Document
NASA/TM-2003-2124S9
Overview of Innovative Aircraft Power and
Propulsion Systems and Their Applications
for Planetary Exploration
Anthony Colozza Analex Corporation, Brook Park, Ohio Geoffrey Landis and Valerie Lyons Glenn Research Center, Cle ve land, Ohio
July 2003
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NASA/TM-2003-2124 S9
Overview of Innovative Aircraft Power and
Propulsion Systems and Their Applications
for Planetary Exploration
Anthony Colozza Analex Corporation, Brook Park, Ohio Geoffrey Landis and Valerie Lyons Glenn Research Center, Cleveland, Ohio Prepared for the International Air and Space Symposium and Exposition cosponsored by the American Institute of Aeronautics and Astronautics Dayton, Ohio, July 14-17, 2003 National Aeronautics and Space Administration Glenn Research Center
July 2003
Acknowledgments Tony Colozza 's work was supported b y the NASA Institute for Ad v anced Concepts (NIAC), under a grant with the Ohio Aerospace Institute and b y the NASA John H. Glenn Research Center.
Av ailable from NASA Cen t er for Aerospace Information National Technical Information Service 7121 St andard Drive 5285 Port Roy al Road Hano v er , MD 21076 Springfield , VA 22100 Available electronically at http: // gl tr s.grc.n asa . gov OVERVIEW OF INNOVATIVE AIRCRAFT POWER AND PROPULSION SYSTEMS AND THEIR APPLICATIONS FOR PLANETARY EXPLORATION Anthony Colozza Analex Corporation Brook Park, Ohio 44142 Phone: 216-433-5293 E-mail: anthony.colozza@grc.nasa.gov Geoffrey Landis and Valerie Lyons National Aeronautics and Space Administration Glenn Research Center Cleveland, Ohio 44135 E-mail: geoffrey.landi s@, nasa.gov, V aJ erie. J. L vons@nasa.gov ABSTRACT Pathfinder/Sojourner mission offered a new opportuni ty in that it was the first time that an autonomous mobile Planetary exploration may be enhanced by the use platform could be used for exploration. This allowed of aircraft for mobility. This paper reviews the scientists the freedom to explore the surrounding development of aircraft for planetary exploration terrain, maneuver to interesting sites, and perform an missions at NASA and reviews the power and anaJ ys is of soil and rock composition over a broader propulsion options for planetary aircraft. Several area. In short, the scientific community has many more advanced concepts fo r aircraft exploration, including options. However, the surface rover is limited by th e the use of in si tu resources, the possibility of a flexible terrain it is traversing: large rocks and canyons are all-solid-state aircraft, the use of entomopters on Mars, obstacles that are difficult for a surface rover to and the possibility of aero stat exploration of Titan, are overcome.
presented.
Airborne platforms can achieve science objectives that are difficult to achieve from orbit or from surface INTRODUCTION rovers. They can co ver much larger distances in a single Many technologies currently being developed for mission than a rover and are not limited by the terrain, unpiloted atmospheric vehicles (UAVs) and high- much more easily providing imaging of very rocky or aJtitude aircraft on Earth will be useful in the next steep terrain. Airborne platforms can return images of a magnitude higher resolution than state-of-the-art century for exploring other planets and moons that have enough atmosphere to support flying vehicle s. This orbiting spacecraft. Near infrared spectrometry, which is crucial to analyzing mineralogy on the planet, and paper gives an overview of some concepts for planetary exploration using advanced "rovers" that can fl y and high-spatial-resolution magnetometry, which may provide clues as to the origin of high-crustal magnetism cover m uch greater territory than th e current ground vehicles. se en from orbit, require moving platform s. The resolution and sensitivity of these instruments is further Although many planets and moons within our solar increased by being close to the surface. Finally, system have atmospheres capable of supporting winged atmospheric sampling can be accomplished over a far flight the majority of interest and analysis of the greater space, allowing scientists to study variations possibility of flight on other planets has been focused over a broad area.
on flight Mars.
Mars has been a target of scientific exploration for more than 25 years. Most of this exploration has taken HISTORY OF PLANETARY AIRCRAFT CONCEPTUAL DESIGN place using orbiting spacecraft or landers. Orbiters offer the ability to image large areas over an extended period The notion of flight on Mars has been a subject of of time but are limited in their resolution. Landers can NASA contemplation since Werner von Braun handle surface and atmospheric sampling, but are conceived a rocket plane as a means of Martian limited to th e immediate landing site. Mobility is the exploration in 19 53 . In the 1950s, Mars flight was ke y to expanding the scientific knowledge of Mars. The purely fancy, but in the 1970s, it was revisited more NASAfTM-2003 -212459 1 seriously, being spurred on by the successes of the National Labs conceived a high-speed aerospaceplane Viking Program. named AEROLUS. Unlike the earlier attempts to make a slow-speed aircraft that would be deployed from an One of the most studied airborne platforms for aeroshell after touchdown on the Martian surface, Mars is the airplane, with initial concepts dating back to AEROLUS would make a direct atmospheric entry and the late 1970s. Flying an airplane on Mars represents a then fly through the Martian atmosphere at hypersonic significant challenge, mainly because of the constraints speeds.
posed by the Mars environment. The lift on a wing is proportional to the atmospheric density, velocity, and Throughout the 1980s and early 1990s, a number wing area. The Mars atmospheric density is extremely of studies were conducted to examine various low, approximately 1170 that at the Earth's surface. In approaches to flight on Mars. These studies were order to compensate for this, the wing area and/or the conducted by NASA and various universities. An velocity must be increased to generate sufficient lift. example of some of this work was the long-endurance Wing area, however, is limited by packing, volume, and solar-powered Mars aircraft studied by NASA Glenn deployment constraints. Therefore, in order for flight to (ref. 2). An artist' s concept of this airplane is shown in be feasible on Mars, the plane must travel at higher figure 2. As a technology demonstration for this project, velocities to compensate for the lack of density and the a small model was successfully built and tested to fly in constrained wing area. Furthermore, the speed of sound the Earth' s atmosphere using only power produced by on Mars is approximately 20 percent less than on Earth. high-efficiency GaAs solar cells (refs. 3 to 5), as shown Both of these factors combine to put the plane in a low in figure 3.
