如果现在你还是一名中学生，那么等你三十几岁的时候就可以买到一张前往火星的机票,体验一次真正的长途飞行……

Buzz Aldrin, the second man to walk on the Moon, is a long-time fan of space tourism. Aldrin climbed out of Apollo 11 hot on the heels of Neil Armstrong in 1969.1 Now, at the age of 72, Aldrin is working on a new project that could put more of his fellow humans in space ?nbsp;namely, on journeys to one of our most fascinating neighbors, Mars.

Together with scientists from Purdue University2, the Massachusetts Institute of Technology, and the University of Texas, Aldrin is designing spacecrafts that would perpetually cruise between Earth and Mars. These crafts, known as "cyclers", would ferry people and supplies between the two planets, enabling humans to colonize Mars ?nbsp;something that has long been dreamed about in science fiction.3 "Some day, people will be going to Mars on a regular basis4," says team member James Longuski, a professor at Purdue. "Most people are convinced that we are going to dothis; the only question is when."

The average distance between Mars and Earth is 48 million miles. To get a sense of just how far this is, try doing this calculation: Given that there are 2,500 miles between New York and Los Angeles, how many times would you have to travel from NY to LA and back to cover the same distance?

It sounds like a trip that would require a lot of fuel. According to the engineers, the cyclers may have a natural, renewable "fuel" supply: from the gravitational forces of the Sun, the planets, and their moons. 5

As a spacecraft travels close to a planet, its flight path is bent, causing it to whip6 around the planet and significantly increasing its speed (it's as if the planet's gravity gives the passing spacecraft a kick into space). This is the "slingshot" trajectory7 that you may have seen in movies. It's not just science fiction: it might help us get to Mars with very little fuel on board, in a journey that would take as little as six to eight months.

"The cycler is essentially in orbit around the Sun and makes regular flybys of Earth and Mars,"8 says James Longuski. "Once you put your vehicle into a cycler or bit, it continues on its own momentum, going back and forth between Earth and Mars.9 You may need to carry some propellant for an occasional boost, but it's pretty much a free trip after that.10"

When the cycler flies by Earth, it will be traveling at a speed of about 13,000 miles per hour. Space taxis will be needed to bring people from the surface of the planet to intercept11 the cycler. "This is sort of like a bus that doesn't stop," Longuski says. "When it comes by, you have to run alongside of it and grab on."

Aldrin and his group think that the first cycler could be on its way12 by as soon as 2018. So, if you're in middle school now, you could be taking a trip to Mars by the time you're in your thirties. (It seems a long way off now, but it's closer than you think!)

Fasten your seatbelts and make sure your seatback is in its upright position. Your flight to space may be departing soon.

1. 第二位登上月球行走的人巴兹·奥尔德林长期以来着迷于太空旅行。1969年他紧随阿姆斯特朗之后跨出了“阿波罗11号”登月舱。hot on the heels：紧紧跟在……之后的。

2. 普度大学，位于美国印第安纳州。

3. 这种飞船被称为“骑车人”，将在两个星球间运送人员和供给，使人类成功移居火星，从而实现科幻小说里长久以来的梦想。

4. 定期地。

5. 据工程师设想，“骑车人”有可能使用一种天然的可不断补充的“燃料”：即来自太阳、行星和卫星的引力。

6. whip：急走，急冲。

7. slingshot：弹射飞行（指航天器利用天体引力急剧加速并改变航向的飞行）； trajectory：（射体的）轨迹，轨道。

8. “骑车人”飞行器实际上是沿围绕太阳的轨道飞行，并定点飞过地球和火星。flyby：=flyover（飞机或宇宙飞船的）定点飞越。

9. 飞行工具一旦进入了这样的轨道，就会依靠自身的冲力不停地在地球和火星之间往复运动。momentum：动量，冲力。

10.也许需要携带些燃料偶尔为飞行器提供动力，但其余就完全是无动力的飞行了。propellant：火箭燃料，推进剂；boost：推动。

11. intercept：拦截。

12. on its way：投入使用。