Next came Apollo. NASA conducted four piloted preparatory missions in 1968-1969 ahead of the first lunar landing attempt. Apollo 7 (October 1968), launched on a two-stage Saturn IB rocket, tested the Command and Service Module (CSM) in Earth orbit. The CSM comprised a drum-shaped Service Module (SM) and the conical Command Module (CM) bearing its three-man crew.
As in biological evolution, contingency played a role in spaceflight evolution: for example, Apollo 8, intended originally as a Saturn V rocket-launched high-Earth-orbit test of the CSM and the bug-like Lunar Module (LM) moon lander, became a CSM-only lunar-orbital mission after the LM was delayed and the Soviet Union appeared close to launching a cosmonaut around the moon.
The Apollo 8 astronauts reached lunar orbit on Christmas Eve 1968. In addition to forestalling Soviet attempts to upstage the first Apollo lunar landing mission, Apollo 8's 10 lunar orbits tested upgrades made to the Manned Space Flight Network, NASA's world-wide radio communications and tracking system, and gave console operators in Mission Control early experience in supporting a piloted lunar mission. The Apollo 8 CSM left lunar orbit on Christmas Day 1968, and splashed down in the Pacific Ocean on 27 December 1968.
Apollo 9 (March 1969) saw the first Earth-orbital test of the LM and CSM together. Apollo 10 (May 1969) was a dress-rehearsal in low-lunar orbit for Apollo 11 (July 1969), the first piloted lunar landing.
Apollo 11 is perhaps best understood as an engineering mission; it was a cautious end-to-end test of the Apollo system with a single two-and-a-half-hour moonwalk and only limited science objectives. Apollo 12 (November 1969) demonstrated the pin-point landing capability required for pre-mission geologic traverse planning by setting down near a known point on the moon: specifically, the Surveyor III automated soft-lander, which had landed in April 1967. It also saw a pair of moonwalks lasting nearly four hours each and deployment of the first Apollo Lunar Scientific Experiment Package (ALSEP).
Apollo 13 (April 1970), the first science-focused mission, suffered a crippling explosion midway to the Moon, scrubbing its lunar landing, but its crew's safe return to Earth demonstrated the Apollo system's maturity and the Apollo team's experience. Apollo 14 (January-February 1971) included two moonwalks, each lasting more than four-and-a-half hours. They included a strenuous 1.3-kilometer trek through the hummocky ejecta blanket surrounding 300-meter-wide Cone Crater, a natural drill hole in the scientifically important Fra Mauro Formation.
Apollo 15 (July-August 1971), Apollo 16 (April 1972), and Apollo 17 (December 1972), designated "J" missions, featured a host of evolutionary improvements. Beefed-up LMs permitted surface stay times of up to three days at complex and challenging landing sites, heavier returned lunar samples, and more complex ALSEPs. Space suit improvements and Boeing's Lunar Roving Vehicle enabled geologic traverses ranging over kilometers of the lunar surface. Each "J" mission CSM included a suite of sensors which its pilot could turn toward the moon. Apollo 15 visited the Hadley Rille/Apennine Mountains area; Apollo 16 the central Nearside Lunar Highlands; and Apollo 17, Taurus-Littrow, on the edge of Mare Serenitatis.
One path would see Moon missions continue more or less indefinitely, growing ever more capable and culminating in a permanent lunar base in the 1980s. Alternately, NASA might repurpose Apollo hardware to build, launch, and maintain an evolutionary series of space stations in Earth orbit.
The space station path appeared pedestrian compared to the lunar base path, yet it offered great potential for long-term future exploration. This was because it promised to prepare astronauts and spacecraft for long-duration missions in interplanetary space. In 1965-1966, NASA advance planners envisioned a series of Earth-orbiting space workshops based on the Apollo LM and the Saturn IB rocket S-IVB stage. Apollo CSMs would ferry up to six astronauts at a time to the workshops for progressively longer stays.
Some planners thought that NASA should jump straight from the early space workshops to piloted Mars landing missions using nuclear-thermal propulsion, but others called for a conservative continuation of the evolutionary approach. If the latter had won the day, the mid-1970s might have seen a new-design space station climb to Earth orbit atop an improved Saturn V rocket. Derived from Apollo hardware and new technology tested on board the orbiting workshops, the station would in fact have constituted a prototype interplanetary Mission Module. A crew might have lived on board without resupply or visitors for almost two years to help prepare NASA for its first piloted Mars voyage.
