Prelude to Pioneering (1)
The NASA Plan for Exploration

By IonMars

November 10, 2014


Before Spanish Admiral Pedro Menendez established the first permanent colony in North America in 1565, there were explorers.  In 1513 Juan Ponce De Leon had explored the coast of Florida with three ships from his base in Puerto Rico1. In 1562 Jean Ribault of France had explored the Florida coast and claimed the area for France2. His Lieutenant, Rene Laudonniere, later returned to the same location, established a small fort, and left 304 Huguenot colonists who thereafter     became disillusioned and dispersed. Admiral Menendez dispatched Exploration 1607the remaining Frenchmen and set up Saint Augustine, a town that still exists today3.

Before the Virginia Company of London sponsored the first English colony at Jamestown in 1607, there were explorers.  In 1497 the Italian explorer John Cabot had sailed to the new world on behalf of King Henry VII, claiming all of North America for England4. In 1524, Giovanni da Verrazzano had sailed along the Atlantic Coast5. In 1585, Sir Walter Raleigh had funded a group of colonizers for Roanoke, a small island on the coast of North Carolina. The expedition failed, but it did include a side trip to the James River.

 Before the first pioneer steps off the Mars lander to build a colony, there will be explorers.  The National Aeronautics and Space Administration (NASA), an agency of the US government, will most likely spearhead the exploration and other nations will be asked to participate in this venture. NASA may also lead the colonization phase, but SpaceX, a private US company founded by Elon Musk, will likely be deeply involved. The company’s main purpose is to colonize the Red Planet as a stepping-stone to making the human race a multi-planetary specie6.


The NASA Plan for Mars Exploration

NASA has developed a plan for exploring Mars called the Mars Design Reference Architecture (DRA). This document delineates the course of travel between Earth and Mars, the launch vehicles to be constructed, the landers to be set down, and the surface equipment to be deployed. The Mars DRA has evolved as a series of updated publications beginning with Design Reference Mission 1.0 in 19936. Other updated plans included DRA 3.0, DRM 4.0 and DRA 5.0 in 20097, which is the current plan except for updates. Addendum 1 to DRA 5 included additional analyses that were carried out during the development of DRA 5.08. Addendum 2 (DRA5A2) updates the plan to reflect recent events and the studies and assessments that were conducted between 2009 and 2012. For example, the rocket launcher is now the Space Launch System rather than the Ares 5 rocket9.

DRA 5.0

The Mars DRA5 is a component of a broad plan first published in the NASA Authorization Act of 2005, called the Vision for Space Exploration (VSE). “This vision specifically calls for: (1) implementation of a sustained and affordable human and robotic program to explore the solar system and beyond; (2) extending human presence across the solar system (starting with a human return to the Moon no later than the year 2020), in preparation for human exploration of Mars and other destinations; (3) developing the innovative technologies, knowledge, and infrastructures to support human and robotic exploration; and (4) promoting international and commercial participation in exploration to further U.S. scientific, security, and economic interests10.”

In 2007 NASA established a Mars Architecture Working Group (MAWG) to develop the DRM5. MAWG represented the headquarters office and four major directorates of the agency, with contributions from various employees from the field offices of NASA11. This is a common practice in the establishment of a government plan where the various departments of an agency must cooperate in its development and commit to its implementation.

DRM5 with addendums describes the systems and operations that would be used for the first three missions by humans to explore the surface of Mars. These Cargo LanderExploratory missions would occur on three consecutive trajectory opportunities within the next two decades. A minimum of three was chosen because the development time and cost to carry out a single human Mars mission is difficult to justify, whereas three consecutive missions over 10 years is sufficient to achieve program goals and acquire a significant amount of knowledge and experience.  Before the first three human Mars missions, test missions will be carried out on Earth, in Earth orbit, and on the moon. In addition, robotic missions to Mars will assure a level of confidence in the architecture such that the risk to the human crews is considered acceptable12.

In a nutshell, NASA is carrying out a broad space exploration plan to develop the multi-purpose space vehicles and machines that will be necessary to carry out the exploration of Mars. This development process includes test trips to the ISS and other locations in Earth orbit, trips to the moon, and trips to asteroids. The purpose is to develop incrementally greater capability and to test out vehicles and equipment in nearby locations before committing them to missions far from Earth.

