Category: Other Worlds and Tech

The latest hype cycle about Elon Musk’s Starship / Super Heavy is starting to ramp in the lead-up to the next “integrated flight test” (IFT) of the system (SpaceX stopped calling them “orbital flight tests” aft the first one spectacularly firecrackered less than 4 minutes into the flight), and the second one fared somewhat better, prior to the booster and the starship both going the same way in separate explosions. As usual, the hype is being led by Elon Musk, stating that the third attempt could come on March 14th, 2024.

The Federal Aviation Administration (FAA) investigation into that mishap – actually led by SpaceX (as tend to generally be the case) – closed at the end of 2023; however, the closure did not mean SpaceX would be granted a license for resuming launches. That was dependent upon the company completing all identified remedial / corrective actions the FAA felt required in light of the mishap report. As of the end of February, 2024, it was not clear if all such action points had been addressed. However, SpaceX have renewed preparations for the next launch from the Starbase facility at Boca Chica, Texas.

If this third flight – regardless of when it takes place – does in fact deliver a starship test vehicle to orbit, it will be the first genuine success of the launch attempts thus far (whilst SpaceX fans might have lauded the first two attempts as successes, the fact remains that if ULA, NASA or any other company had seen their vehicles similarly destroyed, their flights would have been seen as abject failures), it is merely the smallest of steps SpaceX is committed to taking if it is to meet its obligations to NASA in providing the agency with a lunar lander vehicle in a timely manner – or at all.

As a quick recap: unlike Apollo, NASA is not relying solely on “in-house” designed hardware and systems for their return to the Moon, but are utilising private sector capabilities as well, theoretically on a fix-price basis. In particular, they have turned to the private sector for the development and operation of their Human Landing Systems (HLS) – that’s lunar landers to you and me.

Originally, two major teams of companies bid for the contracts for NASA’s first HLS systems, one led by Blue Origin (with Lockheed Martin) and one by Dynetics. SpaceX jumped into the proceedings very late in the process with a very questionable proposal to use a modified version of their Starship vehicle, and not only walked off with the contract under somewhat extraordinary decision-making at NASA, actually ended up as the sole contractor, despite NASA stating two contracts would be awarded.

That was in 2021. Since then, SpaceX has failed to achieve every single milestone Musk has set for Starship development, leaving a lot for the company to achieve if they are to meet NASA’s goal of delivering two people to the surface of the Moon and returning them safely to the surface of the Earth by late 2026 / early 2027. In particular, they need to not only get a Starship into orbit, they must:

• Show they can launch a starship / super heavy combination not just once, but multiple times – and show they can actually capture them again on landing at the launch site without actually having them fall short or even crash into the launch / recovery tower.
• Demonstrate this can be done over multiple launches in a relatively short time frame (e.g. at least once a day) without incident.
• Develop, test and prove capabilities to deliver large payloads (100 tonnes) of cryogenic propellants to orbit and transfer them between craft with minimal boil-off, and again do so up to 14 or 15 times.
• Carry out two demonstration flights of the HLS vehicle in orbit, one uncrewed and the other crewed.

Given the company’s rate of progress thus far, a 2 to 2.5 year time frame to complete all this is, frankly, liable to be well beyond SpaceX’s capabilities; particularly when you consider that in a Twitter Spaces meeting in December 2023, SpaceX personnel engaged in the HLS development programme admitted they hadn’t even started to conceptualise the crew facilities and support systems the vehicle must carry. Add to that the fact that the only actual hardware under development are both coming in part from NASA: the elevator needed to get the crew down and up the 30 metres of spacecraft and the lunar surface and the docking mechanism to allow the Orion crew vehicle to transfer crew from itself to the lander, once in lunar orbit.

And that’s not me saying it subjectively; Musk himself has stated Starship HLS will take around another 5 years to be realised. That’s 2029, and the time frame of the Artemis 5 mission. Hence why Jim Free, the man at NASA charged with overseeing the Artemis programme, is talking more and more robustly about bypassing SpaceX altogether in terms of that first crew landing. And there is a strong contender to take SpaceX’s place to take over the primary slot: Blue Origin.

