The landing on Mars shortly after the 200th Independence Day of the USA required over a decade of planning, right from the beginning of the space age * Part one of four - which will conclude the 'History of the Space Program' series
The way of the Viking program
In the years 1961-1963, the scientists of the Jet Propulsion Institute Pasadena (JPL) conceived an idea about landing a spacecraft on Mars. A spaceship with a spherical structure that is lowered by means of a parachute and upon reaching the ground unfolds six leaves that support it, and thus it stands on the ground. Mariner 4's observations showed that parachute landing alone is not possible due to the thinness of the atmosphere.
In 1965, NASA scientists developed a new concept. This is a spacecraft named Voyager. It is a two-stage spacecraft weighing 2,950 kg that uses the Saturn B1 Centaur launcher. The spacecraft enters orbit around Mars, photographs and surveys it, and at the end of the survey, lowers a lander to the surface. A test flight will be conducted in 1969, a first operational flight in 1971 and a second operational flight in 1973. In 1975, a biological research laboratory weighing 2.5 tons will be launched.
Congress had reservations about the plan and in the research budget for 1967, it made available to NASA a budget of 10.4 million dollars instead of 17.1 million dollars the previous year. Meanwhile, the Saturn 5 launcher was in its final stages of development and it seemed that there was a lot of logic in utilizing the launcher for Voyager purposes. A proposal was made to launch two spacecraft in Saturn 5, only one in 1973 and another attempt would be made in 1975. The budget that NASA allocated for this purpose in 1968 was 71.5 million dollars. NASA hoped to use this launcher to explore the planet Venus in 1977. The projected budget for the exploration of Mars and Venus until 1977 was 2.2 billion dollars. The weight of each spacecraft is 3.55 tons. This over-ambition was in the hands of the project and in February 1968 Congress canceled Operation Voyager. A more modest proposal was to make a transit flight in 1971.
In the next budget year of 1969, NASA planned a new strategy based on the expected Mariner flights in 1971 and 1973. The two spacecraft will be launched in 1971 by the Atlas-Centaur launcher to perform a comprehensive and thorough mapping of the planet's surface from orbit around it, and in 1973 two cells will make hard landings on its surface. The weight of each rocket is 420 kg, including 67 kg of scientific equipment, and the weight of each lander is 345 kg. The cells are equipped with equipment for soil analysis.
A few months later, at the beginning of 1969, part of the plan was changed. According to the new plan, two soft landings will be made. The Langley Research Center was appointed to conduct the research. In 1967 and 1979, the price of the project was estimated at 402.5 million dollars. A reassessment made a few months later raised the price to $694.8 million. At the end of 1969, NASA had to postpone the project until 1975.
According to the original plan, the first launch was to take place on June 30, 1973, entry into orbit around Mars would be on February 25, 1974 and landing on March 10, 1974. NASA had two options:
A. Entering the runway and reviewing the landing and landing sites. The lander must transmit the results of its measurements. Based on these results, the landing site for the second spacecraft will be selected.
B. The spacecraft enters orbit, immediately lands the lander and transmits its findings to Earth before the second spacecraft enters orbit. These measurements make it possible to correct the trajectory of the second spacecraft on the eve of its landing at a different latitude if necessary.
The year 1975 is not convenient for launching since it requires a greater power of the launchers.
At the beginning of 1970, NASA made it clear to Congress that the project, now named Viking, would cost 800 million dollars. Next year the price will rise to 880 million dollars. In 1972, it was decided to reduce the number of spacecraft tests on their systems in order to stay within the limits of the 880 million dollar budget. These actions did not help. Before the end of the year, the budget rose to 916 million dollars. Unexpected difficulties were discovered in the spacecraft's instruments and with the contract recipients - Martin Marietta who builds the lander and the Jet Propulsion Institute. Despite this, the Congressional Committee on Space Affairs had to accept a total price of 1974 million dollars in early 950, with the final price being 1,026 million dollars. Double the price of the original estimates but half of the Voyager.
Reductions in the project budget
In order to reduce unnecessary expenses, NASA decided in 1974 to implement this plan without the preparation of an emergency spacecraft. One spacecraft will be launched on August 11, 1975 and the second spacecraft will serve as an emergency spacecraft and will be launched on August 21. Viking B will serve as a source for spare parts for Viking A. If time does not allow it, she will be launched instead. Spare parts for Viking B in the event of a malfunction before launch, will be provided from the second Viking spacecraft. If the two spacecraft are not disinfected (sterile) sufficiently, launching the spacecraft in the August "window" will be difficult, if it is even possible. The internal disinfection process lasts five days. If an internal repair needs to be done, the disinfection must be done again. The original design called for the use of an emergency spacecraft to avoid wasting time re-sanitizing.