The Mars component13 of the space exploration plan will contain the following elements: 

  1. A crew of four would carry out each of the three exploration missions to Mars. The crew size was selected from different options of three, four, or six. Once chosen, the crew size determined the size of the systems required to get the explorers to Mars and back as well as the capacities of the auxiliary equipment.
  2. These missions would utilize conjunction class trajectories that allow a long stay on Mars.  Conjunction class means taking advantage of certain alignments of Earth and Mars whereby the trajectory of a spacecraft can follow a high efficiency, low cost route from Earth to Mars. A long stay of about 500 days is required to wait for another desirable alignment of the planets for the return trip that is also fuel-efficient. These planetaryalignments only occur about every 26 months.Long Stay
  3. A space capsule called Orion will carry the exploration crew into Earth orbit and return them to the Earth’s surface at the end of the mission.
  4. A heavy lift vehicle (HLV) will be required to deliver the components of a Mars-bound vehicle into a low Earth orbit where they will be assembled into a fully fueled spacecraft. In the 2009 plan this HLV was the Ares V whereas the 2012 addendum calls for the Space Launch System (SLS). Two versions of the HLV will be required, one for crew and one for cargo.
  5. The cargo version of HLV would be sent on one or more early trips to pre-deploy equipment on Mars or in Mars orbit. Some of this equipment will be employed robotically in advance of the crew. Upon arrival, the crew will deploy the rest of the equipment. Seven launches of the HLV will be required to deliver equipment for the first two missions.
  6. A Mars Transfer Vehicle (MTV) will be comprised of all the modules, tanks, and propulsion units required to transport crew, cargo and vehicles from Earth orbit to Mars orbit.
  7. The crew will live in a space habitat (SHAB) during their voyage to Mars, a trip of six to eight months. The habitat will provide life support machines and protection against galactic and cosmic radiation.
  8. A descent vehicle will transport the crew from the SHAB to the pre-selected landing site on Mars. It would have capabilities for entry into the atmosphere, descent to the surface and landing (EDL)
  9. A key strategy for the Mars missions will be in-situ resource utilization (ISRU) to produce oxidizer and methane fuel from the Mars atmosphere for the return trip. An ISRU production unit is one item to be pre-deployed so that when the crew arrives they will be assured of the necessary fuel and oxidizer for the return trip.
  10. A fission surface power system (FSPS) would drive the ISRU unit and supply electricity for the needs of the crew. Photovoltaic panels would also contribute to the power system, but in a secondary role.
  11. While on the surface the crew will live in a Mars surface habitat that was either pre-deployed or brought to the surface along with the crew. The habitat will contain the same type of life support system (LSS) as the in-space version of habitat.
  12. While on the surface the crew will employ transport vehicles to carry out their exploration forays. These vehicles may be pressurized to allow the crew to operate in shirtsleeves, or non-pressurized whereby the crew would catty out a foray in spacesuits.
  13. At the end of the mission, an ascent vehicle will transport the crew from the surface back to the SHAB for the long return trip to Earth.
  14. Once in Earth orbit Orion will once again detach from SHAB and perform EDL to safely deliver the crew back onto the Earth surface.


StudyingA prospective colonist should take particular interest in the vehicles and machines under development by NASA. They will likely be the vehicles and machines that he will employ on Mars, especially for the first stages of colonization. A colonist should become intimately familiar with the function of each machine and its maintenance and repair. While he/she will not likely be the person responsible for every item, he could encounter an emergency that would require this knowledge.

This article briefly introduces the machines of DRA5. At this time there are no handbooks and no detailed instructions to peruse, however, when a colonist sets forth on his/her journey to Mars the initial exploration missions should already have been completed successfully. The vehicles and machines to be employed by a colonist will have been well tested and a he can begin in earnest to learn the details of their usage.



This capsule-shaped transporter has the capacity to carry up to six persons on a trip into space. Orion consists of a crew module and a service module. The crew module features a life support system (LSS) that incorporates a nitrogen/oxygen atmosphere and a “camping” style waste disposal device. For each launch it sports a launch abort system LAS) consisting of a rocket tower to boost the crew capsule away from the rest of the rocket system in the event of an emergency. 

CapsuleThe Orion service module is a cylinder mounted underneath the capsule during launch. It contains a disposable power generation unit and expendable supplies unit that are discarded after each mission. It can sustain the crew up to 21 days with no outside facilities or supplies. Orion is designed to attach to other vehicles or modules through a NASA docking port. 

