The Heartbeat of the Mars Exploration Rovers 

An artist’s concept of the Mars Exploration Rovers.

In space, there is no place for a spacecraft to plug in a power cord. Not even with an adapter or wireless source of electricity.Traveling millions of miles from Earth, spacecraft must rely on the sources of power they carry onboard.

NASA’s Mars Exploration Rovers are no exception.

Both rovers, dubbed Spirit and Opportunity, are dependent on solar panels for power during daytime operations and advanced lithium ion rechargeable batteries for operations during the night. These batteries are advanced versions of those used in laptops, camcorders and cell phones. NASA researchers specifically designed and developed these power sources to operate efficiently at temperatures as low as -20?C (-4?F).

On any given day, NASA’s Mars rovers each require about 100 watts of steady power to operate — the same amount that illuminates a standard living room light bulb. This is in contrast to the Sojourner rover, whose solar arrays provided only 16 watts of power, about the same as an oven light. Sojourner used non-rechargeable lithium-thioinyl chloride batteries that eventually ran dry, leaving only the solar panels to fill its power needs. So NASA developed a new generation of battery that would add extra power when needed and store unused power.

The advanced lithium ion batteries will allow Spirit and Opportunity to perform on-site scientific investigations during the course of their 90-day missions and trek up to 40 meters (131 feet) per day.

Opportunity looks back at its landing site.

Building a Better Battery MER rechargeable batteries are based on lithium-ion chemistry, and are considerably different than that of the more traditional nickel-cadmium or nickel-hydrogen batteries that are used in other space missions. 

Beginning in 1994, researchers at the NASA’s Jet Propulsion Laboratory (JPL) began to develop low temperature rechargeable lithium ion batteries for space applications that could survive in the low, harsh, cold temperatures of space. The batteries needed to be able to handle temperatures as low as -30?C.

All batteries contain two electrodes — one positive and one negative. In the new lithium-ion batteries, the positive electrode (called a cathode) contains high-voltage lithium metal oxide and the negative electrode (called an anode) contains lithium intercalation carbon, which prevents volatile reactions by the highly reactive lithium metal. The batteries also contain an advanced organic electrolyte. Developed by JPL, the electrolyte was specifically designed to handle low temperatures, and is composed of lithium salt dissolved in a mixture of organic solvents.

In 1998, Air Force Research Laboratory (AFRL), JPL and NASA’s Glenn Research Center(GRC) formed a consortium to develop lithium ion cells for aerospace applications. Under this collaborative program, Lithion (a division of Yardney Technical Products) developed cells and qualified them for both aircraft and space applications.

Sunset on Mars.

In 2002, Lithion fabricated the rover batteries using the battery housings designed by JPL for rover applications. Each rover has two batteries, and they each have an energy content of about 300 WH and weigh about 8 pounds (3.1 kilograms). These lithium ion batteries offer 3-4 times mass and volume savings compared to the traditional Ni-Cd and Ni-H 2 batteries.The Long, Cold Night 
Solar panels can meet rover power needs during the day, but what happens when the sun goes down on Mars?

The sole source of power on a rover becomes its rechargeable battery, which allows the systems to survive the cold Martian night, and extreme temperatures of space. The Li-Ion batteries are also used during the day when a little extra juice is needed to add extra power to solar arrays when the rover is transmitting data from the Mars rover to Mars Odyssey orbiter.

To get the most out of the technology, the batteries are stored in warm “boxes,” which contain heaters to maintain the temperature of the batteries in the extremely low temperatures of space and on Mars. The solar arrays on top of the box attract sunlight as a source of energy and generate up to 140 watts of power. This stored energy will power the rover as it explores the planet’s surface.

The Mars Exploration Rover mission is the first major NASA planetary exploration mission to use the advanced lightweight rechargeable lithium-ion batteries, which are three to four times lighter than their nickel counterparts. In addition, the battery can last five times as long as the planned 90-day primary mission.

Because of the tremendous success of these batteries on the Mars Exploration Rovers, NASA plans to continue to develop these advanced lithium ion batteries for future space missions with more challenging environments, such as Venus (460?C/860?F) or the Neptune atmosphere (-170?C/-274?F), or to the icy moons of Jupiter.

Written by Samantha Harvey

A two-seat Dimona motor-glider with a 16.3 meter (53.5 foot) wingspan was used as the airframe. Built by Diamond Aircraft Industries of Austria, it was modified by BR&TE (Boeing Research & Technology Europe, a part of Boeing Phantom Works) to include a PEM fuel cell system, supplied and developed by Intelligent Energy, configured as a hybrid with lithium-ion batteries to power an electric motor coupled to a conventional propeller.

Boeing announced details of the flights at a media event in Madrid on the 3rd of April. The event was attended by senior Boeing representatives Matt Ganz (President, Phantom Works Advanced Technologies) and John Tracy (CTO, Boeing Corporation) as well as Intelligent Energy Chief Technology Officer Phil Mitchell.

Three test flights took place in February and March from Ocaña, airport. During the flights, the experimental airplane climbed to an altitude of 3,300 feet (1,000 meters) above sea level using a combination of battery power and power generated by the fuel cell system. Then after reaching cruise altitude and disconnecting the batteries, the pilot flew straight and level at a cruising speed of 62 mph (100 kilometres per hour) for approximately 20 minutes on power solely generated by the fuel cells.

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Boeing Fuel Cell Demonstrator Airplane 

Early in 2008, a pilot boarded a small one-seat propeller-driven airplane at an 

airport in Ocana, Spain, taxied to the runway and took off.  After climbing to an altitude 

of about 1,000 meters above sea level, the pilot leveled the wings, flew straight ahead 

for 20 minutes, and then returned. 