Each spaceship flies its own unique trajectory. Viking B is equipped with 84 kg of additional fuel compared to Viking A. If Viking B replaces Viking A, the launcher will not be able to accelerate it to the minimum speed required for Type 2 flight due to its extra weight. A Type 2 orbit is an orbit in which the spacecraft flies in an arc greater than 180 degrees around the Sun in preparation for its meeting with Mars. All previous NASA flights had an arc of less than 180 degrees. The new orbit was forced by reality due to the relative position of the Earth and Mars in 1975 - an inconvenient year for launches.
The structure of the spaceship
The Viking spacecraft consists of two parts - a capsule and a lander. The total weight is 3.46 tons. The height of the spaceship is 4.9 meters and its diameter is 3.6 meters, excluding the sun shelves which are 9.8 meters long. Before launch, the spacecraft is sterilized for 24 hours at a temperature of 93 degrees.
the circle
The circle in its shape is an advanced development of the Mariner 9. The most notable difference between the two spacecraft is the Viking's larger fuel tank. A hyphen has the shape of an octagonal prism (8 sides) with equal sides. It measures along its diagonals 216-252 cm. The weight of the car is 2.34 tons, of which 1.34 tons is fuel. A special layer of insulating material prevents overheating of the fuel tank. The area of the four solar shelves is more than 15 square meters and they have a power of 620 watts near Mars. In times of overload or when the compass is from the sun and beyond, nickel cadmium batteries with a capacity of 30 amps per hour are used. Navigation engines are attached to each shelf.
The equipment of the Mekpet is more sophisticated than that of Mariner 9 and also more sensitive. The spacecraft's instruments are cooled by shutters installed around the octagonal base. The hatches open and close automatically to allow "personal" cooling for all 16 separate equipment compartments. The compass has two computers and a comprehensive communication system. The planned lifespan is 140 days, but it is expected that the Mikapet will operate for two years. The Mekapet will crash on the surface of Mars 50 years after launch. One satellite can lower the altitude of its orbit to improve the photographs of interesting areas, while the second satellite monitors the two landings and transmits the information of both to Earth.
The scope devices
1. Two television cameras whose role is to discover the properties of Mars compared to the data of the landing sites on it and its conditions, to carry out an accurate mapping of Mars to prepare an atlas and photograph its moons for navigational purposes. In the entire coffee, the cameras cover an area of 80 by 1,050 km with a resolution of 80 meters. The most optimal resolution in low Phrygia is 37.5 meters.
2. An infrared spectrometer for mapping the content of water vapor and ozone in the atmosphere.
3. An infrared radiometer for measuring the temperature of Mars at night and during the day for thermal mapping. The accuracy range of the radiometer is two degrees.
4. Radio subsystem for measuring the atmosphere, the ionosphere and the magnetic field.
5. An X-ray spectrometer for measuring this radiation in the Martian sands and for measuring the gas in the atmosphere and on the surface of the ground.
6. Infrared sensing devices for locating warmer areas, to know what is being done underground.
All devices are placed on a coverage platform along a common axis, so they can cover the same area at the same time.
landed
The weight of the landing gear is 1,120 kg, of which 139 kg is fuel. The weight of the devices is 60 kg. Its lifespan is 90 days to a year. The landing gear has a hexagonal base and has three landing legs. Each leg has three arms that come out of its ribs and meet inside a plate. The landing system includes braking engines, an aerodynamic shield and a parachute with a diameter of 16.8 meters. The low atmospheric pressure of Mars required the combined use of a parachute and braking engines.
The aerodynamic shield has two parts and it closes the lander hermetically. In the upper part are the parachute and the braking motors which are also used to move the lander from the orbital path for landing. This shield can withstand a speed of 6.5 km/h and it absorbs most of the friction during entry into the atmosphere in the segment of the orbit that ranges from 6.7 to 200 km from the ground. The shield is made of a thin aluminum sheet with a thickness of 0.86 mm reinforced with a concentric ring and a thin layer of a cork-like material resistant to temperatures of 1,500 degrees is glued to its outer surfaces. The shield shields the lander from all the aerodynamic and thermal loads generated during entry into the atmosphere. The landing gear is "trapped" inside the shield so that all its protruding parts are folded. The landing legs can only be deployed to the site where the shield is disconnected near the landing.
