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| The Project Hyreus mission emblem. Image credit: University of Washington Department of Aeronautics and Astronautics. |
In Greek mythology Hyreus (pronounced "HY-ree-us") is Orion's father. Students in the University of Washington (UW) Department of Aeronautics and Astronautics had a different take on this obscure figure, however. The end of the Cold War and efforts to rein in a galloping U.S. Federal deficit yielded a decline in aerospace spending in the late 1980s/early 1990s. This led to "downsizing" and corporate mergers in aerospace industry. New hires slumped, confronting aerospace engineering students with an uncertain future.
According to the 28 UW students who contributed to the 1993 Project Hyreus report, Hyreus (pronounced "HIRE-us") was a mortal who succeeded in living off the land in the barren underworld, and for that achievement was made the God of Gainful Employment. The students performed the Project Hyreus Mars Sample Return (MSR) study in UW's Space Systems Design course as part of the NASA/Universities Space Research Association (USRA) Advanced Design Program (ADP). Dr. Adam Bruckner was their instructor.
Hyreus was a follow-on to UW's 1992 Project Minerva NASA/USRA ADP study, which proposed a piloted Mars expedition based on the 1990 Martin Marietta Mars Direct plan. The Minerva study had found feasible Mars Direct's reliance on Earth-return rocket propellants manufactured from martian resources, a technique called In Situ Propellant Production (ISPP). In the Mars Direct, Minerva, and Hyreus plans, ISPP relied on carbon dioxide gas in the martian atmosphere because it is readily available all over the planet. Carbon dioxide makes up about 95% of the martian atmosphere, which is only about 1% as dense as Earth's atmosphere.
The UW students emphasized a Sabatier/Reverse Water-Gas Shift (RWGS) ISPP system, which would produce liquid methane fuel and liquid oxygen oxidizer, though they also examined a carbon monoxide ISPP system. The UW students explained that Hyreus aimed to demonstrate ISPP technology in a critical mission role at a relatively low cost ahead of a piloted ISPP Mars mission.
Assuming that Hyreus succeeded, the mission would exploit the mission-enhancement potential of ISPP by returning to Earth a Mars surface sample with a mass of from 25 to 30 kilograms — that is, one more than 10 times larger than in most other MSR proposals. Analysis of such a large sample would enable scientists to locate water deposits and seek life on Mars, the students contended.
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| Hyreus Sabatier/Reverse Water-Gas Shift (RWGS) In Situ Propellant Production (ISPP) system. Image credit: University of Washington Department of Aeronautics and Astronautics. |
The 400-kilogram Sabatier/RWGS ISPP plant would need a total 122 kilograms of cryogenic liquid hydrogen feedstock brought from Earth. The hydrogen would gradually boil and escape, so Hyreus would depart Earth with an extra 88 kilograms on board to make up for losses.
The Sabatier/RWGS plant would take in dust-laden martian air at a rate of 9.6 kilograms per day. The air would pass through a hydrocyclone dust filter to a compressor, then to a condenser that would liquify its carbon dioxide. Residual trace gases (nitrogen and argon) would be vented overboard, and the carbon dioxide would be pumped to the ISPP unit. There it would be combined with 0.24 kilograms of liquid hydrogen feedstock per day to produce carbon monoxide gas and water.
The plant would vent the carbon monoxide overboard and pump the water to an electrolyzer, which would split it into gaseous hydrogen and oxygen. The oxygen, produced at a rate of 4.62 kilograms per day, would go to a liquifier, then to its final destination in the Earth Return Vehicle (ERV) oxidizer tank.
The hydrogen, meanwhile, would go to the Sabatier reactor, where it would be joined with martian carbon dioxide in the presence of a nickel or ruthenium catalyst to yield water and methane gas at a rate of 1.15 kilograms per day. The methane would go to a liquifier, then to the ERV's twin fuel tanks. The water, meanwhile, would return to the electrolyzer. Over 1.4 years the Sabatier/RWGS ISPP system would produce 480 kilograms of methane and 1921 kilograms of oxygen for the ERV's single rocket engine.
