Editor's Note

Dear Fellow Space Elevator Enthusiasts,

I have good news and bad news. The bad news first…the Space Elevator Conference will not be held in-person this year. This means that I will miss seeing all of my fellow space elevator nuts! The good news is…this means that more people will be able to attend as it will be an online event!

It will be held over two days in September to accommodate a wider range of time zones. Check the ISEC website at this page for updates and sign up as soon as the registration opens!

Sandee Schaeffer
Newsletter Editor

Chief Architect’s Corner

by Pete Swan

ISEC will be instrumental in the presentation of new ideas for the movement off planet and the maintenance of our world at the upcoming International Space Development Conference. The afternoon of activities will provide insight into many research projects and challenge the community about “How do we bring stuff back from Space?” Orlando in the early summer will be delightful as we are on the doorstep of space access at Cape Canaveral. Please join us!

Modern-Day Space Elevators: You Dream it – We Deliver
Saturday, June 21, 2-6 pm. ISDC Orlando

The Space Elevator Tether and Space Debris:
Irresistible Force Meets Impenetrable Object?

by Adrian Nixon and Blaise Gassend

Blaise and I are currently working together in one of the ISEC study groups. We got into a discussion about whether a tether made from graphene super laminate would withstand impacts from space junk.

Artistic impression of space debris impacting on a graphene super laminate tether

Artistic impression of space debris impacting on a graphene super laminate tether. Image generated by an AI and further edited by Adrian Nixon.

What we know from tests on graphene in peer-reviewed literature.

Rice University performed experimental tests firing micro bullets at samples of multilayer graphene [1]. They found that graphene could absorb 0.92 MJ/kg for 600m/s and 0.86 MJ/kg for 900 m/s for approximately 300 graphene layers.

The multilayer graphene was made by exfoliating multiple layers from high oriented pyrolytic graphite. This means the sample was a Van der Waals homostructure multilayered single crystal graphene (graphene super laminate).

Another study by teams from Brazil and Italy performed molecular dynamics simulations and found that the penetration energy for approximately 350 layers of graphene was 0.9 MJ/kg for an impact velocity of 900 m/s [2].

In these experiments, when the projectile impacts the graphene super laminate, it stretches it into a cone shape. The energy needed to cause all that stretching is taken from the kinetic energy of the impactor, which slows as a result. The metric used is called the specific penetration energy (SPE, measured in MJ/kg). The SPE is the energy absorbed by a target material during an impact or penetration event normalized by the mass of the target directly in the path of the impacting object. It's a measure of how efficiently a projectile's kinetic energy is used to penetrate a material.

Both of these studies found that the SPE decreased as the number of layers increased. This does not mean that graphene laminates get weaker as more layers are added, just that the penetration energy per unit mass of material decreases with the number of layers. In other words, the penetration resistance of graphene super laminate increases with more layers, just not as much as you might expect. This is because graphene is a two-dimensional material, not three dimensional.

Cranfield University in the UK studied how thicker panels of graphene super laminate would resist impacts using computer modelling. They found, “…the ballistic limit of 3 mm thick graphene panels was found to be 3.375 km/s, resulting in an impact resistance 100 times greater than for aluminium or CFRP, making graphene the most suitable material for high-velocity impact protection” [3].

These tests show that in principle, a material made from graphene super laminate will be a highly effective lightweight armour capable of resisting impacts from bullets and tank shells. However, space debris travels at faster speeds than projectiles from a gun.

What we know about space debris in Earth orbit.

Objects at geostationary Earth orbit (GEO) travel at speeds of 3.07 km/s. The tether travels at the same speed at this point, so the relative speed with space debris is close to zero. A study in 2010 of the perturbation of space debris by gravity concluded that the relative velocity of GEO debris must be a distribution between 0 and 1.59 km/s [4].

NASA monitors space debris orbiting around the Earth. At low Earth orbit (LEO) debris travels much faster, at least 7.8 km/s [5]. At LEO the tether will be moving at around 500m/s, so all space debris is going faster than 7.3km/s relative to the tether.

Initial estimate of the ability of a tether to resist impact.

A velocity of 7.3km/s means the energy is 27MJ/kg. If making an assumption that the space debris is in the form of an aluminium sphere, then the tether ribbon thickness has to be 23 times greater than the diameter of an impacting sphere in order to deflect the impact [6].

