A BOLD, NEW PROGRAM FOR MARS: 1969

Campaign objectives:

Since their origins in 1960 the Soviet Mars and Venus programs had been strongly intertwined, using slightly different versions of the same spacecraft. When NPO – Lavochkin took over the planetary program it set out to transform OKB-l’s 3MV-3 design into a 1,000 kg spacecraft to be launched on an upgraded Molniya-M at the 1967 flight opportunity to Mars. But this approach was soon abandoned. The Mars program had been a disaster. Seven attempts in the period 1960 through to 1964 had failed, including one test mission. Then the Zond 2 Mars flyby spaeeeraft created an embarrassment by failing as Mariner 4, launched by the US at almost the same time, went on to make a successful flyby in July 1965. In that same month Zond 3, after operating successfully at the Moon, failed its Mars deep space test flight objectives. Aware that the US was turning away from Venus in favor of Mars, starting with dual flybys planned in 1969 and with orbiters and landers to follow, perhaps as early as 1973. the Soviets decided to perfect a Mars lander that would outdo the American flyby missions.

Spacecraft launched
First spacecraft:	М-69 Ко. 521
Mission Type:	Mars Orbitcr
Country; Builder:	l JSSR NPO-L avoc h к і п
Launch Vehicle:	Proton-K
Launch Date; Time:	March 27, 1969 at 10:40:45 UT (Baikonur)
Outcome:	Launch failure, 3rd stage explosion.
Second spacecraft:	М-69 Ко.522
Mission Type:	Mars Orbiter
Country і Builder:	USSR, NPO-Lavochkin
Launch Vehicle:	Proton-K
launch Date ‘: 1 їте:	April 2, 1969 at 10:33:00 UT (Baikonur)
Outcome:	Launch failure, booster explosion.

The entry vehicle for the 3MV Mars spacecraft had been designed in the early 1960s on the presumption that the atmospheric pressure at the surface was between 80 and 300 millibars. The Mariner 4 flyby in July 1965 showed it to be a mere 4 to 7 millibars. The design of the 3MV entry probe was therefore fatally flawed. A new technique would be required to perform entry, descent and landing in such a rarefied atmosphere. In October 1965 NPO-Lavochkin abandoned the 3MV for Mars, but retained it for Venus because it was suitable for that dense atmosphere. The Soviets skipped the 1967 Mars launch opportunity to develop a more capable spacecraft for the 1969 opportunity.

The powerful Proton launch vehicle made its debut in 1965. It doubled the mass that could be delivered to low Earth orbit compared to the three-stage Molniya. and when augmented by the Block D fourth stage (as the Proton-K) it facilitated a whole new generation of heavier, more capable and complex lunar and planetary spacecraft than the Molniya-launched 3MV. Capable of dispatching over 4 metric tons onto an interplanetary trajectory, the Proton-K became the standard launcher for lunar and Mars missions after 1966, and for Venus missions after 1972.

The engineering requirements for new Mars and Venus missions during the time period 1969 73 were defined in March 1966 by the head of NPO-Lavochkin, Georgi Bab akin:

1. Use of the Proton-K to achieve parking orbit and escape onto an interplanetary trajectory

2. IJsc of a "universal” multi-purpose, modular on board propulsion system for trajectory correction while coasting and then insertion into an orbit around the target with a pericenter about 2,000 km and apocenter not exceeding

40.0 km

3. Use of descent-from-flyby and descent-from-orbit mission designs for soft landers to place instruments on the surface

4. Use of the main spacecraft as either a flyby vehicle or an orbiter to relay information from the lander at about 100 bits/s to the Earth

5. IJsc of a telemetry system capable of transmission from the main spacecraft of about 4,000 bits/s.

It was decided that in addition to trajectory correction maneuvers, entry vehicle targeting and planetary orbit insertion and trim maneuvers, the universal propulsion system should also participate in establishing the desired interplanetary trajectory by firing after the spent Block D stage was jettisoned.

These requirements were not applied to Venus until the successful Venera type of the 3MV had fulfilled all of the objectives for that planet in 1972, but they were applied immediately to Mars for the 1969 opportunity. Also, it was decided that for the initial Mars mission the descent module would be an atmospheric probe to obtain the data required for designing a landing system for that rarefied atmosphere. Another key objective was to improve the ephemeris for Mars for future missions. The science objectives for Mars missions using this new spacecraft system were: [1] [2] [3] [4] [5] [6] [7] [8] [9] opportunity that was only 33 months away, an incredibly short period of time in which to try to develop a spacecraft of such an unprecedented complexity. And by devoting part of this time to modifying the 3MV to score a success at Venus in 1967 they left themselves with only 20 months to develop the new spacecraft. Then problems with the design left them with only 13 months. Given the intense pressure to outdo the US at Mars, the risks taken were enormous.

