Historical: 1965 Mars Flyby CSM

RobertDyck · 2015-04-09 21:23:29

North American Aviation’s 1965 Mars/Venus Piloted Flyby Study: the Flyby CSM

The most obvious change in the Block II Apollo CSM for NAA’s piloted Mars/Venus flyby missions would be the replacement of the single SPS main engine with three LEM descent engines. The throttleable LEM engines, each with independent propellant tanks and plumbing, would provide propulsion redundancy during long voyages between planets.
Any single engine could perform all necessary maneuvers, NAA declared. Under normal circumstances, however, the middle engine would perform course corrections and the two outboard engines would perform a retro burn beginning not more than two hours before Earth-atmosphere reentry at the end of the Mars or Venus flyby mission.
NAA calculated that its flyby CMs would usually return to Earth traveling faster than the planned maximum Apollo lunar-return velocity of about 36,000 feet per second. Flyby mission reentry speed would depend on many factors; for example, a close Mars flyby typically meant a fast Earth-atmosphere reentry. The company calculated that 47,500 feet per second was a typical Mars flyby Earth approach velocity, while 44,000 feet per second was typical for a Venus flyby.

NAA told MSC that the CM’s bowl-shaped heat shield (A in the drawing above) could, in theory, be beefed up to withstand reentry at a blistering 52,000 feet per second. The company argued, however, that “engineering conservatism” made high-speed reentries unattractive. Hence the retro burn, which would slash reentry velocity to no greater than 45,000 feet per second. NAA told MSC that the Block II Apollo CSM heat shield would need only modest modifications to withstand reentry at that velocity.
NAA reported that the Block II Apollo CSM would have a total mass of 57,690 pounds. Hydrazine/nitrogen tetroxide propellants would account for 37,360 pounds of that total. The Venus flyby CSM would have a mass of 34,840 pounds with 16,000 pounds of propellants on board and the Mars flyby CSM would have a mass of 73,080 pounds with 44,770 pounds of propellants. The Mars flyby CSM would thus have more than twice the mass of the Venus flyby CSM, while the Venus flyby CSM would have a little more than half the mass of the Block II Apollo lunar CSM.
During the Mars flyby Earth reentry retro burn, the more extreme of the two, the outboard engines could fire for up to 29 minutes to slow the flyby CSM by up to 12,400 feet per second. The flyby SM would then separate, exposing the CM’s modestly beefed-up heat shield. During passage through Earth’s atmosphere, the heat shield might attain a temperature of 5000° Fahrenheit.

NAA recommended a crew of four for most of the piloted flyby mission scenarios it studied, though it conceded that a Venus flyby mission might get by with only three astronauts. To make room for a fourth crewmember in the flyby CM, the center launch-and-reentry couch (B1) would be relocated forward of its Apollo CM position, placing it closer to the main display and control console.
The new fourth couch (B3) would be mounted on the aft interior bulkhead about two feet behind and slightly above the relocated center couch. Some equipment would be moved to accommodate the new couch. The left-hand couch (not shown) and the right-hand couch (B2) would remain in their Apollo CM positions.
The remaining labeled systems on the drawing above were designed to link to other flyby spacecraft modules. The Apollo-type probe docking unit (C), for example, would link the CSM with a modified Apollo-type drogue docking unit on top of the flyby spacecraft’s main living and working volume, the three-deck Mission Module (MM).
As noted above, the Block II Apollo CSM included a single housing for umbilicals and cables that linked the SM and the CM. These carried water and electricity from fuel cells and gaseous oxygen from cryogenic tanks in the SM to the CM. Data, including voice signals transmitted through the CSM’s SM-mounted high-gain antenna, traveled in both directions. They also linked the CM Environmental Control System (ECS) to radiators on the SM hull. The umbilicals were severed and the housing hinged out of the way as the SM was cast off just before CM reentry.
NAA’s Mars flyby CSM would include two umbilical housings. The larger of these (D), present also on the Venus flyby CSM, would cover hoses for supplying the CM with water, oxygen, and nitrogen from tanks in the SM and cables for data transfer between the SM and the CM. Oxygen and nitrogen would be stored in separate tanks as high-pressure gas. Addition of nitrogen to the flyby CM’s breathing mix reflected NAA’s decision to abandon the Apollo CM’s pure oxygen atmosphere; the company made this choice in large part because data on the health effects of long-term exposure to a pure oxygen atmosphere were lacking.
Nitrogen would slowly seep into the flyby CM while it was unoccupied – that is, while the crew was in the MM – to make up for inevitable slow cabin leakage. To cool the flyby CM while a crew was on board, water would vent into space through an evaporative cooling chamber. Replacing the ECS radiators on the flyby SM hull with the evaporative system would not only simplify the flyby CSM ECS design, it would also largely eliminate the risk of ECS meteoroid damage. NAA considered this especially important for the Mars flyby CSM, which would skirt the inner edge of the Asteroid Belt after its Mars flyby.
NAA reminded its MSC audience that the flyby CSM would support its crew for a much shorter period of time than would the Block II Apollo CSM. The flyby crew would reach and depart Earth-orbit in the flyby CSM, return to Earth in the flyby CM in the event of an abort immediately after Earth-orbit departure, briefly power up the flyby CSM and fire its center engine during course corrections, and return to Earth’s surface in the flyby CM at the end of their mission. The company estimated that the flyby astronauts would live inside the flyby CM cabin for no longer than 72 hours at a stretch, not the 10 or more days of a lunar mission.
The smaller of the two umbilical housings (F) on the Mars flyby CSM would cover umbilicals forming part of its electrical power system. These would circulate coolant from a compact plutonium-fueled mercury-rankine isotopic system (E) in the flyby CM to redundant curved radiator panels on the flyby SM’s hull and back again in a continuous loop.

