Editor’s Note

Dear Space Elevator Enthusiasts,

Woohoo!

This is me, excited. Why am I so excited? The Space Elevator Blog is back in operation! Welcome back, Ted Semon. We missed you!

After a ten-year hiatus, Ted will now be resuming his posts. Catch up at https://www.spaceelevatorblog.com/. I admire the work he has done in the past and look forward to more in the future!

I would like to insert a disclaimer that this is a personal blog that reflects the author's opinions which may not necessarily represent the views of all members of the International Space Elevator Consortium.

Newsletter Editor
Sandee Schaeffer

President’s Note

by Dennis Wright

Top Five Challenges for the Space Elevator - Space Debris

In previous installments, we showed that the challenges of producing a strong and light tether and the construction of a climber to ascend it could be met. But what would happen after the space elevator was deployed? Could it operate within the field of space debris? What could be done to increase space elevator survivability given the projected increase in space debris density? These and related questions were addressed in detail in two ISEC studies. The results of the studies are available in the reports Space Elevator Survivability (https://www.isec.org/studies/#SurviveMitigate) and Assured Survivability Approach for Space Debris (https://www.isec.org/studies/#SpaceDebris).

The bulk of space debris occupies Low Earth Orbit (LEO), with considerably fewer objects in Medium and Geosynchronous orbits (MEO, GEO). Today, small, untracked debris (< 10 cm) in LEO would impact the space elevator once every 10 days and tracked debris would impact once every 100 days. Projecting to 2030 the latter rate becomes once per 40 days. These rates are based on data and projections from NASA. They seem high but can be mitigated in the following ways.

The first step is to remove junk by capturing or de-orbiting it. Many plans for this step exist that would significantly reduce the space debris density. This would benefit everyone operating in LEO.

Tether design is crucial. If the tether were made of graphene and were thick enough, it could actually deflect impacts of smaller objects. Even head-on collisions with the tether could be survived; if the resulting hole were small enough, tether integrity could be maintained long enough for repairs to be effected. The tether could also be made wide enough at LEO altitudes that the risk of tether severance by a single object would be greatly reduced. Bigger, continuously tracked objects can be avoided by inducing oscillations in the tether. Cooperation with debris monitoring systems would provide warnings of potential collisions in time for space elevator operators to take action.

Repair and backup will be an essential part of space elevator operations. Special climbers would be developed for tether repair. Multiple tethers should be built so that one could serve as a backup and aid in repairing another. Guy-wire tethers, attached to the main tether at 2000 km (above 99% of debris) would also provide backup.

Taken together, these operational approaches would increase the lifetime of a space elevator to ten years or more, which coincides with the projected replacement rate of the space elevator tethers due to fatigue and upgrades.

Details in the next newsletter: dynamic control of space elevator motions. 

Dennis Wright

Chief Architect’s Corner

by Pete Swan

Transformation of Flights to Mars with the Modern-Day Space Elevator

I recently did the below article for LinkedIn. I usually do not repeat my writings in both the monthly newsletter and the LinkedIn; however, this one is especially close to my heart. We – as a community – need to explain often our big advantages that will lead to a revolution. As such, please forgive me if you have read it before:

Fastest: Can you imagine 61-day flights to Mars? Initially lifting cargo and later humans? Modern-Day Space Elevators will be able to send logistics support to Mars every day of the year without waiting for a “launch window” of every 26 months. While the fastest trip with space elevators is about 61 days, the average over this 26-month repeating relationship of planets will be around 125 days. Several, for logistics support only, would be over 400 days - but delivered "on time." The secret is simple: the release of payloads at 100,000 km altitude from the Apex Anchor enables flights with speeds of 7.76 km/sec [17,358 mph] and with essentially no gravitational drag from the Earth. This incredible speed enables logistical spacecraft to “cut the corner” and take a very large elliptical path to Mars. Of course, the spacecraft will need to have rocket motors to slow down and rendezvous or land on Mars. These flights can be short, compared to rocket missions of from 8 to 9 months. As the positions of the two planets vary, the angle of the ellipse changes with respect to the departure planet to ensure routine flights. Some of them might be 400 days long, but this won't matter if the payload is only hammers and nails or other construction materials. The short flights will include pizzas and other necessities! The students at Arizona State University, who studied the flight of space elevator releases, were excited when they recognized that the Space Elevators will be on a daily, safe, routine, inexpensive transportation infrastructure that enables the development of a “Bus Schedule to Mars” – releasing from six operational Apex Anchors each day. [See “Apex Anchor: Full-Service Logistics Transportation Node at the Top of the Gravity Well,” ISEC 2024 study at www.isec.org/studies.]

