Human

Rocket man

 By Nicholas Newman

This year is an exciting time for science fiction fans, with films like Star Wars, Star Trek, Independence Day, and the Martian out on release. The trouble is very little is ever said about how the vessels you see dashing across the galaxy are powered. The possibilities are endless including rockets, atomic, solar cells, reaction motors, solar sails, warp drive etc. Nicholas Newman looks at the various ways current and future spacecraft are likely to be powered…

It’s undeniable that 2016 is an exciting time for science-fiction fans, with films like “Star Wars,” “Independence Day” and “The Martian” out on release. However, for those of us who like to know how things really work, these fictionalized accounts say very little about what actually powers spacecrafts as they dash across the galaxy. The possibilities are apparently endless, ranging from rockets, nuclear power, solar cells, reaction motors, solar sails to warp drive. Yet, despite the apparent ease with which “Star Trek’s” Captain Kirk or “Star Wars'” Han Solo cross the galaxy, the scientific reality is that getting into space is incredibly difficult, and to make the 4.37 light-year journey to Alpha Centauri, the nearest star system to our solar system, may well be impossible.

Back on earth, chemical-based rockets still prevail. Every few days, Soyuz and Arianespace rockets blast off with supplies and astronauts to the International Space Station, or place satellites in orbit, or launch deep space probes to far distant Mars or Saturn. Space agencies, such as America’s National Aeronautics and Space Administration (NASA), Russia’s Russian Federal Space Agency (ROSCOSMOS) and Europe’s European Space Agency (ESA), all rely on chemical-based rocket engines to place objects into orbit around the earth, and the really astonishing thing is that much of the technology in use today would look familiar to rocket experts working more than half a century ago, such as Russia’s Sergei Pavlovich Korolev and America’s Wernher von Braun.

Why we are still using chemical rockets to get into space?

What is the possible alternative to chemical rockets? In an interview with Tony Schönherr of the ESA, Research Fellow in Electric Propulsion explains that, essentially, the thrusts of contemporary electric propulsion systems are too weak to power a rocket beyond the earth’s gravity system. Therefore, chemical-based rockets will prevail until current research into alternatives (such as beamed energy propulsion, space lifts and the design of a plane that can operate both in orbit and in the atmosphere) yield results.

The search for new launch solutions

One concept being explored by Colorado-based Escape Dynamics is beamed-energy propulsion. In theory, a ground station emits a high-power repetitive laser or microwave burst at a spacecraft in order to produce thrust and the surrounding air would fuel the spacecraft as it lifts off. This approach would reduce the launch vehicle’s payload devoted to propellant to 70 percent and “this means you have a full 30 percent to allocate to payload and structure,” states company president, Laetitia Garriott de Cayeu. She adds, “This is plenty in a world where chemical rockets have only 10 percent.” To date, only minor experiments to understand the physics and the infrastructure requirements of the ground station have been carried out, so it is too early to tell whether this approach could be a game-changer.

Another concept, the space lift, is under investigation by Canadian-based company Thoth Technology. Here, the basic idea is for “astronauts to ascend 20 km (12 mi) by electrical lift, from where space planes would launch in a single stage to orbit, returning to the top of the tower for refueling and re-flight” says Thoth CEO Caroline Roberts. For instance, Thoth Technology Inc. anticipates that the space lift would be 30 percent cheaper than the fuel used by a conventional rocket and, as it would be re-usable, costs would be even lower. Despite its conceptual attractions, constructing a tower from earth to the edge of space is both technically and materially challenging given the present state of technology and materials.

Star Trek calendar 2016

A more contemporary and practical potential option comes in the form of a space plane using the proposed British BAE Sabre (Synergetic Air-Breathing Rocket Engine), a new aerospace engine class, that combines both jet and rocket technologies to deliver people into space. Already, the British Government together with BAE, have invested over $113 million in this project, reports BAE. Not yet commercialized, unlike current chemical rocket engines, Schönherr predicts that “it is unlikely that such systems will replace the current chemical launcher capabilities in its entirety.”