One of the original bidders for the first HLS contract, Blue Origin were awarded a contract to develop NASA’s “sustainable” lunar lander in May 2023 (the “sustainable” term a tacit admission by NASA that the SpaceX design, with its maximum 2 landing capability and the need for as many as 15 support launches to get it to the Moon is entirely unsustainable). Since then – and allowing for the fact they continued to develop their lander idea between 2021 and 2023 in the form of a cargo variant (“Blue Moon 1”) which shares several significant systems as the crewed lander proposal (“Blur Moon 2”), including navigation and landing systems, propulsion module / landing legs and power generation – the Blue Origin design is potentially far ahead of that of SpaceX.

Specifically, Blue Original have already delivered to NASA a walk-through mock-up on the lander’s pressurised module, allowing NASA engineers and astronauts to properly determine how the module should be laid out, workspaces and living areas be defined, and where and how all the required internal systems and services should be best installed.

In addition, the development of the cargo lander has reached a point where Blue Origin has announced it plans to send the lander to the Moon at its own expense, with the first taking place in 2025. Whilst these will deliver science payloads to the Moon, their primary goal will be to check-out those same navigation, propulsion, power and landing systems that will be used on the crewed lander, thus demonstrating their fitness for purpose (and flight readiness).

Given all this, and the pace of development at Blue Origin, it is possible their Blue Moon 2 lander system could be ready to fly in late 2027 – still outside of the NASA time frame, but likely well in advance of SpaceX’s HLS. This is something Free has openly acknowledged, expressing the point of view that if SpaceX isn’t ready, not only will they be held accountable for failing to meet their contract, the Artemis 5 mission featuring the first use of Blue Origin’s lander could be brought forward as the first Artemis crewed landing mission, and Artemis 3 shuffled back.

That said, the Blue Origin / Lockheed approach must clear some of the same hurdles as face by SpaceX in order to be able to perform crewed landing on the Moon. These include developing the means of transferring cryogenic propellants between spacecraft, and limiting propellant boil-off. However, the overall scale of operations is much smaller: Blue Origin and Locked are only dealing with tens of tonnes of propellant transferred in relatively small quantities (but stored in lunar orbit for a much longer period), rather than up to 1000-1200 tonnes for Starship HLS. This means that a Blue Origin lander only needs a single refuelling launch to see it through a number of lunar landings / lift-offs, not anything between 10 and 15 required by Starship HLS requires.

Another critical aspect of the Blue Origin lunar capabilities is to enter service this year: the New Glenn rocket. Capable of delivering 45 tonnes to low Earth orbit and smaller payload out as far as Mars, New Glenn will enter service in August of this year, its maiden flight being to launch NASA’s EscaPADE spacecraft to Mars. With the lunar missions, it will be lifting the cislunar transporter (under development by Lockheed Martin) and the fuelling / refuelling tank the mission will require, as well as the lander itself. Providing there are no issues with the August 2024 launch, New Glenn should have an established track record by the time Artemis 5 is ready to fly.

This gives rise to the possibly that NASA might, if Blue Origin and their team are ready, simply drop the SpaceX option altogether. Why have a non-sustainable, complex lander system utilising a vehicle inherently unsuited to the task, when there is a sustainable, proven vehicle already doing the work? The issue here would be one of when such a decision should be taken. NASA has already contracted SpaceX to the tune of close to US $3 billion for Starship HLS – and has precious little to show for it; given the contract negotiated between SpaceX and a former NASA deputy administrator who might be said to have been overly biased towards SpaceX (the company now employing her as a senior executive), it is hard to know what, if any, penalty / get out clauses might have been written-in.

That said, there are those – such as NASA’s own Office of Inspector General and the federal Government Accountability Office (GAO) – who feel that the Artemis programme is inherently too costly to be sustained beyond the currently defined missions (Artemis 3 through 9), and that it might be too costly to even go beyond Artemis 5 or 6. As such, a move to cut (and perhaps reclaim) costs associated with the system that is somewhat questionable in its ability to meet the requirements placed on it, and which could be redundant by the time it is ready, might go some way towards NASA demonstrating it really is trying to manage its costs effectively.

Continue reading “Space Sunday: landing humans on the Moon and an ISS taxi” →

The China’s Manned Spaceflight Agency (CMSA) has revealed the names and preliminary drawings of the vehicles China plans to use to deliver its own astronauts – called taikonauts in Chinese – to the lunar South Polar Region.

For their human missions to the Moon, China is going the “easy” (that is, largely tested) way. No complicated drives to HALO orbits around the Moon and high-risk approaches such as 14 refuelling flights for the lunar lander after it has reached Earth orbit just so it can get to the Moon (yes, I’m looking at you, NASA – chuck the SpaceX idiocy, will you, please?). Instead, China is going a-la Apollo, using a two-ship system.

