Named after the Roman god of war, looking fiery red in our telescopes, the fourth rock from the sun, our first stepping stone into "outer space" and perhaps even future home for humans, Mars has always elicited wonderment from us. Until quite recently, in terms of planetary ages, we really didn't know much about the Red planet... here's a brief timeline:
In 1877, Mars' two moons were discovered by astronomer Asaph Hall, and were named Deimos (panic) and Phobos (fear)-after the horses that pulled the chariot of the Roman god of war.
In 1971, Mariner 9 orbited Mars, becoming the first space probe to orbit another planet. It took pictures of the Martian surface and discovered Mount Olympus, the largest known volcano in our solar system-27 kilometres tall (Mount Everest is a mere 8.8 kilometres high), and a whopping 550 kilometres wide!
In 1975, the Viking I and II spacecraft landed on Mars. They sampled the soil and rocks and sent back vital information.
Since then, there have been numerous spacecraft that have orbited, flown by or landed on Mars, each one making new discoveries. For example, we now know that the elixir of life, good old liquid H2O, existed on Mars at one point. We also know that there is enough ice at the poles to cover the entire Martian surface with water-if the polar caps were to be melted.
Why Should We Go There?
The conditions on Mars are hostile-400 kmph winds, icy cold, carrying tiny particles of rust. The atmosphere is sparse, made up of mostly carbon dioxide (95%), nitrogen (3%), argon (a little over 1.5%) and mere traces of oxygen. The atmospheric pressure is similar to what you'd feel if you were hovering 35 kilometres above Earth-basically nothingness! Life ~as we know it~ could not survive in such conditions. So why go there?
The key is "as we know it": the idea is to find life in other forms. Our own oceans cause us to believe in the impossible, with organisms that live underwater, close to under-sea volcanoes, thriving in that sulphur-rich, superheated hostile environment... There's reason to believe that life exists in extreme conditions, and there's evidence to prove that Mars has ice, water vapour and, albeit for short stints, liquid water. There are also huge caverns on Mars, so deep that natural light from the sun never reaches their bottoms, and these are well-shielded from the extreme climate that ravages Mars' surface. The bottom-line, however, is that we'll never know-not until we get there ourselves and have a look-see.
Advances in technology are shaping our future, making the impossible possible. People with no legs are running races, dead hearts are being replaced by machine pumps, people are videoconferencing from across the globe, bombs more destructive than fission reactions and that leave no long-term radiation effects have been tested... Trillions of dollars are being spent on defence-that's a 13-figure number-by various countries, and over a billion people have been exposed to PCs. It's all happening, and happening now.
Those of us old enough to read this magazine have seen more change in our lifetimes than a human of any other time has ever seen since the beginning of recorded history.
That digression was necessary to try and give you a sense of wonderment at our achievements, some pride in the capabilities of the human brain... mainly so that we could bring you crashing down again, to reveal to you a harsh reality: man went to the moon decades ago, and since then has been content to stay right here. Impetus in space explorations has slowed to a crawl when compared to the space race of the sixties and seventies. We're stirring though, looking upwards, dreaming of distant worlds-again.
The maximum distance from the Earth to the Moon is roughly a little over 400,000 km; the minimum distance from Earth to Mars, however, occurred on 27 August 2003, after 60,000 years, when Earth and Mars were a mere 56,000,000 km apart. Think of those numbers as 4 lakh and 5.6 crore, and you will better appreciate the vast distances involved in landing a human on Mars.
It's all well and good to sit here in our comfortable chairs and theorise, day-dream and wonder, but the task of attempting to put a man on Mars is several magnitudes more complex than the famed Moon landing. To put it simply, aiming a rocket at the moon seems easy when you start thinking of travelling to Mars. There are problems, and we're looking to technology to solve them...
Navigation in space is quite different and much, much more complex than most of us imagine. There's gravitational pulls from planets and the sun, meteors, comets, space dust, space junk, and more to avoid. Add to that the fact that you're pointing this tiny speck of a craft-launching it from one planet, moving it at breakneck speeds-at another planet that's hurtling through space, and you get complexities and probabilities that will leave even the best mathematicians amongst us scratching their heads.
When you're sending machines, it's a lot easier, because time isn't of the essence. Robots and Rovers don't get bored, they don't need to be fed, and can be turned off to save power. Most importantly, they can just be left there. A human, on the other hand, has to get there quickly, safely, and then has to be brought back.
