FILE CIA 1989: Opzioni Sovietiche per uno Sbarco Umano su Marte by
Alberto G. is licensed under a
Creative Commons Attribuzione - Non commerciale - Non opere derivate 3.0 Unported License.
Soviet Options for a Manned Mars Landing Mission
An Intelligence Assessment
This paper was prepared by
Office of Scientific and Weapons Research.
Comments and queries are welcome and may be
directed to the Chief
OSWR.
Soviet Options for
a Manned Mars
Landing Mission
Scope Note
This paper examines several options that the Soviets are likely to pursue in
accomplishing a manned Mars landing mission. It does not cover all
available options. They were developed using different scenarios presented
by the Soviets at international meeting:
Key Judgments
Information available as of 1 December 1989 was used in this report.
We believe the Soviets are planning for a manned Mars landing mission some time after the year 2000. Although we believe the mission has not been officially funded, the Soviets have invested in the infrastructure and are engaged in the long-lead research and development necessary for its conduct. Clear indications of Soviet intent to perform such a mission include:
• Continuing long-duration flights aboard the Mir space station that have resumed following the recent short-term hiatus in manned activity.
• The probable development of nuclear rockct engines.
• A planned program of unmanned flights to M2rs over the next 10 years, despite last year's Phobos failures, giving the Soviets data for an attempted manned mission.
• An increasing number of press releases by Soviet scientists, engineers, and cosmonauts discussing their intent to conduct a manned mission.
The Soviets have several available options in mission profile and spacecraft design to accomplish this mission. Balancing the technical demands of each option with the strengths and weaknesses of their space program leads us to believe the Soviets are most likely to pursue:
• An opposition-class mission profile, where Earth and Mars are near their closest approach at the time of arrival at Mars, with a Venus swing-by— to reduce energy requirements.
• Either nuclear or conventional engines using cryogenic propellants—for efficient spacecraft propulsion.
• Aerobraking into Mars orbit—to reduce the propcllant requirement.
Because of the size and mass of the spacecraft, a manned Mars landing mission will require vehicle assembly in low Earth orbit. The Soviets have the Energiya heavy-lift launch vehicle to place the components into low Earth orbit. In addition, they will have a manned space station to support spacecraft assembly and probably a space tug to move large components into position for assembly.
We believe a full-scale, manned Mars landing mission is unlikely without development of an on-orbit cryogenic storage capability and either nuclear engines or aerobraking techniques. If the Soviets use nuclear engines with a liquid hydrogen propcllant, it would substantially reduce the number of launch vehicles required to place spacecraft components in low Earth orbit. The use of cryogenics will require the development of advanced on-orbit refrigeration and insulation techniques to maintain the propellants in a liquid state and reduce their loss because of boiloff. Aerobraking into Mars* orbit would reduce the mass of propellants required in low Earth orbit by as much as 55 percent. This would allow the Soviets to use proven conventional engines with liquid oxygen and liquid hydrogen propellants to achieve roughly the same reduction in the number of launch vehicles needed to place spacecraft components in low Earth orbit as with nuclear engine.
We believe that, if the Soviets proceed with a manned Mars mission, they will pursue a cooperative effort with the United States to defray some of the high cost. Current Soviet estimates range from 40 to 50 billion US dollars for even the most economical launch opportunity.
Introduction
Recent 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 1:998.
• A manned Mars landing mission—possibly between 2010 and 2015.
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 1 we believe that they will apply the lessons learned and pursue a manned Mars mission.
The Soviets also have staled 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, (light 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 Romancnko, 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 long-duration stays in spacc 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 or 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)
1 of 836 seconds (sec) and a total mass on orbit of 1,000 to 1,500 metric tons. Our
1 Figure of merit expressed in sceonds. Increasing Isp improves the propulsion system's ability to produce additional thrust for every pound of propellant burned
assumptions were based in part on this article. Additional assumptions were taken from US concepts for a manned Mars mission:
• Crew of five or six.
1• 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 (lsp 450 sec).
• Venus swing-by to reduce energy requirements.
• Mission module, 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 module's 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 arc 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 are farthest apart at the time of srrivot «i Mars, with a long stopover time at Maty.