In keeping with the evolutionary approach, the first piloted voyage beyond the Moon might have been a Mars flyby with no piloted Mars landing. The piloted Mars flyby spacecraft, which would have carried a cargo of robotic Mars probes, would have been built around the Mission Module tested in Earth orbit. The mission might have commenced as early as late 1975, when an opportunity to launch a minimum-energy Mars flyby was due to occur.
As they raced past Mars in early 1976, the four flyby astronauts would have released automated probes and turned a suite of sensors mounted on their spacecraft toward Mars and its irregularly shaped moons Phobos and Deimos. They would have reached their greatest distance from the Sun in the Asteroid Belt, so asteroid encounters would have been a possibility. As their Sun-centered elliptical orbit brought them back to Earth's vicinity in 1977, they would have separated in an Apollo CM-derived Earth-return capsule and reentered Earth's atmosphere.
In addition to observing Mars close up, the astronauts would have continued the effort, begun in earnest during Gemini flights and continued on board the Earth-orbiting workshops and prototype interplanetary Mission Module, to determine whether extended piloted missions were medically feasible. The flyby crew might have confirmed, for example, that artificial gravity is a must during years-long interplanetary voyages. Their results would have shaped the next interplanetary mission, which might have taken the form of a piloted Mars orbiter in the spirit of Apollo 8 and Apollo 10, or, if the space agency felt sufficiently confident in its abilities, a Mars orbital mission with a short piloted excursion to the martian surface in the spirit of Apollo 11.
|The Orbiter backs away from the Flyby Spacecraft. The two astronauts on the Flyby Spacecraft inspect the Orbiter's exterior and transmit television of its departure to Mission Control on Earth.|
Titus explained that, in the "standard stopover mode," a label that encompassed Mars orbital and landing missions, all major maneuvers would involve the entire Mars spacecraft. This meant that the Mars spacecraft would need a large mass of propellants, which in turn meant that many expensive heavy-lift rockets would be required to launch the spacecraft, its propellants, and its Earth-orbit departure stages into Earth orbit for assembly.
Propellant mass required would vary greatly from one Earth-Mars transfer opportunity to the next over a roughly 15-year cycle because Mars has a decidedly elliptical orbit. Because of this, the Mars spacecraft and the sequence of launches needed to boost its components and propellants into Earth orbit would have to be redesigned for each standard stopover mode Mars mission.
The United Aircraft engineer added that errors or malfunctions during standard stopover mode "high-risk" Mars capture and escape maneuvers could result in "complete mission failure" because the entire spacecraft would be involved. Because the Mars spacecraft would be very massive already, it would be difficult and costly to include extra propellants that would enable a mission abort that could save the crew.
Titus noted that required propellant mass might be reduced and made to vary less over multiple Earth-Mars transfer opportunities if the spacecraft skimmed through the martian upper atmosphere to slow down and capture into Mars orbit (that is, if it performed aerocapture). If, however, artificial gravity were found to be necessary for crew health, then stowing a spinning artificial-gravity system of sufficient radius behind an aerocapture heat shield would probably prove infeasible. The mission would then have to rely entirely on propulsive braking.
Titus explained that his FLEM concept, in addition to forming a natural evolutionary extension of piloted Mars flybys, would address many inherent problems of the standard stopover mode. One part of the FLEM spacecraft, the "parent" spacecraft, would not capture into Mars orbit. It could include a spinning artificial-gravity system. The other part, the "excursion module," would capture into Mars orbit using chemical rockets or, perhaps, by skimming through the martian atmosphere behind an aerocapture heat shield.
In the latter case, the excursion module would not need a large mass of propellants to capture into Mars orbit, making it the least massive of the two FLEM spacecraft. It would thus fire rockets to speed up and reach Mars ahead of the parent spacecraft.