The workload was intense during the last years of the 1960s as the Soviets tried to compete with Apollo. NPO-Lavochkin was overloaded developing the Luna rover and sample return missions, continuing to milk the successful Venus missions, and making a valiant effort on M-69. This was a brand new spacecraft like none built before, and the rushed development showed. Nothing went smoothly. The spacecraft suffered from the same development problems as OKB-l’s early rushed designs and engineers were not terribly optimistic about its chances. The winter of 1968-69 was exceedingly harsh, pipes burst and heating systems failed, creating near-impossible working conditions. Control and telemetry systems were plagued with troubles and the design of the spacecraft actually prevented easy access for servicing. The entry probe had to be deleted very late in the process due to insufficient time and system mass growth, and was replaced by a compartment for additional orbital instruments.

The Soviets were to fail in their first attempt with this new spacecraft in 1969, but the engineering and science requirements for the M-69 program set a precedent for all of the Mars mission designs that were to follow7. At that time almost nothing was known of these missions in the West, and 30 years would elapse before they were described in any detail.

Spacecraft:

The initial design:

As Babakins engineers worked with their OKB-1 colleagues in 1966-67 to prepare a 3MV spacecraft for what would become the successful Venera 4 mission, others at NPO-Lavochkin were working on a new7 spacecraft for the Luna series that would be launched by the Proton-K instead of the Molniya. Unlike the previous 2MV, 3MV and Luna series spacecraft where the avionics compartment was the main structural element, this time a quartet of spherical propellant tanks connected together in the shape of a square using cylindrical inter-tank sections became the element on w7hich everything else was mounted.

Given the short period of time available for the development of a Proton – launched Mars spacecraft, it was decided to exploit this work. The initial M-69 design had the entry probe attached to the tank assembly where the lunar rover w7ould otherwise be carried, and the remaining systems attached to the underside’. The two solar panels were spread out from opposite sides of the square, and the antenna and engine were opposite each other on the remaining sides. This design could meet the schedule, but was not easily reconfigured and failed to satisfy some of the requirements. Also, the designers struggled with a number of engineering

figure 11.17 Drawing of the original Mars-69 concept.

problems in trying to adapt a lunar spacecraft for Mars exploration. The main issues centered on the fundamental tank design, and ultimately it was abandoned, forcing a total redesign 13 months before the launch date.

The final design:

The new design used a single large spherical tank at the center of the spacecraft as the main structural element. The tank had an internal baffle to separate the UDMH fuel from the nitrogen tetroxide oxidizer. The Isayev engine was attached to the base of the tank. A cylindrical interstage with a pressurized container for electronics was attached to the top of the tank, and the entry vehicle was installed above that. Two hermetically sealed cylindrical modules were attached on opposite sides of the tank, one for communication, navigation systems and optical orientation sensors, and the other for science instruments including the cameras. There were also science sensors attached to the outside of ihe spacecraft.

The antenna system, including both a large high gain and small conical antennas, was affixed to the cylindrical interstage. The two 3.5 square meter solar panels were mounted outboard of the instrument modules. The panels were supplemented with a NiCad. battery that delivered power at 12 amps with a 110 amp-hour capacity. Both passive insulation and active thermal control vrere employed. The active system operated in the pressurized compartments and consisted of a ventilation and air circulation system to route air between two radiators, one exposed to sunlight and the other to shadow. The thermal control radiators were inboard of the solar panels, between the modules across the main tank. The avionics of the M-69 spacecraft were

Figure 11.18 Final Mars-69 spacecraft design: 1. Parabolic high-gain antenna; 2. Entry system (not flown); 3. Fuel tank; 4. Solar Panels; 5. Propulsion system; 6. Attitude control; 7. Thermal control-cooling side nozzles; 8. Camera viewports; 9. Instrument compartment; 10. Thermal control-heating side; 11. Omni antenna; 12. Navigation system.

much improved over the 3MV series. It was the first Soviet planetary spacecraft to carry a computer. .An advanced data processing system weighing only II kg was provided that could program the instruments and acquire, process and compress the data from both engineering and science systems for transmission to Earth.

A new telemetry system was provided that consisted of a transponder-receiver for

Figure 11.19 Mars-69 spacecraft under test.

non-imaging data and an impulse transmitter for images, a 2.8 meter parabolic high gain directional antenna and a trio of low gain semi-directional conical antennas for decimeter and centimeter bands. The arrangement of the conical antennas was such that when the solar panels were pointed at the Sun, they would be pointing at Earth. The transponder-receiver had two transmitters and three receivers in the decimeter band at 790 to 940 MHz with 100 W of power, and facilitated Doppler tracking at a transmitted data rate of 128 bits/s with 500 data channels. These transmitters and receivers could use either the conical antennas or the high gam. One receiver was always on and connected to one of the conical antennas for continuous reception. The remaining receivers and the transmitters were cycled through these antennas by timers in order to ensure the reliability of the system. As part of the payload, a new film camera system with facsimile processing was developed. The imaging system had a 5 cm impulse 50 W transmitter for a data rate of 6 kbits/s using short pulses at 25 kW.

