09 September 2017

NASA Glenn Research Center's 2001 Plan to Land Humans on Mars Three Years Ago

August 2014. Image credit: NASA
In October 2001, at the 52nd International Astronautical Congress in the European aerospace center of Toulouse, France, nuclear propulsion engineers at NASA's Glenn Research Center (GRC) in Cleveland, Ohio, led by Stanley K. Borowski, Advanced Concepts Manager in GRC's Space Transportation Project Office, described a variant of NASA's 1998 Mars Design Reference Mission (DRM) based on Bimodal Nuclear-Thermal Rocket (BNTR) propulsion. The BNTR DRM concept, first described publicly in July 1998, evolved from nuclear-thermal rocket mission designs Borowski and his colleagues had developed during President George H. W. Bush's abortive Space Exploration Initiative (SEI), which got its start with a July 1989 presidential speech commemorating the 20th anniversary of Apollo 11, the first piloted moon landing mission.

This post contains more than its share of significant acronyms. As an aid to the reader, these are grouped alphabetically and defined at the bottom of the post, just ahead of the list of sources.

NASA's first Mars DRM, designated DRM 1.0 in 1997, was developed by a NASA-wide team during the 1992-1993 period. It was based on Martin Marietta's 1990 Mars Direct mission plan. SEI's demise temporarily halted NASA Mars DRM work in 1994. The civilian space agency resumed its Mars DRM studies after the announcement in August 1996 of the discovery of possible microfossils in martian meteorite ALH 84001. This enabled NASA planners to release their baseline chemical-propulsion DRM 3.0 in 1998. There was no official DRM 2.0, though a "scrubbed" (that is, mass-reduced) version of DRM 1.0 bears that designation in at least one NASA document.

Shortly thereafter, NASA's Johnson Space Center (JSC) in Houston, Texas, which led the DRM study effort, was diverted from DRM work by the in-house COMBO lander study (more on this below). Left largely to its own devices, NASA GRC developed a pair of DRM 3.0 variants: a solar-electric propulsion (SEP) DRM 3.0 and the BNTR DRM 3.0 discussed here.

In BNTR DRM 3.0, two unpiloted spacecraft would leave Earth for Mars during the 2011 low-energy Mars-Earth transfer opportunity, and a third, bearing the crew, would depart for Mars during the corresponding opportunity in 2014. Components for the three spacecraft would reach Earth orbit on six Shuttle-Derived Heavy-Lift Vehicles (SDHLVs), each capable of launching 80 tons into 220-mile-high assembly orbit, and in the payload bay of a winged, reusable Space Shuttle Orbiter, which would also deliver the Mars crew.

The SDHLV, often designated "Magnum," was a NASA Marshall Space Flight Center conceptual design. The Magnum booster would burn liquid hydrogen (LH2)/liquid oxygen (LOX) chemical propellants in its core stages and solid propellant in its side-mounted boosters. Magnum drew upon existing Space Shuttle hardware: its core stages were derived from the Space Shuttle External Tank and its twin solid-propellant rocket boosters were based on the Shuttle's twin Solid-Rocket Boosters.

The mighty Magnum was the conceptual ancestor of the equally conceptual Ares V and the Space Launch System, now under development. Image credit: NASA
SDHLV 1 would launch BNTR stage 1 with 47 tons of LH2 propellant on board. Each BNTR DRM mission would need three 28-meter-long, 7.4-meter-diameter BNTR stages. The BNTR stages would each include three 15,000-pound-thrust BNTR engines developed as part of a joint U.S./Russian research project in 1992-1993.

SDHLV 2 would boost an unpiloted 62.2-ton cargo lander into assembly orbit. The cargo lander would include a bullet-shaped Mars aerobrake and entry heat shield (this would double as the cargo lander's Earth launch shroud), parachutes for landing, a descent stage, a 25.8-ton Mars surface payload including an in-situ resource utilization (ISRU) propellant factory, four tons of "seed" LH2 to begin the process of manufacturing propellants on Mars, and a partly fueled Mars Ascent Vehicle (MAV) made up of a conical Earth Crew Return Vehicle (ECRV) capsule and an ascent stage. The cargo and habitat lander engines would burn liquid methane fuel and LOX.