Considering the mechanical impedance of a graphene super laminate tether.

Blaise considered another argument. Based on the mechanical impedance and strength of graphene he found that if the graphene at the impact site gets accelerated to a speed higher than 2.7 km/s by the impactor then it can't recruit material past the footprint of the impact to help deflect the impactor. Reference 7 shows the reasoning behind this number.

So, if the impactor's thickness is much more than the thickness of the ribbon, it will penetrate the material purely based on conservation of momentum and the ability of the material to transfer momentum away from the impact site.

He illustrated this further with a thought experiment…

"Imagine that you have a superlative material that is able to dissipate all the available energy in a collision. I claim that even in that case, a projectile going too fast for momentum to be recruited would punch through the material. To see why, consider a different thought experiment. On one side, you have a piece of the superlative material of a certain size. You send a projectile with the same size at it. When the two come into contact, the superlative material absorbs all the available energy. Do we end up with both objects fused together and stopped? No, we do not. The center of gravity of the system must continue to move at a constant velocity. Hence you will have the projectile fused with the superlative material, continuing to move at whatever speed the center of mass of the two objects was moving before the collision. In a reference frame at rest relative to the center of gravity, the two objects sped towards each other, and stopped dead. But in the reference frame of the lab in which the superlative material was initially at rest, the projectile came in, and the fused result of the collision sped away at the mass-weighted average of the two initial velocities. You'll note that I said, "all the available energy". It isn't actually possible for the superlative material to absorb all the kinetic energy of the incoming projectile as that would force the fused result to be at rest in the lab frame, which would be a violation of conservation of momentum. The only kinetic energy that is available for absorption is the kinetic energy in the center of gravity frame. If this wasn't so, then you could place yourself in a reference frame moving very fast compared to both of the particles (say 100 km/s). In this frame, the kinetic energy is vastly bigger than in the lab frame. And yet, exactly the same amount of energy is absorbed by the superlative material. The kinetic energy related to the motion of the center of mass is not available to convert into other forms of energy, it has to remain as kinetic energy to allow conservation of momentum to happen."

"So now looking back at the tether: the LEO debris collides with the ribbon. It is going at 7.8km/s, too fast for the ribbon to react so it punches a neat hole in the ribbon. Sure, the ribbon absorbs some energy, but the most it can absorb is the energy of the debris and the punched out bit of ribbon in their center-of-mass reference frame. If the two have comparable masses, the result will still be flying away at 3.9 km/s, the average speed of the bit of punched out ribbon and the impactor."

So, which will win, the tether or the space debris?

It all depends on the speed of the space debris and the way the materials collide.

For objects hitting the face of the tether:

Objects that are blunt enough, thin enough in the direction of motion to be slowed to below 2.7km/s by the ribbon directly in their path, and that have sufficiently low energy will bounce off the tether. Unfortunately, this will be uncommon in the case of orbital debris.

Objects whose dimension in the direction of motion is large enough that the ribbon directly in their path can't slow them down to 2.7km/s will go right through.

In between those two limits, there will be a lot of uncertainty. And the orbital debris distributions that are known really don't give most of the details needed to know how many objects fall under each of our criteria.

For objects hitting the edge of the tether:

Considering a direct edge-on impact, the apparent thickness of the tether is quite large and this means the ribbon could in principle slice the impactor in two, and successfully deflect the part that came into contact with the ribbon. Whether that is actually what happens would require some more concerted experimentation or simulation because the details of the impact will be quite complex. Moreover, this result would quickly go away if the impact isn’t exactly edge on.

In summary, most objects between GEO and LEO are going fast enough to punch through the SE ribbon except for the very thinnest flecks of paint. We have to try hard to avoid any of the larger objects that can be tracked. But for the myriads of smaller objects that are out there, we need to be able to survive the object punching through the ribbon. The ribbon will have to be designed with resilience to penetration built in, and we'll have to have a plan for continuing to operate despite these punctures.

References:

1. Lee, J.-H., Loya, P.E., Lou, J. and Thomas, E.L. (2014). Dynamic mechanical behavior of multilayer graphene via supersonic projectile penetration. Science, 346(6213), pp.1092–1096. doi: https://doi.org/10.1126/science.1258544.