ASU data for Mars transport

Delivery Efficiency: Another major factor in the transformational aspect of space elevators is the efficiency of delivery to the destination. When looking at rocket delivery to Mars’ surface, the delivery of payloads are well below 1% of the total rocket mass on the pad on Earth. In other words, the other 99% is consumed or in several cases – parts are reused. The delivery of cargo by space elevators to the surface of Mars is projected to be well up in the high 70th percentile of the mass lifted from the Earth Port. Comparisons: Rockets < 1% of pad mass to Mars while Space Elevators delivery efficiency is about 70% vs. less than 1% by rockets.

Assembly above Gravity: This transformation of time of flight is revolutionary, but the other strengths of space elevators are also incredible. When supplying your settlement on Mars from Earth it would be revolutionary to assemble your huge space system at 100,000 km altitude and make it into huge mission capacities. The concept is that daily payloads brought up from the surface of the Earth to the Apex Anchor by electricity [14 tonnes per day continuously in the early days] could be stored until needed [just in time delivery] and then assembled into large space systems with cargo and rockets to transport to the surface of Mars.

Environmentally Neutral: These operations will be the Green Road to Space as they do not burn rocket fuel on the raising of cargo, nor do they leave debris along their path to Apex Anchors.

Indeed, a transformation of Flights to Mars will occur
when the Modern-Day Space Elevators are operational and
revolutionary capabilities emerge, such as massive and efficient movement to Mars.

Current Board Members 2025

ISEC used to welcome each new member of the Board of Directors each time we added one, but time has been travelling at the speed of life and we have missed a few changes!  Let us catch you up on the latest lineup:

This screenshot is taken from the "Who We Are" section of the ISEC website and will be kept as up-to-date as possible! 

Update: Modern-Day Space Elevators: You Dream it – We Deliver!

International Space Development Conference
(ISDC) 2025 Orlando, Florida
Space Elevator Session: June 21st

The space elevator community is gathering its team to support the National Space Society (NSS) at this years’ ISDC. We have many abstracts and hope for an exciting series of talks – with students and from professionals inside our community. The final layout for the presentations will be available around the first of May. However, we have already determined the panel topic and the members on the panel. This one should be exciting and informative as there has not been too much research into the “down-problem.” This update is to show the reader the setup for our panel on 21 June in the afternoon. Please plan on attending and supporting the space elevator community.

Presentations [2:00 – 4:30]: to be selected

Panel [4:30-5:30]: “Solving the Down Problem: Getting Space Resources to Earth”

Preliminary Members: Dennis Wright, Ph.D. President, ISEC; Larry Bartoszek, Vice-President, ISEC; Steven Griggs, Ph.D., President, Space Railway Corp; Isaac Arthur, President, NSS.

Asteroid mining, or other space resource exploitation, will require vast amounts of material to be brought to Earth. Conventional re-entry vehicles will not have the capacity or frequency to accommodate such throughput in a timely and economical manner. This has been referred to as the “down problem.” It is likely that only the space elevator can solve this problem, and it will be useful to discuss how this might occur. Economic considerations will be paramount, and throughput issues will drive the design of any space elevator infrastructure.

The panel will consist of Dennis Wright [moderator], Larry Bartoszek, Steven Griggs, and Isaac Arthur. Each have their own expertise in space elevator architectures, engineering design, economics, and the impact of bringing large amounts of materials back to Earth. The panel discussions will be followed by questions and comments from the audience.

Questions, Answers, Comments [5:30 – 6:00]: “Modern-Day Space Elevators”

Solar System Space Elevators

by Peter Robinson

Part 9: URANUS and NEPTUNE

This is the ninth article of the “Solar System Space Elevators” series. Earlier articles covered Mercury and Venus, the Asteroids, the Moon, Mars, Jupiter, Saturn, and the Gas Giant moons.

1. INTRODUCTION

Uranus and Neptune are the planets furthest from our sun, of similar size and designated as ‘Ice Giants’. Full details can be found in Wikipedia articles [1] [2].

My earlier articles discussed Space Elevators on the larger Gas Giants (Jupiter and Saturn). I will extend that discussion here for Uranus and Neptune. The Table in Figure 1 below contains key physical parameters that are relevant for Space Elevator feasibility.

Figure 1: Comparison of key physical parameter for Uranus & Neptune. Analysis: P. Robinson.

