Mission to Mars (24 page)

Cycler trajectories are the paths that cycler vehicles travel on. In many ways, they can be thought of as the highways on which space vehicles travel. Cycler trajectories are routes used over and over again on paths around the sun. These trajectories are identified by using the laws of celestial mechanics—essentially Newton’s laws.

Interestingly, to create 21st-century sustainable space transportation architecture I’m counting on laws of motion compiled by Sir Isaac Newton in his work
Philosophiae Naturalis
Principia Mathematica
, first published in 1687. Newton’s laws of motion have led to a trio of physical laws that form the basis for celestial mechanics. They describe the relationship between the forces acting on a body and its motion due to those forces. My cycler design depends on these principles.

The Aldrin Cycler is a cycler trajectory that travels around the sun, making close flybys of Earth and Mars, a trajectory that takes
years to complete and then repeats every succeeding
years. If a vehicle is launched into the Aldrin Cycler trajectory, it would continuously shuttle between the two planets forever, without requiring a significant amount of propellant to keep on track.

The cycler vehicle does not stop when it flies by Earth. The astronauts have to board a small but speedy space taxi that catches up with the cycler. The cycler is like a bus that repeats its route over and over, but never stops. As a future space traveler you’ll have to run fast to catch up and get on the bus!

But once the astronauts are on the cycler vehicle, they can relax and enjoy the ride to Mars. When they arrive at Mars they must board a small vehicle that makes a fiery entry into the atmosphere of Mars. If the astronauts do not get off at Mars, then they will travel back to Earth, getting off
years after they first left Earth.

By using the Aldrin Cycler trajectory it takes less than 6 months to get to Mars. However, any astronaut not disembarking at Mars would spend 20 more months getting back to Earth. My Purdue University associates have identified Aldrin Cycler trajectories that make a short trip—6 months—to Earth from Mars, and a long trip—20 months—to go from Earth to Mars.

NASA’s Mars Atmosphere and Volatile EvolutioN (MAVEN) will explore the upper atmosphere of the red planet
.

(
Illustration Credit 7.14
)

Therefore, a complete Earth-to-Mars human transportation system would include two cycler vehicles, one using the “outbound” or “up escalator” trajectory to get to Mars and the other using the “inbound” or “down escalator” trajectory.

Once these cycler vehicles are built and placed in orbit about the sun, they will continue to freely travel back and forth. Propellant will be required, however, now and then, to keep the Aldrin Cycler going—but the cost of refueling is not prohibitive.

What are the biggest challenges?

The Aldrin Cycler requires very high rendezvous velocities at both Earth and Mars—typically 6 kilometers a second (over 13,400 miles an hour) at Earth and as high as 10 kilometers a second (22,370 miles an hour), or more, at Mars. Those speeds make it very difficult for the space taxis to catch up. Think of it this way: If a bus were going 5 miles an hour, riders could easily jump on, but not if the speed was 50 miles an hour!

A future Mars lander—InSight—will investigate the internal geology of the red planet
.

(
Illustration Credit 7.15
)

Can anything be done about the high rendezvous speeds? Yes.

My Aldrin Cycler idea has inspired the search for other Earth-Mars cycler concepts. For example, there are “low-thrust”
cyclers that use electrical propulsion to reduce the approach speeds. There are also “four-vehicle” cyclers that take
years to complete their trajectories. Then there are powered three-synodic-period cyclers that require three cycler vehicles. There is even a one-vehicle cycler.

All of these new cyclers are spin-offs of my original Aldrin Cycler thinking, and all have much lower flyby velocities. Each has its advantages and disadvantages. As always, economics is a factor as more vehicles mean more cost. Overall, powered and low-thrust cyclers will demand advancements in propulsion technologies—but this type of progress is well within reach.

So, how shall we go to Mars?

The best, most effective way is still under intensive review. But I’m happy to report that the Purdue/Aldrin Cycler and its offspring will continue to be an important mission design concept in the future development of an Earth-Mars transportation system for human space travel.

Neil Armstrong and Buzz Aldrin erect U.S. flag on the moon
.

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Illustration Credit 7.16
)

Humanity is destined to explore, settle, and expand outward into the universe.

But doing so urgently requires a rekindling of America’s space program. A Unified Space Vision can ignite a new wave of support and participation in the United States and elsewhere. This is a spot-on space trek of inspiration, one that can impel youth to engage in science, technology, engineering, and math. Younger readers have probably heard their parents or grandparents say: “The world is yours.” I want to take it one step further and say: “The worlds are yours.”

When I was a young person, I wasn’t the only one in the neighborhood who looked upward and dreamed about going to the moon or stepping onto other planets. I was a reader of
science fiction. At that moment in time, no one had traveled into space. Everyone, including me, had to bank on imagination to conjure up ways to make those dreams come true.

To the younger reader, Will you be one of the first people to walk on Mars? You could even be among the first human settlers to colonize that planet. There are out-of-this-world things to accomplish—all fostered by the ability to reach for places that no one has ever reached for in the past.

Earth isn’t the only world for us anymore.

The space voyages beyond our Earth over the next 25 years will also motivate the next wave of technology entrepreneurs. This search for new horizons will enhance America’s global leadership and encourage international cooperation among spacefaring nations.