How Long Does It Take to Get to Mars?

Mars at its closest point to Earth in 2003

 

Mars is the fourth planet from the sun, and the second closest to Earth (Venus is the closest). But the distance between the two planets is constantly changing as they travel around the sun.

In theory, the closest that Earth and Mars would approach each other would be when Mars is at its closest point to the sun (perihelion) and Earth is at its farthest (aphelion). This would put the planets only 33.9 million miles (54.6 million kilometers) apart. However, this has never happened in recorded history. The closest approach of the two planets occurred in 2003, when they were only 34.8 million miles (56 million km) apart.

The two planets are farthest apart when they are both at their farthest from the sun, on opposite sides of the star. At this point, they can be 250 million miles (401 million km) apart.

The average distance between the two planets is 140 million miles (225 million km).

The speed of light

Light travels at approximately 186,282 miles per second (299,792 km per second). Therefore, a light shining from the surface of Mars would take the following amount of time to reach Earth (or vice versa):

  • Closest approach: 182 seconds, or just over 3 minutes
  • Farthest approach: 1,342 seconds, or just over 22 minutes
  • On average: 751 seconds, or just over 12.5 minutes

Fastest spacecraft so far

The fastest spacecraft launched from Earth was NASA’s New Horizons mission, which is en route to Pluto. In January 2006, the probe left Earth at 36,000 mph (58,000 kph). The time it would take such a probe to get to Mars would be:

  • Closest approach: 942 hours (39 days)
  • Farthest approach: 6,944 hours (289 days)
  • On average: 3,888 hours (162 days

But then things get complicated …

Of course, the problem with the previous calculations is that they measure distance between the two planets as a straight line. Traveling through the farthest passing of Earth and Mars would involve a trip directly through the sun, while spacecraft must of necessity move in orbit around the solar system’s star.

Although this isn’t a problem for the closest approach, when the planets are on the same side of the sun, another problem exists. The numbers also assume that the two planets remain at a constant distance; that is, when a probe is launched from Earth while the two planets are at the closest approach, Mars would remain the same distance away over the course of the 39 days it took the probe to travel. [Countdown: The Boldest Mars Missions in History]

In reality, however, the planets are continuously moving in their orbits around the sun. Engineers must calculate the ideal orbits for sending a spacecraft from Earth to Mars. Their numbers factor in not only distance but fuel efficiency. Like throwing a dart at a moving target, they must calculate where the planet will be when the spacecraft arrives, not where it is when it leaves Earth. Spaceships must also decelerate to enter orbit around a new planet to avoid overshooting it.

How long it takes to reach Mars depends on where in their orbits the two planets lie when a mission is launched. It also depends on the technological developments of propulsion systems.

Here is a list of how long it took several historical missions to reach the red planet. Their launch dates are included for perspective.

  • Mariner 4, the first spacecraft to go to Mars (1964 flyby): 228 days
  • Mariner 6 (1969 flyby): 155 days
  • Mariner 7 (1969 flyby): 128 days
  • Mariner 9, the first spacecraft to orbit Mars (1971): 168 days
  • Viking 1, the first U.S. craft to land on Mars (1975): 304 days
  • Viking 2 Orbiter/Lander (1975): 333 days
  • Mars Global Surveyor (1996): 308 days
  • Mars Pathfinder (1996): 212 days
  • Mars Odyssey (2001):  200 days
  • Mars Express Orbiter (2003): 201 days
  • Mars Reconnaissance Orbiter (2005): 210 days
  • Mars Science Laboratory (2011): 254 days

Reusable Rockets Could Change The Economics Of Going Into Orbit.

EVERYTHING about space flight is superlative. Even relatively modest rockets are hundreds of feet high. The biggest (the Saturn V, which launched astronauts to the Moon) remains the most powerful vehicle ever built. But space flight is superlatively expensive, too. One reason is that, for all their technological sophistication, rockets are one-shot wonders. After they have fired their engines for a few minutes they are left to fall back to Earth, usually splashing ignominiously into the ocean.

 

Rocket scientists have therefore long dreamed of making something able to fly more than once. Such a reusable machine, they hope, would slash the cost of getting into space. The only one built so far, America’s space shuttle, proved a dangerous and costly disappointment, killing two of its crews and never coming close to the cost savings its designers had intended. But hope springs eternal, and several of America’s privately run “New Space” firms are planning to try again.