Both planets possess a rock and ice core surrounded by a thick atmosphere, with no clearly defined solid surface. The nominal radius is exhibiting one standard Earth pressure.

2. ELEVATOR CONCEPTS

A space elevator on either planet would be a conventional centrifugal type (as could be built on Earth or Mars), with a tether extending from a Stationary Node up to an Apex Anchor and down to a Planetary Node at some altitude on or near the equator. The Stationary Node altitudes are 60% and 64% respectively greater than Earth’s GEO altitude, though the higher Ice Giant rotational speeds mean the total tether length may not need to be higher than for an Earth Elevator.

See my earlier article on Saturn [3] for a discussion of a planetary node suspended in a giant planet atmosphere.

Note: The Stationary Altitude calculations in Figure 1 are based on a sidereal day derived from the rotation of the planetary magnetic fields; this may not align with the planetary atmosphere rotation. In the case of Neptune, the wide equatorial atmospheric zone rotates with a period of about 18 hours, slower than the nominal 16.1-hour magnetic rotation period.

2.1 Uranus

I had initially planned to include stock Voyager-2 images of Uranus, but the reader can readily find those on Wikipedia [1]. Instead, I will include the excellent artwork below by Dr. Mark A. Garlick imagining the view of Uranus from the small moon Miranda, incorporated here with his permission.

Figure 2: Uranus from Miranda, artwork with permission of Dr. Mark A. Garlick.

Uranus has only been visited by one spacecraft, Voyager 2, in 1986, which returned a substantial quantity of data and photographs to Earth. More recent data has been collected by the Hubble, James Webb, and other telescopes.

Figure 3 below depicts Uranus atmospheric conditions, showing temperatures falling as low as 50K, the lowest of any body in the solar system [1]. In addition, wind speeds have frequently been observed up to 360 kph, with a speed of 820 kph observed briefly in 2004. The ‘weather’ is a complex hydrocarbon-driven process, with extreme seasonal variation caused by high axial tilt. During the Voyager 2 fly-by some 140 lightning flashes were detected from 600,000km distance, each of which was much more powerful than lightning on Earth.

Figure 3: Uranus Atmosphere Profile. Credit: Ruslik0, CC BY-SA 3.0 via Wikimedia Commons.

The extreme atmospheric conditions indicate that any tether suspended in the atmosphere would need to be of very robust construction, in addition to having a high specific strength as discussed in the ‘Analysis’ section below.

2.2 The Moons of Uranus

Uranus has 28 known moons, divided into three groups: thirteen inner moons, five major moons (Miranda, Ariel, Umbriel, Titania, and Oberon) shown in Figure 4 below, and ten distant irregular moons. None of these moons possess any appreciable atmosphere, with even the largest (Titania, 1578 km diameter) having a surface pressure of less than 20 nanobars.

Figure 4: Uranus Major Moon Montage: Miranda, Ariel, Umbriel, Titania & Oberon. Collage of Voyager 2 photos (1986). Credit: NASA.

An extensive description of the Moons of Uranus can be found on Wikipedia [4]. Regarding Space Elevator feasibility, each of the major moons are tidally locked and so could host an ‘L1-type’ Elevator system, but their distance from Uranus means tethers many tens of thousands of kilometres long would be required. None of the moons have any appreciable atmosphere, meaning that direct surface access would be relatively simple using spacecraft similar to that being developed to access Earth’s Moon.

The lesser moons of Uranus have not been closely studied, but their negligible gravity would render a Space Elevator even less necessary than the larger moons.

2.3 Neptune

Neptune has only been visited by Voyager 2, some three years after its encounter with Uranus. Substantial data was also gathered from that fly-by, augmented more recently by telescope observations.

Neptune is slightly more massive than Uranus but is similar in many ways. It is composed primarily of gases and liquids, with a thick atmosphere of 80% hydrogen and 19% helium making up 5-10% of the planet mass. This atmosphere has the strongest sustained winds of any planet in the Solar System, as high as 2,100 km/h (580 m/s; 1,300 mph) during storms. Temperatures can fall to 55 K.

Increasing concentrations of methane, ammonia and water are found in the lower regions of the Neptune atmosphere: at a depth of 7,000 km the conditions may be such that methane decomposes into diamond crystals ‘hailstones’, as may also occur on Jupiter, Saturn, and Uranus. It has been suggested that the top of the mantle may be an ocean of liquid carbon with floating solid diamonds.