The first of these has been in development for a while, and has been referred to in the past as China’s “next generation crewed spacecraft” designed to replace the Soyuz-inspired Shenzhou vehicle the country currently uses to reach low Earth orbit, as well as forming a basis for excursions further afield – such as to the Moon.

As announced by via Chinese state media on February 24th, 2024 during the Lantern Festival – the last day of traditional Chinese new year festivities and which takes place, appropriately enough during a full Moon -, the new class of crewed space vehicle will now be called Mengzhou (“Dream Vessel”). The name was selected after China held a national competition to name the programme, and is in keeping with the naming convention for its orbital classes of space vehicle (e.g. Shenzhou and Tianzhou).

Mengzhou is a two-stage craft comprising a useable capsule system capable of seating up to six taikonaut, and an expendable service module providing propulsion, power and life support. The vehicle’s overdesign is fairly advanced: a scale model version of the capsule was flown in space in 2016 on a mission designed to provide engineers with the data they required to finalise the capsule’s overall design and flight characteristics.

A second flight in 2020 using a full-scale proof-of-concept vehicle used to evaluate vehicle avionics, orbit performance, new heat shielding, parachute deployment and a cushioned airbag landing and recovery system. Currently, the first crewed test flight of the craft in either 2026 or 2027.

Four lunar missions, Mengzhou will fly with a crew of three and extended life support capabilities and additional supplies. It will be joined on missions by the Lanyue (“embracing the Moon”) lander. This again borrows somewhat from the Apollo missions of the late 1960s / early 1970s, being a spindly-legged craft built around a squat crew compartment supporting (initially) two taikonauts. Like the Apollo lunar lander, the craft is two staged; unlike the American lunar lander – which landed on the Moon fully intact, with the lower (“descent”) stage becoming a launch pad for the upper (“ascent”) stage for getting the crew back up to lunar orbit – Lanyue will use the same stage for both the landing and ascent phases of a mission.

The second stage of the vehicle will be a propulsion module which will power the lander to lunar orbit and then “park” it there. The crew will then travel to lunar orbit aboard a Mengzhou vehicle and dock with Lanyue. Two will transfer to the lander vehicle and undock to use the lander’s propulsion module to decelerate out of lunar orbit and into a descent towards the surface. Once the descent commences, the propulsion stage will be jettisoned to crash on the Moon, while the lander/ascent stage will continue on to a soft landing.

Information on how long a time the initial crews will spend on the Moon is unclear, as the details thus fair released are ambiguous in their interpretation. For example: the term “six hour stay” is used, but both in terms of the complete surface mission and in reference to crew EVA time. Most analysts in the west believe the first missions will equate to the stays of Apollo 11 and Apollo 12 – so “six hours” refers to actual EVA time -, with subsequent missions staying for increasingly extended periods, up to the limitations of the lander in terms of consumable supplies.

Plans for Lanyue include the provision of a collapsible rover vehicle of a similar nature to the Apollo Lunar Rover, and several models of the lander show the rover stored on its flank. However, it is not clear if it will be part of the first landing(s) or a subsequent addition to missions.

For lunar missions, both Mengzhou and Lanyue will be launched by China’s upcoming Heavy Lift Launch Vehicle (HLLV) Long March 10. Due to make a maiden flight possibly as early as the latter half 2025, this booster is an evolution of China’s Long March 5, and is slated to be able to deliver up to 70 tonnes to LEO or send up to 27 tonnes on its way to the Moon. As noted above, each lunar mission will comprise two Long March 10 launches, one for the lander vehicle and its propulsion module, and one for the crewed vehicle. In addition and when used on Earth orbital missions, elements of the Long March 10 might be evolved to be reusable.

Currently, China is looking at 2030 for their first crewed landing on the Moon, with subsequent mission intended to establish a research outpost in the lunar South Polar Region. From around 2034/35 onwards, China claims this outpost will be expanded into a permanently occupied base open to all countries joining its International Lunar Research Station Cooperation Organization (ILRSCO), seen as a direct alternative / “competitor” to the American-lead Artemis Programme.

One Lander Goes to Sleep, Another Unexpectedly Awakens

They are in many ways the joint tale of two lunar landers, both of which suffered mishaps as they arrived on the Moon, and both of which have nevertheless met the majority of their mission expectations.