For the attitude control system, new Sun and star sensor systems and new nitrogen gas micro-engines were developed. There were two Sun sensors, two star sensors, two Earth sensors, and two Mars sensors. Nine helium-pressurized tanks provided nitrogen gas stored in ten separate tanks to eight attitude control thrusters,
two each for pitch and yaw and the other four for roll. The nitrogen lank pressure of 350 bar was regulated to 6 bar for maneuvering and 2 bar for attitude maintenance. During cruise and routine operations the vehicle used one set of sensors to maintain itself in a rough attitude that faced the solar panels towards the Sun. For high gain antenna operations, midcourse maneuvers, and orbital mapping, it used a more accurate set of sensors for precise З-axis stabilization. Both optical sensors and gyroscope control were provided for the altitude control system.

The entry system was a prototype of that which would be used in 1971, and was to have been deployed w hile 2 days from Mars. But it was ultimately deleted from the 1969 mission due to mass growth of the spacecraft and insufficient time to test the parachute descent system in balloon drops. The entry probe w as designed around a large spherical tank with three attached pressurized compartments. No other details are available.

Launch mass:

Or hi ter mass:

Probe mass:

Payload:

Or biter:

1. Facsimile imaging system (FTU)

2. Infrared Fourier spectrometer (UTV1) for atmosphere and surface studies

3. Infrared radiometer (RA69) for surface temperature

4. Ultraviolet spectrometer (USZ) for reflected radiation

5. Water vapor detector (I VI)

6. Mass spectrometer for ionosphere composition and hydrogen, helium detection (UMR2M)

7. Multi-channel gamma-ray spectrometer (GSZ)

8. Low – energy ion spectrometer (RIB803)

9. Charged particle deteetor (KM69) for solar electrons and protons

10. Magnetometer

11. Micrometeoroid detector

12. Low frequency radiation detector

13. Cosmic ray and radiation belt detector

14. X-ray radiometer

15. Gamma-ray burst detector

Total mass: 85 kg.

The new FTU was an advanced film facsimile imaging system consisting of three cameras, each with red, green and blue color filters. The image format was 1,024 x 1,024 pixels. One camera had a 35 mm lens, a second had a 50 mm lens and a field of view of 1,500 x 1,500 km, and the third had a 250 mm lens and a field of view of 100 x 100 km with a best resolution of 200 to 500 meters. The film was processed on

board, encoded digitally and supplied to the impulse transmitter. The film was to be chemically activated upon arrival at Mars in order to avoid damage by radiation in cruise. Each camera had sufficient film for 160 images.

Atmosphere probe (deleted):

1. Pressure sensors

2. Temperature sensors

3. Accelerometers for atmospheric density

4. Chemical gas analyzer

Total mass: 15 kg.

Mission Description:

The plan was to use the first three stages of the Proton and the Block D upper stage to achieve parking orbit. After one orbit, the Block D would be reignited for the first part of the escape sequence under the control of the spacecraft. After burnout of the Block D and separation, the spacecraft would fire its main engine for the final boost onto the interplanetary trajectory. This would be the first time that this new scheme was used, adding more risk to an already challenging project. The spacecraft engine w ould also be used for two trajectory corrections during the 6 month cruise to Mars, one 40 days out from Earth and the other 10 to 15 days prior to arrival. The fourth burn of the engine would be made at the closest point of approach to Mars in order to enter a 1.700 x 34,000 km orbit inclined at 40 degrees to the equator with a period of 24 hours. No immediate trim burns were planned, despite the expectation that the errors would be considerable. After some photography and other science from this initial orbit over several weeks, the periapsis would be lowered to about 600 km for an additional 3 months of imaging and data collection. At that point the mission was expected to be concluded.

Unfortunately, neither spacecraft even reached Earth orbit. М-69Л was lost to a third-stage explosion when a rotor bearing malfunction caused a turbopump to fail and catch fire. The engine shut down at the 438 second mark and the stage exploded. M-69B was lost when one of the six first stage engines exploded just at launch. The vehicle continued to climb on the five remaining engines until the 25 second mark, at which time it tipped over to the horizontal at an altitude of 1 km. The remaining engines shut down and 41 seconds into the flight the vehicle fell to the ground 3km from the pad and exploded. Remarkably, the second stage landed intact.

The failure of the Soviets to exploit the 1969 opportunity for Mars passed largely unnoticed in the West, mainly because the two attempted launehes failed so early in flight. But the Protons may have saved the Soviets from the larger embarrassment of another Mars mission failing due to the spacecraft being rushed too hard through its design and development. As one of its designers remarked, M-69 was an example of how’ not to build a spacecraft.

Results:

None.

The Proton was experiencing its worst period in development at this time, with a very high failure rate. It was responsible for the loss of many spacecraft including a large number of lunar missions. The failure of the M-69 launches was a bitter pill for the spacecraft team to swallow after all the difficult and frantic work that had gone into the preparation. To rub salt into the wound, soon thereafter the US achieved the Apollo 11 lunar landing and the successful Mariner 6 and 7 flybys of Mars.