Therefore, for the near future, we remain reliant on powerful chemical rockets. A case in point is Arianespace’s Ariane 5 heavy-lift launcher, which carries up to 200 metric tons (220 short tons) of liquid propellant in its tanks and another 240 metric tons (265 short tons) in its solid propellant boosters to kick an impressive 800 metric tons (882 short tons), in a controlled explosion, vertically off a launch pad and deliver a 20-metric ton (22- short ton) space-station supply vehicle to orbit a few minutes later. Unfortunately, such expensive rockets are used only once before crashing into the sea.

However, the era of the disposable chemical rocket is in sight with the incipient commercial introduction of such reusable rocket launch solutions as Space X and Blue Origin. At the current rate of progress, re-usable scheduled rocket launches should become commonplace by the end of the decade and the prospect of second-hand rockets being offered for sale on EBay is not unthinkable!

 

SEE MORE: Space race to power the final frontier by Amanda Saint

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In orbit: satellites and spacecraft

Traditionally, satellites use solar cells, batteries or nuclear-based technologies to provide electrical power on board. Solar Electric Propulsion (SEP) technologies, under development at NASA, could provide sufficient power for a future Asteroid Redirect Mission, which aims to move a large near-Earth asteroid into orbit around the Moon. “SEP works by utilizing magnetism and electricity to drive a ship through space. Electricity, generated by the ship’s solar panels, gives a positive electrical charge to atoms inside the chamber, which is pulled by magnetism towards the back of the ship and then pushed, by magnetic repulsion, out of the ship. (This resembles what happens when you hold the same pole of two different magnets close to each other. They repel each other.)

This steady stream of atoms, coming out of the spacecraft, gives it the thrust it needs to go forward through space. This combination of solar power and electric propulsion, so-called Solar Electric Propulsion (SEP), is and will be, a prominent choice for future space missions,” predicts Schönherr.

SpaceX's flagship Falcon 9 rocket (by www.qz.com)

Getting to Mars

Chemical rockets can reach as far as Mars. However, the success of ROSCOSMOS‘s launch of 32 spacecraft’s between 1970 and 1988 equipped with thermoelectric nuclear power plants has encouraged today’s space agencies to revisit nuclear-powered rockets. Sergey Kirienko, head of Rosatom says, “nuclear engines cut the journey time from Earth to Mars to just 30 days instead of one and half years.” In addition, since the propulsion used by nuclear engines would be half that of chemical rockets, larger loads could be carried and at greater speed. Moreover, unlike chemical engines, which are stuck with fixed trajectories, nuclear power allows craft to maneuver throughout the journey.

Both America’s Lockheed Martin and Russia’s Rosatom are currently developing nuclear-powered engines and the latter will test its design prototype in 2018. As to whether nuclear engines will be used on future Mars and Pluto missions will largely depend on risk assessments and familiarity since, as Schönherr advises, “policy makers will demand the use of well-known and often-tested technologies to minimize the chances of failure.”

(Explaining EmDrive, the ‘physics-defying’ thruster even NASA is puzzled over)

From research to science fiction

Ideas originating in the world’s space research centers are being popularized in current science-fiction literature and it has sometimes won the interest of space scientists. In “Star Trek’s Deep Space Nine,” solar or magnetic sail spacecraft capture light momentum with large, lightweight mirrored surfaces such as sails to provide perpetual thrust facilitating journeys from one planetary system to another. However, the reality is somewhat different. Demonstrations by The Planetary Society have highlighted the limitations of sails in particular; their sensitivity to environmental conditions such as the magnetic field of planets or variations in the solar cycle are likely to restrict mission opportunities. Under current technological knowledge, achievable speeds are rather slow, making them unsuitable for crewed missions.

As for other science-fiction based concepts, such as warp driveshyper- drives and reaction-less drives (such as the famed EmDrive), Schönherr suggests that “we either lack the theoretical understanding to support the claim for them to be a viable alternative, or lack the technological possibilities by a far reach, to demonstrate such a claim is viable.” However, the same was said in 1916, when Albert Einstein published his concept of gravitational waves. It took a century to prove their existence. It is more than likely that progress in replacing chemical rockets is likely to be incremental, repeating the pace of rocket development over the past century, rather than a sharp and sudden improvement as the result of discontinuous innovation.

about the author
Nicholas Newman
Freelance energy journalist and copywriter who regularly writes for AFRELEC, Economist, Energy World, EER, Petroleum Review, PGJ, E&P, Oil Review Africa, Oil Review Middle East. Shale Gas Guide. https://nicholasnewman.contently.com/