Space Elevator FAQ

What is a Galactic Harbour?

Why space elevators?

How strong does the material have to be?

What is the ISEC Space Elevator Baseline Concept?

A  Space Elevator (SE) can be thought of as a vertical railroad into space. A tether (cable) stretches from the ground to an Apex Anchor (counterweight) 100,000 km up/out in space. Elevator cars (tether climbers), powered by electricity travel up and down the tether and carry cargo and eventually humans to and from space. The space elevator is the most promising transportation infrastructure on the drawing boards today, combining scalability, low cost, quality of ride, massive payload throughput and safety to deliver truly commercial-grade space access – practically comparable to a train ride into space. The massive movement capability as well as the low cost ensure that the infrastructure approach is "right."

The Space Elevator Transportation Infrastructure is based on a thin vertical tether stretched from the ground to a mass far out in space with electric tether climbers that drive up and down the tether. The rotation of the Earth keeps the tether taut and capable of supporting the climbers. The climbers travel at speeds comparable to a fast train, and carry no fuel on board – they are powered by a choice or combination of sunlight and laser light projected from the ground. While the trip to space takes several days, climbers are launched once per day with a first “baseline” design of 20 metric ton climbers.  However, as the infrastructure matures, by maturing the tether (stronger or thicker), we can grow the Space Elevator to lift 100 metric tons at a time. In addition to launching payloads into orbit, the space elevator can also use its rotational motion to inject them into planetary transfer orbits – thus able to launch payloads to Mars, for example, once per day.  This release from the Apex Anchor can enable massive movement of cargo and supplies daily and with fast transit vs. the Hohmann only once every 26 months.  Imagine the kind of infrastructure we can set up there, waiting for the first settlers to arrive.  Looking back from the year 2100, the construction of the space elevator will be considered to mark the true beginning of the Space Age, much like the advent of the airplane or steamboat heralded the true commercial use of the air and sea.  A complementary infrastructure of rockets and space elevators will make this happen.

#2 What is a Galactic Harbour?

The idea of a space elevator can be attributed to several different visionaries spread over more than 125 years. In 1895, a Russian scientist named Konstantin Tsiolkovsky first proposed a tower into space. In 1959, another Russian scientist, Yuri Artsutanov came up with the idea of a tensile structure, something being pulled away rather than built up, to get into space. This idea used a satellite in Geosynchronous Orbit (GEO) to send a tether down to the Earth. In 1966, the idea moved in the U.S. with four American scientists writing an article about their “sky-hook” in the journal Science. American Jerome Pearson independently ‘discovered’ the idea of a Space Elevator and, in 1975, published his concept of the “Orbital Tower”. By 1979 the concept was being spread to a larger audience by Arthur C. Clark in his novel “The Fountains of Paradise.”  Today, Artsutanov and Pearson are recognized as co-inventors of the concept with Bradley Edwards providing a solid design for the modern day, achievable, space elevator in 2002. For more information see the Space Elevator Historical Documents on our History page.

This key question must be answered each time ISEC produces a book or report as we must encourage, enthrall, challenge, explain, and provide hope for readers. To anyone who looks up from their chair periodically and searches the heavens for the future of mankind, it is obvious that we are moving off-planet in a major fashion, and in the near future. Besides regular American, Russian and European space activities, the Chinese have landed a rover on the Moon and are planning a space station, the Indians have orbited a spacecraft around Mars, and the Japanese have a module attached to the International Space Station (ISS). The National Aeronautics and Space Administration (NASA) Jet Propulsion Lab (JPL) has identified over 1,300 near-Earth asteroids that are compatible with rapid trips made from Earth. There are three companies investing in mining resources on asteroids while there are multiple companies preparing to create small habitats on the Moon. In addition, there is a rocket company (SpaceX) that plans on building a colony of greater than 10,000 people on Mars within its CEO’s lifetime.

