HomeNASANo Scarcity of Desires: MSSR as MEM (1967-1968)

No Scarcity of Desires: MSSR as MEM (1967-1968)

Scary trip: second stage and crew cabin of the Bellcomm minimal Mars Tour Module (MEM) ascent car. The unpressurized cabin would have included few shows and minimal communications. Picture credit score: Bellcomm/NASA.

The NASA Planetary Joint Motion Group (JAG) noticed the addition of the Mars Floor Pattern Returner (MSSR) probe to the piloted Mars/Venus flyby mission eventualities it studied in 1966 as a pivotal innovation. Earlier than the arrival of the MSSR, the piloted flyby mission seemed to be more and more threatened by profitable robotic flyby missions. The MSSR, members of the Planetary JAG contended, gave the piloted flyby mission an added functionality that would not be reproduced by an entirely robotic Mars mission.

The piloted flyby spacecraft would have launched the MSSR maybe 10 days earlier than Mars shut encounter. A rocket motor on the MSSR would have boosted it towards Mars, enabling it to succeed in the planet and land at a preselected web site a number of hours earlier than the piloted flyby spacecraft arrived. 

The crew on board the piloted flyby spacecraft would have used quite a lot of pattern collectors on board the MSSR to collect about two kilos of Mars floor materials and air by distant management because the planet grew ever bigger of their viewports. These would have been packed right into a three-stage ascent car and launched to the piloted flyby spacecraft. 

Partial cutaway of Mars Floor Pattern Returner (MSSR) probe. A = Mars intersect trajectory injection stage with toroidal propellant tank; B = pattern canister; C = ascent stage with three phases, every with a toroidal propellant tank; D = folded touchdown leg (considered one of 4); E = aeroshell warmth defend; F = toroidal descent stage propellant tank; G = descent stage engine warmth defend cap. Picture credit score: NASA/DSFPortree.

The astronauts on board the piloted flyby spacecraft would have captured the pattern canister and ascent car third stage utilizing a boom-mounted docking ring and linked them to a port main right into a hermetically sealed organic laboratory. The MSSR probe would, it was anticipated, allow evaluation of Mars samples inside an hour of their assortment, serving to to make sure that any martian organisms they contained would nonetheless be alive. 

Section 1 of the Planetary JAG piloted flyby examine ended with distribution of an NASA report on 3 October 1966. The group then started work on Section 2 of its piloted flyby examine. Some members of the Planetary JAG foresaw a rosy future for the idea — they anticipated that MSSR examine contracts is perhaps awarded in Fiscal 12 months 1968 and the piloted flyby mission may develop into a NASA new begin venture in Fiscal 12 months 1969.

Even earlier than the AS-204/Apollo 1 hearth (27 January 1967), nevertheless, NASA planning for missions past Apollo was on shaky floor. Neither the Administration of President Lyndon Baines Johnson nor the Congress supported bold plans for post-Apollo spaceflight — for instance, a long-term lunar base or people on Mars. By the summer season months of 1967, the fireplace, racial and anti-war tensions throughout the nation, issues concerning the Federal funds deficit, and navy setbacks in Indochina had offered opponents of an expansive U.S. future off the Earth with ample justification for curbing NASA efforts to outline its future.

Not all advance planning halted, nevertheless. Bellcomm, NASA’s Washington, DC-based planning contractor, continued its work as a matter after all. Most Bellcomm research within the 1967-1969 interval aimed to outline the form of the Apollo Program after the primary profitable piloted lunar touchdown, in addition to that of Apollo’s deliberate successor, the Earth-orbital and lunar Apollo Purposes Program (AAP). A modicum of labor towards extra bold targets past Earth orbit and the Moon additionally continued.

In July 1967, for instance, Bellcomm planners D. Cassidy and H. London accomplished a brief technical memorandum during which they explored how the MSSR probe may kind the idea for a piloted Mars Tour Module (MEM) lander. Their examine kicked off a collection of associated research at Bellcomm within the 12 months that adopted. 

Cassidy and London assumed a 15,000-pound MSSR with a two-stage ascent car able to launching 80 kilos to a passing piloted flyby spacecraft launched in 1975, 1977, or 1979 on a Mars Twilight flyby path. The “Twilight” mission owed its identify to the geometry of its Mars flyby — closest method to Mars befell over the planet’s evening hemisphere close to the daybreak terminator, the road dividing pre-dawn darkness from daylight. 

The Bellcomm engineers calculated that MSSR Mars environment entry velocity would attain 32,500 toes per second (fps) in 1975, 34,500 fps in 1977, and 39,000 fps in 1979. Because it handed at a shallow angle by the skinny martian environment, the automated MSSR would bear deceleration equal to as much as 40 instances the pull of gravity on Earth’s floor (that’s, 40 Gs). To perform rendezvous with the passing piloted Mars flyby spacecraft, the MSSR ascent car must enhance an 80-pound third stage and pattern container to 36,000 fps in 1975, 38,000 fps in 1977, and 42,500 fps in 1979. 

