Top 10 Conceptual Spacecraft Engines

Launching a ship into space is a weird science and engineering process that takes a long time and costs a lot of money. Basically, we need rockets, which are very powerful motors that use high-speed propellant exhausts to move forward. By the standards of the last century, the way they work is a miracle of technology, but the basics are pretty simple. When the pressure is high, an igniter makes the fuel and a source of oxygen explode in a combustion chamber (usually liquid). As reaction mass, the fluid that comes out of the end nozzle is the result.

Unlike jets, which use air to move, rockets can’t use atmospheric gases to move because the atmosphere gets too thin at orbital heights. So, a rocket engine must use the fluid that comes out of it to move. Looks easy, but the technical issues involved in designing, building, putting together, and testing working spacecraft send the cost of any satcom launch through the roof.

Chemical rockets that use exothermic reactions to move seem to be able to go no further than getting past Earth’s gravity and into space. Luckily, applied science is less about going against the laws of physics and more about figuring out how to make them work in a good way. Here are 10 ideas for spaceship drives that could help humans learn more about the universe.

10. Synergistic Turbojet

The single-stage-to-orbit (SSTO) approach is an idea for a propulsion system that doesn’t need to throw away parts to reach orbital height. It could be used to make spacecraft cheaper. During launch, it would use air from the atmosphere to feed the engine’s burning reaction. This way, it wouldn’t need to carry extra oxidizer, which would make it lighter.

In response to this idea, the British company Reaction Engines Limited (REL) made its Skylon spaceplane work with a concept engine called SABRE. To get thrust from only its own hardware, SABRE will be able to switch between two modes of operation: a typical turbojet that runs on air from the atmosphere and a traditional rocket engine that runs on liquid oxygen.

9. A Nuclear Thermal Rocket

Rosatom, a Russian government company that handles nuclear issues, is building a rocket engine that could get people from Earth to Mars in 45 days (against the current 18 months). This kind of tech will be like the nuclear thermal rockets (NTRs) that the URSS made during the Cold War. In an onboard reactor, splitting atoms releases energy that is used to superheat working fluid. This creates high pressure and thrust, just like what happens when propellant burns in a chemical rocket. Because nuclear fuel packs a lot of energy into a small area, NTR engines are lighter and use less fuel.

In the same way, NASA brought back its NTR project 40 years after the NERVA programme ended. The space agency is also looking at a wider range of nuclear power ideas, such as fusion-powered rockets and nuclear light bulbs.

8. Antimatter Thermal Drive

Matter makes up every physical thing in the universe. Matter is made up of particles, and every particle has a dark twin called an antiparticle. An antiparticle is the same as its opposite in every way except that it has the opposite charge. When both twins get together, they destroy each other and let out a lot of energy in the process. NASA scientists want to use this power to speed up rocket engines so that they can be used to travel between stars.

Like NTRs, antimatter annihilation would heat up working fluid to make thrust, but it would do so with a much smaller amount of fuel. 100 milligrammes of antimatter is enough to get to Mars, but for a manned mission, a chemical rocket would need tonnes of fuel. Researchers even want to use Kickstarter to raise money for a ship made of antimatter.

7. Propulsion by a nuclear pulse

What about a trip to Alpha Centauri where you drop atomic bombs to move your spaceship along? Nuclear pulse propulsion could be the best way to travel between stars. Project Orion was started in 1958 as a DARPA project. Its goal was to build a real space opera ship, with 200 crew members and a takeoff weight of thousands of tonnes, and send it into orbit using nuclear pulse propulsion. Theoretically and technically, everything is possible.

An Orion engine could make megatons of thrust by using small nuclear explosions to push against a big plate of steel that was attached to the spacecraft with shock absorbers. However, political issues and the cost of the project turned out to be bigger problems than the technical ones. After a number of successes, Project Orion was shut down in 1965. However, similar ideas like the Medusa spacecraft and antimatter-fission propulsion are still being studied.

6. Nanoparticle Micropropulsion

Electrically charging propellant molecules and then boosting them with magnetic fields is a very effective way to move a spacecraft. Even though ion thrusters have a small impulse force, they use many times less energy than chemical rockets and eventually catch up with exothermic propulsion. By the way, that was how the Dawn spacecraft moved until it reached Vesta and Ceres.