The above details combine to indicate that any Space Elevator suspended to any depth into Neptune’s atmosphere would (like Uranus) need to be of extremely robust construction.

2.4 Triton

Triton [5] is the largest Neptunian moon at 2,707 km diameter, accounting for more than 99.5% of the mass in orbit around Neptune. Unlike all the other smaller moons it has a retrograde orbit, suggesting that it may well be a captured dwarf planet from the Kuiper Belt.

Figure 6: Triton Image & Size Comparison

My analysis indicates that the Neptune-Triton L1 point is 14,100 km above the surface of Triton, meaning that an L1-type Space Elevator on Triton would be much shorter than on the larger moons of Jupiter or Saturn. See the Analysis section below for more details.

The surface of Triton is of solid nitrogen, but below this is a substantial layer of water, ice, and a liquid water layer heated by cryovolcanic and tectonic activity. This has led to speculation regarding life, with recent news of a possible Chinese landing mission.

Triton’s thin atmosphere has a surface pressure of just 1.4 Pa (.000014 atm) and should not prevent easy surface access by spacecraft.

2.5 Neptune’s Lesser Moons

In addition to Triton, Neptune has 15 other known moons. Inward of Triton are seven small regular satellites, depicted in Figure 6 below, and eight more irregular satellites beyond Triton in high inclination orbits.

Figure 7: Orbits of the Inner Moons of Neptune Credit: NASA, ESA, and A. Field (STScI0 Public Domain)

More details of all fifteen small moons can be found in Wikipedia [6], but the limited information available at present does not suggest any are prime candidates for hosting a Space Elevator. Direct surface access would be straightforward given their lack of atmospheres, and it is not even clear how many exhibit the essential characteristic of being tidally locked with Neptune.

3. ANALYSIS

3.1 Uranus and Neptune

My analysis used my spreadsheet method as described in earlier articles and my IAC2022 paper [7].

One key parameter for any Space Elevator extending into the atmospheres of either Uranus or Neptune is the tether specific strength. A lower tether material strength will require a higher taper ratio to permit the tether to support its own weight (this is the ratio of the highest and lowest tether cross-sectional areas). Figure 8 below extends earlier analysis for Jupiter and Saturn to include analysis for Uranus and Neptune.

Figure 8: Taper Ratio v. Specific Stress for Gas and Ice Giants. Analysis: P. Robinson

Note the Y-axis log scale, highlighting the extreme sensitivity of taper ratio to the material working specific strength (= working stress / density). As the taper ratio increases, the total tether mass will rise, assuming that the load capacity of the tether at the base is held constant to maintain lift capacity and surface retention force.

Of interest in Figure 8 is the comparison between Uranus, Neptune, and Saturn. Neptune has a higher ‘surface’ gravity than Saturn due to having over double the mean density. This (with other factors) results in the perhaps-surprising similarity between the taper values for these two planets. Uranus is far less massive than Neptune with a lower surface gravity (less than 1g), resulting in the much lower taper ratio.

That said, the required taper for Uranus can be seen to be still higher than that required for an Earth elevator, meaning that a significantly stronger material would be required to avoid the tether mass becoming excessive. The Earth tether strength requirement is considered to be near the limit for known materials technology, so an elevator into the atmosphere of Uranus is unlikely to be practical in the foreseeable future.

3.2 Triton

My analysis for Triton has again assumed a 5-tonne climber and Graphene Super Laminate (GSL) material, with a constant tether area of 5 mm^2 stressed to only 7 GPa. This is little more than offered by existing available materials and well below the forecast strength of GSL, but the extremely low temperatures at Neptune’s distance from the sun mean that a considerable safety margin might be prudent.

Figure 9 below shows the masses of both tether and counterweight against the altitude above Triton’s surface through the Triton-Neptune L1 point.

Figure 9: Triton Tether and Counterweight Masses. Analysis: P. Robinson

The L1 altitude of 14,100 km is relatively low compared with other larger moons, but a tether length far in excess of 20,000 km would still be needed. The tether length is (as usual) a trade-off between tether mass and Apex Anchor mass, with the latter probably best assembled from local orbital material.

4. CONCLUSIONS and SUMMARY

The remote location of Uranus and Neptune mean that construction of any Space Elevator would not be for many decades, probably not even this century. An Elevator on either planet would require a tether material significantly stronger than that required for the Earth, and at present there is no suitable material concept. Both planets also exhibit extreme weather, with high wind strengths and low temperatures that would further challenge the integrity of any tether.