An MSSR-derived MEM launched throughout piloted Mars orbiter method to Mars — that’s, earlier than the orbiter fired its rocket motors to decelerate in order that Mars’s gravity might seize it into an elliptical orbit with a one-day interval — would, then again, in 1978, 1982, 1984, 1985, and 1986 enter the martian environment shifting at between 20,000 fps and 25,000 fps. It might decelerate at about 10 Gs, which Cassidy and London judged to be acceptable for an astronaut. 

MSSR-derived minimal MEM. Picture credit score: Bellcomm/NASA.
Two methods of touchdown on Mars: Direct Entry Mode would see a pair of minimal Mars Tour Modules (MEMs) and a shelter deployed from a Mars orbiter (labelled “S/C”) throughout method to Mars. The orbiter would then hearth rocket motors to seize into an elliptical Mars orbit. If the orbiter couldn’t seize into orbit, the dual MEMs would abort their touchdown, fly previous Mars, and rendezvous with the orbiter. Entry from Elliptical Orbit would see minimal MEM and shelter separation after the Mars orbiter captured efficiently into Mars orbit. Picture credit score: Bellcomm/NASA.

An equal MEM launched in Mars orbit would enter extra slowly and topic its occupant to a diminished G load whereas additionally enabling extra exact touchdown web site concentrating on. The MSSR-derived MEM ascent stage might enhance a 900-pound third stage and crew capsule containing a single astronaut to a velocity of 18,000 fps to a rendezvous with the piloted orbiter in an elliptical Mars orbit with a interval of in the future. 

Cassidy and London defined {that a} separate Bellcomm examine, not but accomplished once they completed their July 1967 memorandum, had decided {that a} minimal one-person MEM with a crew capsule weighing as little as 600 kilos with out an astronaut on board is perhaps attainable. Such a MEM would carry solely sufficient life help consumables to stay on Mars for a short while and no scientific exploration tools. 

Anticipating {that a} mission so restricted may not get pleasure from a lot help, they briefly examined one which employed three MSSR-derived landers: a pair of minimal MEMs carrying one astronaut every and an automatic one-way cargo lander for delivering 5,500 kilos of life help provides and science gear. The three landers would contact down close to one another in order that the 2 astronauts might meet up and make use of the cargo.

In contrast with the MSSR-derived MEM ascent car, the single-seat Mercury spacecraft — proven right here with its retrograde propulsion system (backside, strapped to bowl-shaped warmth defend) and crimson launch escape tower — was massive, heavy, and sophisticated. Picture credit score: NASA.

The examine of a 600-pound MEM crew capsule Cassidy and London referenced was carried out by M. Skeer in session with Cassidy and unnamed McDonnell Plane engineers. Skeer, a newcomer to Bellcomm in 1966, summed up outcomes of his examine in a technical memo dated two months after the Cassidy and London examine. 

Skeer explored whether or not the design of the one-man McDonnell-built Mercury capsule, which carried six astronauts on suborbital and orbital missions in 1961-1963, may comprise weight-saving classes for designers of an MSSR-derived MEM ascent car. The 4600-pound Mercury capsule, he defined, was a sensible choice for his examine as a result of, just like the minimum-mass MEM ascent car, it had comparatively easy mission targets in contrast with the Gemini or Apollo Command and Service Module (CSM) and Lunar Module (LM) spacecraft.

The minimal MEM would descend from a spacecraft in a extremely elliptical Mars orbit with a interval of from 24 to 48 hours. A spacecraft in such an orbit could be certain loosely by Mars’s gravity, so would require minimal propellant expenditure to depart the planet when the time got here to return to Earth. Descent from the extremely elliptical orbit to the floor of Mars would final about six hours and return from the floor of Mars to extremely elliptical orbit would require about two hours. 

Skeer eradicated 47% of Mercury’s weight instantly by deleting the 1119-pound launch escape tower, 315-pound warmth defend, 317-pound retrograde propulsion system (used to deorbit the Mercury capsule), touchdown methods and restoration gear collectively weighing 343 kilos, and 51 kilos of experiments. He then handled remaining Mercury methods intimately. He wrote, for instance, that McDonnell engineers had instructed him that the 75-pound Mercury sofa might be trimmed to fifteen kilos. Skeer arrived at a complete MEM ascent stage weight of 738 kilos together with a 170-pound astronaut. 