The students found that the carbon monoxide ISPP system had two advantages over the Sabatier/RWGS system: it would need no Earth-supplied feedstock and would be smaller, simpler, and less massive (just 300 kilograms). On the other hand, the carbon monoxide and oxygen it produced constituted a propellant combination less efficient than methane/oxygen. This meant that the carbon monoxide ISPP plant would need to manufacture 3440 kilograms of carbon monoxide and 1960 kilograms of oxygen to make up for the reduced performance.
Both ISPP systems would rely for electricity on a nuclear-fueled Dynamic Isotope Power System (DIPS) attached to the ERV. The DIPS would also power other MLV systems. The Sabatier/RWGS and carbon monoxide ISPP systems would draw from the DIPS 1.2 and 1.1 kilowatts of electricity, respectively.
Landing its hydrogen feedstock and heavy ISPP unit on Mars would mean the Sabatier/RWGS Hyreus spacecraft would need a sturdier lander structure, a larger aerobrake, larger parachutes, and more landing propellant than the carbon monoxide Hyreus spacecraft. The carbon monoxide Hyreus would, on the other hand, need a larger ERV to enable it to hold enough carbon monoxide/oxygen propellants to reach Earth. The students calculated that the Sabatier/RWGS Hyreus would have a mass of 4495 kilograms at launch from Earth; the carbon monoxide Hyreus mass would total 4030 kilograms.
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| Hyreus "raked sphere-cone" aerobrake. Image credit: University of Washington Department of Aeronautics and Astronautics. |
At launch, the Hyreus spacecraft would comprise an aerobrake and a Mars Landing Vehicle (MLV) bearing the Satellite Observation and Communication at Mars (SOCM) orbiter, Special Planetary Observation Transport (SPOT) rover, and the ERV. Hyreus would leave Earth between 22 May and 20 June 2003 on a $400-million, 940-metric-ton Titan IV/Centaur rocket, the most powerful U.S. launcher expected to be available.
Two solid-propellant rocket motors would boost the Titan IV off the launch pad, then the first stage would kick in a little more than two minutes after liftoff. During first-stage operation, the 7.5-meter-diameter launch shroud would split and fall away, exposing Hyreus atop the Centaur upper stage. After Titan IV second stage separation, the Centaur would fire to place itself and the Hyreus spacecraft into parking orbit 300 kilometers above Earth.
The Hyreus aerobrake would include two folding "flaps" so that it could fit within the confines of the Titan IV launch shroud. After arrival in parking orbit, the flaps would hinge into place and lock to give the 11.3-meter-long aerobrake its full 9.4-meter width. The students chose a "raked sphere-cone" aerobrake over one with a biconic shape because it would be 20% lighter and have an open back that would offer more options for deploying the SOCM orbiter.
A second Centaur burn would push Hyreus out of parking orbit toward Mars, then the Centaur would detach and fire its engine a final time to avoid striking and contaminating the planet. Depending on the exact Earth launch date, Earth-Mars transfer would last from 188 to 217 days. Hyreus would perform course corrections during the transfer using the MLV's four descent rocket motors.
On 25 December 2003, Hyreus would enter the atmosphere of Mars traveling at 5.69 kilometers per second. Aerodynamic drag would slow the spacecraft so Mars's gravity could capture it into the desired near-polar orbit. Hyreus would descend to an altitude of 55 kilometers, then would skip out of the atmosphere and climb to apoapsis (the high point of its orbit) 2470 kilometers above Mars. There the MLV descent rockets would ignite briefly to lift the spacecraft's periapsis (the low point of its orbit) out of the atmosphere to an altitude of 250 kilometers.
Mars would rotate beneath the orbiting Hyreus spacecraft, gradually positioning the selected landing site so that descent could begin. A second apoapsis burn would put Hyreus on course for its second aerobraking maneuver, which would place it into an orbit with a 580-kilometer-high apoapsis and a periapsis beneath the martian surface near the planned landing site.