On a Mars expedition, Orion will carry an exploration or colonization crew from Earth surface to Earth orbit where they will transfer to a space habitat for the long Mars journey. On the return trip Orion will ferry the crew from the Mars transporter back to the Earth’s surface. For Earth EDL it utilizes a high-speed entry heat shield and employs a parachute system for soft landing14.


Space Launch System

SLS Block 1The Space Launch System (SLS) will be the heavy lift vehicle that will loft a colonist inside the Orion capsule into Earth orbit. There they will join the other modules that are assembled together to comprise the Mars transfer vehicle (MTV). The Mars DRA5 plan originally envisioned the use of the Ares I and Ares V rocket launchers; however, the program was cancelled during the Great Recession. A new program was established in 2010 that specified the SLS as the HLV for Mars expeditions and other destinations beyond Earth orbit15.

The core stage of the SLS is common to all vehicle configurations, whether for cargo or for crew. It consists of a Space Shuttle external tank with the aft section adapted to accept the Main Propulsion System (MPS) and the top adapted to an inter-stage structure. Various second stages will be attached for different missions.

The SLS is to be developed over a period of time, each increment increasing in power and capability. The first version (Block I) of the core stage MPS will utilize four RS-25 engines. This engine was used as the one main engine of the Space Shuttle; SLS block I will have the capability to launch 70 tons into low Earth orbit. Block II will use four advanced RS-25D/E engines and will have the capability of launching 130 tons into low Earth orbit16.

During the first two minutes of flight, the engines of the core stage will be assisted by two solid-fuelled rocket boosters (SRBs) mounted to either side of the core. Block I and block IB of the SLS will employ SRBs from the Space Shuttle program that were extended from four segments to five. Each five-segment SRB will have a thrust of 3,600,000 lb.

In future versions (block II) NASA will switch to upgraded boosters. These may be either the advanced SRBs or liquid-fuelled rockets. These upgrades will make possible the HLV capacity required for the Mars expeditions.


Mars Transfer Vehicle (MTV)

MTV Assembly
The MTV will be comprised of major components that are lifted into Earth orbit and assembled together in space. Each component will be comprised of smaller modules of cargo or crew equipment. The picture below shows an assemblage of two components that comprise a cargo MTV, a nuclear thermal reactor (NTR) component and an aeroshell containing cargo. The aeroshell containing cargo is the first of two components that comprise a cargo MTV. The second is the nuclear thermal reactor (NTR) propulsion unit. Each component will be lofted into orbit by one launch of the SLS17.  

The aeroshell is the first part of the atmosphere-entry system and is constructed to withstand the initial shock and heat of encountering the Mars atmosphere at hypersonic speed. After an initial slowdown the aeroshell will break away and a rocket propulsion system (with or without parachute) will gently lower the cargo to the surface. 

NTR Engine
The other component of the MTV cargo assembly is the NTR propulsion system that will propel the MTV from Earth orbit to Mars orbit. The NTR component is illustrated in the schematic diagram below. As indicated, liquid hydrogen (LH2) is forced by dual turbine pumps to flow through a mini nuclear reactor. The hydrogen expands exponentially as it passes through the reactor and nozzle and into space. A side loop cycles some of the LH2 around the nozzle and reactor walls to cool them. Nuclear propulsion with a high Isp will allow the transfer to Mars to occur within a reasonably short time and will reduce the amount of radiation exposure to the crew from galactic and cosmic sources.


Crew MTV Component

The second version of the cargo MTV assembly is a crew MTV assembly. This version will consist of the same NTR Propulsion component connected to a crew component such as the one diagrammed below. The crew component will consist of an Orion module, a transfer habitat module (also called Transhab or Spacehab), a side docking module, and a contingency consumables canister for emergency food and water. The crew component is enclosed inside a shroud rather than an aeroshell because it will not be landed on Mars. The shroud will protect this package from vibration and noise during the launch from Earth; then it will be discarded. Once it arrives in Mars orbit, the Transhab will remain there until the crew returns from its mission on the Mars surface. The crew will then enter this habitat for the return trip to Earth18.


