With a focus on building the archetypal missions for NASA’s new Space Launch System rocket, the U.S.-based Boeing Corporation has outlined their view of what technologies can be used to accomplish humankind’s goal of visiting crews to the Martian system – missions Boeing believes are possible through the combination of the SLS rocket’s lift capability, the bourgeoning Solar Electric Propulsion technology field, and Bigelow’s soon-to-be-tested inflatable habitat modules.
From the Earth-Moon system to Mars:
Continuing from their initial presentation on potential SLS rocket uses beyond the opening two circumlunar missions, the Boeing Corporation has presented their idea of how to execute a phased approach to deep space exploration – with an eye for the eventual goal of landing human beings on the surface of Mars.
The approach, as outlined in the company’s “The Space Launch System Capabilities for Enabling Crewed Lunar and Mars Exploration” presentation available on L2, follows from the EMLP (Earth-Moon Lagrangian Point) platform – otherwise known as the L2 Gateway – to be used for lunar sortie operations and relies heavily on that lunar mission architecture to extend to Mars exploration operations.
The connection between the lunar missions and the proposed Mars missions would be made through a phased exploration approach that would utilize the technologies of the lunar sortie missions and the EMLP platform to see a “cycling [of] systems between the moon and EMLP [to] demonstrate long-term operations with in-space systems and provide the operational experience needed for longer duration missions.”
This EMLP platform would, in short, serve as the base of operations for the vehicle that will, under Boeing’s presentation, take humanity to Mars.
The Mars Transfer Vehicle – To Mars with heritage technologies:
Taking into consideration the already-acknowledge difficulties of mounting a crewed mission to Mars – not the least of which being the distance involved, the time to get a crew to Mars and back, and the harsh environment of the inner solar beyond Earth’s protective geomagnetic field – there is another ‘given’ for crewed missions to Mars.
The vehicle that will take us to the Red Planet will have to be constructed on Earth and then assembled in space.
Skillfully, the world’s prominent spacefaring nations have already gained invaluable information and practice in assembling a large Earth-constructed, space-assembled vehicle with NASA, RSA (Russian federal Space Agency), ESA (European Space Agency), CSA (Canadian Space Agency), and JAXA’s (Japan Aerospace and eXploration Agency’s) contributions and missions to the International Space Station.
Taking those lessons learned during construction of the ISS and applying them to the eventual Mars Transfer Vehicle (MTV) will allow all nations involved in what is shaping up to most-certainly be an international effort to land humans on Mars to capitalize on past best practices while still employing new technologies and innovations.
One of those “new technologies and innovations” proposed by Boeing for use as part of the MTV is an inflatable Crew Transfer Habitation (CTH) module based on Bigelow’s soon-to-be-tested inflatable module for the ISS in 2015.
Under this design, an evolved SLS rocket would be used to launch the CTH into Low Earth Orbit (LEO) along with all of the other elements that will make up the core of the MTV – including all the technology and hardware required for the Solar Electric Propulsion (SEP) stage of the complex.
Once in LEO, the CTH would be inflated and the SEP stage’s solar arrays deployed. Checkout operations would follow, with full confirmation of operational systems by ground personnel before the MTV would be allowed to self-ferry to the EMLP platform.
This self-ferry would be accomplished using MTV propulsion – a Solar Electric Propulsion system utilizing either Xenon or Krypton gas.
Under this system of propulsion, the MTV’s SEP stage (SEP more colloquially referred to as ion propulsion) would contain a series of thrusters that would fall into one of the following three categories of electric propulsion: electrothermal, electrostatic, or electromagnetic.
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Electrothermal propulsion, as used in resistojets and arcjets, is achieved by the acceleration of a propellant gas via the application of electrical heat and the resultant expansion of the propellant gas through a convergent/divergent nozzle.
Electrostatic propulsion, on the other hand, is achieved by applying an electric field to an ionized propellant gas – as seen on gridded ion thrusters, colloid thrusters, and Field Emission Electric Propulsion units.
This kind of SEP actually produces the highest specific impulse capability – through the gridded ion thrusters – of an operational 3000 s.
Conversely, electromagnetic propulsion uses the application of both magnetic and electric fields to accelerate ionized plasma gas for use in Hall thrusters, pulsed plasma thrusters, pulsed inductive thrusters, and magnetoplasmadynamic thrusters.
SEP is often viewed as superior to traditional-based chemical propulsion because unlike chemical propulsion, SEP is not limited to an internal power source (a chemical propellant) that must be carried with the spacecraft at all times.
Instead, SEP is achieved through an external power source.
In the case of MTV, this external energy would be the solar energy captured by the MTV’s SEP stage’s solar arrays.
The arrays, like those on the ISS, would be photovoltaic solar panels that would derive electricity from sunlight.
The electricity from the arrays would then be used to not only power the SEP but also to provide the power to the MTV as a whole.
(NOTE: To date, at least 68 spacecraft have used a form of SEP in their operations, including NASA’s Dawn spacecraft – which stands to become the first spacecraft to enter into orbit of two different celestial bodies because of its SEP systems – and JAXA’s Hayabusa spacecraft.)