Reynolds number, hlgh Mach number flight regime that is rarely encountered here on Earth. The high velocities limit imaging camera stability and resolution. Also, given the rocky Martian terrain, it is virtually impossible for a plane to land and take off again, thus limiting a mission to a single flight.
The NASA Dryden Research Center, Developmental Sciences, Inc., and the Jet Propulsion Laboratory (JPL) proposed unmanned aircraft designs for Mars exploration in 1977 and 1978 (ref. 1). Their concept was a propeller-driven fixed-wing aircraft fueled by hydrazine. This aircraft was based on the Mini-Sniffer high-altitude aircraft. A prototype of this aircraft was constructed and some testing was performed (fig. 1).
A decade later, JPL sponsored a Mars airplane study in which Aurora Flight Sciences proposed the Figure 2.-Artist 's concept of a proposed long- electrically propelled "Jason" aircraft. About the same endurance solar-powered Mars aircraft (ref. 2).
time, NASA Ames Research Center and Sandia
~ .I I
' - Figure 1.-Mini-Sniffer Hydrazine Engine-Powered Figure 3.-NASA Glenn solar-powered aircraft Mars Aircraft concept.
demonstrator (ref. 3).
NASAlTM- 2003-212459 2 -- -- ----- Successes with the Mars Pathfinder and Global Surveyor programs renewed interest in Mars flyers for exploration. In 1995, NASA Dryden and Ames Research Centers once again considered unmanned aerial vehicles to extend the reconnaissance range of Mars landers. The new concept was to launch a small unmanned aerial vehicle (VA V) from the lander after it had stabilized on the surface. The UA V would provide video of the immediate vicinity of the lander (within several thousand meters) to provide feedback as to the most interesting areas for investigation by ground-based rover s. The expendable, one-flight UA V would be electrically powered with rocket-assisted takeoff.
Figure 4.-JPL Kitty Hawk glider Mars aircraft In 1996, the Ames Research Center proposed an concept.
unmanned Mars aircraft in response to a NASA Announcement of Opportunity for Discovery Exploration Missions. Ames' approach was to use a propeller-driven, low-drag plane configuration that they called Airplane for Mars Exploration (AME). On the following NASA Announcement of Opportunity for Discovery Exploration Missions in 1998, JPL submitted a proposal for a multiple glider system (dubbed "Kitty Hawk ") with which several areas could be investigated during a single mission. This concept is shown in figure 4. As gliders, the vehicles were obviously limited in endurance but benefited from the lack of weight an d complexity associated with a propulsion system in return for redundancy of numbers. NASA Ames again proposed a motorized UA V, a concept named ''MAGE'' (fig. 5). This aircraft was based on a similar hydrazine propulsion system as the Mini-Sniffer concept. Both Figure S.-Artist 's concep t of the propose d Am es MAGE aircraft.
concepts deployed from an aeroshell once it had become subsonic, approximately 12 000 meters above the Martian surface. Again, neither concept was selected for the Discovery mission.
On February 1, 1999, NASA Director Daniel Goldin announced a "Mars Airplane Micromission," which would have been the first NASA micromission program to launch on an Ariane 5 rocket. The flight would have had the first Mars airplane arriving on the Red Planet arOlmd December of 2003 , coincidenta ll y close to the hundredth anniversary of the Wright Brothers' first flight. Although conceptual designs of the plane were completed, the project was cancelled without fanfare due to funding constraints.
The latest attempt at a Mars aircraft mission is the NASA Langley/JPL aerial regional-scale environmental survey (ARES) concept, being developed by NASA Ames Research Center, in collaboration with a number Fi gure 6.- The pr oposed ARES Scout mi ss ion Mars of other institutions including NASA Glenn and Aurora aircraft. Top: A rt ist's conceptio n of ARES a ir cra ft Flight Systems in Manassas, VA. This aircraft is rocket in rocket-powe red flight. Bo tt om: Aurora Fl i ght powered and is being proposed for the 2007 Mars Sciences half-scale ARES air cra ft test mode l in SCO UT mission. This concept is shown in figure 6.
flight at 30 km altitude (frame from tail-ca mera video).
NASAlTM- 2003-212459 3 POWER AND PR OPULSI ON SYSTEMS FOR • Combustion engine propulsion systems PLANETARY AIRCRAFT • Piston expander combustion • Four-cycle internal combustion For all aircraft, the characteristics and capabilities of the propulsion system are key elements in • Two-cycle internal combustion establisillng the aircraft' s feasibility and flight envelope • Rocket systems (refs. 6 and 7). Tills is especially true for an aircraft that • Bipropellant rocket propulsion is to fly on other planets. The planetary environment, as • Monopropellant rocket propulsion well as the launch from Earth and transit in deep space, • Unpowered systems (gliders) produces additional obstacles to an aircraft 's performance capabilities. Aircraft volume is critical Figures 7 and 8 show a basic concept and block- since the aircraft must be stowed and fit into an diagram for the electrical propulsion systems, using fuel aero shell capsule for transit and entry into the planetary cells or battery storage, respectively.
atmosphere. Therefore, propulsion system volume is Figure 9 shows the block diagram for the piston also critical and any components (such as a propeller) expander propulsion cycle, willie figure 10 summarizes that are large would also need to be stowed.
the internal combustion conceptual design.