Following the second apoapsis burn, Hyreus would deploy the 282-kilogram SOCM orbiter. After deployment, SOCM would fire thrusters to raise its periapsis to 580 kilometers and circularize its orbit. The solar-powered SOCM would carry a Ground-Penetrating Radar to seek subsurface water and a wide-angle camera for monitoring weather at the MLV landing site. The orbiter would transmit its data to the MLV for relay to Earth.
After the second apopasis burn, the Hyreus spacecraft would fall toward its landing site. The students proposed three candidate sites within 15° of the martian equator. Near-equatorial sites were preferred, they argued, because the planet's rotation would give the ERV an extra boost when the time came for it to lift off from the planet. All of the landing sites included smooth areas large enough to permit a safe off-target landing, as well as a variety of sampling sites within rover range (~20 kilometers) of the MLV.
The UW students' prime Hyreus landing site was at 148.1° W, 13.8° S in Mangala Valles, a 350-kilometer-long outflow channel. In addition to the channel itself, Mangala included young volcanoes, ancient rocks, and young and old impact craters. The first backup Hyreus site was at 63° W, 16° N in Valles Marineris, a system of wide, deep canyons with horizontally layered walls. The second backup, at 45° W, 20° N, was in Chryse Planitia, an ancient flood plain near the site where Viking 1 set down on 20 July 1976. The students noted that a visit to the derelict Viking 1 lander "would offer the chance to get first hand analysis of the aeolian and other weather effects on the lander over the 20 years it has been there."
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| Hyreus Mars Landing Vehicle (MLV) entry, descent, and landing. Image credit: University of Washington Department of Aeronautics and Astronautics. |
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| Hyreus MLV in Mars landing configuration. The drawing is somewhat inaccurate; by the time the MLV rested on its deployed landing gear on the surface of Mars the SOCM orbiter and parachute canister would be absent. Image credit: University of Washington Department of Aeronautics and Astronautics. |
The aerobrake would slow the Hyreus MLV to a speed of 220 meters per second 10 kilometers above Mars, then a tractor rocket would deploy the lander's first parachute. As it unfurled, explosive bolts would fire to jettison the aerobrake.
Two more parachutes would deploy eight kilometers above Mars. The parachute cluster would slow the MLV to 40 meters per second 500 meters above the landing site. Explosive bolts would then fire to jettison the MLV's upper structural frame and the attached parachute cluster, exposing the ERV. Four throttleable landing rockets would ignite a moment later.
The MLV would feel a maximum deceleration of 6.5 times Earth's gravity as its four footpads contacted Mars. At touchdown, the MLV would have a mass of 2650 kilograms.
Mars surface operations would last from 547 to 574 days. The Hyreus mission would focus on the three Mars surface activities. The first, ERV propellant loading, would begin immediately after landing. Controllers on Earth would check out and activate the Sabatier/RWGS ISPP plant. Valves would open to admit martian air into the hydrocyclone filter and release hydrogen feedstock. The electrolyzer would switch on after it filled with water, then the Sabatier reactor would activate after it received sufficient hydrogen from the electrolyzer. Unless a malfunction occurred, the ISPP plant would fill the ERV's propellant tanks without human intervention after it was switched on.
The second major Mars surface activity, sample acquisition, would be the primary task of the 185-kilogram SPOT rover. SPOT would comprise three sections one meter wide by 0.44 meters long joined by ball-and-socket joints. Each section would include one pair of 0.5-meter-diameter wire wheels. Hub-mounted electric motors would independently power the wheels on the front and middle sections, while the wheels on the rear ("trailer") section would be passive rollers.
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| Hyreus Special Planetary Observation Transport (SPOT) rover. Image credit: University of Washington Department of Aeronautics and Astronautics. |
SPOT's front section would carry a pair of cameras for science and navigation and a Remote Manipulator Arm (RMA) with four interchangeable sampling tools. These would include a scoop/grabber ("scoobber"). The trailer section would include a large drill for subsurface sampling. After SPOT collected a sample, it would seal it within a Cylindrical Sample Collection Cell (CSCC) and place it into a sample storage bay in its front section.
