-69 orbiter would carry a film camera capable of taking 160 images of the Martian surface. (633)
By the end of the third quarter 1968, the M-69 project was severely lagging behind its tight schedule. With the US getting ahead on all fronts of the space race, the Soviet government would not take no for an answer. At the peak of the spacecraft assembly, the work at NPO Lavochkin had to be conducted in three shifts with specialists sleeping on folding beds at their workplace! The Space Research Institute, IKI, in Moscow responsible for scientific instruments of the mission was able to deliver the payload for the second of two spacecraft along with its data processing system to NPO Lavochkin at 11 p.m. on Dec. 31, 1968.
The integrated testing of the first spacecraft and the assembly of the second probe was completed at Lavochkin in the middle of January 1969. To save time it was decided to conduct electric tests for the second spacecraft at the same time with final checks at the launch site. Soon after the hectic M-69 launch campaign had shifted to Tyuratam in the winter of 1969, the giant N1 rocket made its first ill-fated launch attempt on February 21, in a desperate effort to catch up with the US in the Moon Race. The resulting explosion shuttered windows in hotels hosting members of the M-69 team. With temperatures outside reaching minus 30 degrees C, the central heating system was quickly frozen dead. Windows were quickly replaced, however it would require weeks to repair damaged pipes and radiators. Tasting potential Martian conditions, residents had to survive with electric heaters that were barely able to bring temperature inside their rooms above zero! Five days after the N1 crash, NASA engineers in the comfort of Florida watched their Mariner-6 spacecraft successfully depart toward Mars for a flyby mission.
Despite an uphill battle, the Soviet team did bring the M-69 spacecraft to the launch pad, even though some doubted that hastily assembled probes would be as enduring as their creators. For better or worse, they never had a chance to prove their doubts. (633)
A Proton rocket carrying the first M-69 spacecraft lifted off on March 27, 1969, from Pad No. 23 at Site 81. (202, 400) Those present at the launch site were listening to loudspeaker announcements of mission milestones. The normal separation of the first and second stages, as well as jettisoning of the payload fairing was announced, however, the confirmation of the third stage operation never came, replaced with a "no signal" message. Then reports came that the third stage of Proton had exploded and crashed somewhere in the mountainous Altai region of the southern USSR, along with its hard-won payload. (633)
The investigation later showed that the engine had been prematurely shot down at T+438.66 seconds in flight due to a fire in its turbopump caused by imbalance of its rotor. To make this pill even bitter for the Soviets team, on the same day, NASA successfully sent its second spacecraft of the season -- Mariner-7 -- to Mars.
The second M-69 spacecraft was launched from Pad No. 24 in Tyuratam on April 2, 1969, just few hundred meters where its ill-fated predecessor had lifted off less than a week ago. This time, just 0.02-0.03 seconds after liftoff one of six RD-253 (11D43) engines shot down causing the launch vehicle to crash 30 seconds after a liftoff. (202)
According to Major General Vasily Shirshov, who witnessed the launch, the rocket lifted above the launch pad for about 100 meters and then started slowly descending with its remaining five engines still firing, seemingly trying to take the vehicle away from the launch pad. The rocket crashed just outside the fence surrounding Site 81 at the western corner of the facility. It barely missed a nearby Pad No. 23.
The post-launch investigation showed that a drain port in the oxidizer pump cover was missing a hydraulic lock plug. As a result, the oxidizer gas rushed into the drain port cavity inside the rocket and ignited a pump shaft, leading to the engine failure. It was the 17th mission of the Proton rocket. (400)
Next chapter: RD-253 / RD-275 engine
Mars-69 mission at a glance:
Mars-69 spacecraft at a glance:
Scientific instruments onboard Mars-69 spacecraft:
Scientific instruments onboard Mars-69 lander:
Page author: Anatoly Zak; Last update: June 2, 2015
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A E-8 Luna lander became a basis for Mars-69 design at the start of the project. Click to enlarge. Copyright © 2000 Anatoly Zak
The initial design of M-69 spacecraft. Credit: NPO Lavochkin
The Mars M-69 spacecraft during the assembly. Credit: NPO Lavochkin
Ill-fated launch of the Proton rocket with Mars-69 spacecraft on April 2, 1969. Credit: Roskosmos
Stage 3 of the Proton rocket doomed the first launch of Mars-69 probe. Credit: GKNPTs Khrunichev