The 1370-pound isotopic system would generate four kilowatts of electricity for the flyby CSM, the MM, and the Probe Compartment attached to the MM. Shielding, water, and equipment would protect the flyby astronauts from the power system’s low-level radiation during the brief time they would ride in the CM.
The chief justification for an isotopic source on the Mars flyby CSM was the Mars flyby mission’s maximum distance from the Sun (about 2.2 times the Earth-Sun distance), which would render electricity-generating solar cells largely ineffective. The Venus flyby, on the other hand, could depend on an ample solar energy supply. NAA assumed when making its Venus flyby CSM mass estimate that a 525-pound solar-cell power system would be mounted on the Venus flyby spacecraft’s Probe Compartment.
If, however, NASA chose to make the piloted flyby CSM designs for Mars and Venus more or less the same (to reduce development costs, for example), it might choose to use an isotopic system in both the Mars and Venus spacecraft. In that case, the Venus flyby CSM would also include two umbilical housings and would have a correspondingly greater mass.

References
“An Evolutionary Program for Manned Interplanetary Exploration,” M. W. Jack Bell; paper presented at the AIAA/AAS Stepping Stones to Mars Meeting in Baltimore, Maryland, 28-30 March 1966.
Manned Mars and/or Venus Flyby Vehicles Systems Study Final Briefing Brochure, SID 65-761-6, North American Aviation, Inc., 18 June 1965.

RobertDyck · 2015-04-09 22:16:56

After EMPIRE: Using Apollo Hardware to Explore Venus and Mars (1965)