The most notable are the four landing legs folded up along the side of its first stage. If everything goes to plan, once that stage has finished its job and detached itself from the rest of the rocket, it will fire its engines again. Instead of crashing into the sea, it will make a controlled descent, deploy its legs, slow almost to a stop off the coast of Cape Canaveral, and then drop itself delicately into the drink. Mr Musk gives himself a slightly-less-than-even chance of pulling this off.

Will you walk with me, Grasshopper?

If it does work, though, it will be the most dramatic demonstration yet of technology that the firm has been working on for several years. In 2012 SpaceX began flying an unwieldy-looking legged test rocket called Grasshopper. This was able to hover, manoeuvre around in mid-air, and land itself back on the pad that launched it.

Then, last September, it attempted to organise the controlled descent of a legless first stage. In what the firm’s engineers call a useful failure, the rocket’s engines restarted as planned, but as the stage descended it began spinning, flinging its remaining fuel against the walls of its tanks and starving its motors, causing it to crash.

This week’s test is intended to end up with the rocket in the ocean, chiefly for safety reasons in case something does go wrong. But SpaceX’s ultimate goal is to have the first stage fly all the way back to the pad it was launched from, and to land itself facing upwards. It will then be taken away, serviced, refilled with rocket fuel and readied to fly again. The firm wants, one day, to recover the Falcon’s second stage, too—though the greater altitude and speed the second stage reaches makes this a far tougher proposition.

Still, being the biggest, the first stage is the most expensive part, so retrieving it should make a huge difference to launch costs. SpaceX already offers some of the lowest prices in the business. Its launch costs of $56m are around half those of its competitors. Mr Musk has said in the past that a reusable rocket could cut those costs by at least half again.

If SpaceX can make its technology work, that will be the biggest advance in rocketry for decades. Whether it will translate into higher demand for space flight is less clear. Jeff Foust, who edits the Space Review, an industry newsletter, argues that even dramatically lower launch costs will do little to change the economics of the industry, at least for the governments and firms that make up almost all of its current customers. Launch costs, as Mr Foust points out, are but a small part of the total cost of developing, building and running a satellite network.

Mike Gold, an executive at Bigelow Aerospace, a firm that makes inflatable space stations—and which has an agreement with SpaceX to launch its products—thinks that most of the interest will come from people and organisations so far denied access to space. “Putting a big rocket like the Falcon in range of mid-size companies, research institutions and even wealthy private individuals, that’s a game-changer,” he says. “When the laser was first invented, no one had any idea what it might be used for. Today they’re everywhere. We’re still at that early stage with cheap rockets.”

Perhaps. But although SpaceX is a commercial firm, simple profitability is not its only goal. Mr Musk has been perfectly frank about his long-term aim: “to die on Mars, preferably not on impact.” After the Falcon 9, the firm plans a beefier version called the Falcon Heavy. That, in turn, would be a dress rehearsal for something called the Mars Colonial Transporter.

Mr Musk wants to build a machine that would let him offer prospective colonists a (one-way) trip to the Martian surface for about $500,000—or, as he puts it, roughly the cost of a nice house in California. Perfecting reusability is essential for achieving that dream.

If you build it, will they come?

Hard-headed commentators may roll their eyes at such ambition. And history suggests reusability is difficult to do properly. The shuttle itself, for instance, was intended to fly every week. In the end, it made only 135 trips over the course of 30 years. There is a credible case that it proved more expensive, in the long run, than old-fashioned throwaway rockets would have done. Yet SpaceX has already shaken up an industry once mired in stifling conservatism. A successful fully reusable rocket would just be the latest example in a long tradition of it confounding its critics.

 

The Billionaire Headed For The Moon

“It’s clear that the baton has been passed from the government to the private sector” when it comes to space exploration, Jain said. “Now it’s going to take an entrepreneurial spirit to do it at a better cost and to build a business around it.”

Jain, 55, is co-founder of Moon Express, a Mountain View, Calif.-based company that’s aiming to send the first commercial robotic spacecraft to the moon next year. This serial entrepreneur-he founded Internet companies Infospace and Intelius-believes that the moon holds precious metals and rare minerals that can be brought back to help address Earth’s energy, health and resource challenges.