SDHLV launch 3, identical to SDHLV launch 1, would place into assembly orbit BNTR stage 2 containing 46 tons of LH2 propellant. SDHLV launch 4 would place the unpiloted 60.5-ton habitat lander into assembly orbit. The habitat lander would include a Mars aerobrake & entry shield/launch shroud identical to that of the cargo lander, parachutes, a descent stage, and a 32.7-ton payload including the crew's Mars surface living quarters.

The BNTR stage forward section would include chemical thrusters. These would provide maneuvering capability so that the stages could dock with the habitat and cargo landers in assembly orbit. During flight to Mars, the thrusters would provide each stage/lander combination with attitude control.

2011: the unmanned BNTR 1 stage/cargo lander and BNTR 2 stage/habitat lander spacecraft orbit the Earth prior to departure for Mars. Image credit: NASA
The BNTR 1/cargo lander combination would have a mass of 133.7 tons, while the BNTR 2/habitat lander combination would have a mass of 131 tons. Both combinations would measure 57.5 meters long. As the 2011 launch window for Mars opened, the BNTR stages would fire their engines to depart assembly orbit for Mars.

Each BNTR engine would include a nuclear reactor. When moderator elements were removed from its nuclear fuel elements, the reactor would heat up. To cool the reactor so that it would not melt, turbopumps would drive LH2 propellant through it. The reactor would transfer heat to the propellant, which would become an expanding very hot gas and vent through an LH2-cooled nozzle. This would propel the spacecraft through space.

Following completion of Earth-orbit departure, the BNTR engine reactors would switch to electricity-generation mode. In this mode, they would operate at a lower temperature than in propulsion mode, but would still be capable of heating a working fluid that would drive three turbine generators. Together the generators would make 50 kilowatts of electricity. Fifteen kilowatts would power a refrigeration system in the BNTR stage that would prevent the LH2 it contained from boiling and escaping.

Much like the LH2 propellant in BNTR propulsion mode, the working fluid would cool the reactor; unlike the LH2, however, it would not be vented into space. After leaving the turbine generators, it would pass through a labyrinth of tubes in radiators mounted on the BNTR stage to discard leftover heat, then would cycle through the reactors again. The cycle would repeat continuously throughout the journey to Mars.

2012: Cargo lander/Mars Ascent Vehicle Landing. Image credit: NASA
As Mars loomed large ahead, the turbine generators would charge the lander batteries. The BNTR stages would then separate and fire their engines to miss Mars and enter a safe disposal orbit around the Sun. The landers, meanwhile, would aerobrake in Mars's upper atmosphere. The habitat lander would capture into Mars orbit and extend twin solar arrays to generate electricity. The cargo lander would capture into orbit, then fire six engines to deorbit and enter the atmosphere a second time. After casting off its heat shield, it would deploy three parachutes. The engines would fire again, then landing legs would deploy just before touchdown. The GRC engineers opted for a horizontal landing configuration; this would, they explained, prevent tipping and provide the astronauts with easy access to the lander's cargo.

As illustrated in the cargo lander image above and the MAV launch image below, the four MAV engines would serve double-duty as cargo lander engines. In addition to saving mass by eliminating redundant engines, this would test-fire the engines before the crew used them as MAV ascent engines.

2012: Automated propellant manufacture for MAV ascent begins. Image credit: NASA
The cargo lander would touch down on Mars with virtually empty tanks. After touchdown, a teleoperated cart bearing a nuclear power source would lower to the ground and trundle away trailing a power cable. Controllers on Earth would attempt to position it so that the radiation it emitted would not harm the astronauts (for example, behind a sand dune or boulder pile). The reactor's first job would be to power the lander's ISRU propellant plant, which over several months would react the seed hydrogen brought from Earth with martian atmospheric carbon dioxide in the presence of a catalyst to produce 39.5 tons of liquid methane fuel and LOX oxidizer for the MAV ascent engines.