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
1A crew of six was determined to be the optimum size required to conduct a manned Mars mission. Although the crew size could be reducted, it is unlikely that a mission would be conducted with fewer than five members. A crew probably would consist of at least a commander, a pilot, a flight engineer, and two mission specialists- one of whom might be a physician. We believe that at least three crewmembers would go to and from the surface of Mars in an excursion module while the other two to three crewmembers would remain in orbit around Mars in a mission modulrepeats 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 reducc 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 staytime at Mars appropriately (340 to 550 days). Total mission time for a conjunction-class mission will vary from approximately 950 to 1,000 day:
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 staytime 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 aerobraking 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 component fnr it in low Earth orbit are determined for each case.
Mars Spacecraft Mass—An Estimate There are major factors for determining spacccraft mass on orbit. These include the propulsion system, spacccraft design, launch opportunity, and crcw 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 wc examined were:
• Conventional engines using liquid oxygen and liquid hydrogen in all three stages.
Figure 1
Typical Mission Profiles For a 60-Day Sfopover at Mars
• 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, calculates were made for:
• All-propulsive maneuvers for all phases, including Mars entry and Earth reentry.
• Aerobrake at Earth reentry, with remaining maneuvers propulsive.
• Aerobrake at Mars entry, with remaining maneuvers propulsive.
• Aerobrake 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, Vtnuscwing-by launch opportunities (see appcndijt).
Mass for the different options for all-propulsive maneuvers ranges from approximately 745,000 kg to 2,745,000 kg. Aerobraking at Mars could reduce the mass requirement by 15 to 55 percent, depending on the propulsion option and launch dale chosen. In fact, aerobraking 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. Aerobraking at Mars, however, reduces launch vehicle requirements to a low of 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-aday turnaround time for each launchpad.
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)
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-1990s.
Space Station on Orbit. To support assembly of the Mars spacecraft, a space station on orbit will be required. The Mir modular spacc station now is on orbit and could support the construction of a Mars spacecraft. The Soviets already have announced Mir-2, a larger modular space station, which we (...) be launched in the 1994 to 1996 time frame.
Space Cryogenics.
Advanced refrigeration and insulation techniques will be required to prevent excess loss of cryogenic propellants caused by boiloff. 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 propellant however, will have to be stored for up to two or three years for a manned Mars mission.
On-Orbit Shelf 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 spacc station. The Soviets have demonstrated increased lifetime with their manned spacecraft by having crews on board to repair and replace component.
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 spaceflight 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 after 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 study
Orbital Maneuering Vehicle.
An OMV, also known as a space tug, will be required to move large components cf the Mars spacecraft into place for assembly following delivery to the space 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:
• Aerobraking.
• Nuclear propulsion.
• Closed ecological system.
• Artificial gravity
Aerobraking.
Aerobraking involves using a planet's atmosphere to dissipate an entry vehicle's energy and reduce its speed. Aerobraking 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 heatshield (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 heatshield.
Aerobraking into Mars orbit would reduce the mass of propellants required in low Earth orbit by as much as 55 percent (see figure 2)
The Soviets have slated that they intend to use aerobraking on their unmanned missions, and they do have some experience with aerobraking on earlier Mars missions. The Mars 2, Mars 3, and Mars 6 lander missions used an aeroshell brakin» 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 may be testing advanced reactors lo be used as power and propulsion plants 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 'We systems will be used on future space station
Artificial Gravity.
The long-duration effects of weightlessness are not fully understood, and counter- measures 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 he 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".
Soviet Investment
The most economical launch opportunities for a manned Mars mission most likely will cost from 40 to 50 billion US dollars. 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, il 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 1990s, the cost of manned spacc 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 cconomy. 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 Slates 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 arc 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 aerobrake 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 aerobrake techniques, nuclcar 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 aerobraking techniques, the most likely option would be to use proven conventional engines with liquid oxygen and liquid hydrogen propcllants. Without aerobraking, nuclear engines probably would be used in the mission to reduce the number of launch vehicles required. Without aerobraking or nuclear engines, and a cryogenic on-orbit storage capability, wc 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.
FILE CIA 1989: Opzioni Sovietiche per uno Sbarco Umano su Marte by
Alberto G. is licensed under a
Creative Commons Attribuzione - Non commerciale - Non opere derivate 3.0 Unported License.