Among the moon’s vast riches: gold, cobalt, iron, palladium, platinum, tungsten and helium-3, a gas that can be used in future fusion reactors to provide nuclear power without radioactive waste.

It’s an exciting prospect, considering supply on Earth for such rare minerals as palladium-used for electronics and industrial purposes-is finite, pushing prices to $784 an ounce on April 2.

“We went to the moon 50 years ago, yet today we have more computing power with our iPhones than the computers that sent men into space,” he said. “That type of exponential technological growth is allowing things to happen that was never possible before.”

Jain’s Moon Express is not alone in its quest to harness the moon’s riches. Several other Silicon Valley start-ups, such as Planet Labs and Masten Space Systems, have been making headlines recently as they enter the space exploration market, an endeavor long associated with, and controlled by, the government. At the same time, the global race is heating up with the Chinese government’s recent success in landing a robotic rover on the moon in December.

To fast-track innovation and bring a deep well of space knowledge to the company, Moon Express made a strategic-and highly symbolic-hire in mid-March when it announced that Andrew Aldrin, 55, son of Apolloastronaut Buzz Aldrin, is joining the company as its president. He is an industry veteran who was the former director of business development for Boeing NASA Systems who has a track record of commercializing space technologies.

Helping to drive this newfound interest in privately-funded space exploration is the Google Lunar X Prize. It’s part of the X Prize Foundation, an educational nonprofit organization that looks to address the planet’s biggest challenges by creating and managing large-scale, high-profile competitions to stimulate investment in research and development.

Moon Express is one of a handful of teams from around the world competing for the $30 million Lunar X Prize, a competition organized by the X Prize Foundation and sponsored by Google. It will be awarded to the first team that lands a commercial spacecraft on the moon, travels 500 meters across its surface and sends high-definition images and video back to Earth-all before the end of 2015.

Jain’s own belief in attempting outsized challenges began in the early 1980s when he immigrated to the United States. Soon after finishing his MBA in India, he was recruited by IT company Unisys (NYSE:UIS –News) and worked in Silicon Valley as a computer programmer for several years. In 1988 he married and moved with his wife to Seattle. “She thought the Pacific Northwest was a wonderful place to live, and I figured that if we were going to make that move, I might as well send my résumé to Microsoft,” Jain recalled with a laugh.

The résumé landed him an interview, a job offer, and resulted in a seven-year stint at the software giant. It also solidified for Jain what he really wanted: to start and run his own company. He left Microsoft in 1996 and founded InfoSpace, an online email and phone directory company that he took public. It was valued at $30 billion several years later. In 2003 Jain started Inome (formerly named Intelius), an online database and public records company that has grown into one of the largest information commerce companies, with more than 25 million customers.

“In a large company, you never know if people admire you because of what you’re accomplishing or what’s on your business card,” he said. “In life, everyone wants to be successful, but few people think about being significant. I believe that as an entrepreneur, I could have a much bigger impact on society.”

With Moon Express, Jain feels he has that opportunity. Along with partners Dr. Robert Richards, a physicist and founder of International Space University, a nonprofit organization that offers space training programs, and Dr. Barney Pell, Silicon Valley technology pioneer and a former NASA manager, Jain says Moon Express can offer more “democratic” access to the moon.

“Now that we’re shifting from U.S. government-sponsored space exploration to privately funded expeditions, it’s important to look at how the resources of the moon could benefit everyone,” he said.

For instance, Jain explains that helium-3 is a source of energy that is rare on Earth but abundant on the moon. It is a possible fuel for nuclear fusion that could solve energy demand on Earth for 10,000 years, at least. Platinum, another rare mineral here on Earth, is believed to exist in large quantities on the moon and could be used in various energy applications, he said. “Once you take a mind-set of scarcity and replace it with a mind-set of abundance, amazing things can happen here on Earth,” Jain said. “The ability to access the resources of the moon can change the equation dramatically.”

There are about 50 employees at Moon Express, Jain said, and the goal is to complete its moon launch during the second half of 2015 for under $50 million. “If our software knows how to land safely and send pictures back, we are proving the concept,” he explained. The fact that a company with just 50 employees can successfully land on the moon is something Jain excitedly calls a “singular event.”

“Once we can accomplish that, then the second or third mission can involve bringing things back from the moon,” he added.

By Susan Caminiti & Robert E.