The larger moons of both planets are tidally locked with their primaries and so potentially could host ‘L1-type’ elevators, but all are airless and so could be accessed readily using conventional rocket-powered landers.

NEXT TIME: Pluto, Charon, and the Kuiper Belt.

5. REFERENCES

[1] ‘Uranus’ Wikipedia page: https://en.wikipedia.org/wiki/Uranus

[2] ‘Neptune’ Wikipedia page: https://en.wikipedia.org/wiki/Neptune

[3] ISEC December-2024 Newsletter, ‘Saturn’: https://www.isec.org/space-elevator-newsletter-2024-december

[4] ‘Moons of Uranus’ Wikipedia page: https://en.wikipedia.org/wiki/Moons_of_Uranus

[5] ‘Triton’ Wikipedia page: https://en.wikipedia.org/wiki/Triton_(moon)

[6] ‘Moons of Neptune’ Wikipedia page: https://en.wikipedia.org/wiki/Moons_of_Neptune

[7] “Space Elevator Climber Dynamics Analysis and Climb Frequency Optimisation.”, P. Robinson, IAC2022 paper IAC-22,D4,3,8,x68299: https://www.isec.org/s/ISEC-2022-IAC-space-elevator-climber-dynamics-paper.pdf

Tether Materials

by Adrian Nixon

A Tether Made from Graphene Becomes Tougher with More Layers

As you will know graphene is the strongest material known. This is why we consider it one of the leading candidate materials for the space elevator tether.

Large area chemical vapour deposition (CVD) graphene can now be made at scales of centimetres and metres by batch and continuous processes. In a previous ISEC newsletter article [1], we discovered that test methods can now be performed on one atom thin layers of graphene at centimetre scales. Work by the Center for Multidimensional Carbon Materials (CMCM) in South Korea has performed tensile tests that show monolayer graphene is the strongest material tested at the centimetre scale.

This work also revealed that the way the graphene sheet finally failed was due to fracture cracks that propagate from the edges of the sheet and cause the material to tear apart. This was done with a single atom layer sheet of graphene. Sheets of graphene can also be made in more than one layer.

Figure 1: Graphite, CVD graphene and graphene laminate.

Multilayered graphene is often thought of as graphite and dismissed as a familiar and lesser material. However, regular readers will be aware that when large area sheets of graphene are layered, this creates and entirely new ultra strong material. This is known as a van der Waals homostructure of graphene [2]. Figure 1 shows the difference between graphite and graphene laminate.

We now need to consider how the fracture resistance of multilayered graphene differs from single layer graphene. Experimental work has recently been published that investigated how a graphene van der Waals homostructure (graphene laminate) behaves as the number of layers is increased.

Researchers at the University of Texas, Austin, USA made multilayered graphene using the CVD method. They also developed a custom-made tensile tester that could measure the force involved to tear samples with different numbers of layers. This tearing is the fracture resistance and is measured in joules per square metre (J/m2).

Figure 2: Fracture toughness increases with the number of graphene layers.

Figure 2 shows the results of the experimental work. The team found that the more layers of graphene in the graphene laminate stack, the higher the fracture resistance [3]. This makes sense because we know that fracturing starts from defects at the edges of the graphene sheet. When considering a multilayered structure, it is improbable that all the edge defects will occur at exactly the same place, and this becomes increasingly improbable with more layers in the material.

This means that while monolayer graphene is the strongest material ever tested at the centimetre scale, graphene laminate will be even stronger. This also means a space elevator tether made from graphene laminate will become more fracture resistant as its thickness increases with the number of layers of graphene.

References

1. Nixon, A. (2025). Tether materials: How the Edges of Graphene Affect the Tensile Strength. [online] International Space Elevator Consortium. Available at: https://www.isec.org/space-elevator-newsletter-2025-march/#tether [Accessed 28 Mar. 2025].

2. Nixon. A., 2021. The graphene and graphite landscape: Indications of unexplored territory. Nixene Journal, 5(10), pp.9-20

3. Joon Hyong Cho, Cayll, D.R., Ladner, I.S., Gorman, J.J. and Cullinan, M. (2024). In-situ fracture toughness measurement of multilayer graphene. Engineering Fracture Mechanics, 295, pp.109798–109798. doi:https://doi.org/10.1016/j.engfracmech.2023.109798.

 Leverage the Body of Knowledge for the Modern-Day Space Elevator 

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Over 800 references and citations with access to videos and articles/papers/studies and more!

 

The Space Elevator Blog by Ted Semon is now back in operation!

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