Is it cheaper to buy a kilogram of European white truffles, or send a kilogram of rocks into low Earth orbit (LEO)? The answer may surprise you: while the average cost of sending a kilogram of anything into orbit varies considerably (anywhere from approximately 5,000 to 45,000 US dollars), the truffles actually cost less, if one assumes a representative launch cost to LEO of 20,000 US dollars per kilogram. Lowering the cost of space access has been one of the major goals of the space transportation industry, but what technologies can help to reduce the cost of access to space?
Why are rockets so expensive?
It is not the fuel: although enormous amounts are required – approximately 10 kilograms of propellant per kilogram launched into orbit, or 100 metric tons for a “typical” 10-ton payload – fuel constitutes less than one percent of the cost of a current rocket. While a lot of the cost certainly has to do with the extensive research, development and testing that goes into building each type of rocket, and the current lack of industrial scale manufacturing, the main reason is that all commercial rockets are currently discarded after a single use.
This sounds crazy – imagine how expensive it would be if a car or airplane were discarded after a single trip? But it has thus far been extremely difficult to design a rocket that can safely reenter the Earth’s atmosphere after use and perform reliably over multiple cycles.
At orbital speeds, the compression of the thin air in the upper atmosphere acts like a searing flame, generating punishing heat against the exterior of the spacecraft. Most vehicles simply burn up (as all discarded rocket stages do now).
Vehicles designed to survive reentry use special heat-resistant materials and carefully-designed aerodynamics, and are often reusable; the most familiar example is the recently-retired Space Shuttle, but the reentry vehicle represents a small fraction of the initial launch mass (and cost) of the spacecraft, so to significantly bring down overall cost, the majority of the hardware must be reused as well.
Effective ways to reduce the cost of access to space
It now appears that this goal maybe within reach. Multiple commercial space companies are developing reusable launch vehicles using different approaches. Some are developing reusable first-stage rockets that separate after a burn of approximately three minutes and deploy aerodynamic fins and brakes while simultaneously firing their engines once again to slow down for a soft landing.
Others are pursuing an entirely different launch strategy – taking off via ordinary airplane with a rocket-equipped spacecraft strapped underneath, which then launches at maximum cruising speed high in the stratosphere. This saves fuel by taking advantage of the airplane’s aerodynamic lift, and both the plane and spacecraft can be re-used.
Still other strategies include supplying energy externally rather than carrying it along in the form of fuel. This approach has been used for decades in much smaller thrust applications for small spacecraft already in orbit; electric power from a solar array or nuclear reactor is used to heat (and in some cases ionize) a small amount of gas that is carried onboard. The kinetic energy is supplied not from chemical energy in the gas, but from this external power source.
Using this same idea for ground-based launch may sound preposterous at first, but it is just a matter of transmitting the energy, estimated in this case to be 325 kilowatt-hour (or about 10 days’ of an average U.S. home’s consumption) per kilogram of payload. Microwaves – of a similar wavelength to those found in a kitchen – are used to send the energy to a heat-absorbing material on the underside of the spacecraft, where it heats hydrogen to above 2000 degrees Celsius, producing sufficient thrust.
Finally, a strategy that, while not yet a viable business, is inching closer to reality is that of a space “elevator,” or cable between the Earth’s surface and geostationary orbit (at 35,786 kilometers) or higher. Once built, spacecraft “climbers” would slowly ascend it over several days, powered only by electricity, to reach almost any desired orbit; spacecraft returning to Earth would similarly descend slowly, without the need for reentry shielding. The technical limitation is a strong enough cable material, but recent advances point toward a possible solution.
How does the reduced cost of access to space affect the future space travel?
Any one of these approaches hold the promise of reducing launch costs to LEO by at least tenfold and possibly a hundredfold or more eventually. In economic terms, this means that the cost of sending a kilogram into LEO might one day be on par with shipping it around the world via overnight delivery. In more human terms, a person and their effects (perhaps 150 kilograms in total) might one day pay $30,000 or less to fly into space – for a joy ride, few days’ leisure in an orbiting space hotel, business meeting in a commercial space station, or docking for an interplanetary journey.
Together with improvements in reliability and reduction in delays that come with routine operation, such a cost point would represent a transformational bargain, and would usher in many business opportunities that are simply not viable today, but could be worth trillions of dollars in the future.
What do you think significantly lower cost access to space would mean for your business or humanity in general? Share your thoughts in the comment section.
Please note that this article expresses the opinions of the author and does not reflect the views of Move Forward.