It's obvious that NASA is leading the world in space exploration technologies, and it has already sent various probes to Mars-even landing the Mars Rovers, Spirit and Opportunity, on the Martian surface in 2003. As of now, the two Rovers have overcome all odds and are still exploring the Martian surface, over three years after their intended 90-day life expectancy passed.
It takes quite a big rocket to launch even a small rover into space-consider that the rockets that launched the Rovers weighed about 2,85,000 kg, of which a mere 1,000 kg was the actual spacecraft that went on to Mars. The fuel and oxygen are used to create the burn at lift off, and a complicated turbo-turbine pump ensures that the amount of fuel and oxygen increases in the engine to break away from the Earth's gravity. The rocket also contains complicated gimbals and gyroscopes to make sure that the rocket stays on its path upwards. (Gimbals are devices used to ensure that an object is always kept horizontal.) The entire rocket engine is mounted on gimbals, and is thus actually movable.
Now there are two smaller engines on either side of the rocket that fire only when the rocket is going off course or tilting towards one side. These also work with the gimbals to ensure that the rocket stays pointed straight up during the launch. As if that weren't enough, there are the nine additional rockets attached to the side of the rocket to provide additional thrust-think nitro boosters of popular car racing games. These nine rockets run on a solid fuel called hydroxyl-terminated polybutadiene (HTPB), held in shells made of graphite-epoxy-up to five times lighter than most metals. That completes Stage I of the rocket motors.
When the rocket is about 130 km above Earth, Stage II kicks in. Stage II is made of a rocket that burns a mixture of Aerozine 50 (50% hydrazine, 50% unsymmetric dimethyl-hydrazine) and nitrogen tetroxide or N2O4 (an oxidiser). Because of the lack of an atmosphere in space, fuels that need ignition cannot be used, and this second-stage fuel is made just for that-the fuel automatically burns when the ingredients are mixed. The Stage II rocket fires once in order to get the spacecraft into orbit around Earth. Only after all the calculations are done, and the Stage II rocket is lined up with its final destination, does it fire again. Here, too, gimbals and gyroscopes are used to make sure that the spacecraft stays on course. Computers onboard the spacecraft do all the manoeuvring and rocket firing.
Many of us Indians are quite used to power cuts, and life just goes on. However, millions of kilometres away from Earth, with no free air to breathe, a spacecraft to man, running computers that an astronaut's life depends on, power shortages are unacceptable! Currently, power is derived from the biggest power source in our solar system-our sun. Even the two nomad rovers that are wandering about exploring the Martian surface are solar powered...
The solar panels used on the rovers are not your ordinary run-of-the-mill solar cells; they're tri-layered cells stacked one on top of the other to absorb every last ray of solar power that they can. Currently the two rovers carry two 8 amp-hour batteries that are charged using the solar panels. Each rover was able to produce between 400 and 900 watt-hours of power per Martian day-that's enough to power a 100 watt light bulb between 4 and 9 hours! Of course, when designing all electrical systems and electronic components, NASA's engineers are notably stingy with power consumption values-which results in such a reduced load that the power generated by the solar cells is quite sufficient (unless an astronaut decides to plug in his boom-box for some entertainment!).
The drawback of solar power is that it requires rovers or astronauts to remain in sunlight-rich areas-of Mars or otherwise. This is generally the equatorial region, and trips to the bottom of Martian chasms are a strict no-no. Alternative power generation techniques are being researched, and it's quite probable that the first human exploration of Mars will be nuclear-powered.
A lot of mankind's space exploration attempts have ended in disaster. A lot of us know about the Challenger disaster in 1986, where seven astronauts were lost. More recently, space shuttle Columbia, with Indian-born Kalpana Chawla onboard, broke up on re-entry in February 2003. Such are the risks associated with human space flight, and these are examples of the worst type of disaster. However, a seemingly smaller and more niggling problem lies in the communication systems. This is more pronounced in unmanned flights, where computers cannot just fix themselves, and often the end result is loss of the spacecraft. Just last year, in November 2006, NASA lost contact with their Mars Global Surveyor, a craft that had been orbiting Mars since 1997. It's still there, orbiting Mars, but NASA just cannot contact it or get it to respond.
