ch8-7

On Mars: Exploration of the Red Planet. 1958-1978



PREPARING FOR LAUNCH


[271] The first Viking flight hardware arrived at the Kennedy Space Center (KSC) during November and December 1974. This material included the Titan IIIE core vehicle (liquid-fueled rocket stage), the solid-fueled rocket motor components (strap-on booster stages) and the Centaur upper stage.^* All of the elements were as close to flight configuration as practical when delivered, so that the major tasks remaining were only assembly and testing. The Centaur standard shroud the "nose cone" that protected the orbiter and lander during ascent through Earth atmosphere, was delivered ready for the addition of such bolt-on items as electrical harnesses, instrumentation, and insulation. Upon delivery, launch vehicle B, which would be used for the first mission, was prepared for the mating tests scheduled for April 1975.
Viking lander capsule l arrived at the Cape on 4 January 1975, and engineers made a detailed inspection and subjected the capsule and lander to a series of verification tests, which included compatibility checks between the S-band radios and the Deep Space Network. Last minute modifications followed, based on the test information, after which the radioisotope thermoelectric generators were installed and the lander system was finally built up for mating tests. Meanwhile, the first Viking orbiter arrived on 11 February and was put through the same rigorous verification tests.

Up to this point, the flight lander and orbiter had never been physically or electrically in direct contact, having been assembled over 1600 kilometers....



(Work progresses on the Viking lander 1 (foreground) and 2 at the Martin Marietta plant in Denver in the fall on 1974.)


[272]....apart. Viking orbiter l , and Viking lander capsule 1 were mated for the first time on 8 March. More than two weeks of interface and system testing indicated that they would work together satisfactorily. The next hurdle was encapsulating the orbiter-lander assembly inside the Centaur shroud on 27 March. The specialists in Florida would then run some additional tests before the whole unit was moved to launch complex 41 where the Titan IIIE stood assembled. After the assembly had been hoisted and mated to the launch vehicle on 31 March, another series of tests were carried out on this 48.5-meter-high stack of hardware. A flight events demonstration, Viking orbiter precount. Viking lander prelaunch, and terminal countdown-all were completed successfully.
After mating tests, the orbiter and lander were removed from the launch vehicle and returned to the assembly facility for flight compatibility tests. The Viking flight team monitored these examinations from the Viking mission control and computing center in building 230. The Deep Space Network provided communications for telemetry and spacecraft commands. Concurrently, the second orbiter and lander were going through the checkout process so successfully that it became feasible to use either of the two craft for the first launch. This additional capability gave Jim Martin and his people a dose of extra confidence.
As work on the hardware moved along according to schedule, the men who would control and command the craft during the flight were also simulating mission activities. Members of the orbiter performance and analysis group participated in seven separate tests during April. For each activity through launch, the group had at least one test exercise that would prepare them for the real thing. The flight path analysis group simulated a midcourse maneuver exercise on 14 April, and the results were so successful that a repeat exercise was canceled. ³⁷
May was an equally active month at Kennedy, with some occasional troubles. Grounded circuitry delayed for two days the important plugs-out test (during which the spacecraft was on internal power) of Viking lander capsule l, and some communications problems between ground data system and the Deep Space Network required additional tests. Orbiter performance and analysis group personnel experienced some difficulties with a computer program and had to reschedule orbiter simulations. Still, build up and checkout of both Viking spacecraft were proceeding according to the latest schedules. All flight equipment, except for the gas chromatograph-mass spectrometer, had been installed on the first lander. Viking orbiter 1 was undergoing the system readiness test at the end of May, while installation of the high-gain antenna was begun on Viking orbiter 2. ³⁸
A lightning bolt that struck the Explosive Safe Area Building caused momentary excitement. Electrical charges from the strike induced currents that damaged two pressure transducers on the orbiter propulsion module S/N-005. After a quick review, the Viking managers decided not to fly this unit. Instead, S/N-006, being readied for the second launch, was assigned to the first spacecraft. Once again, the modular approach to building spacecraft....

[273] (Viking orbiter 1, top left, is mated to Viking lander 1 at Kennedy Space Center on 8 March 1975. Above, technicians lower the launch shroud over the spacecraft on 27 March. At the left, the shrouded orbiter and lander move toward 31 March mating with the Titan IIIE launch vehicle, for more tests.)

[273]....had paid off. To be able to substitute assemblies when required was clearly advantageous. Caution was a major element in preparing for a successful mission Orbit propulsion module S/N-005, its propellants unloaded. was refurbished as a spare. The previously designated backup was upgraded to flight unit status and assembled to the second orbiter. Buildup and checkout continued into June, interrupted now and then by thunderstorms and lightning alerts. To protect personnel and hardware, safety regulations at KSC stipulated that all activities had to be halted when a lightning alert was declared. ³⁹