Between August 1963 and November 1964, a 13-member team at NASA’s Marshall Space Flight Center (MSFC) in Huntsville, Alabama, conducted a detailed in-house study of Mars and Venus flyby missions. These would see a manned flyby spacecraft depart Earth orbit, coast past its target planet, and return to Earth. Only small course-correction maneuvers would be necessary after Earth-orbit departure.
The study, led by Harry O. Ruppe of the MSFC Future Projects Office (FPO), was a follow-on to the Early Manned Planetary-Interplanetary Roundtrip Expeditions (EMPIRE) study, which had lasted from May 1962 to February 1963. MSFC FPO had directed EMPIRE contractors Ford Aeronutronic, Lockheed, and General Dynamics to study manned Mars and Venus flyby and orbiter missions in the early 1970s as a means of justifying early development of nuclear-thermal rockets and launch vehicles more powerful than the Apollo Saturn V. MSFC FPO stressed these technologies in EMPIRE because MSFC was NASA’s lead center for large rocket development and because it was involved in the joint NASA/Atomic Energy Commission nuclear propulsion program through the Reactor In-Flight Test (RIFT), which sought to launch a nuclear rocket into space in 1967.
The new manned planetary flyby study acknowledged changes in the advance planning environment within NASA. Whereas the EMPIRE contractors had been instructed to “attempt” to use Apollo hardware in their spacecraft designs – and had responded by designing all-new systems with little Apollo heritage – the MSFC in-house study adhered strictly to the rule that Apollo technology should be used everywhere possible. This reflected increasing restrictions placed on NASA advanced technology development by President John F. Kennedy and his successor, President Lyndon Baines Johnson. Put succinctly, NASA planners had begun to realize that a commitment to the goal of a man on the moon did not imply a commitment to the goal of a man on Mars.
The MSFC team declared, nonetheless, that it was “inconceivable” that the “tremendous” technology that NASA had developed for Apollo would not lead eventually to a manned Mars landing. It was simply a matter of which course NASA should follow to get there. An Earth-orbiting space station or a moonbase were 1970s goals that could use Apollo hardware and provide “training” for manned Mars landings; like Apollo, however, these would operate “within the Earth’s ‘sphere of activity.'” Manned Mars/Venus flybys in the mid-to-late 1970s, on the other hand, could be based on Apollo systems, yet would venture beyond the safe harbor of the Earth-moon system.
Little was known of Mars’s atmosphere or surface conditions when Ruppe’s engineers performed their study. A manned Mars flyby in the 1970s could, they argued, provide data they would need to design a 1980s Mars landing mission. They proposed that, in addition to exploring Mars closeup with remote-sensing instruments mounted on their spacecraft, flyby astronauts should serve as caretakers for a small armada of automated probes. These would include “landers, atmospheric floaters, skippers, orbiters, and possibly probes. . .to perform aerodynamic entry tests [of spacecraft] designs and materials.”
Automated probes would need caretakers, the MSFC team believed, because they had had a checkered history. Mariner II had flown past Venus successfully in December 1962, near EMPIRE’s end, confirming what astronomers had already begun to suspect: that the planet’s dense clouds hid a hellish surface. The Ranger VII moon probe had returned images of southeast Oceanus Procellarum as it plunged toward planned destructive impact in July 1964, thereby providing engineers designing the Apollo Lunar Module lander with essential data on the moon’s surface. Mariners I and III had, however, failed, as had the first six Rangers. Mariner IV had been launched toward Mars on 28 November 1964, as editing began on the Ruppe team’s study report. As it saw print in February 1965, the 261-kilogram solar-powered robot remained healthy. It was, however, anyone’s guess whether Mariner IV would survive until its planned Mars flyby in July 1965.
The MSFC engineers believed that “the major emphasis of the manned flyby-unmanned probe combination” should “be focused on assisting later [Mars] landing missions.” Engineers who lacked data on Mars conditions would, they explained, have little choice but to design the Mars landing spacecraft for “worst conditions.” This would tend to increase its mass and thus the number of costly booster rockets necessary to place its components into Earth orbit for assembly.
Conversely, adequate knowledge of Mars would enable engineers to cut costs by taking advantage of the conditions there. Of particular importance, they wrote, would be probes that would test propellant-saving aerodynamic braking maneuvers in the martian atmosphere and prospect for “usable indigenous materials. . .such as water” on Mars’s surface. They estimated that, lacking adequate prior knowledge of Mars, the first manned landing mission “would probably transport 2 or 3 men to the surface of Mars for a few days. . .[at a cost of] a billion dollars per man-day on Mars.” If on the other hand, “the physical properties of Mars were well known, we could think. . .of the first landing as a long-duration base, reducing cost to less than 10 million dollars per man-day.”
The MSFC team consulted Ruppe’s published launch opportunity tables to determine that several Mars and Venus flyby launch windows would open in the mid-to-late 1970s. Because Venus has a nearly circular orbit around the Sun, opportunities to reach it would vary little in terms of amount of energy required, mission duration, and Earth-return velocity (all critical factors in interplanetary mission design). Mars, on the other hand, has a noticeably eccentric (elliptical) orbit, which means that these factors vary considerably from one launch opportunity to the next. For their detailed analysis, the MSFC engineers opted for a “typical” Mars flyby that would leave Earth orbit in September 1975, and a corresponding “typical” Venus flyby that would depart Earth orbit in August 1978.
An “improved” two-stage variant of the Apollo Saturn V would serve as the manned flyby program’s workhorse Earth-to-orbit booster. The first payload it would place into orbit for any flyby mission would be the 125-ton flyby spacecraft with a multipurpose “aft skirt assembly.” Stacked atop the two-stage Saturn V and covered with a streamlined launch shroud, the flyby spacecraft/aft skirt assembly would outwardly resemble the Skylab Orbital Workshop, which was launched on a two-stage Saturn V in May 1973, eight years after Ruppe’s team completed its study.
The three-stage Saturn V configured for Apollo moon flights stood 363 feet tall, while the two-stage Saturn V with Skylab on top measured 333.6 feet tall. The two-stage Saturn V with the flyby spacecraft/aft skirt assembly combination on top would stand 332 feet tall. Skylab measured 84.5 feet long at launch, while the flyby spacecraft/aft skirt assembly would measure 89 feet long with its launch shroud (A in the drawing below) and 81.6 feet long in orbit, after its shroud had been discarded.