The shield itself is covered with a biological shield that is also attached to the dash. It is made of two parts. The biological shield maintains the sterility of the aerodynamic shield and the lander subject to the most severe international agreements to prevent the contamination of planets by terrestrial bacteria.
Communication equipment includes an S-band receiver transmitter and the lander's power supply, which is basically a system of two nuclear power units with a power of 35 watts each, and a computer. The lander can maintain direct contact with the Earth or through the mother spacecraft - the Mekapat. Due to the limitations of the power supply, the transmissions to Earth are limited to a few hours a day.
landing gear
1. Mapping devices:
A. Two panoramic TV cameras placed one meter apart to survey the surface in color, black and white and near infrared. The coverage range of each camera is 360 degrees. The cameras should help with the selection of the soil samples being tested, observations of clouds and wind-borne dust. XNUMXD photographs can also be taken.
B. An infrared spectrometer for reviewing the concentration of water vapor in the atmosphere.
third. An infrared radiometer for reviewing surface temperatures. The purpose of the mapping is to locate humid areas where there is a high chance of finding any life forms.
2. A device for measuring the dependence of the current of charged particles on altitude to test the interaction between the solar wind and the Martian atmosphere. This experiment is carried out during the landing stages.
3. Meteorological unit - devices for measuring atmospheric pressure, temperature, wind speed and humidity during the day to learn about the physical processes at the landing site.
4. Research cells - the cells are in the body of the lander and have prominent openings on the platform of the instruments.
A. Three biological research cells.
B. GCMS cells (gas chromatograph mass spectrometer) for analyzing soil samples, identifying organic compounds and testing gas samples.
third. Luminescent X-ray spectrometer for performing geophysical experiments. The spectrometer can detect atmospheric concentrations as low as 200 ppm.
5. An arm that can be extended a maximum of three meters and at the end of it a spoon for collecting soil samples that are inserted into the research cells. Attached to the spoon below are two magnetic rods for measuring the cohesion between the soil particles, their porosity and their hardness. In this way you can learn about the nature of the soil and its composition - whether it is powdery, clayey, dry or moist.
6. A magnetometer for measuring the magnetic properties of the ground at the landing site.
7. Triaxial seismometer. The seismometer is designed to measure fluctuations in the crust of Mars, volcanic activity, meteorite impacts and also the vibrations of the lander when its instruments are working. The seismometers in the two landings are designed to determine the onset of earthquakes and their direction.
Combined utilization of the communication systems in the lander and in the lander allows complex experiments to be carried out to measure the magnetic field of Mars, the inclination of the axis of rotation, finding additional proofs for the justification of certain theoretical assumptions in the theory of relativity and more.
תקשורת
The control center cannot simultaneously monitor the landings and landings. While one spacecraft is working, the other must be shut down, whether on the ground (landing) or in orbit (launching) and vice versa. The broadcast hours are limited not only due to the limitations of the power supply in the lander, but also due to the movements of Mars and the Earth around their axis. Like the Earth, Mars also rotates around itself once every 24 hours, so the connection between the lander and the control center is cut off for more than 12 hours. When contact with the lander is restored, it is done with the help of the large antennas, in California, Australia and Spain. The connection can continue continuously for no more than two hours due to fear of the equipment heating up. Contact via the circle can only be made while it passes over the landing site, and even then it lasts less than an hour.
Experiments
1. Experiments in biological research cells:
A. An experiment of chemical separation by dry heat (pyrolysis) - a soil sample is placed in a chamber with atmospheric conditions, a natural Martian atmosphere and the star's daylight (produced by a filter lamp). The cell atmosphere is enriched with water vapor, CO and 2 CO. Some of their carbons have radioactive 14C. It is likely that organisms, if they do exist on Mars, utilize the 2 CO and solar energy similar to plants and other photosynthetic creatures on Earth that assimilate the CO2. At the end of five days of incubation, the atmosphere is removed from the cell. The sample is heated to a temperature of 600 degrees. A temperature high enough for the vaporization of organic substances. If there are organisms in the sample, they absorb the 2 CO. In terrestrial photosynthetic processes. The vaporized gas from the sample incinerator contains radioactive CO 2 .