With help from the Air Force Office of Scientific Research, the University of Michigan is making an experimental ion thruster called NanoFET. Through nanoelectromechanical systems, the engine would fire trillions of nanoparticles of propellant. This would open the door to the idea of a “thruster on a chip,” which could power the small satellites of the future. Grids of NanoFET modules could be changed and scaled up to meet the needs of different designs and engineering tasks.

5. Q-Thruster

Newton’s third law says that rockets have thrust when they release propellant. But what if a drive could break this basic rule of nature? When Roger Shawyer, a British aerospace engineer, proposed the radio frequency resonant cavity thruster, or EmDrive, in 1999, he thought it was a good idea (Electromagnetic Drive). In an EmDrive, microwaves would be bounced around inside a cone to push toward the narrow end. Even though Chinese, German, and NASA scientists repeated Shawyer’s steps and got the same results, the experiment still caused a stir in the scientific community.

EmDrives are still on the edge of physics in terms of how they work. The theory of quantum fluctuations says that energetic particles pop in and out of the real world through vacuum. A ship could get thrust by using microwaves to interact with these particles.

4. Thruster with a photonic laser

Young K. Bae is a physicist with a Ph.D. and the founder of the Y. K. Bae Corp, which studies “green” technologies in the energy and space travel fields. Photonic railways, a new class of molecules, and the Photonic Laser Thruster are some of Bae’s patents (PLT). NASA gave Bae money to study the PLT, and he came up with an idea for a space driver that wouldn’t need to carry fuel tanks. Instead, lasers will be fired at the PLT in order to give it thrust. Since there is no friction in a vacuum, a PLT-powered ship would slowly gain speed and reach Mars in a few days.

Developments in Directed Energy technology will be necessary to make laser beams with many megawatts that can propel a spacecraft through space. This will make it possible to build a spacecraft without heavy parts like fuel and main power supplies.

3. Space Launcher with a Coilgun

Since the 1960s, authors of science fiction like Arthur C. Clarke and Robert Heinlein have used electromagnetic catapults as plot devices. Even though it seems like science fiction now, scientists like Dr. James Powell and Dr. Gordon Danby think it will be possible to use magnets to speed up a payload hundreds of miles above Earth. Powell and Danby came up with superconducting maglev (magnetic suspension), which led to the development of EM trains. Now, with their Startram Project, they want to use the same technology for space travel.

In Powell and Danby’s plan, coils would create a strong magnetic field that would propel a spaceship or payload at high speed over miles of railroad, similar to how a coilgun’s projectile moves. The track will be several miles long and cost tens of billions of dollars, but its creators say that’s a small price to pay for the future.

2. Stellar Windjammer

The Sun, like all other stars, is always spewing out charged particles—a real gale of protons and electrons going very fast. This kind of pressure from radiation can push against a magnetic field and make thrust.

After ten years of travelling through space, a sunjammer spaceship would be able to cross the far edges of our solar system without wasting any fuel. It would do this by using the magnetic and gravitational fields of exoplanets to adjust its path. By changing the sail to match the solar wind, the direction of the thrust could be changed.

Since the force of propulsion would depend on the size of the magnetic field, a solar sail would need hundreds of metres and kilometres of superconductor material to make its magnetic field, making it look more like cyclopean loops of wire than the wind-catching canvases of the Navigation Age.

1. Alcubierre Drive

Einstein’s field equations say that spacetime can be bent by energy and matter. Speculatively, it might be possible to make a ship appear to travel faster than light by stretching space behind it and contracting it in front of it. Like a scrolling game, the space would move, not the ship, so no relativistic law would be broken. Riding on a warp bubble of spacetime waves, our ship could travel at speeds many orders of magnitude faster than light. Even Mars could be reached in less than a second, but I think slowing down would be a problem.

Miguel Alcubierre, a Mexican physicist, came up with the Alcubierre drive or just “warp drive” as a way to solve Einstein’s field equations, which say that energy and matter can bend the spacetime mesh. Using a field with less than zero mass, the warp drive would twist and move through space.

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