SDHLV launch 5, identical to SDHLV launches 1 and 3, would mark the start of launches for the 2014 Earth-Mars transfer opportunity. It would place BNTR stage 3 into assembly orbit with about 48 tons of LH2 on board. Because it would propel a piloted spacecraft, its BNTR engines would require a new design feature: each would include a 3.24-ton shield to protect the crew from the radiation it produced while in operation. The shields each would create a conical radiation "shadow" in which the crew would remain while they were inside or close to their spacecraft.

2013: the BNTR 3 stage and the first Crew Transfer Vehicle components dock automatically in Earth orbit. Image credit: NASA
Thirty days after SDHLV launch 5, SDHLV launch 6 would place into assembly orbit a 5.1-ton spare Earth Crew Return Vehicle (ECRV) attached to the front of an 11.6-ton truss. A 17-meter-long tank with 43 tons of LH2 and a two-meter-long drum-shaped logistics module containing 6.9 tons of contingency supplies would nest along the truss's length. BNTR stage 3 and the truss assembly would rendezvous and dock, then propellant lines would automatically link the truss tank to BNTR stage 3.

A Shuttle Orbiter carrying the Mars crew and a 20.5-ton deflated Transhab module would rendezvous with the BNTR stage 3/truss combination one week before the crew's planned departure for Mars. Following rendezvous, the spare ECRV would undock from the truss and fly automatically to a docking port in the Space Shuttle payload bay. Astronauts would then use the Orbiter's robot arm to hoist the Transhab from the payload bay and dock it to the front of the truss in the spare ECRV's place.

2014: Crew and a deflated Transhab arrive on board a Space Shuttle Orbiter to complete Crew Transfer Vehicle assembly. Image credit: NASA
The Mars astronauts would enter the spare ECRV and pilot it to a docking at a port on the Transhab's front, then enter the cylindrical Transhab's solid core and inflate its fabric-walled outer volume. The inflated Transhab would measure 9.4 meters in diameter. Unstowing floor panels and furnishings from the core and installing them in the inflated volume would complete assembly. Transhab, truss, and BNTR stage 3 would make up the 64.2-meter-long, 166.4-ton Crew Transfer Vehicle (CTV).

The CTV's truss-mounted tank and BNTR stage 3 would hold 90.8 tons of LH2 at the start of CTV Earth-orbit departure on 21 January 2014. The truss tank would provide 70% of the propellant needed for departure. In the most demanding departure scenario, the BNTR engines would fire twice for 22.7 minutes each time to push the CTV out of Earth orbit toward Mars.

2014: Crew Transfer Vehicle departs Earth orbit. Image credit: NASA
Transhab cutaway (weightless design). Floor and ceiling would be reversed in the NASA Glenn artificial-gravity design. "Down" would thus be toward the top of this image, where the airlock and Earth Crew Return Vehicle capsule would be located. Image credit: NASA
Following Earth-orbit departure, the crew would jettison the empty truss tank and use small chemical-propellant thrusters to start the CTV rotating end over end at a rate of 3.7 rotations per minute. This would create acceleration equal to one Mars gravity (38% of Earth gravity) in the Transhab module. Artificial gravity was a late addition to BNTR DRM 3.0; it made its first appearance in a June 1999 paper, not in the original July 1998 paper describing BNTR DRM 3.0.

In artificial-gravity mode, "down" would be toward the spare ECRV on the CTV's nose; this would make the Transhab's forward half its lower deck. Halfway to Mars, about 105 days out from Earth, the astronauts would stop rotation and perform a course-correction burn using the attitude-control thrusters. They would then resume rotation for the remainder of the trans-Mars trip.

The CTV would arrive in Mars orbit on 19 August 2014. The crew would halt rotation, then three BNTR engines would fire for 12.3 minutes to slow the spacecraft for Mars orbit capture. In its loosely bound elliptical Mars orbit, the spacecraft would circle the planet once per 24.6-hour martian day.