To travel from Earth to Mars or vice versa the Crew component will be joined with the same type of NTR component to complete the spaceship assembly and provide propulsion for Trans-Earth Injection (TEI). The dramatic picture by artist Boronski (2012) shown above depicts a MTV assemblage, called Copernicus that will transport a crew to Mars19. The NTR component is on the right,

the Orion/habitat component is on the left and a disposable H2 fuel capsule is in the middle. The extra fuel is required to propel the crew on a faster and safer trajectory than that used by cargo flights18.


Descent Vehicle

To descend from Mars orbit to the surface, the crew and cargo will require a vehicle designed for the purpose. The picture below depicts the horizontal cargo lander (descent vehicle) as specified by DRA5. For EDL, the cargo or habitat lander will be packed inside an aeroshell; it will use a combination of hypersonic aeroassist and supersonic propulsive braking. The lander’s triconic aeroshell will provide lift and deceleration through the hypersonic regime. At a lower but still supersonic speed the exhaust outlets in the bottom of the aeroshell will open out and propulsive braking will begin. The upper half of the aeroshell will be jettisoned and parachutes will deploy briefly to help pull the lander away from the bottom portion of the aeroshell. This allows the top half-shell to fall away to the surface while the lander continues its propulsive descent towards the pre-selected landing site20. 

The artist’s rendering shows a Dynamic Isotope Power System (DIPS) stowed in the forward section of the cargo lander. DIPS will be utilized in the Small Pressurized Rover (SPR) also placed in the forward section. The crew will deploy the SPR to carry out surface explorations. The mid section of the lander is

Ascent Engine

devoted to the Mars Ascent Vehicle (MAV). Note that some engines that are used in propulsive descent to the surface are also components of the MAV that will be employed to lift the crew back to Mars orbit. The engines are propelled by liquid oxygen and liquid methane because these chemicals will be produced on Mars by an ISRU unit that will re-fuel the MAV. The aft section will stow the Fission Surface Power System (FSPS) that will be employed on Mars to energize the ISRU unit and crew surface habitat. Other unspecified equipment is also stowed above the FSPS. This lander is eerily similar to the one sketched out in the DRA (2001) as displayed earlier in this article. A horizontal lander continues to be chosen for its packaging efficiency and off-loading features. Note that the landing legs also serve as ladders.


Surface Habitat

The potential Mars surface habitat as described in DRA5 is the subject of operations testing by voluntary crews at analogue Mars test sites on Earth. All the test habitats are rudimentary copies of Mars habitats that would be landed on Mars’ surface. One of the more complete versions may be the NASA demonstration habitat at the Desert Research and Technology Studies (DRATS) site near Flagstaff, Arizona. As shown in the above photo, the test habitat is two Deep Space Habitat
stories tall and features side hatches (airtight doors) that allow direct connections to other habitats, surface rovers, or modules such as the hygiene module in the photo. The interior space is subdivided into workspaces, kitchenette and sleeping quarters.


Fission Surface Power System


The FSPS is a nuclear reactor used to produce electric power to drive the ISRU production unit and to serve the power needs of the crew.  It is designed to provide 40 kWe and have an 8-year service life21.

In 2008 NASA selected the liquid-metal-cooled reactor as the planning model for Mars exploration. It employs a Stirling power conversion unit and water-based heat rejection panels. The reference concept layout is shown in the adjacent figure. The reactor core is to be placed at the bottom of a two-meter deep excavation with an upper plug shield to protect the equipment above from direct radiation. The NaK pumps, Stirling convertors, and water pumps are mounted on a 5-m-tall truss structure that attaches to the top face of the shield. Two radiator wings for heat rejection are deployed from the truss via a scissor mechanism. Each radiator wing is approximately 4 m tall by 16 m long and is suspended 1 m above the Martian surface. In its stowed configuration, the FSPS is approximately 3 by 3 by 7 m tall.

The reactor uses uranium oxide (UO2 ) fuel pins inside a hexagonal core. It features an external radial reflector and control drums, as indicated in the adjacent FSPS layout. Heat is transferred to the Stirling power convertors by a sodium-potassium (NaK) reactor coolant loop. The core structure and coolant pipes are constructed of stainless steel and the radial reflector is composed of Diagramberyllium in a stainless-steel shell. The control drums are beryllium and boron carbide (B4 C), also enclosed in stainless steel.

Waste heat from the converter is removed by a coolant loop whereby water is pumped through a series of two-sided radiator panels as displayed in the layout. The panels are composed of titanium-water heat pipes in a composite sandwich.

