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//Soviet Options (1989) for a Manned Mars Landing Mission /1/
[Scope Note: This paper examines several Options that the Soviets are likely to pursue in accomplishing a manned Mars landing mission. lt does not cover all available options. They were developed using different scenarios presented by the Soviets at international meeting:] /1/
Recent (1989) public statements by Soviet officials have confirmed that the Soviets are continuing research for a possible manned Mars mission. In March 1989 Soviet space scientists attending a space symposium outlined the following long-term Soviet Mars space program:
- The launch of a Mars and lunar-polar orbiter in 1992.
- The launch of two spacecraft to Mars, including an orbiter, atmospheric balloon, and/or soil penetrators, in 1994.
- Mars sample return mission with rover in 1998
- A manned Mars landing mission-possibly between 2010 and 2015.
[Now 2015 we know that nothing of the above did happen - largely due to the Soviet Union collapse in 1991 In 1996 Russians sent Mars 96 (or Mars 8) but the launch failed. In 2011 Russians sent Fobos-Grunt lander for a sample return mission but it also failed. Mars-Grunt robot is pushed somewhere future to 2020's and its fate is unknown when writing this. See also this link for more information about Mars robots.]
The successful completion of unmanned missions will give the Soviets valuable data on spacecraft component on-orbit lifetimes, landing sites on Mars, and command and control of interplanetary spacecraft. Despite the Soviets' recent failure to complete their Phobos mission we believe that they will apply the lessons learned and pursue a manned Mars mission.
The Soviets also have stated publicly that the long term effects of weightlessness on humans must be fully understood before a manned mission to Mars can be accomplished. Soviet cosmonauts have been in space continuously for up to 366 days. Vladimir Titov, crew commander, and Musa Manarov, flight engineer, were on board the Mir space station from 21 December 1987 through 21 December 1988. (They exceeded the previous 326-day record, held by Yury Romanenko, on 11 November 1988 and became the fourth and fifth cosmonauts to accumulate more than a year in space.) We believe that the Soviets will attempt a manned mission of 18 months or longer within the next few years. Continued bag-duration stays in space by Soviet cosmonauts (not required for space-station operations) and planned unmanned missions to Mars are our strongest indicators of continuing Soviet plans for a manned Mars mission.
Planning for a Manned Mars Mission
Planning for a manned mission to Mars is a complex undertaking. Basic mission requirements include:
- Definition of mission goals.
- Selection of a launch date (dictated by orbital mechanics).
- Selection of the type of propulsion used.
- Determination of spacecraft trajectory.
- Design of the spacecraft.
- Selection of amount and type of scientific equipment carried on the spacecraft.
Changes to any of these requirements could change the mission profile.
Assumptions Considered for a Manned Mars Mission
An article in the 1985 edition of the Encyclopedia of Cosmonautics characterized a manned Mars mission as lasting one and a half to two years and using nuclear engines and liquid hydrogen propellant. with a specific impulse (Isp) of 836 seconds (sec) and a total mass on orbit of 1.000 to 1.500 metric tons. Our assumptions were based in part on this article. Additional assumptions were taken from US concepts for a manned Mars mission:
|1985 Encyclopedia of Cosmonautics|
- Crew of five or six.
- Mars spacecraft assembled in and departing from low Earth orbit with space station support.
- Nuclear engines using liquid hydrogen propellant (Isp 836 sec) or conventional engines using liquid oxygen and liquid hydrogen propellants (Isp 450 sec).
- Venus swing-by to reduce energy requirements.
- Mission modules to remain in Mars orbit. with a weight of 54,000 kg. plus 6,800 kg return weight for Earth reentry module.
- Mars excursion module: to transport Mars landing crew and equipment to and from Mars surface. The modules weight will be 60.000 kg. plus an additional 4.500 kg for nuclear shielding.
- Required velocities achieved by three propulsion stages.
- Stage structure factor for nuclear engines using liquid hydrogen is 20 percent: conventional engines using liquid oxygen and liquid hydrogen is 9 percent.
- Elliptic capture orbit at Mars and Earth.
Mars Mission Opportunities
Opportunities for direct flights to and from Mars occur near the Earth-Mars opposition, approximately every 26 months. Two general classes of direct round trip mission profiles to Mars are available:
- Opposition-class mission - where Earth and Mars are near their closest approach at the time of arrival at Mars, with a short stopover time at Mars.
- Conjunction-class mission - where Earth and Mars arc farthest apart at the time of arrival to Mars, with a long Stopover time at Mars.