The MSFC engineers tapped as their rocket engine for course corrections the Apollo Lunar Module Descent Engine (B). It would draw hypergolic propellants (that is, fuel and oxidizer that ignite on contact with each other) from four spherical tanks (I). The tanks were designed to hold enough propellants to change the flyby spacecraft’s speed by 500 meters per second (mps). The 0.5-kilometer-per-second course change would need 26,272 pounds of propellants for the 1975 Mars flyby and 20,583 pounds for the 1978 Venus flyby.
A pair of 5000-pound “radioisotope power supply systems” would be mounted to the flyby spacecraft near the course-correction engine, well away from the spherical, 20-foot-diameter Lab/Crew Living area (M). During ascent to Earth orbit, these would remain folded inside the launch shroud (C). Some time after shroud separation, they would pivot outward to their flight positions (D) and begin to make electricity.
The flyby spacecraft’s pressurized Hangar (E) would fill the space between the course-correction engine and the course-correction propellant tanks. The three-man flyby crew would reach the Hangar from their main living area via an airlock tube (J). The Hangar would contain at its center a modified Apollo Command and Service Module (CSM). The Ruppe team felt it necessary to cocoon the CSM within the Hangar to protect it from “micrometeoroids, outgassing, and other detrimental effects” of long space exposure.
The CSM warranted special protection for two reasons. First and foremost, it was the flyby crew’s end-of-mission Earth-atmosphere reentry vehicle. The astronauts would ride in its conical Command Module (CM) (F) and would use the Service Propulsion System (SPS) main engine (H) on its drum-shaped Service Module (SM) (G) to slow to Apollo lunar-return speed of 11 kilometers per second (kps) before they reached Earth’s atmosphere. Cocooning the CSM in the Hangar would also limit the amount of costly redesign and retesting the CSM would need before it could be used for manned Mars/Venus flyby missions. The CM for flyby missions would lack a docking unit, but otherwise would closely resemble the Apollo lunar CM. It would, therefore, need no new testing.
For Venus flybys, the SM also could remain unchanged. The Mars flyby SM, on the other hand, would approach Earth moving fast enough that its SPS engine would need to fire for up to 536 seconds longer than the Apollo lunar SPS and burn up to 2790 pounds more propellants than the Apollo lunar SM could hold. The Mars flyby SM would thus need longer propellant tanks and either a redesigned SPS or a pair of conventional SPSs operating in tandem or in series. A new engine rated for a longer burn time was also a possibility, though that option would not be in keeping with the MSFC team’s goal of reliance on Apollo hardware.
In addition to the Earth-atmosphere reentry CSM, the flyby spacecraft Hangar would house five tons of automated probes destined for release near the mission’s target planet. As noted above, the astronauts’ main job would be to ensure that the probes remained functional until they reached Mars or Venus. The crew would thus have available within the Hangar 1000 pounds of tools and supplies for servicing the probes. The MSFC engineers also placed an airlock for spacewalks in the Hangar, though they doubted that it would see much use, as well as a stock of emergency life support provisions.
When not attending to their cargo of probes, the three flyby astronauts would live and work in the Lab/Crew Living Area, where they would breathe a half-oxygen, half-nitrogen atmosphere at a pressure of 10 pounds per square inch. The Lab/Crew Living Area and the Hangar could each be repressurized 12 times during a Mars flyby mission and eight times during a Venus flyby mission. Repressurization would occur in the event that a meteoroid punctured the spacecraft hull or after scheduled periodic air dumps that would purge the atmosphere of toxic trace gases outgassed from furnishings and equipment and generated by experiments and cooking. Each repressurization would need 1885 pounds of gases, bringing the total breathing gas carried to 22,650 pounds for the typical Mars flyby spacecraft and 15,050 pounds for the Venus flyby spacecraft. A system for recycling air between purges would have a mass of 1800 pounds on both the Mars and Venus flyby spacecraft.
The Ruppe team’s engineers cited a study by the MSFC Research Projects Laboratory (RPL) when they rejected specialized radiation shielding for the flyby spacecraft’s bottle-shaped emergency shelter (K). The RPL had found that solar flares powerful enough to harm flyby crews were unlikely to occur in the mid-to-late 1970s. In place of 1000 pounds of shielding, the MSFC team proposed a double-walled shelter with the crew’s water supply stored between its walls. Two 500-pound water reclamation systems (main and spare) would recycle cabin air moisture, wash water, and urine. Equipment and food would be arranged around the shelter’s exterior to provide additional radiation protection. The crew would sleep inside the shelter to minimize their exposure to cosmic rays. In the event of fire, catastrophic pressure loss, or other emergency, the shelter, which would contain a duplicate set of spacecraft controls, could be sealed off from the rest of the flyby spacecraft.
The MSFC engineers calculated that building the flyby spacecraft so that it could spin to create artificial gravity would add 69,000 pounds to its mass. The engineers rejected this in favor of providing a small centrifuge (L) capable of holding two astronauts at a time. Support arms would attach the twin centrifuge gondolas to a motorized ring around the hatch leading into the emergency shelter.
The Lab/Crew Living Area would nestle in a bowl-shaped recess in the aft skirt assembly (O). At its front end, the aft skirt assembly would match the 22-foot diameter of the flyby spacecraft; at its aft end, it would match the 33-foot diameter of the S-II second stage of the Saturn V that would boost it and the flyby spacecraft into 185-kilometer-high Earth orbit. S-II separation would reveal twin RL-10 rendezvous and docking rocket motors (P) and a large socket-like docking structure (N) on the aft skirt assembly’s aft end. At its front end, the aft skirt assembly would contain a ring-shaped, 22-foot-diameter Saturn V Instrument Unit (IU). In addition to guiding the Saturn V carrying the flyby spacecraft during its ascent to Earth orbit, the IU would provide guidance control for Earth-orbital assembly maneuvers and for Earth-orbit departure.
The number of two-stage Saturn V rockets required to place into Earth orbit the flyby spacecraft, its S-IIB Orbital Launch Vehicle (OLV), and liquid oxygen (LOX) for the S-IIB OLV would depend on the amount of energy required to place the flyby spacecraft on course for its target planet. Even in the least demanding opportunities, Mars flybys would require more energy than Venus flybys, so would need more Saturn V rockets.
The MSFC engineers described in detail the assembly campaign for the Mars flyby mission that would leave Earth orbit in September 1975, during a launch opportunity lasting 28 days. The first two-stage Saturn V in the assembly campaign would lift off from one of the two Complex 39 Saturn V launch pads at Cape Kennedy, Florida, on 28 April 1975. If the Saturn V rocket failed and the flyby spacecraft/aft skirt assembly it carried was destroyed, then a backup would lift off on 24 June 1975.
The next Saturn V in the series would launch on 28 June 1975, bearing the first of four LOX tankers to 185-kilometer orbit. The Ruppe team’s tanker could transport about 95 tons of LOX. Three more successful tanker launches would be needed; these would occur on 6 July and 7 July and 3 September 1975. A single backup tanker would be available in the event of a launch failure; if it became necessary, then it would launch on 6 September 1975.
With a Mars flyby spacecraft/aft skirt assembly and four LOX tankers safely orbiting the Earth, the sixth and last Saturn V would launch the S-IIB OLV into a 485-kilometer-high orbit on 13 September 1975. As its name implies, the S-IIB OLV would be a derivative of the Saturn V S-II second stage. Modifications would include deletion of two of its five J-2 engines and improved insulation to retard boil-off and escape of the roughly 80 tons of liquid hydrogen it would carry into orbit. The MSFC engineers expected that an S-IIB OLV could be developed that would retain enough liquid hydrogen for flyby spacecraft Earth-orbit departure 72 hours after its launch from Complex 39, but aimed for an Earth-orbit departure 50 hours after Earth launch.
Using the twin RL-10 engines in its aft skirt assembly, the unmanned flyby spacecraft would climb to a 485-kilometer circular orbit and rendezvous with the S-IIB OLV as soon as the latter was confirmed to be safely in orbit. It would then back up and dock with the S-IIB OLV. Next, the four LOX tankers would climb to 485-kilometer orbit and dock one at a time with the S-IIB OLV. Each would pump its cargo into the S-IIB OLV’s LOX tank, then would undock and move away, clearing the way for the next in the series.
The astronauts would board the Mars flyby spacecraft 20 hours before planned launch from Earth orbit. If NASA had a space station in Earth orbit in 1975, they might board from that. An alternate plan would see the flyby astronauts reach their spacecraft on board an Apollo CSM launched from Earth on a Saturn IB rocket. After entering the flyby spacecraft and checking out its systems, they would cast off the CSM.
The S-IIB OLV’s three J-2 engines would burn for about eight minutes on September 26, 1975 to push the flyby spacecraft/aft skirt assembly combination out of 485-kilometer Earth orbit and place it on course for Mars. The burn would add about five kps to its speed. After the flyby spacecraft/aft skirt assembly combination separated from the S-IIB, the RL-10 engines in the aft skirt assembly would be used to fine-tune the flyby spacecraft’s course. The aft skirt assembly, its work done, could then be cast off or retained for at least part of the mission to provide additional radiation/meteoroid shielding for the Lab/Crew Living Area.