The reactor is located at the bottom of an excavated pit about two meters deep. Thus the Martian regolith will limit radiation exposure to the crew to less than 5 rem/year at a 100 m radius from the reactor. The FSPS Stirling convertors will generate single-phase alternating current (AC) electric power that is converted to direct current (DC) so as to be compatible with the other equipment at the base location. Electric power will be delivered to the other surface equipment through a 100+ m cable21.


Surface Transport Vehicles

In developing the DRA5, NASA considered three different strategies for exploring the surface of Mars: the “mobile home” scenario, the “commuter” scenario and the “telecommuter” scenario22.

The mobile home surface mission scenario would be an entirely mobile operation. The crew would inhabit two large pressurized rovers that would carry out extended traverses, spending 2 to 4 weeks away from the landing site. These rovers would serve as habitats and still have the interior space and equipment for on-board science experiments while on traverses. The landing site would be the base location for the ISRU plant and the fission surface power plant; it would also serve as a warehouse for food and supplies.

In the “telecommuter ” scenario the crew would be based in a centrally located, habitat at the landing site. The crew would only employ unpressurized rovers for EVAs with only short traverses of 15 kilometers. Robotic rovers would conduct the long-range traverses and would be teleoperated by the crew from their habitat. Some of these rovers could be airborne. As in the mobile home scenario there would be an ISRU plant, an FSPS unit and a supply depot at the landing site. Commuter Scenario

In 2008 NASA chose a “commuter” scenario as the basic model for planning purposes. The commuter surface mission scenario assumes a centrally located, monolithic habitat as shown in the above drawing. It also includes two small pressurized rovers, two unpressurized rovers, two small robotic rovers, and a drill.  An FSPS will be deployed in advance with the decent-ascent vehicle to provide power to the ISRU plant that will produce some of the ascent propellant.

In the commuter scenario the exploration traverses will be limited by the capability of the small, pressurized rovers. These vehicles will have a modest one-week habitation capability before being resupplied. A crew of two will travel up to 100 kilometers total distance. However, they will be capable of placing the crew close to features of scientific interest, even in rough terrain. They will tow a trailer mounted with equipment to drill to moderate depths of several hundred meters in a search for water and signs of past life. While some of the crew is exploring the surface, others will remain in the base habitat22.


Space Exploration Vehicle

Surface VehicleSo far, the NASA surface vehicle that has been most developed for the commuter scenario is the Space Exploration Vehicle (SEV). It comes in two versions, one to employ in outer space and one to employ on the surface of a planet such as Mars. The only version that has been constructed is a demonstration model of the surface version; it displays the main features and provides a test model23.

As shown above, the SEV is the size of a small pickup truck. It is designed to carry two astronauts on an exploration foray and can house them up to two weeks without additional supplies or equipment. In an emergency it can accommodate four persons. The vehicle consists of a chassis and a pressurized cabin module. The cabin contains a small bathroom with privacy curtains and a showerhead to produce water mist for a sponge bath. It also contains cabinets for tools and a workbench. The front driving area features large windows with a wide visual field and two crew seats that can fold back into the cabin for access.

Astronauts can enter and exit the SEV cabin directly from the demonstration habitat unit or from another SEV because all the modules will utilize the same air pressure and oxygen level. This means that the burdensome process of pressurization and depressurization through an airlock can be avoided and astronauts can move between modules within minutes.  Astronauts can also

employ suitports attached to the rear of the cabin. In this device the spacesuits are attached to the outside of the cabin so that a person can enter his spacesuit through a hatch on the backside of the suit, also without depressurization.

The SEV chassis is equipped with 12 wheels that can pivot 360 degrees. This allows it to drive over rough terrain and to change direction quickly. The aft end of the chassis will allow tools such as cranes, cable reels, backhoes and winches to be attached23.

Summary of SEV specifications: 

  1. Speed: 19 km/h (12 mph)
  2. Range: 240 km (150 mi)
  3. Mass: 3,000 kg (6,614 lb.)
  4. Payload: 1,000 kg (2,205 lb.)
  5. Length: 4.5 m (180 in)
  6. Wheelbase: 4 m (160 in)
  7. Height: 3 m (120 in)
  8. Wheels: 12 cm (4.7 in) x 99 cm (39 in) in diameter, 30 cm (12 in) wide


Ascent Vehicle

The Mars Ascent Vehicle (MAV) will be landed on the surface along with prepositioned cargo and will not initially have a crew. They will only enter the MAV after the surface exploration is completed and just before ascending to the Transhab that will be circling in high Mars orbit The normal return route to Transhab will require 12 hours, but in the case of a missed takeoff opportunity it could be as much as 42 hours. The design criteria for the MAV took this contingency into account.