This is perhaps the biggest risk of unmanned flights, and while it does not involve loss of human life, billions of dollars in research and development can go down the drain if one antenna fails to point in the right direction. Communication is the key, and it can spell the difference between a miracle man-made robotic explorer and good old space junk.
In order to stay in constant touch with all the spacecrafts out there in space, NASA has what they term the "Deep Space Network" (DSN). This consists of three high-tech communication facilities-one in California's Mojave desert, another near Madrid in Spain and the last one near Canberra in Australia. Working in tandem, these antennas, the most powerful and sensitive telecommunications equipment known to man, can communicate with all working space probes and crafts that have been sent out, no matter where they are.
As for the spacecraft out there in space, communication is taken care of by two main antennas-a low gain, omni-directional antenna and a mid- / high-gain directional one. The low gain antenna is used when the spacecraft is close enough to Earth to not require focused communicating rays, but once the distance starts increasing to the order of a few million km, the mid-/high-gain antenna is needed to stay in touch with Earth. The drawback of directional antennas is that they are motorised, so there's a highly increased risk of failure. In fact, just before they finally lost contact with the Mars Global Surveyor (MGS), it communicated to NASA that it had a mechanical problem with a solar panel, and rotated itself to make sure it got enough sunlight. However, this rotation pointed the high-gain antenna away from Earth and also exposed the battery to direct sunlight, heating it up beyond tolerance levels and leaving the MGS dead in space.
|Super Solar Sail
|The rovers took seven months to reach Mars from Earth on conventional propulsion techniques. Drawing inspiration from science fiction, there are many alternative propulsion techniques that authors have written about. Some will stay fiction forever, one is already a reality. Introducing the solar sail, which science fiction works tell us is a huge sail attached to a spaceship that uses the light (photons) emitted from the sun as a "solar wind," propelling the craft attached to it away from the sun. Traditionally, sci-fi writers have spoken of solar sails as engineless, unmanned spacecraft. This would be a good solution for sending a probe out to another solar system, for example, because, honestly, we don't care how long it takes.
You've heard of the Wright brothers… get ready for the Benford twins from Alabama. In 2005, the brothers developed a sail that they claimed could have gotten the two rovers to Mars in under a month! The principle is to not depend on the sun as the energy source, but to generate our own "wind". They created a sail made of a carbon mesh that they hit with directed microwaves. The result was that carbon monoxide was being given off and the sail experienced a considerable "push". They then worked on the theory that a sail could be painted with a film of specially created paint that, when heated, gave off gas and propelled the sail (and the craft attached to it) away.
According to their calculations, if a spacecraft in Earth orbit were to unfurl a square sail 100 metres across, and was bombarded for an hour by a 60 megawatt microwave, the spaceship would accelerate to a speed of 60 kilometres per second-faster than any spaceship has ever gone. This would enable a ship from Earth to reach Mars in under a month.
Now, 60 megawatts is a lot of power, and though a lot of people are working on building sails, none that can be folded or stored are possible yet. Perhaps the future will see a combination of the solar sail and nuclear-powered propulsion to get Man to Mars.
Getting to the meaty part for us Digit-ians, we want to know what kind of computers are used in spacecraft. We'll take a look at what powers the two rovers currently on Mars to give you an idea.
If you're expecting a supercomputer, you're going to be very disappointed. The computational power on a rover is about as good as the average budget laptop! Why? Take a glance back at Power Generation above...
Aerogel's almost not even there, yet it's stronger than most
The CPU used in the rovers was a specially designed 32-bit Rad 6000 processor, which is shielded against radiation and is based on the PowerPC architecture-yes, like the ones the older Apple Macs used to run. The CPU is capable of a modest 20 million calculations per second, and is supported by a mere 128 MB of RAM. There's also 256 MB of Flash memory and various other smaller amounts of non-volatile memory. The system is designed specially to waste almost no energy in heat dissipation, and is completely sealed inside what NASA calls a "Warm Electronics Box" (WEB).
Unlike here on Earth, in space, computers have to be protected against radiation and extreme cold. Considering that the temperature of an average Martian night is about minus 90 degrees Celsius, the air is filled with rust-dust and the atmosphere offers no protection against solar radiation (no ozone layer or even air to help out), it's no wonder the "brains" of the rovers are sealed in the WEB.