Ruppe’s team provided an example heliocentric orbital plot for a manned Mars flyby mission leaving Earth on September 26, 1975. The dashed line on the plot represents the flyby spacecraft’s path around the Sun. Flight to Mars would require 130 days. Halfway to Mars, on November 30, 1975, the crew would adjust their spacecraft’s course using the course-correction engine. The MSFC engineers budgeted enough propellants for the first midcourse burn to change the flyby spacecraft’s speed by 150 mps. The crew would eject “consumed life support” (that is, body and food waste, saturated absorbent charcoal, used filters, and other trash) shortly before the course-correction burn so that it would continue on the flyby spacecraft’s original course and not intersect Mars.
Mars flyby would occur on 3 February 1976, when Mars and the flyby spacecraft were 0.86 Astronomical Units (AU) – that is, 0.86 times the Earth-Sun distance – from Earth. The flyby spacecraft would approach Mars’s day side, reaching a distance of 200,000 kilometers from the planet’s center 6.5 hours before closest approach. It would pass 792 kilometers from Mars’s surface moving at about 11 kps relative to the planet, then would retreat from Mars’s night side. During approach to the planet, the astronauts would release 2.5 tons of robot probes and carry out continuous observations. Near closest approach, they would ignite the course-correction engine a second time.
During retreat from Mars, the astronauts would release an additional 2.5 tons of probes. While the flyby spacecraft remained close to Mars, it would relay data from the probes to Earth at a high data rate. The flyby spacecraft would, however, spend only one hour within 18,250 kilometers of Mars’s center. Five and a half hours after closest approach, it would pass beyond 164,000 kilometers from the planet’s center, and shortly after that the Mars probes would switch to direct transmission to Earth at a low data rate. The crew would then begin a grueling 539-day journey home.
A few weeks later, the crew would become the first humans to enter the Asteroid Belt. Maximum distance from Earth (3.21 AU) would be attained on September 13, 1976, about one year into their mission. At about the same time, Earth would move behind the Sun as viewed from the flyby spacecraft. The crew would then perform the mission’s final course-correction burn, changing their spacecraft’s speed by up to 200 mps.
The flyby spacecraft would pass inside of Mars’s orbit on 31 May 1977 at a distance of 0.353 AU from Earth. Over the following two months, it would gradually catch up with the homeworld. On 19 July 1977, six days before planned Earth atmosphere reentry, the crew would transfer to the modified Apollo CSM in the Hangar and check out its systems. Two days before reentry, the CSM would emerge from its cocoon and abandon the flyby spacecraft. On 25 July, with Earth looming outside its small windows, the crew would turn the CSM so that its engine or engines pointed in its direction of flight. A burn lasting up to 19.4 minutes would reduce the CSM’s speed from up to 15.8 kps to Apollo lunar-return speed of 11 kps, then the conical CM would detach and, using small rocket motors, orient its bowl-shaped heat shield for reentry. Minutes later, the CM would deploy three parachutes and lower gently into the ocean.

