The layers of earth's atmosphere & suborbtial arc shown in very rough scale. Illustration by Karen Wehrstein

Suborbital flight will open up access to space for us regular folks, we children of Apollo (Or in the former USSR, children of Soyuz) who’ve gazed skyward with a heaping helping of awe tinged with a touch of envy for half a century and counting. In 50 years of exploration only about 500 human beings have been lucky enough to go into space. Most of them are government or civilian pilots, a few scientists, engineers, and medical doctors, and a handful of privately funded astronauts lumped – unfairly as we’ll see in future posts — into the category of space tourists. In the next decade or two more than ten times that many will get to go. Among them will be the first rock and roll star, the first paraplegic (Who may find the freedom afforded by weightlessness to be so enjoyable they may not want to come back!), and the first head of state. They’ll be followed, sooner or later, by the first teenager, the first President, even the first infant.

Adventure is reason enough! But there’s science to do up there too. Our atmosphere is actually thousands of miles thick, but it’s not a continuous, gradually thinning blanket of cooler and cooler air as one might think. It’s a thing of layers, like an onion, each marked by abrupt changes in temperature and other properties. The part we’re most familiar with, the part containing every forest, coastline, and hanging valley, is the Troposphere. It starts at the surface, what scientists call the planetary boundary layer, and extends all the way past the thin wispy cirrus clouds that fly above the tallest thunderstorms. Only the highest flying birds and the peaks of the world’s greatest mountains soar into the next layer, the Stratosphere. The stratosphere is a layer of stable air that acts like a lid on weather systems embedded in the troposphere, limiting the vertical development of thunderstorms and blizzards. This is the realm the protective ozone that shields the planet’s surface from harsh ultraviolet light like a global sunscreen.

The highest flying rocket planes like the legendary X-15 and the proposed Lynx, shown right, penetrate the layer after that, the Mesosphere, where the air is many times thinner than on Mars. It is the coldest part of our fragile atmosphere, around 135 degrees below zero on average, the stage where grand electrical discharges called sprites and jets are conducted, and shooting stars end their brief dazzling lives. Beyond that are the Thermosphere and Exosphere, both so rarefied and distant that we’ve adopted another, simpler word to describe their properties: space.

The sleek suborbtail Lynx under development by XCOR

Notice there’s no hard altitudes associated with the descriptions above. That’s because the earth’s atmosphere expands and contracts with heat and cold. The altitude of each layer changes constantly, as a function of temperature, season, and geography, by a 100 percent or more in some cases. Over the equator, the troposphere extends upward for 12 miles, but above the poles it is only 5 miles thick.

Suborbital spacecraft can take direct readings and collect samples that provide the precise mixture of gases and pressure, including the amounts of industrial pollutants like greenhouse gases or ozone destroying chlorofluorocarbons. Scientists collect a lot of similar data from satellites flying much higher and aircraft flying much lower, but samples from the intermediate alititudes are hard to come by. Just as data collected by hurricane hunter aircraft provide specific and at times critical details about storm intensity and storm surge unavailable to weather satellites, data and samples taken from the upper atmosphere give meteorologists and climate scientists a far better, more detailed understanding of what’s going on in real time. The Mesosphere in particular remains one of the least understood layers of the atmosphere, too high for most aircraft to penetrate and too low for a spacecraft to maintain orbit.

Spacecraft engineering is another area that can benefit from suborbital flight. Here on earth we take gravity, engineers are no exception. That office water cooler depends on gravity to feed water through the valve and into a cup. Fuel tanks in every car and on most airplanes rely to some degree on gravity to help prime the pumps and deliver fuel to the engine. But a tank full of water or fuel in microgravity behaves differently. Unless the tanks, valves and pumps are specially designed to operate in zero G, water or other substances like fuel might glob up, slosh around inside the tank, without making reliable contact with inlets. Pumps in particular have a well known tendency to choke and sputter when they’re forced to try and move both liquid and air. And in space, where replacement and repair are hundreds of vertical miles and millions of dollars away, something as simple as a failed pump can mean a lot more than mere inconvenience, it can mean the difference between life and death.

Likewise, experiments designed to operate in zero G benefit from live tests. Research on materials and processes in microgravity have already resulted in breakthroughs in drug production, silicon wafer fabrication, and molecular biology. There may come a time when automated orbiting mini-factories grow flawless microchips of such quality, or produce pharmaceutical isomers of such purity, that our current earthbound efforts are crude by comparison. Just like pumps and valves, testing these experimental packages before spending millions of dollars to send them to space might save a ton of money for manufacturers.

One fascinating spin-off from commercial suborbital flight could change passenger travel in the same way airlines revolutionized transatlantic travel. Suborbital airlines — or perhaps space lines would be more accurate. Today a flight from New York City to Tokyo takes about 14 hours. And that’s for a non stop flight. A suborbital hop between the two cities might take less than an hour. A passenger could travel from Chicago to London for a lunch meeting and be back in time for dinner with the family.

The cost for a quick trip into space, high enough to earn astronuat wings, usually defined as 100 km (65 miles) above sea level, is expected to run between $100,000 to $200,000. Prohibitive to be sure, but near the range of the middle class. And the cost will drop as more tickets are sold. Wanna take a ride? Space Adventures, Virgin Galactic, and XCOR would all love to talk to you.