Because of the unique flight environments of the The electrical and combustion-engine propulsion planetary environments, such as the thin atmosphere on systems both use propellers for propulsion, while the Mars, where the surface atmospheric density is rocket system uses a rocket engine directly. The glider comparable to that at 30 km (110 kft) here on Earth, or system uses the potential energy of the initial the cold environments of the outer planets, the ability to deployment altitude for propulsion; since planetary generate lift and operate the aircraft may be difficult.
exploration systems typicaJly start from orbit, in To compensate for unusual flight conditions, winged principle a large amount of energy is available.
aircraft may need to operate in ways different then on Earth in order to fly.
F or propeller systems, the propeller must be designed for operation in the planetary environment of For example, on Mars the aircraft would need to interest. For Mars, the low atmospheric density requires fly fast and limit its mass as mu ch as possible to a large propeller; the propeller operation is similar to compensate for the low atmospheric density; on Venus the operation of aircraft at altitudes on Earth of about the aircraft would need to be sealed from the corrosive 30 to 40 km (ref. 8).
environment and (for low-altitude flight) constructed of materials tolerant of illgh temperatures; and for the Each of these systems should be capable of outer planets, cold temperatures, low sunlight operating within all of the known atmospheric availability, and illgh gravity will drive the design. For environments within our solar system. The main all these environments and potential aircraft designs, drawback for these systems is their Limited duration.
the aircraft will be able to fly only as long as the Since all of these systems use consumable fuel or propulsion system can operate.
energy sources they will be limited in operational duration. However the technology for these systems is Without the ability to refuel, mission duration wiJl well understood and in many cases would require very be limited to the amount of energy that can be stored little development. Because of tills, the first generation and carried onboard the aircraft. Therefore, mission of aircraft for planetary exploration will most likely be duration will depend on the efficiency of the propulsion based on one or more of these types of propulsion system: the more efficient and lightweight the system systems.
is, the longer the mission and the more capable the aircraft.
Another constraint on each of these systems is that there is no readily available source of oxygen within There are four main types of conventional any known planetary atmosphere within our solar propulsion systems that can be considered for planetary system (outside of Earth). Because of this, these types flight. These main types of systems are of propulsion systems will need to be modified to • Electrical propulsion systems operate on a monopropellant fuel , like the Mini-Sniffer • Fuel cell power propulsion system discussed previousl y, or carry along an oxidizer.
• Battery-powered propulsion system • Solar propulsion ~ystem NASAffM-2003-212459 4 Vent System evaluated: Flow control Pressure regulator valve Hydrogen!
oxygen-fueled PEM Output Input -----l fuel cell stack
c:'·' _Il
i !
!
Fuel cell L..-_..,.J
b Pressure sensor
p~ - ~ Gearbox Electric Propeller
'"
'"
motor Motor controller Figure 7.-Fuel cell propulsion system layout.
Batteries
I
I
• Silver zinc • NiCd • Nickel hydrogen • Li-ion • Li thinyl chloride ~ "" Gearbox Electric • Li sulfur chloride Propeller motor
"
• Li oxyhalide • Li Mn 02 Motor controller Figure 8.-Battery-powered system layout.
NASAITM-2003-212459 5 • Can operate on monopropellants or bipropellants .1 . 62 kW/kg • SFC 0.37 kW-hr/kg (hydrazine) • Based on the Navy's torpedo motor • Requires full development Fuel • 7% thermal efficiency Propeller ,
/
Piston expander pyrovalve engine
!
pyrovalve "'..
From power system bus Pyrovalve Catalytic combustion --- chamber alternator To power / alternator system bus Fuel pump Monopropellant system Bipropellant system Figure g.-Piston expander propulsion system layout.
Figure 1 D. -Intemal combustion aircraft characteristics.
NASAffM-2003 -212459 6 No
~ Manual valve
No Nonnally closed
c(] Pressure regulator m Thermocouple pyrovalve
Ifil Pressure transducer
No Normally open _ Line filter ~ Check valve ~ Thruster onloff valve pyrovalve
¢ Pressure burst disk
,.0., Pressure relief
~ Bulkhead
[}::J Service valve
U valve
Figure 11.-Regulated rocket system layout.
SOLAR -PO WERED AmCRAFT FOR MARS AND SOLAR AIRCRAFf FOR MARS One option for exploration of the atmosphere of Mars is a solar-powered airplane. Fleets of solar- powered aircraft could provide an architecture for efficient and low-cost comprehensive coverage for a variety of scientific missions. For long (multiple day) flight duration, solar aircraft (ref. 2) will require storage, such as a battery, to enable operation during the night. However, a short-duration ilight, flying only during the daylight, could potentially be an extremely small and light airplane (ref. 9). A concept for such an Figure 12.-Mars solar a ir plane concept.
aircraft is shown in figure 12.
Solar aircraft operate on Mars at an atmospheric density equivalent to the atmosphere of Earth at 30 to 35 km above the surface. Since in the terrestrial flight regime solar-powered aircraft have successfully operated at this altitude (fig. 13), even at relatively high of Mars is less than that of sun-angles, and the gravity Earth, it is clear that operation of a solar aircraft on Mars is physically plausible. Analyses of the solar energy availability for flight on Earth and Mars can be Figure 13.-Aerovironment Pathfinder solar-powered found in references 10 to i2.
aircraft.