Minimal MEM entry and touchdown. Picture credit score: Bellcomm/NASA.
Helpful payload: two-stage minimal MEM ascent car. Picture credit score: Bellcomm/NASA.
Minimal MEM liftoff, ascent, and orbital insertion. After rendezvous in Mars orbit the only astronaut would fly the capsule right into a hangar on the Mars orbiter or would abandon the capsule and enter the Mars orbiter by spacewalking. Picture credit score: Bellcomm/NASA.
The MEM cabin would offer simply 92 cubic toes of quantity for the astronaut — 26 cubic toes lower than the cosy Mercury cabin. A “plastic shroud” measuring simply 30 inches vast by 60 inches lengthy, it might be neither pressurized nor insulated. Skeer estimated that it might weigh as little as 200 kilos, about 415 kilos lower than the Mercury cabin construction. The cabin’s small quantity would stop the astronaut from shifting a lot; Skeer argued that astronaut immobility would simplify ascent stage steering and management by avoiding center-of-gravity shifts. 

The astronaut packed into the coffin-like MEM cabin would rely for all times help on a 40-pound house go well with with a 100-pound life help backpack containing adequate life help consumables for 12 hours of operations. This mix would change a Mercury cabin life help system weighing 248 kilos. 

Skeer briefly examined a two-person minimal MEM with a descent stage not primarily based straight on the piloted flyby MSSR. This may, he wrote, have a complete weight of lower than 35,000 kilos. Of this, 1360 kilos would comprise the MEM ascent stage and crew. He clearly favored the single-person minimal MEM, nevertheless. 

Skeer subsequently carried out a pair of follow-on research of MSSR-derived piloted spacecraft. The primary, accomplished on 8 Might 1968, checked out a 4064-pound MSSR-derived two-person floor shelter that will allow a two-week Mars floor keep by astronauts landed individually in a pair of MSSR-derived minimal MEMs. Expendables supporting the two-week keep — largely for all times help and energy era — would account for 1053 kilos of the shelter’s weight.

Cutaway view of MSSR-derived Mars floor shelter. Picture credit score: Bellcomm/NASA.
Plan view of MSSR-derived Mars floor shelter. Picture credit score: Bellcomm/NASA.

The 575-cubic-foot shelter would come with a 60-cubic-foot airlock accessed from the martian floor by a “hoist” (apparently a one-person open elevator platform). A pair of 25-cubic-foot compartments accessed from throughout the shelter (not from the airlock) contained 4 full house fits so every crewmember might have a spare. A laboratory space accounted for 50 cubic toes of the shelter’s quantity.

Scientific exploration tools accounted for 1460 kilos of the shelter’s weight. This included a single 367-pound one-person floor rover or flyer with a complete vary of 420 kilometers, 77 kilos of multiband images/radiometry tools, a 107-pound shelter-mounted drill able to reaching a depth of 30 meters, 100 kilos of “surveying instruments,” a 250-pound “Emplaced Science Station” and three “satellite tv for pc science stations” (complete weight 140 kilos) meant to be left behind on the martian floor, and “native sampling and environmental tools” weighing a complete of 395 kilos. The shelter’s pressurized cabin would comprise 50 kilos of apparatus for geologic evaluation. (Skeer made no reference to return of samples within the two minimal MEM automobiles; presumably pattern evaluation on Mars was meant to interchange return of samples to Earth.)

Skeer’s second follow-on examine, a extra detailed examination of the minimal MEM ascent stage dated 8 July 1968, sought to determine “fruitful areas of technological analysis and growth wanted for analysis and future program planning choices.” He argued for growth of latest propulsion methods able to burning new high-energy propellants (for instance, fluorine-LOX/methane), compact and light-weight refrigeration methods for long-term storage of such propellants, and growth of latest light-weight supplies to allow additional minimal MEM weight discount. 

He additionally famous that flights of MSSR probes throughout piloted flyby missions might be seen as check flights of minimal MSSR expertise. Sadly, by the point Skeer accomplished his second follow-on examine, work throughout the NASA Planetary JAG towards a piloted flyby with MSSR probe had been largely deserted for practically a 12 months.


“MSSR/MEM Commonality – Case 233,” D. E. Cassidy and H. S. London, Bellcomm, Inc., 19 July 1967.

“Preliminary Sizing of a Mars Tour Module Ascent Capsule Primarily based on Mercury Spacecraft Design – Case 233,” M. H. Skeer, Bellcomm, Inc., 25 September 1967.

“Preliminary Mars Tour Module Shelter Design – Case 730,” M. H. Skeer, Bellcomm, Inc., 8 Might 1968.

“Mars Tour Module Ascent Propulsion Stage Design,” M. H. Skeer, Bellcomm, Inc., 8 July 1968.

Extra Info

A New Step in Spaceflight Evolution: To Mars by Flyby-Touchdown Tour Mode (1966)

NASA’s Planetary Joint Motion Group Piloted Flyby Examine (1966)

Triple-Flyby: Venus-Mars-Venus Piloted Missions within the Late Nineteen Seventies/Early Eighties (1967)

Flyby’s Final Gasp: North American Rockwell’s S-IIB Interplanetary Booster (1968)



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