Because of the eccentricity of Mars' orbit, the mission profile changes from one opposition to the next. The mission profile variation is cyclic, and the pattern repeats every 15 years or every seven oppositions. The relative positions of Earth and Mars for a short stopover time at Mars (30 to 60 days) require excessive energy for the spacecraft propulsion stages to perform a direct round trip mission. To reduce the energy requirement for an opposition-class mission, the gravity field of Venus can be used either en route to Mars for an outbound swing-by or en route to Earth for an inbound swing-by. Total mission time for an opposition-class mission will vary from approximately 550 to 740 days. Energy requirements can be reduced for a conjunction-class mission because low-energy, near-Hohmann-type (minimum energy) transfers can be used on the outbound and inbound trip by extending the stay time at Mars appropriately (340 to 550 days. Total mission time for a conjunction-class mission will vary from approximately 950 to 1,000 days.
|Figure 1 - Typical Mission Profiles for a 60-Day Stopover at Mars. (Note: trajectories are not to any scale!)|
There are a wide range of mission options available; for the purposes of this paper, we will assume a Soviet manned Mars mission with a 60-day stay time on the surface of Mars and will use an opposition-class mission profile with a Venus swing-by to reduce total energy requirements (see figure 1). Data considering conventional and nuclear propulsion, including the effects of aero braking at Mars and Earth, are presented. The total on-orbit mass of the Mars spacecraft and the number of launch vehicles required to place the necessary components for it in low Earth orbit are determined for each case.
Mars Spacecraft Mass - An Estimate
There are major factors for determining spacecraft mass on orbit. These include the propulsion system, spacecraft design, launch opportunity, and crew size. We calculated the total mass required on orbit for the Soviet Mars spacecraft assuming three propulsion stages were used to conduct the mission from low Earth orbit. The propulsion Options we examined were:
- Conventional engines using liquid oxygen and liquid hydrogen in all three stages.
- Nuclear engines using liquid hydrogen in all three stages.
- Nuclear engines using liquid hydrogen in the first and second stages, and conventional engines using liquid oxygen and liquid hydrogen in the third stage.
For each option, calculations were made for:
- All-propulsive maneuvers for all phases, including Mars entry and Earth reentry.
- Aero brake at Earth reentry, with remaining maneuvers propulsive.
- Aero brake at Mars entry, with remaining maneuvers propulsive.
- Aero brake at Mars entry and Earth reentry, with remaining maneuvers propulsive.
We selected two launch opportunities - the years 2001 and 2007 - for an opposition-class mission for our calculations. The dates represent the approximate minimum- and maximum-energy requirements for selected future opposition-class, Venus swing-by launch opportunities.
|Conventional Engines with
Liquid Oxygen and Liquid
|Nuclear Engines with liquid
|Nuclear Engines with Liquid
Hydrogen (Third-Stage Conventional
Engines with Liquid Oxygen and
|Aero brake Earth|
|Aero brake Mars|
|Aero brake Mars and Earth|
Table:: Total Mass on Orbit and Number of Launch Vehicles Required (By launch year)
[Note: The number of launch vehicles required to place components in low Earth orbit was calculated by assuming that the HLLV has a 100,000-kilogram payload capacity. Assuming a propellant tank 7 meters in diameter and 20 meters tall, the volume would be sufficient to carry only 50,000 kgs of liquid hydrogen (because of its density). The same size tank would easily carry the full 100,000 kilograms of liquid oxygen. Tbe mixture ratio (mass for liquid oxygen and liquid hydrogen propellants in normally 6:1, and that ratio was used to determine launch vehicle requirements.]
Mass for the different options for all-propulsive maneuvers ranges from approximately 745,000 kg to 2,745,000 kg. Aero braking at Mars could reduce the mass requirement by 15 to 55 percent, depending on the propulsion option and launch date chosen. In fact, aero braking at Mars would have a major impact on the number of launch vehicles required to place Mars spacecraft components in low Earth orbit, especially during launch opportunities with higher energy requirements (see table). The number of launch vehicles required for all-propulsive maneuvers ranges from 15 to 35. Aero braking at Mars, however, reduces launch vehicle requirements to a low 13 and a high of 17 for any propulsion option chosen at any launch opportunity. This significant reduction would make proven conventional engines with liquid oxygen and liquid hydrogen an attractive option, eliminating the need for nuclear engines and reducing the radiation shielding for crew protection.
Calculations for crews of six and three were performed and analyzed to determine the impact on total spacecraft mass. Depending on the launch opportunity and propulsion system selected, a reduction in crew size from six to three would produce a savings of 5 to 20 percent of the total spacecraft mass required in low Earth orbit. This would result in a savings of one to seven launch vehicles. By selecting only favorable launch opportunities, the savings in launch vehicles becomes one to three. These resultant savings were considered minimal when compared to the advantages afforded by the larger crew and are not further discussed in this paper.