2014: Crew Transfer Vehicle arrival in Mars orbit. Image credit: NASA
The crew would pilot the CTV to rendezvous with the habitat lander waiting in Mars orbit, taking care to place it in the CTV's radiation shadow. If the cargo lander on the surface or the habitat lander in Mars orbit malfunctioned while awaiting the crew's arrival, then the crew would remain in the CTV in Mars orbit until Mars and Earth aligned for the flight home (a wait time of 502 days). They would survive by drawing upon contingency supplies in the drum-shaped logistics module attached to the truss.

If the orbiting habitat lander and landed cargo lander checked out as healthy, however, then the crew would fly the spare ECRV to a docking port on the habitat lander's side. After discarding the spare ECRV and the habitat solar arrays, they would fire the habitat lander's engines, enter the martian atmosphere, and land near the cargo lander.

The habitat lander's horizontal configuration would provide the astronauts with ready access to the martian surface. After the historic first footsteps on Mars, the astronauts would inflate a Transhab-type habitat attached to the side of the habitat lander, run a cable from the habitat lander to the nuclear power source cart, unload at least one unpressurized crew rover, and commence a program of Mars surface exploration that would, if all went as planned, last for nearly 17 months.

In case of hardware failure or other emergency, the crew could retreat to the MAV and return early to the orbiting CTV. They would, however, have to wait in Mars orbit until Mars and Earth aligned to permit a minimum-energy Mars-Earth transfer (that is, until the originally planned end of their stay at Mars).

2014-2015: The first Mars campsite. In the foreground is the habitat lander with inflated Transhab surface habitat; in the background, the nuclear power source cart and the cargo lander with Mars Ascent Vehicle. Image credit: NASA
2014-2015: Exploring Mars with a crew rover and two teleoperated robot rovers, one small and one large. Image credit: NASA
2014-2015: Drilling for water, geologic history, and, just possibly, life. Image credit: NASA
2015: Mars Ascent Vehicle liftoff. Image credit: NASA
Near the end of the surface mission, the unmanned CTV would briefly fire its nuclear engines to trim its orbit for the crew's return. The MAV bearing the crew and about 90 kilograms of Mars samples would then lift off. Taking care to remain within the the radiation shadows of the CTV's BNTR engines, it would dock at the front of the Transhab, then the astronauts would transfer to the CTV. They would cast off the spent MAV ascent stage, but would retain the MAV ECRV for Earth atmosphere reentry.

The CTV would leave Mars orbit on 3 January 2016. Prior to Mars orbit departure, the astronauts would abandon the contingency supply module on the truss to reduce their spacecraft's mass so that the propellant remaining in BNTR stage 3 would be sufficient to launch them home to Earth. They would then fire the BNTR engines for 2.9 minutes to change the CTV's orbital plane, then again for 5.2 minutes to escape Mars and place themselves on course for Earth.

Soon after completion of the second burn, the crew would fire attitude-control thrusters to spin the CTV end-over-end to create acceleration equal to one Mars gravity in the Transhab. About halfway home they would stop rotation, perform a course correction, then resume rotation. Flight home to Earth would last 190 days.

2016: Return to Earth. Image credit: NASA
Near Earth, the crew would stop CTV rotation for the final time, enter the MAV ECRV with their Mars samples, and undock from the CTV, again taking care to remain in the BNTR engine radiation shadows as they moved away. The abandoned CTV would fly past Earth and enter solar orbit. The MAV ECRV, meanwhile, would reenter Earth's atmosphere on 11 July 2016.