Ascent Vehicle

For the short trip to Transhab the following capabilities would be required: 

  1. 48 hours of shirtsleeve crewed systems checkouts prior to liftoff.
  2. Return 250 kg of cargo (i.e., soil samples) from the Martian surface.
  3. Ingress and egress from Mars surface.
  4. Launch from Mars surface.
  5. Operate in the vicinity of the Transhab.
  6. Dock with Transhab.
  7. In-space ingress and egress from Transhab via NASA docking hatch.
  8. Monitor and control the subsystems.


If the MAV ascent were to be more than 12 hours, the following additional capabilities will be required: 

  1.  Hands and face cleansing.
  2.  Waste disposal.
  3.  Consuming meals.
  4.  Sleeping.
  5.  Dressing and undressing.


Other features of the MAV: 

  1.  The crew will manually unlatch the MAV’s structural restraints from the base cargo vehicle – no pyrotechnics to be used.
  2.  Manual or remotely actuated tunnel between MAV and other surface modules, such as rovers.
  3.  Power, and fluids interfaces between the MAV and the Cargo Lander, particularly for ISRU fuel transfer.
  4.  Minimum power supplied by FSPS during long inactivity on the surface

Much of the bulk size of the MAV is due to the long contingency trip to Transhab. If this particular possibility is not included in the scenario, then the vehicle becomes much more trimmed down, particularly in the size of fuel and oxidizer tanks, as shown in the above figure.



Like colonization expeditions of past centuries, the colonization of Mars will be preceded by a period of exploration.  NASA has been planning for the exploration of Mars through a series of planning documents that specify the techniques to be employed as well as what facilities, vehicles and equipment will be required. A Mars pioneer should become knowledgeable about them because these equipment and vehicles will likely be employed in colonization.

In the NASA plan, six Astronaut/Explorers will be launched from Earth inside an Orion spacecraft atop the Space Launch System (SLS). Once in orbit they will transfer to Transhab, one of three components of a Mars Transfer Vehicle (MTV). The other components will be a Nuclear Thermal Rocket (NTR) propulsion system and a large, disposable fuel tank. Once in Mars orbit, the crew will transfer to a Mars habitat/lander that will place them onto the surface of Mars.

At the landing site the crew will engage with cargo that was pre-deployed to the same location. This will include an In-situ Resource Utilization (ISRU) plant to produce fuel and oxidizer for the return trip. It will also include a Fission Surface Power System (FSPS) to provide electrical power for the ISRU plant and for crew requirements.  The crew will deploy a two-man rover to explore Mars’ surface. After the mission is completed, they will launch inside a Mars Ascent Vehicle (MAV) that was previously landed with a cargo lander as a DAV. They will re-enter the Transhab for a long trip to Earth orbit, where they will land on Earth in an Orion capsule.



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  9.  “Human Exploration of Mars Design Reference Architecture 5.0 Addendum #2” (March 2014) NASA/SP-2009-566-ADD2, Retrieved 10-11-2014 from
  10.  Ref.8, p. 1.
  11.  Ref. 8, p. 1.
  12.  Ref. 7, p. 2
  13.  S. K. Borowski, D. R. McCurdy and T. W. Packard (2009) “’7-Launch’ NTR Space Transportation System for NASA’s Mars Design Reference Architecture (DRA) 5.0,” 45th Joint Propulsion Conference & Exhibit, August 2-5, 2009, American Institute of Aeronautics and Astronautics, AIAA-2009-5308.
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  16. “Space Launch System” (2012) NASA Facts FS-2012-06-59-MSFC, Retrieved 10-25-2014 from
  17.  Ref. 7, p. 21
  18.  Ref. 8, p. 26
  19.  “Space Launch System/interplanetary stage,” (Nov 2014) Wikipedia, Retrieved 11-4-2014 from
  20.   Ref. 9, p. 242, “Descent Module Design.”
  21.  Ref. 9, p. 387, ”Surface Power Systems.”
  22.  Ref. 8, p. 249, “Surface Systems.”




Appendix: Mars Mission Plan per DRA5 (2009)