Are space elevators realistic?

In 1895, Konstantin Tsiolkovsky, the grandfather of astronautics, proposed for the first time the concept of space elevator. Since that time, there was considerable skepticism towards this concept. However in December 2013, the International Academy of Astronautics “Concludes Space Elevators Seem Feasible” as described in the book “Space Elevators: An Assessment of the Technological Feasibility and the Way Forward”.

Will we ever see an astronaut exploring space launched by a space elevator?

Alternative launching system

A space elevator is a mass transport system to reach space. The concept consists of a very long cable attached near the equator of the planet and extended into space beyond geostationary orbit. Most current concepts are proposed for Earth implementation but it could take place on another planet. This alternative to large rockets would be an asset for space exploration.

In 2003, Dr. Bradley C. Edwards established guidelines for the construction in his book “The Space Elevator: A Revolutionary Earth-to-Space Transportation System”. Most of designs include four basic elements:

  • Anchor station: an anchor that could be on mobile a platform in the ocean or static on the top of a mountain. The location will be preferably near the equator in order to benefit of natural Earth velocity.
  • Ribbon: it has to support a colossal tension which varies with the altitude and a large weight (its own weight and the climber). It is a guide for the climber.
  • Climber: in that case, the cable doesn’t pull the cabin, it must climb by itself. It could carry payloads and crew to space for Earth orbit or for further space destinations. A good velocity is 200 km/h which means a 180 hours (<8 days) trip to geosynchronous orbit (36 000km).
  •  Counterweight: it could be a space rock or a specific station. Earth’s rotation creates upward centrifugal force on the counterweight. Cargo carried from the surface would allowed to be launched into interplanetary space thanks to the considerable velocity gained relatively to the Earth.
Space elevtor mechanics - Credits: unkwon

Space elevtor mechanics – Credits: unknown

Once the expensive job of building the elevator is completed, an indefinite number of loads can be transported into orbit at reduced cost.

This machine could carry payload and human into space, up to geostationary orbit and beyond. The ascension would be less stressful for the human body, safer and cheaper on a routine basis. It is a nice opportunity to make space more accessible to a larger amount of people.

The cost of a space elevator

In his book Leaving Earth (2013), Andrew Rader provides some numbers about big building projects:

“Other notable megaprojects in this price range include (2013 dollars): the Manhattan project ($26 billion), the English Channel tunnel ($17 billion), the Boston “Big Dig” tunnel system ($15 billion), the Arabian canal ($11 billion), the John F. Kennedy airport expansion ($10 billion), the Yucca mountain nuclear waste depository ($9 billion), and the Atlanta-Jackson airport expansion ($9 billion).”

Current estimations start from US$6 to US$20 billion for building one space elevator from Earth’s equator to geostationary orbit. This prices includes: in orbit construction, ribbon, power beaming stations, climbers, anchor station, tracking facilities, insurance, testing and contingency. This budget fits into the range of similar super structures and should provide some revenue.

Currently, the cost for sending a cargo to the geostationary orbit with a thermal rocket is around US$20 000/kg and the cost to send a cargo with a space elevator would be around US$250/kg (Edwards). Most of the price covers the power supply, the maintenance and the operating. It is not crazy to imagine a return on investment within 10 years.

The challenge

Space elevator - Crédits: unkwon

Space elevator – Crédits: unknown

Currently, there are many technologic challenges to build a space elevator. It might be difficult to see such a structure in a near future. Scientists and engineers should fix some remaining problems:

  • The construction of the ribbon: currently, there is not any existing material with a sufficient high tensile strength and with low density capable to comply with the structure requirements yet.
  • Prevent the swing: the ribbon and the climber will undergo some swing generated by the gravitational effect from the Moon and the Sun. It will also suffer from the Coriolis Effect (problem also evocated in the article about artificial gravity).
  • Risk of collision: that will have an impact on the air traffic. Plus, there is a risk of impact with a space object (satellites, debris, meteorites, …)
  • Environmental damage: the system will suffer from corrosion and radiation.

All those problems will jeopardize the total integrity of the space elevator. However, many researches are conducted all around the world about those topics. Astronauts will not escape from the Earth’s gravity via a space elevator tomorrow but we prefer to believe that it’s remain possible.

Next big conference about space elevators takes place in Seattle (USA), August 22-24, 2014 – ISEC Space Elevator Conference

Space elevator and fiction

Space elevators are also very popular in fiction. Sci-Fi novels, fairy tails, anime, manga and comics are fond of crazy technologies and often precursors of innovation: Jules Verne and Hergé went to the Moon a long time before the NASA. Star Trek’s TOS communicator has been inspiration for the first handheld mobile phone. It has also a large place in futuristic games like Syndicate Wars, Civilization IV and, Halo. However, it is underrepresented in TV series and movies: Star Trek and Doctor Who save the situation.

Because we are all Born For Space!

Mass Driver: an alternative launching system

Gerard K. O’Neill was an American physicist who strongly believed in the human settlement of outer space. He also imagined an innovative launching system named ‘mass driver’, also known as the “electromagnetic catapult”.

Technical description of a mass driver

Basically, a mass driver is a catapult tube using coils of wire powered by electricity. It produces magnetic fields to accelerate a bucket through an accelerator tube.  The method is very different to the conventional use of chemical rockets.The tube consists of several coils, the ‘drive coils’. The bucket also contains a coil named the ‘bucket coil’. The ‘bucket coil’ is accelerated by the ‘drive coils’ while passing through, due to the electromagnetism. The drive coil only turns on when the bucket coil is inside.

Click to see the GIF

Mass Driver

Mass Driver (GIF)

So what?

This launching system has advantages and disadvantages.

Regrettably, this launching system doesn’t allow mid-course correction. The launch window must be as accurate as possible.

As long as the spacecraft uses ‘distant forces’ and doesn’t use chemical explosions for the propulsion, the launching system and the spacecraft are reusable. This is more financially favorable in the case of regular and long term use compared to single use systems.

At the moment, it is still very difficult to have this kind of system on Earth because of the high gravity and dense atmosphere. Nevertheless, the Moon looks to be very appropriate for mass drivers. Indeed, it would also preserve the lunar environment by reducing the creation of an unwanted atmosphere due to rocket fuel propellant.

The launch track would be very long and could reach the target velocity relatively smoothly, preserving passengers from harmful acceleration.

The space industrialization

The expansion of the mass driver was very popular during the 70s due to the push from Gerard K. O’Neill, Freeman Dyson, and Henry H.Kolm. Today this technology is mainly studied for military purposes.

The mass driver could be used as daily transport system from the Moon to lunar orbit for industry purposes. This would involve a massive industrialization of the Moon and- large scale infrastructure.

Moon industrialization & Mass driver. Credits: Pat Rawlings/Lunar Planetary Institute

Moon industrialization & Mass driver. Credits: Pat Rawlings/Lunar Planetary Institute

Most of the research has been performed so far has been conducted by the Space Studies Institute (SSI).

Further information are proposed on the PERMANENT website.

Because we are all Born For Space!