The walls of the WEB are painted with gold to reflect radiation; the box itself is completely air-tight and insulated with aerogel-a compound that's made up of 99.8 per cent air and 0.2 per cent silica dioxide, is light as a feather, extremely solid and is sometimes referred to as "solid smoke" by NASA engineers.
A Mars rover hard at work
On the left is a before, on the right is during a dust storm-now that's a storm!
To give you a better idea about how well aerogel can insulate, consider this: you could take a thin sheet of aerogel, hold a blowtorch under one end and actually place your hand on the other end without feeling anything more than "warmth." It's "solid" too-a slab of aerogel as big as an adult human weighs a mere 455 gm, and can support an object that weighs 500 kg! Don't expect to see it in your local hardware store anytime soon though-it costs way too much to create. Still, if you have money to burn, hop on over to www.aerogel.com and see what you can afford.
Software And Navigation
When man does finally go to Mars, he will not be alone. Space exploration relies heavily on robots and vehicles that work as autonomous entities. Computers need to just calculate and work instead of sitting around dumb, the way the average PC does, waiting to be told what to do. During lift-off and early flight, computers do almost everything to make sure that the rocket stays on course. During landing on Mars as well, computers have proven to be quite capable-again, we'll cite the example of the two rovers that were successfully landed on Mars. Humans on Mars will use vehicles to get to and from exploration sites there, and these vehicles cannot be as dumb as the average road car. Let's look at what makes the Mars rovers tick to better understand what will power future landings on Mars-manned or otherwise.
Carnegie Mellon University developed the "navigation and hazard avoidance software" (NHAS) that the two rovers depend on to keep themselves out of trouble on Mars. Using this software, the rovers have achieved an average autonomous driving speed of 34 metres an hour. Before you laugh-out-loud incredulously, exclaiming "34 metres an hour?", you should understand the complexities involved.
Mars is a crater-ridden, rock strewn, dusty and stormy planet. With volcanoes three times the size of Mt. Everest, and canyons that dwarf the Grand Canyon, and billions of rocks on its surface, Mars is even the bravest off-road driver's worst nightmare. (Damn those Martians-why couldn't they build highways!) Add to that the fact that each rover is carrying rather expensive and critical information and equipment, and you should understand why the rovers don't just race along the Martian surface, bouncing off boulders sending back messages to Earth that say "Whee, this is fun!".
Each rover is equipped with pairs of stereo cameras to give depth perception similar to what the human eyes afford, and click pictures of the paths in front of them. When the rovers are given a destination (in coordinates) by technicians on Earth, they first identify the destination, clicking pictures of the straight-line path there. Next they start identifying obstacles on the path using the NHAS developed at Carnegie Mellon to examine the high resolution stereo images they click and plot multiple paths. After all calculations, permutations and combinations are done, the rover identifies the shortest path of least resistance (lowest hazard risk path) and then moves between half and two metres. Once it's moved, it re-clicks stereo images and the whole computation process is repeated. Incidentally, the rovers are capable of identifying and measuring the distance to about 16,000 points in each stereo photograph they click!
Calculating their own movement is not left to simple odometers either. (For those who don't know, an odometer is a device found on cars and motorcycles that calculates the speed and distance traversed by a wheel; it measures this by calculating how fast the wheel is turning and how many times it has turned.) On a rocky, dusty surface with slopes, the possibilities of a rover slipping down a slope-backward or forward-is very real. The rovers adjust for this by calculating distances moved using visual odometer software. What this software does is "remember" previously-identified points on its path and then compare the distance moved by looking at before-and-after images to give much more precise calculations.
The rovers are designed this way to avoid bumping over rocks, falling into canyons and running into walls, so as to protect its fragile interiors, which are already running in extreme conditions. Remember, there's no margin for error on a delicate machine that's on another planet, a hundred million kilometres away from us.
The whole point of sending unmanned spacecraft to Mars is to photograph it in order to collect as much visual information about the planet before we send humans there. The results that the rovers have sent back to us are the most exciting images of space exploration we've seen till date-it's about as close as we can get to "experiencing" Mars without going there ourselves.
The cameras on the rovers were perhaps the most high-tech in the world at the time they were made, and they're still being improved. Between the two rovers and the Mars Landers that carried them, NASA has been receiving images from 20 different high-quality, high-resolution cameras at regular intervals. However, it's not the hardware that's impressive, it's the software that manipulates and sends back those images that is of more interest.