Titus calculated that separation 60 days ahead of the Mars flyby would enable the excursion module to reach the planet 16 days ahead of the parent spacecraft; separation 30 days before flyby would enable it to reach Mars when the parent spacecraft was nine days behind it. While it awaited the arrival of its parent, the excursion module might remain in Mars orbit or all or part of it might land on Mars for a stay of several days.
Assuming that the mission took place as planned, the excursion module would ignite its rocket motors as the parent spacecraft passed Mars to depart Mars orbit and catch up with it. Following rendezvous, docking, and crew transfer, the excursion module would be cast off.
The maneuver would be optional in the sense that, if it could not occur, the FLEM spacecraft's Sun-centered orbit would return it to Earth, though after a longer than expected trip. During return to Earth after a powered flyby, the FLEM spacecraft would pass as close to the Sun as orbits the planet Mercury.
Titus determined that a powered-flyby maneuver in 1971 would have almost no effect on spacecraft mass at Earth-orbit departure — both the standard ballistic and powered-flyby FLEM spacecraft would have a mass of about 400,000 pounds — but would slash trip time from 510 to 430 days. The most dramatic improvement would occur in 1978, when the ballistic-flyby FLEM spacecraft's mass would total nearly two million pounds and its mission would last 540 days. The powered-flyby FLEM spacecraft would have a mass of just 800,000 pounds at the start of Earth-orbit departure and its mission would last only 455 days.
The FLEM concept apparently influenced NASA piloted flyby studies that occurred under the auspices of the Planetary Joint Action Group (JAG). The NASA Headquarters-led Planetary JAG, which met between 1965 and 1968, included representatives from NASA Marshall Space Flight Center, NASA Kennedy Space Center, and the NASA Manned Spacecraft Center, as well as Washington, DC-based planning contractor Bellcomm. The Planetary JAG's work will be described in detail in subsequent posts.
http://william-black.deviantart.com/) and are used by special arrangement with the artist.
Manned Mars and.or Venus Flyby Vehicle Systems Study — Final Briefing Brochure, SID 65-761-6, North American Aviation, 18 June 1965.
"FLEM - Flyby-Landing Excursion Mode," AIAA Paper 66-36, R. R. Titus; paper presented at the 3rd AIAA Aerospace Sciences Meeting in New York, New York, 24-26 January 1966.
Planetary Exploration Utilizing a Manned Flight System, Planetary Joint Action Group, NASA Office of Manned Space Flight, 3 October 1966.
"Manned Expeditions to Mars and Venus," E. Z. Gray and F. Dixon, Voyage to the Planets, Proceedings of the Fifth Goddard Memorial Symposium, 14-15 March 1967, pp. 107-135.
Wonderful Life: The Burgess Shale and the Nature of History, Stephen Jay Gould, W. W. Norton & Co., 1990.
After EMPIRE: Using Apollo Technology to Explore Mars and Venus (1965)
Relighting the FIRE: A 1966 Proposal for Piloted Interplanetary Mission Reentry Tests
To Mars by Way of Eros (1966)
Apollo Ends at Venus: A 1967 Proposal for Single-Launch Piloted Venus Flybys in 1972, 1973, and 1975
Triple-Flyby: Venus-Mars-Venus Piloted Missions in the Late 1970s/Early 1980 (1967)
Since there have been so many robotic exploration concepts for Mars that haven't yet been tried, like lander networks, aircraft, balloons, MSR and rovers working in tandem, it's difficult to see a coherent justification for a manned or crewed (piloted/unpiloted is not a term which I think makes any sense) mission to Mars, at least not in a relatively near future.ReplyDelete
There's room for both, perhaps in combination (that is, during one mission). I'm fond of the HERRO concept, which has scientists on board a Mars-orbiting spacecraft teleoperating surface rovers in real-time for months.Delete
Where is the Apollo capsule for the return on earth?ReplyDelete
Safely tucked away behind the four engines and donut-shaped propellant tanks in the Flyby Spacecraft. See the caption for image #6. William Black is working on a new illustration to show the Earth reentry burn and the Apollo CM.