NASAfTM-2003-212459 7 Solar Venus Aircraft well as other planetary bodies with atmospheres. The The atmosphere of Venus provides sever al solar aircraft provides some significant benefits in that advantages for flying a solar - powered aircraft (refs. 13 its flight duration would be much longer then any to 15). At the top of the cloud level, the so lar intensity previously proposed aircraft, on the order of 7 days if is comparable to or greater than terrestrial solar the flight were to take place near one of the polar intensities. The atmospheric pressure makes fl ight regions. Figure 15 shows a schematic diagram of such much easier than on planets such as Mars. Also, the an inflatable-wing airplane in fo lded and unfolded slow rotation of Venus allows an airplane to be form.
designed for fl ight within continuous sunlight, Several inflatable-wing aircraft test models have eliminating the need for energy storage fo r nighttime been built and flown at NASA Dryden Research Center flight. These factors make Venus a prime choice for (ref. 16) as shown in figure 16. These models, with a long-duration so lar-powered aircraft. Fleets of solar- wingspan of slightly under 2 meters, have demonstrated powered aircraft could provide an architecture for inflation and transition to level flight at Earth efficient and low-cost comprehensive coverage for a atmospheric conditions.
variety of scientific missions.
Figure 14 shows a concept for a small solar- powered airplane deploying from an aeroshell and operating in the Venus atmosphere.
Inflatable Solar Aircraft for Polar Mars Exploration Inflatable structures integrated wi th thin-film photovoltaic arrays could be used to produce an aircraft for planetary exploration. It could be used on Mars as Figure 15.-Concept of an i nflatable-wing Mars ai rcraft , shown in deployed and partially folded configurat ion.
Figure 14 .-Deployment of a folding solar-powered Figure 16.-lnflatable-wing aircraft tests at NASA aircraft in the Venus atmosphere. The deployment Dryden Research Center (ref. 16). Top: two test of the flying surfaces is shown in the upper right: models of inflatable-w ing aircraft. Bottom: unfold ing (top ) folded configuration , (middle) tail unfold , of inflatable wing in flight.
(bottom ) w i ng panels unf old.
NASAffM-2003 -212459 8 "SOLID-STATE" AIRCRAFT back down to the starting altitude. This cycle is shown in figure 19.
Due to the recent advancements in photovoltaics, batteries, and polymer materials, a unique type of During gliding, the wing shape can be altered to unmanned aircraft may be feasible. This aircraft is a enable steering and control of the aircraft. This control "solid-state" aircraft with no moving parts (ref. 17). An mechanism is similar to that of gliding birds, changing artist rendering of the concept is shown in figure 17. the angle of attack and/or wing shape to produce The unique structure combines aerodynamic lift, directional lift on a given wing. This variation in shape propulsion, energy collection, energy storage, and can be achieved through a grid of electrodes that are control. Thin-film solar arrays are used to collect computer controlled. The voltage potential can be sunlight and produce power that is stored in a thin-film varied over the grid thereby tailoring the electric field lithium battery. This power is used to fly the aircraft by generated to produce a nonuniform bending in the setting up an electromagnetic field (EMF) along the wing. This variation in lift can be used to steer and wing of the vehicle. The wing, made with ionic control the aircraft. The force vectors generated by the polymeric-metal composite (IPMC) synthetic muscles, wing are shown in figure 20 for the upstroke and bends in the presence of this EMF producing the downstroke.
desired flapping motion. This layering of the various component materials is shown in figure 18 .
This aircraft would fly in a similar fashion to a hawk or eagle. It would glide for long distances and flap infrequently to regain altitude. The solid-state nature of the aircraft allows it to be very robust, extremely lightweight, and capable of flight unlike any other present day air vehicle.
This type of air vehicle has a number of potential applications as a research platform on Venus or Mars.
Because of its projected relatively small mass and flexibility, the aircraft is ideal for planetary exploration.
These characteristics allow the aircraft to be easily stowed and launched at a minimal cost.
A fleet of these aircraft could be deployed within a Fi gure 17.-Artist 's drawing of t he s olid - st ate air c ra ft planet' s atmosphere and used for comprehensive concept .
scientific data gathering/observation or as communications platforms. A whole planetary science gathering or communications/navigation architecture can be built around these lightweight, easily deployable, and robust aircraft.
The technology to produce this type of aircraft is presently available. There have been great advances in recent years in each of the three main components areas that make up the aircraft (thin-film photovoltaic arrays, thin-film batteries, and polymer composites). Because of these advances this type of aircraft may now be possible.
Vehicle Operation The unique material composition of the aircraft enables flapping motion of the wing to be utilized as the main means of propulsion thereby eliminating the need for a more conventional propulsion system. Figure 18 shows the layering of the "muscle" and "power" systems. The aircraft flight motion will consist of an intermittent flapping and periods of gliding. During the Figure 1 8.-Mai n component s and layout fo r t he flapping portion of the flight, the aircraft will gain solid-state air craft.
altitude. Then, during the gliding portion, will glide NASAITM-2003-212459 Beg in glide Glide du r at i on tg ----- Figure 19.-So lid- state aircraft flap cycle.
Resu lta nt Lift U ps tr oke Resultant fo rce relative Li ft for ce fr ee-s tr eam l veloc ity / Thr u s t-- ---- --~ ~
~ //
~ /
__ --......,L - -- Drag
//
,/ Downs tr oke relative .'
free-stream veloc ity Figure 20. -Ge neration of thrus t.