At least several months would be required to orbit all the necessary components for a Mars spacecraft, assuming a 30-day turnaround time for each launch pad.
Manned Mars Mission Requirements
A Soviet manned Mars mission will involve the development of key technologies. These technologies are of two types - those that will be required for the Soviets to conduct a manned-mission and those that will enhance the Soviet ability to conduct the mission.
Key Technologies Required for a Manned Mars Mission
The required key technologies are:
- Heavy-lift launch vehicle (HLLV).
- Space Station on orbit.
- Space cryogenics.
- On-orbit shelf life of spacecraft components.
- Life sciences and support.
- Orbital maneuvering vehicle (OMV)
|Energya HLLV: The only orbital launch of a Buran-class orbiter occurred at 3:00 UTC on 15 November 1988 from Baikonur Cosmodrome launch pad 110/37. OK-1K1 was lifted into space, on an unmanned mission, by the specially designed Energia rocket.|
Heavy-Lift Launch Vehicle. An HLLV will be required to place propellants and spacecraft components in low Earth orbit. The Soviets successfully launched an Energiya HLLV in May 1987 and November 1988. The vehicle is capable of placing a 100,000 kilogram payload in low Earth orbit and should be fully operational by the mid-1990's.
|Mir on 9 February 1998 as seen from the departing Space Shuttle Endeavour during STS-89|
|LH2 Gyrogenic Tank System|
Space Cryogenics. Advanced refrigeration and insulation techniques will be required to prevent excess loss of cryogenic propellants caused by boil off. Handling and storage of these propellants also is a major problem because no in-flight refueling capability is envisioned during the mission. The Soviets have some experience with liquid oxygen and liquid hydrogen in their HLLV. These propellants, however, will have to be stored for up to two or three years for a manned Mars mission.
|April, 1999, Mir space station crew members test hole-patching equipment during a space walk.|
On-Orbit Self Life of Spacecraft Components. The Soviets have more than five years of experience with the Salyut 6 and 7 space stations. Salyut 7 remains on orbit, providing additional lifetime data, and additional experience will be gained with the Mir space station. The Soviets have demonstrated increased lifetime with their manned spacecraft by having crews on board to repair and replace components.
|A soviet cosmonaut in a centrifuge during his training in Zvezdograd (star city) 1960's|
Life Sciences and Support. Long-duration flights aboard Soviet space stations are providing much of the data necessary to make continual improvements in the life science areas. The harmful effects of weightlessness continue to be a major concern. Soviet cosmonauts have performed continuous space flight in excess of a year. We believe that the Soviets will increase the duration of space station mannings in increments to a period of two years. One or more two-year missions may be needed to fully understand the medical requirements for a manned Mars mission. According to Soviet open sources, readaptation to a gravity field normally takes place within several days, but, in some cases, several weeks may be required. However, the ability of a cosmonaut to perform tasks unaided by a ground crew immediately alter long exposure to weightlessness is questionable. Control of bone-calcium loss on long-duration missions also is not well understood by US or Soviet researchers and is a major issue requiring further studies.
|Boeing's Orbital Maneuvering Vehicle proposal from 1984|
Orbital Maneuvering Vehicle. An OMV, also known as a space tug, will be required to move large components of the Mars spacecraft into place for assembly following delivery to the apace station orbit. The Soviets have used a propulsion module to accomplish approach and docking of the Kvant space station module with Mir. A similar vehicle may be intended for use as an OMV.
Key Technologies That Will Enhance a Manned Mars Mission
Key technologies that will enhance Soviet efforts to conduct a manned Mars mission are:
Aerobrakiag. Aero braking involves using a planets atmosphere to dissipate an entry vehicles energy and reduce its speed. Aero braking can be used to change orbit or to descend to a planet's surface instead of using propulsive maneuvers. An entry vehicle is enclosed within a heat shield (that could be shaped like the US Apollo or Soviet Soyuz entry modules) that provides a relatively low lift-to-drag ratio. The entry vehicle's energy then would be dissipated through ablation of the heat shield.
Aerobrakiag into Mars orbit would reduce the mass of propellants required in low Earth orbit by as much as 55 percent (sec figure 2).
The Soviets have stated that they intend to use aero braking on their unmanned missions, and they do have some experience with aero braking on earlier Mars missions. The Mars 2, Mars 3, and Mars 6 lander missions used an aero shell braking device, although it did not generate any lift.
Nuclear Propulsion. Nuclear engines using liquid hydrogen propellant could provide almost twice the Isp of conventional engines using a liquid oxygen and liquid hydrogen mixture. The increased Isp would reduce the amount of propellant and the total mass required on orbit. A nuclear engine also could provide electrical power for the Mars spacecraft during the mission.
