Well it’s official Rockets are obsolete! Getting of Earth’s gravity well is quite the challenge and conventional rockets just don’t seem to be doing the job efficiently. Thankfully, alternative ways of getting to space are already in the works—and though they won’t replace rockets entirely—our exploration will not be tethered to them. And human’s long-term future may actually depend on these alternatives.
Today, rockets are prohibitively expensive and dangerous. NASA’s new Space Launch system is expected to cost about $500 million per launch, while SpaceX’s Falcon Heavy will be $83 million.
Scientists and engineers have been proposing alternative launch systems for years and some of them have technological promise. According to io9, they can be divided into the following broad categories: (1) alternative propulsion schemes, (2) fixed, tensile, and dynamic transportation structures, and (3) projectile launch systems.
Alternative Propulsion Schemes
Laser propulsion – Could the use of ground-based lasers propel rockets into space? Russian scientists Yuri Rezunkov and Alexander Schmidt certainly seem to think so. They have described a process of “laser ablation” where a pulsed laser beam hits a receiving surface, heats it up, and burns off material to create a plasma plume. The resulting exhaust would generate additional thrust with the capability of pushing an aircraft beyond ten times the speed of sound.
Stratolaunchers – There are plans in process to send aircrafts into space through high altitude air launches or directly via powerful space planes. One of the primary advantages of air launches is that rockets are not required to fly through the high-density atmosphere on their way to space, avoiding extra drafts that slow them down.
Spaceplanes – These reusable launchers are similar to the Space Shuttle, but won’t require rockets to get them into orbit. The British Skylon spaceplane is among the most developed of these, though there are still many technological hurdles to overcome.
Fixed, Tensile, and Dynamic Structures
Can you imagine a fixed tower with a top that reaches past the Earth’s surface? Geoff Landis certainly has—and he believed the tip could be used as a launch site for a conventional rocket. Another proposed static structure is the space elevator, a 22,000-mile cable extending from the surface of the Earth to geosynchronous orbit. Laser-powered climbers would climb the cable, delivering cargo into space.
Though space elevators could certainly revolutionize the way we get ourselves to space, its building is quite complex and it could be some time before the required material to endure the strain will even be developed. The idea of using carbon nanotubes are on the table, or even microscopically small diamonds.
Another proposal on the table are vertical skyhooks—momentum exchange tethers that do not reach the group. A suborbital spaceplane would simply fly to the base and unload its cargo. Skyhooks would not be subject to the same pressures exerted by a space elevator, so they may be a more viable technological option. Still, they would require some kind of propulsion system for altitude control.
And then there are dynamic structures like Space Fountains, the Launch Loop, and Rotovators.
Projectile Launch Systems
It might sound cartoon-worthy, but it is possible we may be able to send objects into space by propelling them with a cannon—assuming the cargo could be designed to withstand extreme forces.
Electrically-driven: In this proposal, devices like rail guns and mass drivers would function as electrically generated cannons, gradually accelerating vehicles during launch—either fired away at escape velocity or launched at orbital velocity. This proposal is both heavy and expensive.
Chemically-driven: Chemical guns work by driving objects with propellant gasses like hydrogen and other combustible compounds. But they would require special cargo and the ability to put the projectile into stable orbit.
Mechanical: Some have even proposed shooting a projectile into space with a slingshot. The device would spin an object around a fixed point as a way to build up high velocity without having to expend much energy.