Combining the unique characteristics of the A control grid will be used to control the motion of the wing. This grid will enable various voltages to be materials enables flapping motion of the wing to be sent to different sections of the wing, thereby causing utilized to generate the main propulsive force. With a varying degrees of motion along the wing surface. The flight profile similar to a hawk or eagle, the solid-state amount of control on the wing will depend on the aircraft will be able to soar for long periods of time and fineness of this control grid. A central processor will be utilize flapping to regain lost altitude. By analyzing the used to control the potential of each of the sections to glide duration, flap duration, wing length, and wing motion of travel, it has been determined that a number produce the correct motion of the wings to sustain biomimetic flight. Figure 21 shows this grid control of design configurations can be produced to enable concept and the material layers of the wing. flight over a range of latitudes and times of the year on Earth, Venus, and Mars.
The most innovative aspect of this concept is the use of an ionic po lymeric-metal composite (IPMC) as Recent discoveries and developments in these the source of control and propulsion. This material has materials have indicated that this concept, on a preliminary level, may provide a robust advanced the unique capability of deforming in an electric field like an artificial muscle, and returning to its original aeronautical architecture suitable for both terrestrial and planetary missions (ref. 17 ).
shape when the field is removed. Combining the IPMC with emerging thin-film batteries and thin-film photovoltaics provides both energy source and storage in the same structure.
NASAffM-2003 -212459 10
~
I Battery
Anode
IPMC I
Cathode 7
Each grid location is individually co ntrollable.
Fi gure 21. -C o n1rol grid for gener at ing desired w ing mot ion.
IN SITU RESOURCE UTILIZATI ON (lS RU) therefore, is limited by the power available. Depending FOR MARS AIRCRAFT on the power supply available, this may require days to months.
For Mars flight systems that use consumable fuels for the propulsion system, resupply of the consumable For winged vehicles on Mars, landing presents a must be accomplished for a repeat flight. For example, significant difficulty. For example, the aircraft proposed a combustion engine will require resupply of the fuel for the Mars Scout mission requires an airspeed of and of the oxidizer. Resupply can be done by 130 m/sec (290 mph) for level flight. Achieving a manufacture of fuel from locally available materials, a successful landing without damage at 130 m/sec on an process known as ISRU. unprepared runway is a difficult probl em. A refuelable aircraft needs to incorporate a low-speed, preferably On Mars, a globally available resource for ISRU is vertical, landing.
the carbon dioxide atmosphere. Other resources include water in the form of atmospheric water vapor, One possible system for such landing is the Mars permafrost, or water ice "snow" on the polar caps.
entomopter concept, discussed in the next section.
Several processes have been proposed to chemically Another approach to flight of a refuel able vehicle is the process Mars atmosphere into propellant. Possible Mars hopper concept proposed by Landis and Linne propellants produced include carbon-monoxide/ox'j'gen, (ref. 18). In this flight concept, a vertical-takeoff, a fuel combination that can be manufactured from Mars vertica l- landing rocket-powered vehicle is used. The atmosphere with no external consumables required, and rocket fuel is generated between hops by production of which can be burned in a rocket engine. Prope ll ants carbon-monoxide/oxygen propellant by use of a solid- such as methane/oxygen and higher hydrocarbons or oxide electrolysis process on the carbon dioxide alcohols are also possible fuels that can be produced atmosphere. Such a vehicle could hop over rugged from Mars resources, but either require a source of terrain and land at a number of interesting scientific hydrogen or water, or else must use hydrogen brought sites. A rocket-powered landing could also be used for a from Earth as a consumable. winged airplane, allowing a low-velocity controlled vertical landing under rocket power. The vehicle could Use of in situ resources will require that the aircraft then use either a vertical or horizontal takeoff, again land on the surface for the duration of time required to under rocket power, to achieve airspeed for either manufacture propellant for the next flight. In essence, powered or gliding flight.
fuel production is a process of fixing energy into chemical form. The rate of propellant manufacture, NASAlT M-2003-212459 ENTOMOPTER CONCEPT For the entomopter to fly, it will need to flap its wings at a specified rate, thereby producing and The very low atmospheric density on Mars poses a shedding the vortices that will generate the lift. The significant problem for conventional aircraft designs. In motion of the wings is a fairly power intensive process order to generate sufficient lift, the aircraft must fly so a given flight mission for the entomopter will be fast. That fact and the rough rock strewn surface of short (on the order of 10 to 15 minutes). These short Mars makes it almost impossible to produce a flight times are due to the amount of fuel it is estimated conventional aircraft that can safely land and take off the entomopter can carry. Because of these short flight again. Therefore, all previously proposed aircraft times, the entomopter would need to be operated as part missions have been limited in duration to the amount of of a system. It is envisioned that this system would fuel the aircraft could carry for one flight.
consist of one or more entomopter vehicles that operate The entomopter (insect-wing) concept is a potential in conjunction with a base vehicle such as a lander or way around this problem of having to fly very fast rover. This base vehicle would provide refueling within the atmosphere of Mars (refs. 19 and 20) by capability to the entomopters as well as act as a data using the low Reynolds number as an ally, rather than relay for the science data and samp les the entomopters as an enemy. The entomopter does not generate lift in collect.
the same fashion as a conventional aircraft. The The most promising scenario is to utilize the entomopter concept uses the same lift-generating means entomopter in conjunction with a rover. The rover that insects do here on Earth to generate lift within the would be capable of slowly moving over the Martian Mars environment. Unlike aircraft or birds, insects surface, while the entomopters fly off to investigate generate lift by the continuous formation and shedding areas inaccessible to the rover. The entomopters could of vortices on their wings. This vortex formation and also be used to guide the rover from the air, indicating shedding produces very high wing lift coefficients on the best path to traverse to scope out interesting terrain the order of 5 compared to maximum lift coefficients of or objects for the rover to further investigate.