The Ruppe team also prepared an orbital plot for the Venus flyby mission departing Earth in August 1978. A shortened S-IIB OLV would add about 3.8 kps to the Venus flyby spacecraft’s speed. The mission would be of shorter duration than the Mars mission – only one year – with Venus flyby occurring low over the planet’s day side on 11 December 1978. The spacecraft would attain its greatest distance from Earth – 0.674 AU – on 15 April 1979. After leaving the Hangar, the CSM’s main engine would trim about 2.6 kps from its Earth-approach speed. Reentry and splashdown would occur on 16 August 1979.
The MSFC engineers outlined a hardware development schedule based (inexplicably) on a Venus flyby in late 1975 and a Mars flyby in 1978 (that is, the reverse of the program detailed above). They also estimated the probable cost of the flyby program. They assumed that no new-start funding for the program would become available in NASA’s budget before Fiscal Year (FY) 1969, after the first successful Apollo lunar landing, which in 1965 was scheduled to take place during 1968. Detailed flyby program planning would begin in mid-1968 and last a year.
LOX tanker, flyby spacecraft, and interplanetary avionics development would commence in the last quarter of 1968. LOX tanker development, at a cost of $380 million, would be completed in late 1974. A pair of LOX tanker flight tests would launch on two-stage Saturn V rockets in 1973 and mid-1974. A flyby spacecraft development test unit would reach Earth orbit on a two-stage Saturn V in 1974; among other things, it would be used for crew training. The flyby spacecraft would cost more to develop than any other hardware element ($1.563 billion). Avionics development (total cost: $325 million) would include a Saturn IB-launched flight test.
S-IIB OLV development (total cost: $425 million) would start in late 1969 and conclude in 1974. S-IIB OLV flight tests would take place in 1973-1974. Apollo SM modifications (total cost: $115 milion) would begin in mid-1970 and end in 1974, and aft skirt assembly development (total cost: $165 million) would span late 1970 through early 1975. An aft skirt assembly flight test using a Saturn IB launch vehicle would take place in 1974.