What was different about this airplane and this flight? 

It marked the first time in aviation history that a manned airplane maintained 

straight-level flight on power generated solely by hydrogen fuel cells. 

The milestone was achieved by an engineering team at Boeing Research & 

Technology Europe (BR&TE) in Madrid, Spain, with assistance from industry partners in 

Austria, France, Germany, Spain, the United Kingdom and the United States. 

The Boeing Fuel Cell Demonstrator Airplane project is an example of how Boeing 

is developing environmentally progressive technologies for aerospace applications.  

A one-seat Dimona motor glider with a 16.3 meter (53.5 foot) wingspan was used 

in the testing. Built by Diamond Aircraft Industries of Austria, it was modified to include a 

Proton Exchange Membrane (PEM) fuel cell/lithium-ion battery hybrid system to power 

an electric motor coupled to a conventional propeller. During takeoff and climb, the flight 

segment that requires the most power, the system drew on the lithium-ion batteries.  

The fuel cell provided all power for the cruise phase of flight.  

BR&TE, part of the Boeing Phantom Works advanced R&D unit, has worked 

closely with Boeing Commercial Airplanes and a network of partners since 2003 to 

design, assemble and fly the experimental craft. 

The group of companies, universities and institutions participating in this project 

includes: 

• Austria  – Diamond Aircraft Industries 

• France – SAFT France 

• Germany – GORE and MT Propeller 

• Spain – Adventia, Aerlyper, Air Liquide Spain, Indra, Ingeniería de 

Instrumentación y Control (IIC), Inventia, SENASA, Swagelok, Técnicas 

Aeronauticas de Madrid (TAM), Tecnobit, Universidad Politécnica de 

Madrid, and the Regional Government of Madrid 

• United Kingdom – Intelligent Energy 

• United States – UQM Technologies. 

Their specific contribution is as follows: 

• Adventia provided the test pilot, Cecilio Barberán. 

• The Madrid-based avionics group Aerlyper performed all minor airframe 

modifications; they also help with the mounting and wiring of the 

components.  

• Air Liquide Spain has been in charge of the detailed design and assembly 

of the on-board fuel system and the refueling station.  

• Diamond Aircraft Industries, an Austrian company, has supplied the 

airplane and has performed all major aircraft modifications.  

• The fuel cell system has been built with Membrane Electrode Assemblies 

(MEAs) from GORE of Germany.  

• INDRA has collaborated in the mechanical design and construction of the 

Power Management and Distribution box (PMAD). 

• The Madrid-based firm IIC (Ingenieria de Instrumentación y Control) has 

built the thermal management system (motor radiator and the water pump) 

for the electric motor.  

• The UK-based firm Intelligent Energy has been responsible for the design, 

development and assembly of the fuel cell system. 

• The Madrid-based firm Inventia has collaborated with BR&TE in 

developing the CATIA model for the airplane and on the preliminary 

design for all components on-board installation.  

• The propeller is one of the original models for the aircraft from the German 

company MT Propeller.  

• Regional Government of Madrid provided assistance during laboratory 

and ground tests. 

• SAFT France has designed and assembled the auxiliary batteries and the 

back-up battery (to be used for feathering the propeller and powering 

other crucial loads in an emergency event).  

• SENASA (Spain) has provided the hangar and maintenance facilities at 

Ocaña airfield in Spain for the flight tests. 

• Swagelok (Spain) provided the high pressure pipes and nuts for the fuel 

system. 

• The Madrid-based firm TAM (Técnicas Aeronáuticas de Madrid) has 

constructed the propeller adapted to mechanically couple the propeller to 

the electric motor.  

• Tecnobit (Spain) has provided technical support in laboratory, ground and 

flight tests 

• The Electronic Engineering Division of the School of Industrial Engineering 

of the University Polytechnic of Madrid (UPM-ETSII-DIE) collaborated in 

the electrical design of the Power Management and Distribution box 

(PMAD). The University also provided the facility to conduct airplane 

bench tests at the Spanish National Institute for Automobile Research 

(INSIA). 

• The electric motor is from UQM Technologies Inc (United States).  

Boeing research in fuel cell technology 

Unlike internal combustion engines – which burn fuel to create heat, convert heat 

into mechanical energy and, finally, mechanical energy into electricity – fuel cells are 

electrochemical devices that convert fuel directly into electricity without combustion or 

mechanical energy. Other than heat and water, fuel cells produce none of the products 

of combustion, such as carbon dioxide. 

Boeing is studying the aeronautical applications of two types of fuel cell 

technology:  

1) Proton Exchange Membrane (PEM) fuel cell technology and  

2) Solid Oxide Fuel Cell (SOFC) technology 

Because PEM fuel cells operate at relatively low temperatures and offer the 

highest power output for the least amount of weight, they are favored by auto 

companies as a replacement for the internal combustion engine.  A PEM fuel cell has 

been used in the Fuel Cell Demonstrator Airplane. 

Solid oxide fuel cells, on the other hand, use a solid ceramic electrolyte, which 

makes them heavier and able to operate efficiently at much higher temperatures.  They 

are thus more suitable for stationary power-generating applications.  At Boeing this 

technology is being studied for secondary power-generating systems, such as auxiliary 

power units.  

While Boeing does not yet envision fuel cells providing primary power for future 

passenger commercial airplanes, demonstrations like this help pave the way for using 

this technology in small manned and unmanned air vehicles for which this technology 

may demonstrate its advantages in specific missions. It also gives us “hands-on 

experience” to complement other fuel cell studies being carried out throughout the 

company.  

# # # 

March 2008 

Contact: Boeing Engineering, Operations & Technology Communications, +1 206-766-2923