2. Bizao, R.A., Machado, L.D., de Sousa, J.M., Pugno, N.M. and Galvao, D.S. (2018). Scale Effects on the Ballistic Penetration of Graphene Sheets. Scientific Reports, [online] 8(1), p.6750. doi: https://doi.org/10.1038/s41598-018-25050-2.

3. Sonmez, M.B., Ghasemnejad, H., Kamran, H. and Webb, P. (2019). Transverse Impact Response Analysis of Graphene Panels: Impact Limits. Open Journal of Composite Materials, 09(02), pp.124–144. Doi: https://doi.org/10.4236/ojcm.2019.92006.

4. Gao, L. (2010). Behavior and Relative Velocity of Debris near Geostationary Orbit. [Pdf] p.11-12. Available at: https://www.diva-portal.org/smash/get/diva2:1029951/FULLTEXT01.pdf [Accessed 27 May 2025]. MSc Thesis.

5. NASA (2010). ARES | Orbital Debris Program Office | Frequently Asked Questions. [online] Nasa.gov. Available at: https://orbitaldebris.jsc.nasa.gov/faq/# [Accessed 21 May 2025].

6. As we know the velocity we can calculate the energy of space junk in low earth orbit

Kinetic energy Energy/kg = (1/2) × velocity2
0.5 x (7.3 km/s2) = 27MJ/kg
So, the energy of space junk is 27MJ/kg and the ability of 300 layers of graphene to resist impact is 0.92 MJ/kg.

The 0.92 MJ/kg that can be resisted is in the footprint of the incoming object, assumed to be a sphere. The mass of a sphere of radius r is 4/3 π⍴sr3, and its energy is therefore 2/3 π⍴sr3v2. Its footprint has an area πr2, and hence corresponds to a mass of graphene π⍴gr2t, which can absorb π⍴gr2tEI, where EI=0.92 MJ/kg is the Specific Penetration Energy for the graphene. Setting these two energies to be equal and solving for t, we find that the thickness of the graphene needed to resist an impact by a sphere is: t = 2/3 ⍴srv2/(⍴gEI). For an aluminum impactor, ⍴s/⍴g=1.17. And we get: t=45r=23d. So, the ribbon thickness has to be 23 times greater than the diameter of an impacting aluminum sphere in order to deflect the impact.

7. The wave impedance for the tether is Z = sqrt(E * rho) * A. This is the tension you get in the tether per unit speed if you start pulling on the end of a stationary tether.

In order to break the tether, you need to pull it fast enough that the impedance force Z v is greater than the capacity of the tether sigma_max A.

This yields:

Z v > sigma_max A
sqrt(E rho) A v > sigma_max A
v > sigma_max / sqrt(E rho) = 2.7km/s

This says that if the impactor gets the graphene at the impact site going faster than 2.7 km/s, the graphene can't recruit material past the footprint of the impact to help deflect the impactor. So, if the impactor's thickness is much more than the thickness of the ribbon, it is going to go straight through, purely based on conservation of momentum and the ability of the material to transfer momentum away from the impact site.

Innovate Summit

by David Armes, Senior Consultant, Unreal Solutions

From Owensboro to Orbit:
Reflections on the Innovate Summit
and the Power of Human Connection 

This May, we had the opportunity to attend The Innovate Summit in Owensboro, Kentucky—a gathering unlike any conference we’ve experienced. From the moment we arrived, it was clear this wasn’t about name tags and business cards. It was about people—real, curious, generous people—coming together with a genuine desire to connect, grow, and collaborate.

Innovate Summit

Photo Credit: Adam Singer

Sure, we talked about our work, our challenges, and our visions for the future but just as often, we found ourselves deep in conversation about health, hobbies, philosophy, and the realities of bringing big ideas to life. In between thoughtful presentations and spontaneous dinners downtown, we shared stories about setbacks, breakthroughs, and the desire to build something meaningful—not just in our careers, but in our communities.