1 to 1.2 for conventional airfoils. This very high lift generating capability is what allows insects to fly, In addition to acting as a scout for the rover, the hover, and maneuver as they do. entomopter could perform a number of science data- gathering tasks on its own. These tasks could include The investigation of the aerodynamics of insect surface imaging in the visible, infrared or other flight is still a new science and the mechanisms for how wavelengths; magnetic field mapping; atmospheric they fly are not completely understood. However, it is science; and surface sample collection and searching believed that their ability to generate these large for the chemical signs for life.
amounts of lift is a Reynolds-number-based phenomena. As Reynolds number increases, the ability For the entomopter to work within the Mars is diminished. environment it will need to be as lightweight and efficient as possible. This means that systems and This high lift-generating capability under low devices on the vehicle will need to perform more the Reynolds number flight conditions poses an interesting one task if possible. This multiple-use philosophy has solution to flight on Mars. Because of the low been integral to the design effort. It begins with the atmospheric density on Mars, a vehicle with a wing- propulsion system. The engine will decompose span on the order of 1 m would be in the same flight hydrazine (a monopropellant) to provide the power to Reynolds number regime as most insects are here on move the wings.
Earth. Because of this, it is conceivable to construct a vehicle that can fly near the surface of Mars (up to Hydrazine was chosen as the candidate fuel 100 s of m in altitude) and generate sufficient lift to because of its high energy density and the fact that it allow it to fly slow, maneuver easily, and land. This was a monopropelJant. Utilizing a monopropellant realization is the genesis for the entomopter concept for simplifies the fuel delivery and refueling systems by Mars. requiring one tank and filling nozzle. Also, hydrazine decomposes when passed over a catalyst, allowing for a The entomopter consists of a central fuselage that low-risk combustion scheme. The gas produced during houses the propulsion system, fuel , and all the decomposition of hydrazine will be used to produce instrumentation. On top of the tubular fuselage are two the wing motion through the reciprocating chemical sets of wings that oscillate 180 out of phase. These muscle engine.
wings provide the flapping motion that generates the lift for the vehicle. Beneath the vehicle are spring-loaded Once the exhaust leaves the engine, it is then legs that absorb energy during landing, assist in passed through the wing and blown out the trailing edge takeoffs, and stabilize the vehicle while on the ground. of the wings. This gas entrainment into the flow field NASAffM-2003 -212459 12 over the wing enables vortex stabilization and greatly AIRSHIP FOR PLANETARY EXPLORATION enhances the lifting capacity of the wing. It is estimated In addition to the aircraft concepts discussed that with the trailing edge blOwing, wing lift airships may also be useful for planetary exploration: coefficients of 10 or greater would be achievable. In Balloons (unpowered aerostats) have been proposed for addition to lift enhancement, the trailing edge blowing Mars exploration, and have been successfully used by will be used as a means of control for the entomopter.
the Russian Vega mission for Venus atmospheric The gas flow to each of the individual wings will be exploration. Airships (powered lighter than air vehicles) controlled to enable differential lift to be generated can be used for exploration for a number of interesting between the wings. To steer the entomopter, lift scientific missions.
variation through control of the trailing edge blowing For the outer gas giant planets, with primarily will be utilized to provide banking and pitching hydrogen atmospheres, airships will require heated gas moments.
for the lifting envelope. For a number of targets The communications system is another example of incl uding Venus (primarily carbon dioxide composition the implementation of the multiple-use philosophy. The of the atmosphere) and Titan (primarily nitrogen), communications system will utilize an ultrawide band airships can be made that use conventional lifting gas
cywB) signal for sending signals to and receiving
such as hydrogen or helium.
sIgnals from the base vehicle. The type of signal Saturn's moon Titan is considered as one of the provides large data transfer rates with very low power prime candidates for detection of extraterrestrial life. A consumption. In addition to communications, the UWB unique combination of dense atmosphere (more than signal can also be used for obstacle detection four times that of the Earth), low gravity (six times less establishing positioning between the entomopters and than on the Earth), and small temperature variations the base vehicle and altimetry. In addition to utilizing makes Titan almost ideal for studies with aerobots.
the communications system, a passive navigation and obstacle avoidance scheme has been devised that Remoteness from the Sun, as well as the opaque utilizes signals sent from the base vehicle to the atmosphere of Titan, makes nuclear energy the only entomopter. practical source of power. Remoteness from the Earth (- 10 AU (astronomical unit) and two-way light-time To power the communication system as well as all - 160 min) imposes restrictions on the data rates and of the electronics and payload will be supplied by a makes impractical any meaningful real-time control.
photovoitaic array and small rechargeable battery. The The super-pressure-powered aero bot (airship) and system provides adequate power for running all of the inflatable rover (aerover) concepts are prime lighter- systems as well as keep alive power for extended than-air (LTA) platforms. The aerobots can be used for periods of time if the entomopter is away from the base in situ studies of the surface while landing (aerover) or vehicle overnight.
winching down an instrumented surface platform In addition to optimizing the operation of the (powered aero bot) (refs. 20 and 21).
various systems and components of the entomopter, the The power system is one of the key components for wing motion itself has to be optimized to produce the successful operation of the Titan airship. This adequate lift while minimizing power consumption. To power will be used for the propulsion system, onboard determine the wing motion characteristics, a design of electronics, and payload. The power system selected for the wing structure had to be performed. The weight of the airship must be capable of meeting the power the wing itself is a critical aspect to the vehicle demands of the vario us systems as weJl as being able to optimization. The wing has to be rigid enough to operate within Titan ' s environmental conditions.