Japan’s SLIM

On January 19th, 2024, the Japanese Smart Lander for Investigating Moon (SLIM – also called “Moon Sniper”) arrived on the lunar surface – upside down (see Space Sunday: a helicopter that could; a lander on its head). Despite this, the landing meant Japan had become only the fifth nation to successfully land a vehicle on the Moon after America, Russian and India, and the mission carried out most of its assigned science despite being inverted, prior to the long lunar night (14 terrestrial days long) settling over it.

Lacking sunlight to provide energy for its batteries, the chances of SLIM making it through the long, cold night were low, but the mission team at JAXA, the Japan Aerospace Exploration Agency, powered-down the craft ahead of night arriving in the hopes its batteries might retain sufficient power to keep the electronics warm until the Sun rose over the landing site once more.

On February 25th, this optimism was rewarded: following sunrise over SLIM, the team were able to establish contact – albeit it intermittently. Attempts were then made to resume some of the lander’s science work, notably with the multiband spectroscopic camera (MBC). Unfortunately, these were unsuccessful, mission engineers believing MBC may have suffered damage as a result of the extreme low night-time temperatures.

Attempts to engage the system were abandoned on February 29th when, with night again approaching, SLIM was once again ordered to go to sleep in the hope its batteries will again see it through to the next lunar midday period in the latter part of March, when the sunlight will again be directly on its solar array.

Continue reading “Space Sunday: More Moon (with people!) and a bit of Mars” →

The second private mission to fly to the Moon under NASA’s Commercial Lunar Payload Services (CLPS) programme, and launched on February 15th, arrived on the lunar surface on February 22nd.

Following a successful launch, the mission – referred to as IM-1, for Intuitive Machines (the company that built the vehicle) mission 1, and the Nova-C lander itself christened Odysseus, had a slight wobbly start to its time in space after successfully being delivered into Earth orbit by a SpaceX Falcon 9 rocket.

Following its separation from the launch vehicle’s upper stage, the 675 kg Odysseus had been due to carry a “commissioning burn” of its main liquid methane / liquid oxygen (“methlox”) engine, firing it, then stopping it and then restarting it, a critical requirement of the motor if the lander was to enter lunar orbit and land. However, issues with the lander’s navigational star tracker and then with the liquid oxygen tank’s cooling lines meant the test had to be delayed until February 16th, when it was completed successfully, marking the first time a methlox propulsion system had ever been successfully re-started in space.

Following its departure from Earth, the craft had been scheduled to make three trajectory adjustment manoeuvres whilst en route to the Moon, but only required the first two, such was the accuracy with which it matched its flight plan. On February 21st, the lander performed a Lunar Orbit Insert (LOI) manoeuvre, firing the main engine for 408 seconds to slow its velocity by 88 metres per second and place it in a 92 km orbit around the Moon.

After 24 hours in orbit, returning high-resolution images of the lunar surface to Earth, the vehicle was prepared to start its decent – and the mission hit another slight hiccup: a safety switch on the primary descent laser rangefinder had not been correctly set prior to launch, leaving the lander unable to accurately determine its distance from the Moon’s surface.

To compensate, the IM team worked with NASA to allow the latter’s experimental Navigation Doppler Lidar for Precise Velocity and Range Sensing system (called simply NDL to avoid a mouthful of an acronym) carried by the lander to take over the role of the laser rangefinder (and thereby also proving the NDL’s ability to guide a vehicle to a precise landing on another celestial body). This allowed the lander to commence its descent; unfortunately, it also meant that one of the other payloads on the lander had to be powered down.

This was EagleCam, a small box of cameras developed by students and designed to be ejected from the lander when it was some 30 metres above the Moon in the hope that it would land ahead of Odysseus and provide the first-ever images of a space vehicle landing on the Moon. But the need to re-route power to NDL meant the ejection system for the camera had to be turned off.

Everything else with the descent seemed to go exactly as planned, and at 23:53 UTC on February 22nd, the lander settled on the Moon close to the crater Malapert A, about 300 km from the lunar south pole, only for another issue to occur: the mission team could not fully acquire the lander’s transmissions. After 15 minutes, it became apparent that whilst the vehicle was safely on the Moon, something was preventing it from sending a full-strength signal, leaving the mission team unable to lock-on to it. During the next several hours, the team worked to establish a firm contact with the lander – which they managed, to a degree – and obtain data on its approach and landing on the Moon, and general condition. The data received allowed them to reach a conclusion as to what had happened.