Upon return to the MLV, the SPOT RMA would hand the CSCCs one at a time to an RMA on the MLV for transfer to the ERV. The ERV would maintain the samples at martian ambient temperature to help keep them pristine.
The third area of Mars surface activity would be MLV science. The MLV would carry 57.1 kilograms of science equipment, including three exobiology experiments, a seismometer (to be deployed by SPOT at least 200 meters from the MLV so that vibration from the ISPP system would not interfere with it), a camera, a weather station, a mass spectrometer, and an RMA with 18 interchangeable tools.
After 1.4 years of operation, the Sabatier/RWGS ISPP plant would run out of hydrogen and shut down. Controllers on Earth would then prepare the ERV for liftoff. The primary launch window for Mars departure would span from 25 June to 21 July 2005. In the event of difficulties (for example, if ISPP needed more time than expected), then launch from Mars would be postponed until the 19 June-22 August 2007 launch window opened.
Explosive bolts would sever connections linking the ERV to the MLV, then the ERV's RL-10-derived engine would ignite to launch it into a 300-kilometer circular parking orbit about Mars. The ERV would orbit Mars until it reached the correct point in its orbit for Mars-Earth transfer orbit injection, then would ignite its engine again to put itself on course for Earth. During Mars-Earth transfer, it would position itself so that the Apollo-style bowl-shaped aerobrake on its Earth Return Capsule (ERC) would shade the samples from the Sun.
Assuming an on-time launch from Mars, the Hyreus ERV would reach Earth's vicinity on 31 March 2006. If launch were delayed to 2007, Earth arrival would occur on 29 April 2008. The battery-powered ERC would separate from the ERV, then the latter would fire its engine a final time to bend its course away from Earth. This Contamination and Collision Avoidance Maneuver would, the students wrote, prevent Mars dust and possible microbes on the ERV's exterior from reaching the homeworld.
Shielded by its aerobrake, the Hyreus ERC would enter Earth's upper atmosphere at a speed of 11.2 kilometers per second. Atmospheric drag would slow it to 7.8 kilometers per second so that Earth's gravity could capture it, then a brief rocket burn would circularize its orbit at 340 kilometers of altitude for recovery by a Space Shuttle orbiter.
The students acknowledged that direct ERC entry into Earth's atmosphere followed by a parachute descent to the surface would cost less than orbital recovery by a Shuttle, but opted for the latter because it would permit astronauts to safely study the Mars samples outside of Earth's biosphere. If their preliminary analysis indicated that the Mars samples posed a hazard to life on Earth, the Shuttle crew could attach the ERC to a Payload Assist Module solid-propellant rocket motor and dispose of it in deep space.
The UW students presented their Hyreus study in July 1993 at the 8th NASA/USRA ADP summer conference near NASA's Johnson Space Center (JSC) in Houston, Texas. Not coincidentally, NASA JSC and contractor engineers were also studying ISPP MSR mission designs at this time. They found the UW students' work sufficiently impressive to ask for a briefing at NASA JSC. NASA engineers subsequently cited the Hyreus report in NASA ISPP MSR documents. The God of Gainful Employment smiled upon the Hyreus students; several subsequently found jobs at NASA centers and with aerospace contractors.
Sources
"Mars Rover Sample Return Mission Utilizing In Situ Production of the Return Propellants," AIAA 93-2242, A. P. Bruckner, L. Nill, H. Schubert, B. Thill, and R. Warwick; paper presented at the AIAA/SAE/ASME/ASEE 29th Joint Propulsion Conference and Exhibit in Monterey, California, 28-30 June 1993.
Project Hyreus: Mars Sample Return Mission Utilizing In Situ Propellant Production Final Report, NASA/USRA Advanced Design Program, Department of Aeronautics and Astronautics, University of Washington, 31 July 1993.
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