Science probe development for the 1975 Venus flyby would begin in mid-1970 and continue through the last quarter of 1975. Mars probe development would start in the last quarter of 1973 and run through 1977. Probe development would cost $220 million for each mission.
The MSFC engineers based their operational cost estimates on learning curves developed through the many Saturn V and Saturn IB launches that they expected would occur by the mid-1970s. They estimated that 62 three-stage and two-stage Saturn Vs would be launched prior to the first Venus flyby Saturn V launch, so that each Saturn V for the Venus flyby would cost $70 million. Fifty-two Saturn IB launches would take place before the first Venus flyby Saturn IB launch, leading to a cost per Venus flyby Saturn IB of $22 million. They assumed that 70 Apollo CSMs would have flown before the first Venus flyby CSM, leading to a Venus flyby CSM cost of $72 million.
For the 1978 Mars flyby, the MSFC engineers assumed that NASA would have already launched 98 three-stage and two-stage Saturn V rockets by the time the first Mars flyby Saturn V lifted off, lowering the cost per Mars flyby Saturn V to only $65 million. Seventy Saturn IB launches would have taken place, reducing the cost for each Mars flyby Saturn IB to $20 million. One hundred CSMs would have flown ahead of the first Mars flyby CSM, reducing the flyby CSM cost to $69 million.
Design and development cost would peak in FY 1972 at $895 million. Operational cost would peak at $497 million in FY 1974. The peak funding year for the program would be FY 1973, when operational and development costs would total $1.222 billion. Development costs would total $3.75 billion between FY 1969 and FY 1978. Operational costs would total $2.671 billion between FY 1971 and FY 1978. The entire manned flyby program would cost $6.421 billion. They estimated that by providing data to engineers, the manned flyby program would reduce by about $4 billion the cost of a follow-on Mars landing mission.
The MSFC engineers also conducted what they called a “mission worth analysis.” They first assumed an undefined “basic space program” for the 1970s and 1980s. Manned Venus flyby missions could, they calculated, be deleted from the program with only a 2% impact on total space program worth and only a 10% reduction in planetary program worth because “it is not possible to land on Venus.” Leaving the Venus flybys in place but deleting the Mars flyby and landing missions would reduce total space program worth by 9% and planetary program worth by half. Deleting all manned planetary missions and relying only on robotic probes would reduce total space program worth by 12% and planetary program worth by 63%.
Mariner IV triumphantly flew past Mars on 14-15 July 1965, five months after the MSFC team’s study report saw print. It returned 21 black-and-white images of the planet’s cratered surface and conducted a radio-diffraction experiment that indicated a martian atmospheric pressure ten times less than expected. Mariner IV revealed a Mars apparently inhospitable to life. The mission also showed that robots could cross the gulf between Earth and Mars and return useful data without help from astronaut caretakers.
Oddly enough, neither Mariner IV’s success nor its discouraging Mars findings undermined the manned flyby concept. The flyby program goal of putting Saturn-Apollo hardware to new uses remained attractive to many in NASA. In April 1966, NASA Associate Administrator for Manned Space Flight George Mueller launched a new manned flyby study under the auspices of the Planetary Joint Action Group (JAG), which drew members from MSFC, the Manned Spacecraft Center in Houston, Texas, Kennedy Space Center in Florida, NASA Headquarters, and NASA planning contractor Bellcomm. The new study, which emphasized the 1975 manned Mars flyby opportunity, sought to flesh out automated probe and on-board instrument designs and to further explore the interplanetary potential of Apollo technology and techniques.

References:
Manned Planetary Reconnaissance Mission Study: Venus/Mars Flyby, NASA TM X-53205, Harry O. Ruppe, Future Projects Office, NASA Marshall Space Flight Center, 5 February 1965.

RobertDyck · 2015-04-10 07:07:09

I find it interesting that NASA had a plan for a Mars flyby in 1965. And the North American plan included 4 astronauts, the same number as Robert Zubrin's Mars Direct. Both plans included a nuclear power source; North American's integrated it with the CSM, Marshall's plan had the reactor separate. Marshall's plan to send something based on Skylab with the CSM encased within, making the Skylab-like module a "hanger", is dumb. But both plans included a separate living space. And both plans used zero-G for the entire 2 years. The other interesting thing is they thought life support would work, even though it was a 2 year mission. They both appear to use the same mission profile; a typical mission would launch 26 September 1977, splash-down 25 July 1979. That's 22 months; the Mars Direct mission was 180 days (6 months) out, 6 months back, and 500 days on Mars, for a total of 28.5 months. The planets line-up to send a mission once every 26 months. So this mission would have been shorter, but they would have been in zero-G the whole way, not in Mars gravity, and the trajectory swings out very close to the asteroid belt raising concerns of meteoroid damage. North American was concerned about the heat shield, so used propulsion to slow before atmospheric entry. That was 1965, in the early 1970s NASA developed the PICA heat shield that could withstand direct entry from Mars. Still, I find it very interesting that they felt they had life support sufficient for Mars. And this was in 1965.

kbd512 · 2015-04-10 11:16:10

What was their plan for dealing with solar flares? Looping out to the asteroid belt? That's slightly insane, but that was probably normal in 1965.

GW Johnson · 2015-04-12 09:17:24

Back then, they understood but chose to ignore the radiation risks. The risks associated with tight confinement were also somewhat-understood from the Gemini-7 mission, yet ignored to some extent. The risks from microgravity diseases were not understood. Nor was the problem of preserved foods that last up to 3 years yet be lightweight and processible in zero-gee. That last is still not "solved" today.

There was a 3-times-in-a-half-century solar flare event in August 1972, between the Apollo 16 and 17 missions. It measured about 3400 REM accumulated over several hours, far beyond the 500 REM fast dose considered to be the threshold for immediately-lethal.

The under-two-weeks duration of Apollo moon missions was considered to be "statistical shielding" against losing a crew. The capsule had essentially zero shielding effect. Had one of the crews been in space beyond the Van Allen belts when this solar flare event occurred, they would have died within hours. And it's a very ugly death.