The Soviets my be testing advanced reactors to be used as power and propulsion plans for future space missions.
At a US conference held earlier this year on space nuclear power systems, a Soviet Scientist presented a paper discussing nuclear electric propulsion (NEP) as one of several options being investigated by the Soviets for use on a Mars mission for electrical power and propulsion. NEP would provide a higher Isp, but with lower thrust levels. NEP engines would probably be designed to burn continuously. and the comparative round trip transit times for a Mars mission would increase significantly, making NEP engine use less desirable for early manned missions.
Closed Ecological System. A closed ecological system could provide life-support consumables (oxygen, food, and water), thereby eliminating some of the mass of expendable consumables. A closed system will have minimal impact on the total number of launch vehicles required to support a mission, however, because the mass of expendable consumables constitutes only a small fraction of the total mass required. Soviet Scientists at the Institute of Biophysics are working on closed ecological systems and have stated that these systems will be used on future space station.
Artificial Gravity. The long-duration effects of weightlessness arc not fully understood, and countermeasures arc continually being implemented to reduce the period of readaptation to gravity. The gravity of Mars is about one-third that of Earth's, and Scientists generally believe that humans would be unable to adapt rapidly to its gravitational field following long periods of weightlessness en route. The Soviets are investigating the possible use of artificial gravity. There are differences of opinion in the Soviet Union, just as there are in the United States, on the benefits and engineering trade-offs required to incorporate an artificial gravity field on the Mars spacecraft.
The most economical launch opportunities for a manned Mars mission most likely will cost from 40 to 50 billion US dollars (1989). These figures assume the supporting infrastructure is already in place. The Soviets will have made a major resource investment before committing themselves to a launch, including:
- A fully operational, permanently manned space station.
- Full development costs for their HLLV.
- Development of modules that could be used for a Mars spacecraft.
Because of budgetary constraints and increasing debates on allocation of future resources for the Soviet space systems it is too early to know if the Soviets will go ahead with a manned Mars landing mission. We project, however, that the overall manned space effort will remain robust, at least for the next five years as the Soviets add new modules to the Mir space station and as the shuttle orbiter becomes operational. In the middle-to-late 1990's, the cost of manned space activities could increase if the Soviets proceed with plans for a follow-on space station.
Soviet space scientists and officials have been trying to deflect Soviet criticism of the enormous expense of space activities by stressing the economic benefits to the national economy. For example, the Soviets claim that an upcoming Mir module will produce profits that will pay for the project many times over. Other claimed benefits from the space station include increased agricultural production, enhanced reforestation programs, and increased harvest by fishing fleets.
Cooperation With the United States on a Mars Mission
The Soviets may seek to cooperate with the United States, which is considering a manned Mars mission, to defray some of the expense of such a mission. Soviet scientists now are pursuing such a cooperative effort: if the United States decides not to participate because of technology transfer considerations or for other reasons, the Soviets are likely to implement a manned Mars mission on their own. They would probably attempt to gain greater cooperation and financial support from France and perhaps other nations that have flown or participated in cooperative efforts on Soviet space station.
Future Indicators for a Soviet Mission
Future developments that would indicate continued progress toward realizing the mission include:
- Development and use of aero brake techniques.
- Advanced refrigeration and insulation on upcoming unmanned space missions.
- Assembly of a Mars spacecraft prototype in low Earth orbit.
- A flight to Mars of an unmanned prototype.
- The possible flight testing of a nuclear engine.
A manned Mars mission most likely could not take place before the year 2000 because of the time required to develop Aero braking techniques, nuclear engines, advanced on-orbit refrigeration, improved insulation techniques, a fully operational HLLV, and possibly a closed-cycle, life-support system. If the Soviets are successful in developing aero braking techniques, the most likely option would be to use proven conventional engines with liquid oxygen and liquid hydrogen propellants. Without aero braking, nuclear engines probably would be used in the mission to reduce the number of launch vehicles required. Without aero braking or nuclear engines, and a cryogenic on-orbit storage capability, we believe it is unlikely that a full-scale manned Mars landing mission could be accomplished. Using storable propellants, which have lower Isps, would require a prohibitive mass on orbit. Such use probably would make a manned mission nearly impossible, especially during launch opportunities necessitating higher energy requirements.//
/1/ Soviet Options for a Manned Mars Landing Mission An Intelligence Assessment -
SW89-10062 December 1989 -
CIA WWW Library, Freedom of Information Act Electronic Reading Room,
This paper was prepared by XXXXXXXXX, Office of Scientific and Weapons Rcsearch,
Comments and queries are welcome and may be directed to the Chief, XXXXXXXXX. OSWR.
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