In that spirit of connection, ISEC Vice President Larry Bartoszek delivered a talk that stopped people in their tracks—about space elevators. Among sessions on entrepreneurship, marketing, and motivation, Larry’s presentation stood out as bold, visionary, and surprisingly down-to-earth. His explanation of a 100,000-kilometer tether stretching from Earth into orbit left the audience buzzing. He described not just the possibility of delivering cargo to space without rockets, but the real-world benefits of the supporting technologies: graphene materials, high-power lasers, and ultra-strong motors. The excitement was palpable. The term “space elevator” became one of the most talked-about phrases at the event.

Photo Credit: David Armes

While no business deals were struck on the spot, the connections made—and the conversations sparked—reminded us that awareness is the first step toward action. More than a few attendees left Owensboro with space elevators on the top of their minds, and perhaps even a new sense of what’s possible when big ideas meet the right crowd.

The Innovate Summit proved that sometimes, getting out of your usual orbit—whether that means a different city, a different crowd, or a different kind of conversation—is exactly what it takes to build momentum for the future.

David

Photo Credit: Sam Khozin

Solar System Space Elevators 

by Peter Robinson

Part 11: FINAL CONCLUSIONS

inner solar system

Image 1: The Inner Solar System to Jupiter. Source: Wikipedia, Public Domain

1. FINAL CONCLUSIONS

Any space elevator system requires technical feasibility and commercial viability wherever it is built. I will summarise my earlier ‘Solar System’ articles by concentrating on these aspects only but will start with a location I did not cover.

1.1 The Earth

I have not directly addressed the Earth Space Elevator earlier in these articles, given that it is the prime focus of most other researchers. Considering the two requirements above, there is little doubt that a functional Earth Elevator would be commercially successful (unless construction costs were excessive): competitively escaping the gravity well and defeating the rocket equation with little environmental impact.

Some consider that the technical issues of an Earth Elevator are too great, but many (including ISEC) believe that mass-production of a sufficiently strong material is within our grasp. Other challenges need to be addressed but can be resolved by the development of existing technologies.

I will assume the Earth Elevator mega-project is moving forward as I go on to address the options elsewhere in the solar system.

1.2 Mercury, Venus [1]

Elevators here are not technically feasible as both planets rotate too slowly, requiring a tether length far longer than Earth. Solar gravity (tidal) forces would also result in severe instability.

Simpler orbital tether variants could be worthy of further study, but these would not be connected to the surface and so should not be classed as ‘Space Elevators’. This also applies to some other solar system bodies. I will not mention them again.

1.3 Asteroids (including Kuiper Belt) [2] [3] [12]

Asteroid space elevators are technically simple in theory due to the low synchronous altitudes and the potential to use existing low-strength tether material, but the instances where they might be economic propositions are limited. The very low surface gravity and lack of any atmosphere means that asteroid surface access is straightforward, using existing rocket technology.

Two potential use cases might be in support of an Earth Space Elevator project or as part of large-scale mining operations, especially on asteroids near the Earth, but in both cases the method of attaching a tether to the surface would need to be carefully addressed.

1.4 Luna (Earth’s Moon) [4]

A Lunar Space Elevator appears to be technically feasible short-term as described in many published papers, but I argue that it may not be logistically or commercially viable due to the necessary long tether length, large anchor mass, low climber/tether mass ratio, and other issues.

1.5 Mars [5] [6]

The two parts of my ‘Mars Elevator’ article describe several potential tether configurations for Mars and its moons, all of which are technically feasible using a tether of lower strength than required for an Earth Elevator.

Commercially viability would depend on sufficient demand for cargo transfer.

Shorter-term, a Mars Elevator might be valuable for development support to the Earth Elevator project, perhaps demonstrating tether deployment strategies, durability, dynamic control and climber operation in the space environment.

1.6 Jupiter, Saturn, Uranus, Neptune [7] [8] [11]

Elevators on these larger planets are not technically feasible in the foreseeable future: they have no solid surface and would require a tether material stronger than for the Earth.

1.7 The Moons of the Gas Giants and Ice Giants

‘L1-type’ elevators would be technically possible on most tidally locked moons but are unlikely to be commercially viable options. Reasons include the long necessary tether lengths, substantial anchor masses and ready access to airless moon surfaces by spacecraft.

For the inner Jovian moons there may also be technical issues associated with the extreme radiation environment. The outer Galilean moon Callisto has less intense radiation but would require a tether perhaps 100,000km long.