It takes about 5 or 6 cm of water to knock that 3400 REM down to about 25 REM. 15 to 20 cm of water knocks it down to 2 or 3 REM, based on NASA's own publicly-released data.

I used their data to estimate exposures and shielding requirements for an upper-bound sort of Mars trip. I posted the results over at my blog site http://exrocketman.blogspot.com, as "Radiation Risks for Mars Trip", dated 4-11-15.

GW

RobertDyck · 2015-04-12 09:59:49

I still say the argument about food is overblown. Here's one food they could use in space. Camping supplies.

Instructions wrote:

1. Open package at tear notch. Remove and discard oxygen absorber from pouch.
2. Carefully add 2 cups (16 oz) boiling water to pouch.
3. Stir thoroughly and close zipper. Let stand 8-9 minutes. Stir and serve. For your convenience, eat right out of the pouch.

Freeze dried, shipping weight 0.46 pounds, net weight 4.30 Oz (122g). Each package is considered 2.5 servings, where a serving is 1 cup. 210 calories per serving. This one is beef stew, but they've got a whole menu of meals: entrees, breakfast, sides, dessert.

Their statement on Shelf life

Pouches — 12-Year Shelf Life *Mountain House Pouch
Based on our ongoing sensory and nutrition testing of actual Mountain House products, in 2014 the shelf life was increased by an impressive 20%, from 10+ years to 12+ years! We add the "+" to let our consumers know that our food will taste virtually indistinguishable from new for at least 12 years and probably much longer than that! We've tasted pouches that were 30 years old and the food was still quite tasty!
Remember that we recommend storing your pouches unopened and avoid prolonged exposure to temperatures above 75° (24°C) to maximize shelf life.

Worried about pouring boiling water into a pouch? Skylab and Shuttle did it, with a sealed pouch that had a plastic tube that could be "plugged into" a hot water dispenser. From NASA's website: Food For Space Flight
(This is getting away from 1960s plans for Mars, but this NASA web page was last updated April 7, 2002.)

Shuttle Galley
The Shuttle galley was redesigned in 1991 to reduce the weight and volume and to update the electronics. The redesigned galley weighs one-third less and occupies one-half the volume of the original galley. The new galley delivers hot or cold water from the rehydration station. The hot water temperature is between 155 and 165deg.F. The hot and cold dispense quantities can be selected in one-half ounce increments up to 8 ounces.
The forced air convection oven heats food and beverages by conduction with a hot plate or by forced convection. The temperature of the oven is maintained at 160 to 170deg.F. The oven holds 14 rehydratable packages plus thermostabilized pouches and beverages.
Space Station Food System
Space Station will become operational on a full time basis with a crew of 4. Later, the crew size will grow to a maximum of 8 people. The crew will reside in the Habitation Module (HAB). Food and other supplies will be resupplied every 90 days by exchanging the Pressurized Logistics Module (PLM).
The food system for SS will be considerably different from the Shuttle food system. Since the electrical power for SS will be from solar panels, there is no extra water generated onboard. Water will be recycled from the cabin air, but that will not be enough for use in the food system. Most of the food planned for SS will be frozen, refrigerated, or thermostabilized and will not require the addition of water before consumption. Many of the beverages will be in the dehydrated form. Food will be heated to serving temperature in a microwave/forced air convection oven. One oven will be supplied for each group of 4 astronauts.
The SS food system consists of 3 different supplies of food; Daily Menu, Safe Haven, and Extra Vehicular Activity (EVA) food.

RobertDyck · 2015-04-12 12:02:45

Image from Wikipedia, showing space food for ISS. Note the beef pattie and creamed spinach require hot water so come in a plastic bag with fitting for a plastic tube. The tube is laying on the spinach. It's also interesting that most NASA food for ISS is labelled in both English and Russian.

Skylab galley...

GW Johnson · 2015-04-13 09:14:25

Last time I saw a documentary about NASA space food, they had troubles with shelf life beyond a year to a year-and-a-half. Yet, the camp food has an advertised shelf life of 10-12+ years. Different manufacturer, obviously.

The disparity between shelf lives is disconcerting, to say the least. Something about getting "space qualified" is really getting in the way. I suspect this is more of a management problem than a technical problem.

GW

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#1 2015-04-09 21:23:29

Historical: 1965 Mars Flyby CSM

#2 2015-04-09 22:16:56

Re: Historical: 1965 Mars Flyby CSM

#3 2015-04-10 07:07:09

Re: Historical: 1965 Mars Flyby CSM

#4 2015-04-10 11:16:10

Re: Historical: 1965 Mars Flyby CSM

#5 2015-04-12 09:17:24

Re: Historical: 1965 Mars Flyby CSM

#6 2015-04-12 09:59:49

Re: Historical: 1965 Mars Flyby CSM

#7 2015-04-12 12:02:45

Re: Historical: 1965 Mars Flyby CSM

#8 2015-04-13 09:14:25

Re: Historical: 1965 Mars Flyby CSM

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