The authors compared their Mars plan with the baseline chemical-propulsion DRM 3.0 and with the NASA GRC SEP DRM 3.0. They found that their plan would need eight vehicle elements, of which four would have designs unique to BNTR DRM 3.0. The baseline DRM 3.0, by contrast, would need 14 vehicle elements, 10 of which would be unique, and SEP DRM 3.0 would need 13.5 vehicle elements, 9.5 of which would be unique. BNTR DRM 3.0 would require that 431 tons of hardware and propellants be placed into Earth orbit; the baseline DRM 3.0 would need 657 tons and SEP DRM 3.0, 478 tons. Borowski and his colleagues argued that fewer vehicle designs and reduced mass would mean reduced cost and mission complexity.

The BNTR DRM 3.0 variant became the basis for DRM 4.0, which was developed during NASA-wide studies in 2001-2002 (though NASA documents occasionally back-date DRM 4.0 to 1998, when BNTR DRM 3.0 was first proposed). DRM 4.0 differed from BNTR DRM 3.0 mainly in that it adopted a "Dual Lander" design concept developed as part of JSC's 1998-1999 COMBO lander study. COMBO was the brainchild of William Schneider, NASA JSC Engineering Directorate boss.

Dual Lander concept. The lander in the foreground is the habitat; the background lander is the Mars Descent/Ascent Vehicle. Image credit: NASA
The Dual Lander concept grew from COMBO's main design guideline, which was to develop a low-mass "Apollo-style" piloted Mars landing mission. A major change from past Mars DRMs was no reliance on ISRU. As in BNTR DRM 3.0, two cargo missions would leave Earth one minimum-energy Earth-Mars transfer opportunity ahead of the crew; in DRM 4.0, however, these would take the form of a Mars lander that would also include an ascent vehicle for returning the crew to the CTV in Mars orbit and a cargo lander with an inflatable donut-shaped habitat. The former could by itself support a short-stay (~30-day) Mars surface mission; the latter would enable a Mars surface stay of up to 500 days.

In 2008, a decade after BNTR DRM 3.0 first was made public, NASA released a version of DRM 4.0 modified to use planned Constellation Program hardware (for example, the Ares V heavy-lift rocket in place of the Magnum and the Orion Multi-Purpose Crew Vehicle in place of the ECRVs). The space agency dubbed the new DRM Design Reference Architecture (DRA) 5.0.

The DRA 5.0 Mars plan acknowledged that, largely as a result of the 1 February 2003 Columbia accident, the Space Shuttle would be retired after the remaining Orbiters - Endeavour, Discovery, and Atlantis - completed their part of the task of building the International Space Station. The last Space Shuttle mission, STS-135, took place in July 2011.

DRA 5.0 saw the return of ISRU. A Descent/Ascent Vehicle (DAV) and a Surface Habitat (SHAB) would capture into Mars orbit in the first minimum-energy Earth-Mars transfer opportunity. The DAV would descend, land, and begin making propellants for its ascent stage. The SHAB would loiter in orbit awaiting arrival of a crew on board the Mars Transfer Vehicle (MTV). The crew would transfer to the SHAB in an Orion/service module and land on Mars near the DAV. After a stay on Mars lasting more than 400 days, they would lift off in the DAV ascent stage, dock with the waiting MTV, and return to Earth.

Though DRA 5.0 exerts influence on NASA planning, the precise form a piloted Mars mission will eventually take remains unclear at this writing. NASA increasingly has shifted its attention toward finding low-cost stepping stones that could lead to a piloted Mars landing in 2033. A Deep Space Gateway space station in cislunar space, for example, could be established by 2026 through a series of Orion missions using the Space Launch System (SLS) heavy-lift rocket (SLS replaced Ares V in 2010). Other possible interim steps toward Mars include an SLS-launched robotic Mars sample-return mission in the mid-2020s and a piloted mission to Mars orbit in 2030 using a Deep Space Transport based partly on Deep Space Gateway hardware.