withstand the rapid acceleration/deceleration associated Because of the distance of Titan from the Sun with the flapping motion. However, the wing mass must
approximately 10 AU , the incident solar intensity i~
be minimized in order to limit the power consumption onJy 14.87 W-m • A thick atmospheric haze in the Titan and reduce wing structural loading.
atmosphere reduces this value even further to the point F or flight on Mars, an estimated vehicle size of that solar energy is not at all feasible for the airship. For 1.2-m wingspan and operational configuration of 6-Hz long-duration missions, the conventional power systems flapping frequency and 75 ° maximum flap angle would discussed previously would not be feasible .
be necessary. This would produce a total lifting This leaves a nuclear dynamic isotope system capacity of 2.5 kg and a cruse velocity of 14 mls. A based on the standard space-qualified radioisotope sequence of images visualizing the entomopter concept thermal generators (RTGs) as a particularly attractive on a mission flight are shown in figure 22.
NASAlfM-2003-212459 13 Figure 22.-Graphics visualization of Mars entomopter concept (refs. 19 and 20).
NASAffM-2003 -2124S9 14 option. This system does not require any fue l, and the waste heat provides a heat source for the other airship's systems. Also the dense atmosphere and low temperature are favorable for minimizing the radiator size for rejecting any waste heat from the system. A Stirling isotope system would be a good choice for this application due to the relatively low power levels needed.
A 55-W Stirling conversion system has been under development at the NASA Glenn Research Center. A layout of two 55-W converters is shown in figure 23.
Operating at a 570 °C temperature difference between a 650 °C heat source and an 80 °C heat sink, each engine would be capable of producing 65 W of power with a direct thermal-to-electrical conversion efficiency of 27 percent ( ref . 22). Presently, the Stirling power system (including the converter and isotope heat source) has a specific power of greater then 4 W/kg. It is estimated that this specific power can be increased to 6 W/kg through proposed near term development work.
A 130 W system would produce approximately 350 W of waste heat that can be utilized to warm the electronics or other vehicle components. This wi ll require some kind of heat distribution system in the form of conduction paths or heat pipes.
There are several advantages to Venus exploration using airships. A Venus airShip could stationkeep over a given surface location in the comparatively co ol Figure 24.-An airc raft or airship in the coo l mi ddle middle atmosphere. Such an airship could in principle atmosphere of Venus could be used as the co m- serve as the "brains" for a relatively simple surface- mand and control element to operate a d um b r obot exploration robot, which would use high-temperature on the hot Venus surface.
electronics and sensors to explore the hot (460 °C) surface environment. This is shown conceptually in CONCLUSIONS figure 24.
Aircraft could expand the range and mobility of planetary probes, and give a new aerial perspective for planetary mapping. There are a large number of concepts for power and propulsion of such winged planetary explorers, and new technologies may allow the poss ib ility of advanced concepts, such as all-solid- state aircraft and entomopters, that could greatly expand the applicability of flight to new worlds.
Figure 23.- A 55-W fr ee -pi st on Stirling engine fo r planetary aircr a ft po w er (ref. 23 ).
NASAfTM- 2003-212459 REFERENCES 14. Landis, G. ; LaM arre, c. ; and Colozza, A.: Venus Atmospheric Ex ploration by Solar Aircraft. IAC 1. Reed, R.D .: High-Flying Mini-Sniffer RPV: Mars Paper 02-Q.4 .2.03 , 53rd International Bound. Astronautics and Aeronautics, vol. 16 , Astronautical Congress/2002 World Space no. 6, 1978, pp.26-39 .
Congress, Houston, TX , Oct. 10 - 19 , 2002.
2. Colozza, A.J .: Preliminary Design of a Long- 15. Landis, G.A.: Exploring Venus by Solar Airplane.
En durance Mars Aircraft. NASA CR - 185243, Presented at the STAIF Conference on Space 1990.
Ex ploration Technology, Albuquerque, NM , AlP 3. Scheiman, D.A. ; Brinker, D.J. ; Bents, D .l; and Conference Proceedings, vol. 552, Feb. 11-15, Colozza, AJ.: Design of a GaAs/Ge Solar Array 2001 , pp. 16-18.
for Unmanned Aerial Vehicles. NASA 16. Murray, l ; Pahle, l; Thornton, S .; Vogus, S. ; TM - 106870, 1994.
Frackowiak, T. ; Mello, l; and Norton, B .: Ground 4. Colozza, A.J. ; Scheiman, D.A. ; and Brinker, D. l: and Flight Evaluation of a Small-Scale Inflatable- GaAs/Ge Solar Powered Aircraft. NASAffM-98- Winged Aircraft. 40th AIAA Aerospace Sciences 208652, 1998.
Meeting and Exhibit, Reno, NY , Jan. 14-17, 2002.
5. Colozza, A.l ; Scheiman, D.A. ; and Brinker, D.J.: 17 . Colozza A.J.: Solid State Aircraft. Phase I Final GaAs/Ge Solar Powered Aircraft. NASAffM-98- Report, prepared for NASA Institute for Advanced 208652, 1998.
Concepts, Nov. 2002.
6. Colozza, A.J.: Eff ect of Power System Technology 18. Landis, G. ; and Linne, D. : A Mars Rocket Vehicle and Mission Requirements on High Altitude Long With In-situ Propellant Production. AIAA Journal Duration Aircraft. NASA CR-194455, 1994.
of Spacecraft and Rockets, (AIAA- 2000-3120), vol. 38, no. 5, Sept.-Oct. 2001 , pp. 730-735.