For the Boeing-proposed MTV, once the SEP transfers the MTV to the EMLP platform, a total of three Mars mission options would be available (all three of which would utilize the MTV): a crewed mission to Mars’s moon Phobos, an uncrewed cargo lander mission to stage a living habitat and supplies on the surface of Mars, and a crewed Mars surface landing mission.
Crewed mission to Phobos:
With the MTV safely at the EMLP platform, another evolved SLS rocket would be launched with a crewed MPCV (Multi-Purpose Crew Vehicle – Orion), an In-Space Stage (chemical propulsion unit), and a top-off supply of xenon or krypton for the MTV’s SEP system.
The MPCV with crew and In-Space Stage would then rendezvous with and dock to the EMLP platform. The crew would then perform final checkouts of the MTV before docking the In-Space Stage and the MPCV to the MTV.
After this, the entire MTV – with MPCV, CTH, and In-Space Stage – would separate from the EMLP platform, and the In-Space Stage would fire to boost the complex into its Trans-Mars Injection (TMI) trajectory.
Once the In-Space Stage’s chemical fuel was expended, the stage would be jettisoned, and the MTV’s SEP systems activated to propel the MTV to Mars.
Arrival at Mars would occur a few months later with a propulsive capture of Mars by the MTV via the SEP – which would subsequently place the MTV into a High Mars Orbit (HMO) before slowly spiraling the MTV down into a Low Mars/Phobos Orbit (LMO).
Once in LMO, the MTV and crew – again, through use of SEP – would rendezvous with Phobos, potentially at Phobos’s Stickney crater which could provide additional and natural radiation shielding for the crew.
Once at Phobos, the crew would explore the surface of Phobos from the MTV CTH and “teleoperate Mars surface assets in real time.”
Once Phobos operations were complete, the SEP would take the MTV back into a HMO and then propel the MTV out of Mars orbit and back onto a return trajectory to Earth.
The MTV would arrive back at the EMLP platform where it would be docked. The crew would then board the MPCV and return to Earth. Once back at the EMLP, the MTV’s systems would be refurbished and prepared for the vehicle’s next trip to Mars.
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Currently, Boeing estimates that the MTV, SEP, and CTH systems could be capable of achieving a 12 year lifetime. If this comes to pass, the MTV would be used for multiple missions to Mars – thus significantly reducing programmatic costs compared to architectures calling for non-reusable MTVs and crew habitats.
Uncrewed Mars surface cargo mission:
Under this proposed mission, an evolved SLS rocket would be used to launch a Mars Cargo Lander (MCaL) with attached In-Space Stage into LEO – with the MCaL then ferried by the In-Space Stage to the EMLP platform and the MTV.
Under this configuration, the MTV’s CTH would be removed and the MCaL attached instead.
With this plan, the MCaLs would serve not only as stock pile locations for crew supplies and storage but would also serve as the primary habitats for Mars crew surface operations.
Departing from the EMLP, the MTV would use the In-Space Stage to transfer itself into a TMI trajectory. After fuel exhaustion, the In-Space Stage would be jettisoned and the MTV’s SEP would carry the uncrewed vehicle to Mars.
After attaining Mars orbit, the MCaL would separate from the MTV and descend to the Martian surface.
Once safely on the surface, the MCaL’s cylindrical surface would be raised and its habitatable volume inflated – again capitalizing off Bigelow’s inflatable habitat technology.
The MTV would then return to the EMLP platform for refurbishment and reuse.
Crewed mission to Martian surface:
The coup de grace.
Launching aboard an evolved SLS rocket, the Martian surface crew would carry to LEO with them an In-Space Stage. A Mars Crew Lander (MCL) would be launched beforehand and transferred to the MTV at the EMLP platform.
After propelling themselves to the MTV, the crew would transfer SEP xenon or krypton resupplies to the MTV, check out the craft’s systems, attach the MPCV, MCL, and In-Space Stage to the MTV, and prepare for their journey to the Red Planet.
After using the In-Space Stage for the TMI burn, the In-Space Stage would be jettisoned, and the MTV would use its own SEP to sail to Mars.
After achieving Mars orbit, the crew would board the MCL and descend to the Martian surface near the already-present MCaL.
During landing, Boeing states that the crew would “land on Mars with ascent and decent stages with CH4 engines, tankage, and other lander systems that demonstrate heritage” from the Boeing-proposed lunar architecture missions.
After safely landing on Mars, the crew would transfer to the MCaL, where they would live and work for the duration of Mars surface operations.
After completing their mission, the crew would transfer back the MCL and ascend to Mars orbit, where they would rendezvous with the MTV.
The MTV’s SEP would then take the craft out of Mars orbit and place it on a return trajectory to the EMLP platform.
Once back at the EMLP platform, the crew would board the MPCV and return to Earth.
(Images: Via Boeing and L2 content from L2’s SLS specific L2 section, which includes, presentations, videos, graphics and internal – interactive with actual SLS engineers – updates on the SLS and HLV, available on no other site. Other image via NASA).
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