To ensure that these dreams are encouraged and made successful, there must be a change in the approach to travel within our solar system. The cost to orbit must become a very small part of the overall investment and the arena must support infrastructures that can be used many times, not thrown away each time they are used. When one looks at the concept of space elevators, the answer is obvious. The future of humanity’s travel within our solar system requires space elevators that provide access to space and that have the following strengths:

• Routine [daily],

• Revolutionarily inexpensive [<$100 per kg]

• Commercial development similar to bridge building

• Permanent infrastructure [24/7/365/50 years]

• Environmentally sound

• Safe and reliable [no shake, rattle and roll]

• Low risk lifting

• Low probability of creating orbital debris

• Redundant paths as multiple sets of space elevators become operational

• Massive loads per day [starts at 20 metric tons]

• Opens up tremendous design opportunities for users

• Optimized for geostationary orbit altitude and beyond.

Recently, with a group of students conducting research into Fast Transits to Mars from the Apex Anchor, new revelations occurred.  The concept of using a 100,000 km high release point expands strengths of space elevators due to the tremendous energy and addresses the opportunities available for massive logistics support.  The three Apex Anchor characteristic strengths not studied before are:

• Fast Transit to destination (Mars as short as 76 days).  Arizona State University (ASU) research into release from an Apex Anchor with the concept of a Lambert Problem solution shows remarkable transit times periodically during the 26 month orbital relationship between Earth and Mars.

• Massive liftoff capability (14 metric tons payload per day to start).  Space Elevators start out with huge throughput capacity with daily liftoffs (5,110 MT per year).  In addition, there will be remarkable growth as the tether material and infrastructures mature.  The Initial Operational Capability starts at 14 MT of payload per day with the Full Operational Capability reaching 79 MTs.  

• Daily departures available (no waiting for 26 month Mars Launch Windows).  The ability to launch each day towards Mars is a revolutionary concept vs. the traditional wait period of 26 months (the dreaded 26 month launch window restrictions currently in place).  Transit times for cargo can vary over the repeating planetary dance; but, they can be started towards Mars each day simplifying the mission support concept.

  The bottom line for space elevators and the solar system is that they open up humanity’s hopes and needs to expand beyond the limited resources and environment of our planet Earth. A space elevator is the enabling infrastructure ensuring humanity’s growth towards the stars. There are two main reasons why the human race needs space elevator infrastructures:

• The realization that chemical rockets cannot get us to and beyond Low Earth Orbit (LEO) economically.  There must be a complementary infrastructure with both rockets and space elevators leveraging each systems strengths.

• The recognition that the ‘Space Option’ may enable solutions to some of Earth’s current limitations (energy, resources, removing nuclear waste etc.)

What kind of specific benefits could we expect to see from a functioning Space Elevator? As with the transcontinental railway, it’s impossible to foretell all of the uses of such an infrastructure, but here are some possibilities

• Colonization of the Moon, Mars and other planets. Currently, establishing and supplying a 6 or 8 person science station on the moon (let alone Mars or anywhere else) is probably at the very limit of our capabilities. Allowing hundreds (or even thousands) of tons to be launched into space every day would allow us to colonize these other worlds. This would provide an insurance policy for humanity, an outlet for those with a pioneering spirit and, almost certainly, increased benefits here on earth as commerce between our planet and others was established.

• Large scale manufacturing in a zero-g environment. If corporations can build manufacturing facilities in space at an affordable price, they will do so. Right now, the cost and weight penalties are too prohibitive to even consider the idea. A space elevator would change that.

• Space Tourism – A Space Elevator could provide a way that most of us could visit space, and even stay for a while if we wanted to.

• Clean Power – Though there are many debates about the economics of establishing solar power satellites to provide Earth with clean, limitless power, there is no doubt that to do so will require the capability to launch enormous quantities of materials into space. Only a Space Elevator can give us that capability.

• More and cheaper satellites. Satellite technology has provided all of us with enormous benefits, from DirecTV to weather satellites to increased national security. Being able to lower the cost and increase the reliability of satellite launches will lead to new technologies that right now we can’t even imagine.

Scalable, inexpensive and reliable access to space will benefit all of us and a Space Elevator is the way to provide this capability.  Indeed, a complementary infrastructure of rockets and space elevators will enable so much more off-planet. 