7. Colozza, A.J. ; Miller, c.J.; Reed, B.D .; Kohout, L.L.; and Loyselle, P.L.: Overview of Propulsion 19. Colozza A.l: Planetary Ex ploration Us ing Systems for a Mars Aircraft. NASAITM- 2001- Biomimetics. Phase I Final Report, prepared for 210575, 2001.
NASA Institute for Advanced Concepts, 8. Colozza, A.J.: High Altitude Propeller Design and Aug. 2000.
Analysis Overview. NASA/ CR -98 -208520, 1998.
20. Colozza A.l: Planetary Ex ploration Us ing 9. Landis, G. ; and Colozza, A. : Small Solar Airplane Biomimetics. Phase II Final Report, prepared for for Mars Exploration. To be presented at the AIAA NASA Institute for Advanced Concepts, Oct. 2002.
Space 2003 Conference, Long Beach, CA, 2003 .
2 1. Hall, lL. ; Kerzhanovich, V.V. ; Jones, J. ; Cutts, J. ; Yavrouian, A.l ; Colozza, A. ; and Lorenz, R. : 10. Lamp, T.R.; Reinhardt, K.C. ; and Colozza, A.J.: Performance Analysis for Solar Powered Titan Airship Ex plorer. IEEE Aerospace Unmanned Aerial Vehicles. ASME Paper Conference, Mar. 2002 .
96-WAIAES-5. Paper presented at the 1996 22. Kerzhanovich, V. ; Yavrouian, A. ; Cutts, l ; ASME International Mechanical Engineering Colozza, A. ; and Fa irbrother, D .: Titan Airship Congress & Exhibition, 1996.
Surveyor. Program Forum on Innovative 11. Colozza, A.J.: Effect of Date and Location on Approaches to Outer Planetary Ex ploration 2001 - 2020, Feb. 2001 .
Maximum Achievable Altitude for a Solar Powered Aircraft. NASA CR - 202326, 1997.
23. Shaltens, R .: Stirling Radioisotope Generator for NASA Space Science Missions. Project Summary: 12. Lamp, T .R.; Reinhardt, K.c. ; and Colozza, A.J.: Photovoltaic Power for Long Endurance NASA Glenn Research Center, M- OS97-4, July 2001.
Unmanned Aerial Vehicles. Aero Propulsion and Power Directorate, Wright Laboratory, Wright- Patterson AFB Report, 1997.
13 . Landis, G. ; LaMarre, c. ; and Colozza, A.: Atmospheric Flight on Venus: A Conceptual Design. AIAA Paper 2002-0819, to be published in Journal of Spacecraft and Rockets, vol. 40, no. 3, 2003.
NASAffM-2003 -212459 16
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1. AGENCY USE ONLY (Leave blank) 12 . REPORT DATE 13. REPORT TYPE AND DATES COVERED July 2003 Technical Memorandum 4. TITLE AND SUBTITLE 5. FUNDING NUMBERS Overview of Innovative Aircraft Power and Propulsion Systems and Their Applications for Planetary Exploration vrBS-22-755-04-02 6. AU THOR (S) Anthony Colozza, Geoffrey Landis, and Valerie Lyons 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) 8. PERFORMING ORGAN IZATI ON REPOR T NUMBER National Aeronautics and Space Administration John H. Glenn Research Center at Lewis Field E-13998 Cleveland, Ohio 44135-3191 9. SPONSORINGIMONITORING AGENCY NAME(S) AND ADDRESS(ES) 10 . SPONSORINGIMONITORING AGENCY REPORT NUMBER National Aeronautics and Space Administration Washington, DC 20546-0001 NASA TM-2003-212459 11. SUPPLEMENTARY NOTES Prepared for the International Air and Space Symposium and Exposition cosponsored by the American Institute of Aeronautics and Astronautics, Dayton, Ohio, July 14-17, 2003. Anthony Colozza, Analex Corporation, Brook Park, Ohio 44142; and Geoffrey Landis and Valerie Lyons, NASA Glenn Research Center. Responsible person, Geoffrey Landis, organization code 5410, 216-433-2238.
12a. DISTRIBUTION/AVAILABILITY STATEMENT 12b. DISTRIBUTION CODE Unclassified -·Unlimited Subject Category: 91 Distribution: Standard Available electronically at http://gltrs.grc.nasa.gov This publication is available from the NASA Center for AeroSpace Wormation , 301-621-0390.
13. ABSTRACT (Maximum 200 words) Planetary exploration may be enhanced by the use of aircraft for mobility. This paper reviews the development of aircraft for planetary exploration missions at NASA and reviews the power and propulsion options for planetary aircraft.
Several advanced concepts for aircraft exploration, including the use of in situ resources, the possibility of a flexible all- solid-state aircraft, the use of entomopters on Mars, and th e possibility of aero stat exploration of Titan are presented.
NUMBER OF PAGES 14. SUBJECT TERMS 15 .
Venus (planet); Venus; Aircraft 16 . PRICE CODE 17 . SECURITY CLASSIFICATION 18. SECURITY CLASSIFICATION 19. SECURITY CLASSIFICATION 20. LIMITATION OF ABSTRACT OF REPORT OF THIS PAGE OF ABSTRACT Unclassified Unclassified Unclassified NSN 754 0-01-280-5500 Standard Form 298 (Rev. 2-89) Prescribed by ANSI Std . Z39-18 298-102 I