Excluding the non-professional astronauts/cosmonauts who were taken into space for political or business reasons over the years, space tourism got off the ground in April, 2001, when the American engineer Dennis Tito traveled to the International Space Station for an eight-day trip. Between then and 2016, a total of seven people each paid tens of millions of dollars to travel up there. Indeed, Dr. Charles Simonyi had so much fun on his first trip that he went for a second flight.
Sometimes called “commercial space travel,” the opportunities for tourists to go into space are about to skyrocket in the next few years. A variety of companies, some owned by countries, some by non-governmental corporations, and some by entrepreneurs (and some in combinations) are developing all aspects of space flight, including launch vehicles, spacecraft, and habitats for visiting or living in space. Let’s consider some of the very real options for space travel in the coming decades.
“Space” is commonly defined to being about 100 km (62 mi) above the Earth’s surface. That boundary is called the Kármán line, after the Hungarian-American engineer, Dr. Theodore von Kármán (1881 – 1963) who did a very interesting calculation related to airplanes and satellites. Kármán knew that the higher you go, the lower the air density (which is why people who go from low-lying communities, like Washington, DC, to places in the mountains, like Denver, Colorado, are often short of breath and have to learn to adapt to living at altitude). The lower air density means that the higher aircraft fly, the less lift their wings experience. Kármán asked and answered the question, “at what altitude would an airplane have to be flying so fast to keep itself aloft that its speed would be the same speed as a satellite (with no engine pushing it) orbiting at that same altitude?” The answer is about 100 km. If you don’t need engines to keep you up, then you are in space.
There are four likely options for commercial spaceflight in the next two decades: suborbital flights; orbital flights; flights around the moon that don’t land; and, flights to the surface of the moon. It is likely that all the spacecraft will have wings that will enable them to glide to a landing. Some of these vehicles will have on-board rockets, some will be strapped to rockets, and some will use both rocket sources.
Let’s briefly consider each of these four space travel opportunities. First, a suborbital flight will be a powered ascent that crosses the Kármán line. These vehicles are designed to use up virtually all their fuel on the way up. After the engine stops firing, the space vehicle will begin slowing down while continuing upward in an arc that eventually levels off and then begins descending earthward. The path will be similar to the path of a baseball hit towards the bleachers. On this journey you will go into space, but not into orbit around the Earth. For about six minutes at the top of your trajectory you will be weightless, during which time you will be able to: see nearly half of the Earth at once; float around the cabin; and possibly, join the 62 mile club. Once you start descending, you will feel your weight return and you will have to return to your seats for the remainder of the trip, which will be a controlled glide back to Earth.
While suborbital flights will require some training, all the other spaceflights in the near future will probably require months of preparation. The second space flight opportunity is going to be travel to low Earth orbit where either you will spend several days or more in the spacecraft that brought you up there or, more likely, to an orbiting space station. Space stations, like the International Space Station, orbit much higher than the Kármán line, to prevent air friction from the very thin air at that altitude causing the space station to lose energy and spiral earthward. Your trip will be in two stages, first a high speed rocket flight to orbit just above the Kármán line, and then a more leisurely spiral out to your destination. This is more economical than flying straight to your final destination.
Once at your destination, you will have a few days of uncomfortable adjustment to prolonged weightlessness, and then the fun begins. Besides experimenting with weightlessness, one thing that most astronauts spend a lot of time doing is looking at the Earth. Since a low Earth orbit takes about 90 minutes, in half an orbit you can see stunning views of both the daylight and night time sides of the Earth, which appear profoundly different from each other and from anything you can see from here on Earth. Often you will be able to see aurorae sweeping around one or both of the Earth’s poles. You will find that your sense of taste, among other things, will be very different than it is on Earth. Things tend to taste blander in space, which is why your travel company will provide spicier foods than those that you have here on Earth. An experience worth considering is going for a “spacewalk” outside your station. Indeed, spacewalks will likely be optional (spelled “additional cost”) opportunities for this trip and all the trips to the moon.
The third option for spaceflights in the very near future will be round trip journeys to the moon, but without landing. There are a variety of paths your spacecraft can take to get you there. In any case, like the Apollo astronauts, you will first rocket into orbit around the Earth. You may stay there or in an orbiting space station until you adjust to weightlessness. When flights to the moon become a serious industry, it is very likely that the spacecraft taking you into orbit and to an orbiting space station will not be the one taking you to the moon. Instead, you will board a “shuttle” for that purpose. This process is much more efficient in terms of fuel and technology, but it is probably several decades down the road. In any event, once in your translunar spacecraft, a rocket attached to it will ignite, taking you via one of a variety of possible routes there. Some trips are more costly in fuel, but take less time than the more fuel-efficient routes. (Although your spacecraft will have wings, they will be useless in the space.)
With present technologies, it takes about three days to get to the moon. During that time, you will be weightless and able to enjoy the flight by watching Earth and moon and doing things in zero gravity. Upon approaching the moon, rockets will fire and slow your spacecraft, so that the moon’s gravitational attraction can grab you and whip you around its far side. Since that side never faces the Earth, you will be one of the few humans to ever see it directly. The best place to see the details on the moon, by the way, is on the boundary between day and night there, where the shadows are longest. This is called the terminator.
The return to Earth will be a reverse of the trip out, also taking about three days. Unless you are traveling via shuttle, your spacecraft will decelerate near Earth and spiral down until the air catches the wings of your spacecraft and you soar down to an airplane-like landing.
The final trip that will be available in the next few decades will likely be trips to the surface of the moon. Like the Apollo lander, you will probably descend in a shuttle rocket that stays on the moon while your spacecraft from Earth orbits the moon. Because the moon has a lower mass and a lower average density than the Earth, its surface gravity is only about 17% as strong as we feel on Earth. As a result, you will weigh less than 1/5 as much there as you do today. One of the many things you will have trained for is walking and getting up when you fall in low gravity.
Among the activities you can do on the surface are hiking, traveling to interesting features, including craters, hills, rock formations, cliffs (called scarps), possibly caves, and, depending on where you land, one of the Apollo landing sites. These sites are likely to be protected as international monuments. Returning to lunar orbit and to your spacecraft, you will fly home as described above for flights around the moon.
Every aspect of the preparation for space travel and the experiences in space is filled with challenges and opportunities, most of which are unlike any you will ever experience on Earth. You can learn much more about the space travel experience, as well as other upcoming space travel opportunities in the book, The Traveler’s Guide to Space: for One-way Settlers and Round-trip Tourists.
Space travel poster images courtesy of NASA.
About the Author
Astronomer and former NASA/ASEE scientist Neil F. Comins is professor of physics and astronomy at the University of Maine. His new book, The Traveler’s Guide to Space, is the go-to resource for anyone interested in space exploration. His other titles include Discovering the Universe, tenth edition (2014), What If the Earth Had Two Moons? (2010), Heavenly Errors: Misconceptions about the Real Nature of the Universe (Columbia, 2003), and What If the Moon Didn’t Exist? (1993)