Developed specially at NASA's Jet Propulsion Lab (JPL), the imaging software uses ICER wavelet-based compression to reduce image sizes by up to 12 times. Each image that is clicked is divided into 30 chunks and transmitted back to Earth-this is to ensure that if packets are dropped, the entire image is not lost. It compresses images progressively, and features Image Context Error Correction, which accounts for any errors that may occur when data is transmitted along the Deep Space Network. Depending on the needs, the software can achieve lossy or lossless compression of images. It's because of this software that we're able to see more pictures that the Mars rovers click, instead of them transmitting fewer RAW images.
Although there are literally thousands of technologies involved in building spacecraft that are capable of trips to Mars, we'd have to continue this story over the next 400 issues of Digit to tell you about them all in detail. Instead, we've clubbed a few interesting technologies together to whet your appetite:
Batteries: As of now, we don't have batteries that can withstand Martian nights, with temperatures of up to minus 110 degrees Celsius. Instead, all batteries on the rovers, and any vehicles to follow, are encased inside insulated boxes with heaters. The batteries can supply power as long as they are above minus 20 degrees Celsius, and need to be hotter than zero degrees Celsius when they are being recharged. Electric heaters and any heat dissipated from other components are used to "warm up" the batteries.
Heaters: The heaters we just mentioned are radioisotope heaters that can produce about a watt of heat for decades. They produce heat through radioactive decay, and using 2.7 grams of plutonium dioxide, encapsulated in plutonium-rhodium alloy and then locked inside several layers of a carbon-graphite composite.
Space Ship: To go on a round-trip to Mars requires a huge amount of food, water, oxygen and most of all, fuel. It's virtually impossible to send a ship that big into space from Earth. However, building the ship on the Moon, or in orbit in space is possible. Several experts believe that this is the way to go ahead building a ship big enough to go to Mars and back.
Food: This really isn't as big a problem as we think. Food in space flights is just painful to store and eat. Astronauts who already spend weeks in space eat three meals a day, use liquid salt and pepper, and ketchup and mustard to enhance the taste of the food according to their individual tastes. They have to eat out of special containers, of course, to prevent the food from floating away. There's an oven provided to warm up the food, and meals include macaroni and cheese, spaghetti, fruit, brownies, juices, tea, coffee, etc.-seriously, it's not like they're eating little pellets. What's more interesting is that for a really long journey, say, to Mars, small women are more desirable than big, strapping men-a small woman would need about 2,000 calories a day, whereas a macho man would eat over 3,000. Maybe the first humans on Mars will be women, considering that a trip to Mars requires over a year's supply of food!
Air: This is where it all gets complex. Taking the example of the International Space Station (ISS), air is recycled and carbon dioxide removed and "scrubbed" back into oxygen. Oxygen is also produced from electrolysis. In addition, air scrubbers also have to remove ammonia and acetone that the human body produces. Interestingly, scrubbers on the ISS have given trouble before, and reserve oxygen from visiting ships have been used in the past. When travelling to Mars, no such luxuries will be available, so systems to cleanse air and generate oxygen will have to be ~much~ more foolproof and numerous. Another option, of course, is to just use plants to cleanse the air of carbon dioxide and produce oxygen, but again, weight and space constraints will play spoilsport with that idea-not to forget the daily dose of sunlight that plants need in order to survive.
A holiday to Mars for the common man is at least a millennium away, but renewed interest in Mars promises to put a man on Mars in a few decades, and most of us will be alive to witness it. Currently, technology is not very far behind what's required to achieve the task, but the prohibitive cost is what's keeping the race to Mars in check. Earlier estimates suggested that it would cost over $300 billion (12 lakh crore rupees) to get a man to Mars, but now NASA hopes to get the job done using less than $50 billion (2 lakh crore rupees) after a couple of decades. Considering the costs, there are many who are against the Mission to Mars, citing the good that the same amount of money could do for humanity here on Earth. However, who knows what untold riches Mars holds in store for humanity, in terms of the discovery of life, new minerals, and an invaluable understanding of the history of our solar system? Perhaps even more clues to the eternal questions "Are we alone?" and "Why are we here?", which humanity certainly cannot place a price tag on?
Image Credit: NASA / JPL / Caltech