B. To check if there is primitive life on the surface of Mars such as bacteria, a soil sample is inserted into another chamber that is also immersed in the Martian atmosphere. The sample is slightly saturated with moisture and fed with a nutrient solution containing carbon 14. The nutrient solution contains formate (salt of formic acid, glycine, salt, lactic acid, alanine and glycolic acid). The sample is incubated at a temperature of nine degrees for 11 days. During this period any organism that has metabolic functions will release gases containing carbon 14.
third. Another sample is placed in a third chamber and fed with richer liquid food without carbon 14. In a chamber atmosphere of helium, krypton and 2 CO. The sample is incubated for up to 12 days. The laboratory checks the atmosphere at regular intervals and looks for gases created in a biological process such as molecular hydrogen, nitrogen, oxygen and 2 CO.
2. Experiments in GCMS:
A. In this facility, molecular analyzes are performed to identify organic molecules in the soil. Soil samples are heated and release volatile gases that are separated by the gas chromatograph and detected by the mass spectrometer. This device can also detect water.
B. The HMS spectrometer measures the composition of the atmosphere near the ground.
3. A soil sample is placed in a closed container containing distilled water. A device is installed on the sides of the tank to absorb the light by the water. If tiny creatures grow in the water, their turbidity increases. The growth rate of turbidity makes it possible to distinguish between water pollution by the dissolution of soil particles and the growth of living creatures.
4. A cell containing only water without nutrients. After a certain period the water is tested to see if there are any changes in it.
the launcher
The launcher is Titan Centaur. It is a launcher capable of putting a payload of 17 tons into low Earth orbit and 4 tons into interstellar flight. It is a combination of the two-stage Titan IIIE and the Centaur D-1T. The Titan has two stages powered by liquid fuel and two large boosters powered by solid fuel attached to it on its sides. These are activated at launch. At the end of their combustion, the second stage powered by liquid fuel is activated. The third stage, the Centaur, went into action when the two Titan stages ended. The height of the launcher is 53 meters and its weight at takeoff is 640.8 tons.
Landing
Once the landing moment is selected, the upper sheet of the aerodynamic shield is removed. Two to five hours later, the lander is separated from the mekpet. The aerodynamic shield engines move the lander to the landing lane. Their role in the atmosphere is to slow down the speed of the lander. At an altitude of 6.7 km, these engines are bled and disconnected, the lower part of the aerodynamic shield is disconnected and a parachute with a diameter of 16.8 meters is deployed. This parachute further slows down the speed of the lander. At an altitude of 1.38 km, the parachute and the upper part of the aerodynamic shield are detached. From here until it touches the ground of Mars, the lander is propelled by the power of three terminal engines which continue to decelerate rapidly and four navigation engines direct it to the landing site. Each of the terminal engines has 18 nozzles arranged in two concentric circles. This is in order to minimize the damage to the ground from the gases emitted from the engines. The final stages of the landing are controlled by an altitude radar located at the end of the lander, so that less than 13 minutes after entering the atmosphere, the lander's legs touch the ground of Mars. At these moments the speed of the landing is 1.3 meters per second. Immediately after landing, the spacecraft's computer evaluates the attitude of the lander in relation to the ground and the power supply charges its batteries.
While passing through the atmosphere, the lander performs various atmospheric measurements that are immediately broadcast to Earth. The physical and chemical properties of the atmosphere are examined. The structure of the atmosphere is tested by pressure and temperature sensors, an altitude radar and an accelerometer. The upper atmosphere is examined by a mass spectrometer. The biological shield base detached from the lander immediately after it separated from the lander.
The landing sites
1. Viking 1 in Chryse. This place is located at W 0 34 - N0 19.5 at the eastern end of the 4,800 km long canyon rift. Mariner 9 discovered this breach. The fissure has a series of spurs that resemble dried river beds. This site is particularly interesting since it is at the lower end of a valley where the largest group of "streams" extending onto Mars begin to branch off from here. Chryse may have been a drainage basin for much of the Martian equator. It is possible that they will find different types of sediment here. This is one of the lowest places measured and explored until the launch of the Viking spacecraft. It is 5 km lower than the surface. The atmospheric pressure measured by Mariner 9 is slightly higher than that of the Cydonia landing site. An alternative landing site for Chryse is Tritonis Lacus W 0 252 N 20.50.