Why was a LEM depicted here in Wade's site?Delete
I do not contribute to Wade's site, except insofar as he reads my work and borrows from it. The LM illustration isn't the only thing wrong with what that page - the Titus paper was published in January 1966, and the MSSR memo was published - not by Titus - on 30 June 1966 in support of the Planetary JAG's piloted Mars/Venus flyby study. Wade dates the Titus paper to 30 June 1966 - he mixes up the two sources. The interpretation that Titus' work influenced the Planetary JAG's plans is original to me - neither the January study nor the 30 June 1966 memo make that connection. There's more, but what's the point of listing it?
I've written about the Planetary JAG study and the possible link to FLEM on various of my websites and blogs over the years. It's also in my NASA-published book HUMANS TO MARS (2001).
Funny you should mention this - I ran across another pretty obvious example of this kind of thing today. It's not uncommon for folks to use my blog/websites/book but cite the source documents, not my blog. Not uncommonly, they blow their cover, but they get away with it because no one checks the sources or they've established a reputation as a clever person who can do no wrong or whatever.
My advice is to read my blog for conceptual study history. I cite my sources scrupulously, and make it clear when what I am writing is informed speculation/interpretation.
The images by William Black add a different dimension to your post. It looks as though photos from an alterate reality, where these missions actually took place, have made there way through to our reality. In cases where the original plans & illustrations are unavailable this ia an excellent way of illuminating what might have happened.
I'm glad you like William's illustrations - I'll pass along your comment. I'm sure he'll appreciate it.
This post has gone through many iterations over the years. I've *never* been sure how to illustrate it. So, when William offered his services, it was high on my list of posts to ask him to illustrate. Because we had absolutely no information on the FLEM spacecraft - apart from Titus's comments on circumstances governing the relative sizes of the FLEM vehicles - and because I see this mission as making sense only as part of an evolutionary program of development, I set as a ground rule use of a well-documented contemporary design as a point of departure. An obvious choice was the 1975 piloted Mars flyby described in the October 1966 Planetary JAG report. The FLEM Orbiter has the shape of the 1975 Mars flyby spacecraft Probe Module. Converting the Probe Module into a two-person Mars Orbiter seemed a sensible thing to do.
We considered for a time retaining the Orbiter after it returned from Mars and including the powered flyby maneuver. I rejected the former because Titus specifically stated that it would be discarded. The latter was William's decision - he was concerned about portraying the powered flyby and the Orbiter rendezvous & docking in a way that was easily understood. The fact that the maneuver would put the Flyby Spacecraft within 0.4 AU of the Sun during solar max, meanwhile, killed it for me. We considered moving the powered flyby to 1981 before putting it off to some subsequent mission.
I played around with a possible evolutionary series of Mars missions. The Mission Module test in low-Earth orbit would occur in 1971-1973, providing time for results from the test to be fed into planning for the 1975 Mars flyby mission. NASA would skip the 1978 opportunity, then would fly the FLEM mission in this post in 1981. I assumed that NASA would want to use the favorable mission opportunity of 1988 for a large conjunction-class (long-stay) landing mission, so worked toward that. A FLEM Orbiter with an automated MEM aerobraking & landing test in 1984; a short-stay piloted Mars landing mission in 1986 (15 days on Mars, 30 days near the planet); and the big conjunction-class (450-days near Mars) mission in 1988.
The 1986 and 1988 spacecraft would be based on the same mission module as the 1975, 1981, and 1984 spacecraft, but would otherwise be very different. I assume chemical propulsion and weightlessness, though nuclear and artificial-G would be possible. Chemical propulsion and weightlessness might enable aerobraking.
I assumed that the 1984 and 1986 spacecraft would release their MEMs (one each) before the Mars orbit insertion burn. The MEM would aerobrake into Mars orbit and the Orbiter would dock with it. For the 1988 mission, the main mission spacecraft would carry four MEMs. All would be released and aerobrake separately. Roughly every 120 days, one MEM would separate and land. It would spend 30 days at a landing site, then return. The fourth MEM would be held in reserve as a rescue vehicle in the event that one of the MEMs became stranded. It would be used to make a trip to Phobos and Deimos after the last Mars landing mission returned safely to the orbiter spacecraft.
I don't know what will come of this timeline - perhaps it will grow into another "Dreaming a Different Apollo" alternate history. I want to try my hand at another narrative vignette like "Victory Lap." Not sure yet if this could become the setting for that.
Sounds intriuging, I look forward to reading it.ReplyDelete