A major milestone many people had worried about was passed when the first lander capsule (VLC-2) was successfully sterilized. Much of the [274] trouble with the design, development, and testing of the lander subsystems had centered on building components that could withstand the high temperatures required to kill all terrestrial organisms. Eliminating microbes without degrading or destroying the hardware had been one of the major challenges of the project. Viking lander capsule 2 was placed in the sterilization chamber at Kennedy on 15 June. For more than 43 hours, the craft and its capsule were subjected to temperatures up to 116.2°C as heated nitrogen gas swirled around the hardware. The poststerilization short test verified that all subsystems were functioning properly. A number of minor glitches arose, but none proved to he a major concern.
Once the Viking management was assured of the first craft's good health, the second, VLC- I, was moved into the sterilization chamber for almost 50 hours. While lander 1 was readied for propellant loading, lander 2 and orbiter 2 were mated for a last time, officially becoming the Viking A spacecraft. By mid-July, the long process of designing, building, assembling, testing, and flight preparation was drawing to a close. The Viking A spacecraft was mated to its Titan launch vehicle on 28 July at launch complex 41. The 3500-kilogram spacecraft was ready to go to Mars. Preparations for Viking spacecraft B were proceeding for the second launch, while emphasis on personnel training increased during the last two months before the first liftoff.
System-level flight operations test and training continued with a series of verification tests. Verification test 3 on 12 June checked out the portion of the mission that included the launch of spacecraft B while spacecraft A was in its cruise phase. All the verification tests up to this point had been classified "short-loop": their data-commands and the like-had been generated inside the Spaceflight Operations Facility at JPL. Beginning with verification test 4, data were exchanged between JPL and the tracking stations in Goldstone, California, and in Spain, test 4 verifying the design and execution of the spacecraft B midcourse maneuver. Verification test 1B was still more elaborate, and the loop was even longer. Simulating the launch portion of the Viking A mission, computers at the Kennedy Space Center generated data for the Viking Mission Operations Facility at JPL. Deep Space Station 42 at Tidbinbilla, Australia, also participated in this test, since it would be responsible for first communication with the spacecraft after launch. The launch phase of this simulation was normal, but trainers threw in a malfunction-an early cutoff of the Centaur engine-to test the reactions of the flight team. The team had to plan and execute an early emergency maneuver with the orbiter propulsion system to place the spacecraft on the proper trajectory to Mars. While no one really expected the Centaur upper stage to give any problems (it had been performing well for nearly a decade), the trainers wanted the flight team to prove its readiness for any contingency.

With these tests completed, the flight team was certified by the successful operational readiness test on 6 August.

Table 47 [275]
Table 47: Viking Demonstration and Training Tests

Date	Test	Nature and Results

2 July	DT-2	Processing uplink commands to lander through orbiter for cruise checkout. Data processing went well, but flight team needed more training.
13 July	DT-3	Fifty-hour cruise operation test culminating mock midcourse maneuver. Working around the clock, flight team met several problems. Successful test.
25-26 July	DT-1	Three-part exercise. Part 1 covered spacecraft powerup through launch to 6 hours into mission. Part 2 covered midcourse maneuver. Part 3, conducted at request of Deep Space Network personnel. covered lander memory-readout sequence. All 3 parts successfull.
10 July	TT-1	Simulation of midcourse maneuver with simulated emergencies. Not successful.
28 July	TT-1	Successfull retest of TT-l.

SOURCE: R. D. Rinehart and H. Wright, " Daily KSC Status (FAX)," memos dated 23, 24, 25, and 26 June 1975; and VPO, "Mission Operations Status Bulletin," no. 7, 23 June 1975, and no.8, 8 July 1975.


[275] During the last week before liftoff, final preparations were made:

29 July	Orbiter precountdown checkout and lander cruise-mode monitoring tests completed.
30-31 July	Lander computer prelaunch checkout.
1 August	Composite electrical readiness test completed.
2 August	Super Zip installed on Viking A shroud. (Super Zip is a linear explosive charge used to seperate the clamshell halves of the shroud after launch).
3 August	Pyrotechnic ordnance devices installed on Viking A.
6-7 August	Propellants loaded into Titan IIIE launch vehicle.

Although a faulty valve and a battery discharge problem would delay the beginning of the journey to Mars by nine days, Viking was otherwise ready. Many had labored mightily to get the project to this point, and the adventure was about to begin. A great amount of work lay ahead of the Viking teams, however, before the landers could touchdown on that distant, alien [276] planet. One of the most important tasks, preparation for which had paralleled hardware development, was the selection and certification of scientifically valid but technologically safe landing sites on Mars. Before examination of the Martian environment could begin-and even while the Viking spacecraft headed out through space-many hours would he spent looking for safe havens for the two landers. ⁴⁰

^* The Titan IIIE core vehicle was shipped by C-5A aircraft from Denver, where it had been manufactured by Martin Marietta. The Centaur stage, built by General Dynamics Convair Division, was also flown to Florida on a C-5A from the factory in San Diego. United Technologies Chemical Systems Division shipped the solid rocket motors from Sunnyvale, California, by rail.


	[273] (Viking orbiter 1, top left, is mated to Viking lander 1 at Kennedy Space Center on 8 March 1975. Above, technicians lower the launch shroud over the spacecraft on 27 March. At the left, the shrouded orbiter and lander move toward 31 March mating with the Titan IIIE launch vehicle, for more tests.)