EXCEPTIONS:

1.7.1 Enceladus [9] has a pristine icy surface over possible life-bearing liquid water. Elevator access would reduce contamination and surface disruption, perhaps making it commercially or scientifically more advantageous. An elevator should be technically feasible, requiring a low-strength tether of length less than 2000 km.

1.7.2 Titan [10] has a thick dynamic atmosphere that makes spacecraft surface access difficult. A long tether would be required for an L1-type space elevator system, with a cable car or some other solution to avoid difficulties associated with operating climbers in an atmosphere.

1.8 Pluto & Charon [12]

The unusual mutual tidal-locking of the Pluto-Charon binary system would enable construction of a space elevator directly connecting the two dwarf planets without the need for a heavy Apex Anchor, with a tether mass only of the order of 200 tonnes. That said, commercial feasibility must be low due to the remoteness from Earth.

2. REFERENCES

The links below go to each newsletter article in the ‘Solar System Elevators’ series. Each in turn has forward links to other reference material.

[1] May 2024 “Part 1: Introduction and the Inner Planets”: https://www.isec.org/space-elevator-newsletter-2024-may/#solarsystem

[2] June 2024 “Part 2a: Asteroids (and Ceres)”: https://www.isec.org/space-elevator-newsletter-2024-june/#solarsystem

[3] July 2024 “Part 2b: Asteroids - Conclusion”: https://www.isec.org/space-elevator-newsletter-2024-july/#solarsystem

[4] August 2024 “Part 3: The Moon (Luna)”: https://www.isec.org/space-elevator-newsletter-2024-august/#solarsystem

[5] September 2024 “Part 4a: Mars – Introduction”: https://www.isec.org/space-elevator-newsletter-2024-september/#solarsystem

[6] October 2024 “Part 4b: Mars (2)”: https://www.isec.org/space-elevator-newsletter-2024-october/#solarsystem

[7] November 2024 “Part 5: Jupiter and Jupiter’s Moons”: https://www.isec.org/space-elevator-newsletter-2024-november/#solarsystem

[8] December 2024 “Part 6: Saturn and the Lesser Saturnian Moons”: https://www.isec.org/space-elevator-newsletter-2024-december/#solarsystem

[9] February 2025 “Part 7: Enceladus”: https://www.isec.org/space-elevator-newsletter-2025-february/#solarsystem

[10] March 2025 “Part 8: Titan”: https://www.isec.org/space-elevator-newsletter-2025-march/#solarsystem

[11] April 2025 “Part 9: Uranus and Neptune”: https://www.isec.org/space-elevator-newsletter-2025-april/#solarsystem

[12] May 2025 “Part 10: Pluto, Charon, and the Kuiper Belt”: https://www.isec.org/space-elevator-newsletter-2025-may/#solarsystem

Around the Web

This article gives a lot of nods to NASA, JAXA, ESA, etc, but only mentions ISEC once and doesn't provide a link. Still, it is well-written and informative. If you visit the link too many times (like this editor did), you can no longer view it without watching an ad. 

https://www.coletivometranca.com.br/en/news_en/space-elevators-the-next-giant-leap-in-space-access-2025/68542/

This game will be released, soon. If you decide to purchase it and try it out, could you write a review and submit it for publication in the newsletter?

https://store.steampowered.com/app/2892810/Space_Elevator_Project/

Upcoming Events: 

International Space Development Conference 2025
Sponsored by the National Space Society
https://www.isec.org/events/isdc2025
https://isdc.nss.org/
Thursday, June 19th, through Sunday, June 22nd, 2025
Space Elevator Session
Rosen Center, Orlando, FL, United States

Virtual Space Elevator Conference 2025
Sponsored by the International Space Elevator Consortium
https://www.isec.org/events/isec2025
Saturday, September 6th, through Sunday September 7th, 2025

76th International Astronautical Congress
Sponsored by the International Astronautical Federation (IAF)
https://www.iac2025.org/about/
Monday, September 29th, through Friday, October 3rd, 2025
International Convention Centre, Sydney, Australia

77th International Astronautical Congress
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https://iac2026antalya.com/
Theme: “The World Needs More Space”
Proposed Dates: October 5th through October 9th, 2026
Antalya, Turkey

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