The Space Elevator stays vertical because of its mass rotating at high velocity at great distances above the Earth.  Imagine you are holding a rope with a weight attached to the end. If you swing the rope in a circle at a sufficient speed, the rope will become taut, revolving about your hand. The force pulling the rope taut is known as centrifugal force. This same centrifugal force, generated by the rotation of the Earth, will pull the space elevator tether upwards into space (outwards from the Earth).  The outward force stabilizes the tether with enough energy to allow 20 metric ton tether climbers to pull down on it and climb vertically.  Routinely and daily a tether climber carrying cargo or people will be attached to the tether at the Earth Port. Tether Climbers will ascend the tether, quickly leave the atmosphere and begin to make their way past Low Earth Orbit altitude, between 160 and 2000 km up. After about seven days, the tether climber will reach Geosynchronous Orbit where cargo can be off-loaded. The cargo that remains on the tether above geosynchronous orbit will be moving faster than required to stay in orbit and can be released and sent to destinations such as the Moon or Mars. The tether climbers will then ascend to the end of the tether where they will become part of the Apex Anchor as counter-weight. 

#6 How strong does the material have to be?

The first important term for this question is Specific Strength. A spider web might not seem very strong but it has a high Specific Strength because of what it can hold versus its thickness. This is very important for a Space Elevator because all of the material will have to be lifted into space and because the Tether will have to be able to hold itself together over a great distance. The standard unit of measurement for Specific Strength is stress/density or Pascal/(kg/m3), for our purposes this can be adjusted to be GPa-cc/g (1Gpa-cc/g = 1 million Pascal/(kg/m3)). For simplicity ISEC has adopted the measurement scale of Yuri’s, named after Yuri Artsutanov, where 1 MYuri is equal to 1 GPa-cc/g. Steel wire has a specific strength of about .5MYuri. Now we enter the realm of what is technically needed to build a Tether into space versus what is required to make a practical Space Elevator. A Tether with a specific strength of 25MYuri could be built but it would require a lot of mass and would not really be able to lift much. In the Space Elevator Feasibility Condition, the Spaceward Foundation’s Ben Shelef discusses this problem in detail and shows how several factors enter into the question. The bottom line is that stronger is better with 30-40 MYuri’s being the best bet for a practical Space Elevator in the near term, well within the predicted limits for carbon nanotubes and single crystal graphene. Less initial material and more payloads to orbit will increase the rate at which a Space Elevator becomes a profitable venture.  The recent discovery and production of a 0.5 x 0.1 meter single crystal of carbon atoms one layer thick has opened up the real possibility that a tether can be developed in the next few years.  The material for the space elevator appears to be here - in the laboratory. 

ISEC realizes that the density of space debris could become a serious hazard in the future.  The 2010 ISEC Study Report presented an honest look at the space debris density numbers, where the Space Elevator is most vulnerable, and what can be done about the problem. It shows that space debris is a manageable problem, giving proper foresight and engineering. The key is that ISEC believes the future will include a large global effort lowering the threats from space debris.  ISEC depends strongly upon the future space community actively addressing this environmental pollution problem with a positive approach before our first tethers in the 2030 time period.  ISEC and the space community looking at the idea of a Space Elevator for the first time are concerned about how the ever-growing problem of Space Debris will affect it. We know the space elevator can safely operate in the environment; however, it would be beneficial if the global space community reduces the hazardous conditions.  In 2020, ISEC published a second study addressing the new density of space debris in 2019 and a NASA projection of the debris density in 2030 after several constellations of satellites are launched and become operational.   With discussions and calculations across three decades, the conclusion stays the same:  for time periods - 2010, 2019 and 2030.

“Space debris mitigation is an engineering problem with definable quantities such as density of debris and lengths/widths of targets.  With proper knowledge and good operational procedures, ... space debris is not a show-stopper by any means.  However, mitigation approaches must be accepted and implemented robustly.”

See:   Space Elevator Survivability Space Debris Mitigation (2010) and Today's Space Elevator Assured Survivability Approach for Space Debris (2020). Each can be dowloaded in pdf (free) from www.isec.org

#8 What is the ISEC Space Elevator Baseline Concept?