Fifty-five years ago on October 4th, the Soviet Union launched Sputnik. Twelve years later two astronauts landed on the Moon and returned to Earth. Today humans occupy the International Space Station for long periods of time studying the effects of space on our physiology while robots explore the surface of Mars and spacecraft orbit planets from Mercury to Saturn. Two spacecraft we launched in the 1970s have reached the outer limits of our Solar System and are entering interstellar space. And a satellite launched a few years ago is discovering remote planets circling nearby stars.
Fifty-five years with so many advances in our knowledge, but very little in the way of advancement in the way we send humans and payloads into space. Because we continue to rely on chemical-based propulsion systems to climb out of the gravity well that is Earth. What if there were another way to get off the planet? What, if instead of putting the propulsion system at the tail end of the payload we want to launch we remove it entirely?
In past blog entries we have talked about the future of rocketry with heavy launch systems, nuclear rockets, solar sails, plasma engines, and other propulsion technologies. Heavy launch whether Ariane, NASA’s Space Launch System, Space X Falcon Heavy, or Russia’s Angara are all chemical-based. The others are technologies that cannot get us off the ground into space but are choices we can make once out of the Earth’s atmosphere.
Currently we have seen the development of hybrid launch technologies for sub-orbital flights. Virgin Galactic is a good example with its White Knight and SpaceShipOne mated configuration. But engineers and scientists have proposed other alternatives as well. These include:
- Space Elevators – We have mentioned space elevators in previous blogs. First proposed in 1960 by a Soviet scientist, Yuri Artsutanov, the idea has recently been revived with the discovery of carbon nanotubes, a material strong enough to tether a ground-based station to a space platform in low-Earth orbit. A space elevator could move payloads into Earth orbit at one hundredth the cost of current chemical launch systems.
- Catapult Launch – Historically catapults were used as siege engines to hurl large projectiles over city walls. The issue is size. To launch a large payload into space would require a significantly larger catapult with a counterweight arm. To launch an unpowered one kiloton payload into orbit at escape velocity would require a massive catapult arm stretching as much as 80 meters in length counterbalanced by a 100 kiloton weight. Doesn’t sound like this has much potential.
- Space Cannon – As proposed by John Hunter, the device, a gas propelled gun, would be a one kilometer (3,600 foot) in length and could send payloads into space for as little as $550 per kilogram ($250 per pound). The gun would use a mechanism to compress hydrogen gas which upon release would propel a projectile at a velocity to escape the atmosphere.
- Maglev Launch – also mentioned in a previous blog posting, uses the technology in maglev trains, superconducting magnets, to accelerate a payload in a vacuum-sealed ascending tunnel to achieve escape velocity speeds.
- Laser and Microwave Propulsion – also known as beamed thermal propulsion would involve pushing an object into space by shining a laser or microwave beam on to a heat exchange system which would then heat on board liquid hydrogen converting it to a gas and pushing it through a rocket nozzle. Such a beamed device would take 8 to 10 minutes to achieve orbit if using a laser, and 3 to 4 minutes if using microwaves as a source. This would be an effective way to launch small payloads into orbit and would be much safer than chemical rockets.
Today we launch satellites from locations at relatively low elevations. The Baikonur Cosmodrome sits 90 meters above sea level. Cape Canaveral sits on the edge of the Atlantic Ocean. The Guiana Space Center is another coastal site from which the European Space Agency launches its satellites. Jiuquan, where China launches its human space flight program sits 1,000 meters (3,300 feet) above sea level. Spaceport America, Virgin Galactic’s new commercial launch site sits 1,400 meters (4.595 feet) above sea level. To minimize the gravity well I wonder why we are not launching rockets from locations at much higher elevations. One could argue the top of mountains would be most suitable. And a mountain top near the Equator would prove to be ideal. Some engineers have suggested that launching from a mountain top would not only dramatically cut down on chemical rocket fuel requirements it would also limit the amount of stress the rocket would experience as it ascends. Current rockets throttle back during ascent to avoid structural damage from air resistance. This is referred to as Max Q or maximum dynamic pressure. In thinner air this would go away. It was during throttle up after passing through Max Q that the Space Shuttle Challenger in 1986 exploded.
As we experience the next 55 years in space it is clear that we will need to change the technology we currently use to make space more accessible from Earth and far more affordable. Advanced chemical-based launch systems may continue to get large payloads into near-Earth space but as the century unfolds where we go will depend on us changing this paradigm. Only then will space become an experience not for just a select few.