BNTR = Bimodal Nuclear Thermal Rocket
CTV = Crew Transfer Vehicle
DAV = Descent/Ascent Vehicle
DRA = Design Reference Architecture
DRM = Design Reference Mission
ECRV = Earth Crew Return Vehicle
GRC = Glenn Research Center
ISRU = In-Situ Resource Utilization
JSC = Johnson Space Center
LH2 = liquid hydrogen
LOX = liquid oxygen
MAV = Mars Ascent Vehicle
MTV = Mars Transfer Vehicle
SDHLV = Shuttle-Derived Heavy-Lift Vehicle
SEI = Space Exploration Initiative
SEP = Solar-Electric Propulsion
SHAB = Surface Habitat
SLS = Space Launch System


"Bimodal Nuclear Thermal Rocket (NTR) Propulsion for Power-Rich, Artificial Gravity Human Exploration Missions to Mars," IAA-01-IAA.13.3.05, Stanley K. Borowski, Leonard A. Dudzinski, and Melissa L. McGuire; paper presented at the 52nd International Astronautical Congress in Toulouse, France, 1-5 October 2001

"Vehicle and Mission Design Options for the Human Exploration of Mars/Phobos Using 'Bimodal' NTR and LANTR Propulsion," AIAA-98-3883, Stanley K. Borowski, Leonard A. Dudzinski, and Melissa L. McGuire; paper presented at the 34th AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit in Cleveland, Ohio, 13-15 July 1998

"Artificial Gravity Vehicle Design Option for NASA's Human Mars Mission Using 'Bimodal' NTR Propulsion," AIAA-99-2545, Stanley K. Borowski, Leonard A. Dudzinski, and Melissa L. McGuire; paper presented at the 35th AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit in Los Angeles, California, 20-24 June 1999

NASA Exploration Team (NEXT) Design Reference Missions Summary, NASA, 12 July 2002 [draft]

"Enabling Human Deep Space Exploration with the Deep Space Gateway," Tim Cichan, Bill Pratt, and Kerry Timmons, Lockheed Martin; presentation to the Future In-Space Operations telecon, 30 August 2017

More Information

A Forgotten Pioneer of Mars Resource Utilization (1962-1963)

Two For The Price of One: 1980s Piloted Missions With Stopovers at Mars and Venus (1969)

Think Big: A 1970 Flight Plan for NASA's 1969 Integrated Program Plan

Humans on Mars in 1995! (1980-1981)

Bridging the Gap Between Space Station and Mars: The IMUSE Strategy (1985)

The Collins Task Force Says Aim for Mars (1987)

Sally Ride's Mission to Mars (1987)

Footsteps to Mars (1993)


  1. If anything this plan proves is the continuity of planning. I have read your posts on the space station planning and the designs are all over, from a simple lab to a full scale spacedock. Right now it seems that NASA has chosen Solar Electric Propulsion for the Mars bound spacecraft, though the ISRU unit might be nuclear. Otherwise though the outline you describe follows the outline of the current plan, such as it is, minus a few selections based on the evolution of the plan. So, they expected to have the shuttle derived heavy lift rocket ready after 10 years from the plan (2001-2011)? If 2004 is taken as the origin of development for Ares V, and SLS flies in 2019, even of you consider that its development has not followed a normal funding trajectory, it still is longer than the DRM 3 plan

  2. The DRM/DRA process has had continuity, though it is very different now from Mars Direct, the mission design it is based upon. At the moment, there's a lot of interest in interim steps. Deep Space Gateway planning grew up independent of the Mars DRM/DRA process as part of the Decadal Planning Team exercise in 1999-2000 and was studied in detail in the 2000-2002 time period. It's not a bad concept, though some would say, "If you want to conquer Vienna, go to Vienna." I think we can reasonably forecast a piloted Mars flyby mission and a piloted Mars orbiter, perhaps in conjunction with a robotic Mars Sample Return mission, ahead of a Mars landing. If anything, concern over toxicity of Mars surface material has grown since Curiosity set to work. MSR is all but mandatory now, and there's plenty of concern over contamination of a planet which might still harbor life (that would be virtually unavoidable if humans land). Hence, the interim steps deliver interesting experience-building steps on the road to Mars's surface *and* provide data which could indefinitely postpone humans on Mars. Which is, I think a good sign that maybe we're grownup enough to explore space without killing everything.