2. Viking in Cydonia. Location Sea Echidlium W 0 10 N0 44.3. The likelihood of having water vapor increases the chances of finding water here. Atmospheric pressure is 7.8 millibars above the critical point of 6.1 millibars needed for the presence of water. Mariner 9 discovered here clouds of water vapor in the amount of 300 ppm. The temperature can reach 0 degrees. The place is north enough for seasonal ice precipitation and south enough since in the summer the temperatures rise to the boiling point. Cydonia is 600 meters higher than Chryse. Geologically this is a smooth area probably formed from basaltic material. The ground is covered with volcanic rock fragments (by winds) and alluvial debris. An alternative landing site for Cydonia is the white area W 0 110 – N 0 44.2.
The two sites are 1,600 km apart but close enough to their seismographs to detect similar earthquakes in both locations. The selection of the two locations took about a year after a careful examination of 22 potential landing sites. Both sites are flat and quiet. They are at the bottom of the star. They were selected according to these criteria:
1. The atmosphere of Mars is thin. The increase in atmospheric pressure increases the safety of the landing performed by combining aerodynamics, parachute and braking engines.
2. Since the purpose of the operation is to search for life, the presence of water is extremely important. Areas of high atmospheric pressure are most likely to contain water. The minimum atmospheric pressure necessary for the presence of water is 6.1 millibars and the minimum temperature is 0 degrees.
The 3 photographs of Mariner 9 were studied thoroughly with an interest in finding flat earthing areas of special geological interest.
4. Strong winds blow on Mars. These winds can be observed with the help of terrestrial telescopes and the findings of Mariner 9. Studying these data makes it possible to choose landing areas where there is no danger of winds. The landings were designed to withstand winds that reach speeds of up to 240 km/h.
5. The clearance of 23 cm under the body of the lander requires a relatively smooth ground and to ensure the stability of the landing, the maximum angle of inclination allowed is 19 degrees. Landing on the face of smooth rock will make it difficult and impossible to collect soil samples. An area that appears to be covered by a deep layer of soft material will be interpreted as having insufficient load.
6. The equator as a landing site for this mission was chosen because it is an area about which much was known. The alternative landing sites were chosen for being the safest for the mission.
Although the landing sites for the mission were planned on the basis of selected constituencies, the spacecraft can locate new landing sites until the last means of repair (10 days before the encounter with Mars). In addition to this, the spacecraft have a limited possibility to change the landing sites if observations from the orbit show that the landing at the selected sites is not safe. The initial and alternative landing sites are in the area where there is priority for maximum biological research in the area of latitudes 40-50 North. Current plans spoke of the latitude 44 degrees and this can be changed to 50 degrees if the observations of the Viking 1 orbiter show that a safe landing place is found at this latitude for the second lander.
There were geologists who were not satisfied with this choice because they claimed there would be no difference in the findings of the two landings. They proposed to land one spacecraft at the North Pole where there is dust trapped within the ice layer. In their opinion, this is also the most suitable area for finding a life. The biologists claimed that the intense cold that prevails in this area is not suitable for the development of life and they prefer the humid "oasis". To strengthen their claims, the geologists brought Serviar's findings on the moon, which were made in almost geologically identical areas. Harsh criticism was leveled against the Apollo operation. It is argued that the Apollo landing sites were not chosen with sufficient care.
Schedule
The aforementioned launch was postponed from July 1973 to a window that opened on August 11, 1975 and lasted 44 days. The two spacecraft, Viking A and Viking B, are launched 10 days apart and first enter a national parking orbit. This is a track that is 184 km from the ground. The engines of the last stages of the launchers are ignited for half an hour and the spacecraft are launched in their direction. They travel 700 million km for about a year. They fly towards a point where Mars is 330 million km away from the other side of the Sun near Mars.
The engines are turned on for an hour and the spacecraft enters a parking orbit around Mars. The distance of the orbit from the ground is 1,538-32,530 km and the duration of the orbit is 24.5 hours. They stay in this orbit for at least 10 days, checking the landing sites thereby ensuring an accurate landing. If the local winds are strong, the spacecraft can stay in this orbit for at least 50 days. At this time the solar arrays provide the electrical power for the landers. Viking 1 was scheduled to land on January 4, 1976, the 200th Independence Day of the United States. Viking 2 was scheduled to land on August 23, 1976. The expected wind speed is up to 70 meters per second.
The two spacecraft finish their mission on November 15, 1976 when the sun is between the Earth and Mars and the connection with the Earth is cut off. Viking's research policy was that if one spacecraft failed the other would land in a safer location.
