Zamiast Voyagerów marsjańskich doczekaliśmy sie udanej misji Vikingów.
'Second-Class Endeavor': Remembering Project Viking, First Fully Successful Mars Landing Mission (Part 1)By Ben Evans, on August 20th, 2018
Artist’s concept of the deployment of the aeroshell-enshrouded Viking lander from the orbiter. Image Credit: Don Davis(...) Viking 1 became the first spacecraft in history to soft-land on Mars and complete its mission, picking up the baton from the Soviet Union’s failed Mars 3, which had successfully alighted on alien soil in December 1971 and produced a partial, though unintelligible image, before transmission ended and contact was lost. The spacecraft also afforded humanity our best and most complete perspective of the planet for the next two decades and the Viking 1 lander survived for 2,307 days from its touchdown on 20 July 1976 through its End of Mission (EOM) on 11 November 1982. (...)
Costing around $1 billion (or $3.8 billion today), the Viking program was the most expensive U.S. mission yet sent to Mars. (...)
Had it borne fruit, Voyager’s 2,400-pound (1,100 kg) orbiter would have established itself into a 12-hour circular path around Mars, whereupon it would have entered “site-certification” operations to scour the surface for an appropriate spot to deposit its lander. Protected during the early stages of its descent by a cone-shaped aeroshell, the 13,000-pound (5,900 kg) lander would have entered the Martian atmosphere and employed on-board engines and parachutes to accomplish a soft landing on the Red Planet. Descending at a rate of between 460 feet (140 meters) and 1,100 feet (335 meters) per second, depending upon local atmospheric density, the lander would be slowed by a system of braking rockets and steered towards its touchdown point by an inertial guidance system and radar altimeter. As it neared the surface, its aeroshell would have been jettisoned, by which time its rate of descent would have slowed substantially to a sedate 5 feet (1.5 meters) per second. The engines would have shut down at 10 feet (3 meters) above the ground, allowing the lander to alight gently onto Mars. (...)
http://www.americaspace.com/2018/08/20/second-class-endeavor-remembering-project-viking-first-fully-successful-mars-landing-mission-part-1/'Hard to Recapture the Mood': Remembering Project Viking, First Fully Successful Mars Landing Mission (Part 2)By Ben Evans, on August 26th, 2018
The aeroshell for the Viking lander undergoes preparation for flight. Photo Credit: NASA(...) Headed by Project Manager Jim Martin, and with Dr. Gerald Soffen as Project Scientist, the Viking Project Office formally opened in April 1969 and its spacecraft quickly expanded beyond anything previously attempted. In its original incarnation, it was based upon the earlier Mariner series, but it soon became clear that significant structural changes to allow for the mating of the orbiter to the soft-lander would be necessary. Power provision for the lander during the trans-Mars cruise was also acutely required, necessitating the enlargement of the orbiter’s solar arrays from 82.8 square feet (7.7 square meters) to 165.7 square feet (15.4 square meters). “The decision to build a large soft-landing craft, instead of a small hard-lander, led to the requirement for a large orbiter,” noted Edward Clinton Ezell and Linda Neuman Ezell in their NASA tome, On Mars. “The orbiter would not only have to transport the lander, it could also have to carry an increased supply of propellant for longer engine firings during Mars Orbit Insertion.”
However, within its first 12 months of life, Project Viking’s costs began to spiral, from $364.1 million when first presented to Congress in March 1969, to over $606 million by August, to an admission from Naugle by year’s end that $750 million was a more realistic figure. Scathing budget cuts throughout 1970—which notably savaged the Apollo lunar program, forcing the cancelation of two landing missions—ultimately led NASA Administrator Tom Paine to only one viable option: to delay the Viking missions by two years to the summer 1975 Mars launch window. Under this revised architecture, the end-of-conceptual-design Preliminary Design Review (PDR) occurred in October 1971, followed by the Critical Design Review (CDR) in July 1973, leading to the testing and shipment of hardware to the launch site at Cape Kennedy in Florida by February 1975.
In their eventual form—whose design had essentially been finalized at the PDR stage—the twin Viking orbiters consisted of octagonal spacecraft “buses”, measuring about 8.2 feet (2.5 meters) across, and equipped with four electricity-generating solar arrays. The later totaled 160 square square feet (15 square meters) in area, with additional power provided by two nickel-cadmium batteries. A dual-propellant system of monomethyl hydrazine and nitrogen tetroxide supported a liquid-fueled rocket engine for mid-course correction maneuvers and Mars Orbit Insertion (MOI), with subsequent attitude control achieved by 12 compressed-nitrogen thrusters. Communications were afforded by an S-band transmitter and a pair of dish-like antennas. Meanwhile, the landers traveled to Mars in a “quiescent” state, encapsulated within their aeroshells and attached to the orbiters. Six-sided and three-legged, each lander’s footpads formed an equilateral triangle of more than 7 feet (2.2 meters) when viewed from above. Propulsion during the Entry, Descent and Landing (EDL) phase of its mission was provided by hydrazine, with electricity produced by means of a pair of on-board Radioisotope Thermoelectric Generators (RTGs). Aboard each lander was a 200-pound (90 kg) payload, including 360-degree scan cameras, a sampling arm with collector head, a meteorology boom, a seismometer, a biology experiment and Gas Chromatograph Mass Spectrometer to explore Mars’ suitability for microbial life, its chemical composition, weather, seismic nature, magnetic properties and overall appearance. Fully fueled, each orbiter/lander combo weighed about 7,780 pounds (3,530 kg).(...)
http://www.americaspace.com/2018/08/26/hard-to-recapture-the-mood-remembering-project-viking-first-fully-successful-mars-landing-mission-part-2/