  3. The possibility depends is to enable individuals from different lands in the world to be the primary candidates to the another wave of people that will be selected to go to Mars. As reported by The Boring State Even people from a nation such as Egypt, Pakistan, Saudi Arabia, have heavily shown affair and they really like to go The Red Planet. A very interesting text can be read here :
    Mars One Fact Or Just Fiction: Will Manned Craft EVER get off the ground

  4. ST:

    Before I say anything else, Mars One is nonsense - their plan has been looked at carefully by experts and found to be unworkable. But I think that must not be the point of what you have written here. You are stating that people from countries that are not normally seen as space-faring deserve a chance to participate in space exploration. I agree completely. Now to come up with a workable mechanism for making that happen.


    1. How would SLS compare with Magnum--could this plan be simplified?

      Solar electric seems to be getting all the attention.

    2. A:

      The NASA GRC folks postulated a Magnum with a payload to assembly orbit of 80 tons. SLS design payloads are all over the map, and I expect we won't know for certain what that family of rockets will be able to do until we get some flight data. However, a quick peek at Wikipedia suggests payloads of from 70 to 130 metric tons. The most capable SLS design is meant to exceed Apollo Saturn V capability.

      Getting to Mars is going to be a complicated endeavor, and anyone who says it isn't is a charlatan. That being said, I think there is plenty of room for simplifying this mission design. One might, for example, launch larger payloads to reduce Earth-orbital assembly. One might do away with making propellants on Mars. The crew could use one lander. They might even eschew a Mars landing and teleoperate separately launched rovers and sample-returners on Mars, as in the HERRO concept.

      SEP is a good tool to have. As briefly mentioned near the beginning of my post, NASA GRC developed an SEP DRM in the 1990s.


  5. The elongated Mars lander reminds me of the moon lander the International Lunar Resources Exploration Concept in your July 9, 2017 post. The two are quite different, but they are long and short landing vehicles, which I usually only see in science fiction concepts.

    Almost all the other direct ascent moon lander concepts I've seen have the lander being tall. I like the ILREC concept not just because it reminds me of the Eagle from Space: 1999, but because the crew could see the moon directly through the windows as they landed. I figured the other direct ascent moon landers would depend on cameras in the base of the vehicle and TV screens in the cockpit so the astronauts could tell where they were landing--hope those cameras and TVs were reliable. Also, the crew wouldn't have to use a long ladder to get to and from the surface. That's dangerous enough on the moon, and I imagine it would be even worse on Mars. And your text says the people who designed the Mars lander were thinking about that.


    1. Phil:

      The same folks were working on the 1990s Mars and moon designs and hoped for some degree of commonality. I think these horizontal rectangular concepts originated with Brand Griffin of Boeing; Paul Hudson painted them, so they became pretty well known. I had a 1986 calendar of Paul Hudson paintings, most of Brand Griffin designs. Wish I still had it.

      If you look back to the Apollo mode decision, you find that the Direct Ascent/EOR advocates understood that a tall lander was a problem. They considered embedding the ascent stage in the descent stage. They made the descent stage more squat (larger diameter, shorter). They even postulated landing the tall lander on its side with its nose pointed 10 of so degrees above the horizon. The Earth-return stage would lift off more or less horizontal to the surface, like an airplane. And they considered the "crasher" concept, which resembled the Soviet N-1/LK piloted lunar landing concept - use a descent stage to get most of the way down to the moon, drop it, then land the Earth-return stage on legs. They'd leave the legs behind when they lifted off.

      Incidentally, the Apollo CM-shaped Mars landers that leapt to the fore after Mariner IV revealed how thin the martian atmosphere is helped in this regard. They were squat, with the ascent stage embedded at the center. Crew could almost step right onto the surface. The old lifting-body Mars lander designs needed to perform an awkward "flip" before landing and they stood tall. The crew generally climbed down *within* the lander, then rode a small elevator the final dozen feet or so to the surface.



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