It had been thought that the 4.3 metre tall craft had made a proper vertical descent, slowing its horizontal speed to zero before lowering itself onto the Moon vertically at a rate of 3.6 km/h. But the telemetry finally obtained by the mission team revealed that at touchdown, the vehicle was vertically descending at close to 10 km/h, and moving horizontally at 3.2 km/h.

This has led Intuitive Machines to conclude the lander was crabbbing sideways immediately before landing, rather than hovering in place, and one of the landing legs snagged on a rock or lip of a crevice, causing the vehicle to gently topple onto its side. Further data suggested that in toppling, Odysseus had ended-up leaning against a rock, allowing it to communicate, but with its antenna mis-aligned.

While communications had been stabilised, as of the time of writing the piece, it was unclear how many of the lander’s science packages would be able to function successfully. Even so, the landing is both a success – the first time an operational lunar lander built and operated by the private sector has landed on another celestial body, and the first time America has returned to the surface of the Moon since Gene Cernan and Harrison Schmitt departed on Apollo 17 in 1972 – and a warning.

Like the planned SpaceX Starship Human Landing System vehicle (HLS) intended to return humans to the lunar surface as a part of the Artemis Project, Odysseus is a tall, slim vehicle in terms of its overall proportions. Even with two extra landing legs compared to the SpaceX HLS (a altogether taller vehicle with a higher centre of mass), The IM-1 mission demonstrates how just a slight horizontal drift can be sufficient for such a vehicle to topple itself where a squatter, broader vehicle probably would not have done so.

Currently, IM-1 has sufficient sunlight to remain in operation through until the latter part of the coming week, after which the sun will set relative to its location on the Moon, depriving it of energy to power its battery systems.

Wooden Wonder

Want to have more eco-friendly satellites? Then why not make them out of … wood.

No, I’m not being sarcastic nor have I gone space happy. The above proposition was first put forward in 2019/2020 by a team of Japanese researchers at Kyoto University. It was born out of concern about the on-going practice of allowing / causing expired satellites to re-enter the upper atmosphere to burn up as a result of the frictional heat created by their passage through the atmosphere.

Whilst this generally results in the destruction of the greater portion of a lump of debris entering the atmosphere and helps reduce the dangerous clutter of junk whipping around the Earth, it is not entirely “clean”: every satellite or piece of rocket that burns up in this way leaves behind a trail of alumina particles which remain suspended in the atmosphere for decades. With the explosion of the private space sector and the growing use of “constellations” of thousands of low-orbiting, expendable satellites such as the (as of January 2024) 5,289 SpaceX Starlink network, these trails or clouds of alumina particles are set to increase exponentially, potentially having an undesirable impact on the upper reaches of the denser atmosphere and the environment as a whole.

So the researchers set out to find an alternative material for making satellites – and came to the conclusion that wood might be the best. Thus, the LignoStella Space Wood Project was born.

When you use wood on Earth, you have the problems of burning, rotting and deformation, but in space, you don’t have those problems: There is no oxygen in space, so it doesn’t burn, and no living creatures live in them, so they don’t rot. Some woods are extremely durable, so we set out to see if wood could be practically applied for use in small satellite systems.

– Koji Murata, LignoStella Space Wood Project

To test their ideas, the team examined various types of wood and determined three –  Erman’s birch, Japanese cherry and magnolia bovate – had the precise properties required of a satellite body: they are lightweight, strong and durable. Just how durable was demonstrated when samples of the woods were flown to the International S[ace Station (ISS) in 2022 and exposed to the vacuum of space and the unfettered blasting of solar radiation for 290 days, being returned to Earth in mid 2023.

Analysis for the samples revealed that despite the harsh conditions to which they had been exposed, they had no measurable changes in mass and showed no signs of decomposition or damage. Meanwhile, tests of the woods on Earth indicated that of the three flown on the ISS, the magnolia wood – Hoonoki in Japanese – offers the best choice in terms of “workability, dimensional stability and overall strength” for use in a satellite design.

Now, and with the involvement of the Japanese Aerospace Exploration Agency (JAXA)  and America’s NASA, the researcher are aiming to launch their first wooden satellite this coming summer. Currently, the plan is to carry it to orbit aboard an Orbital Sciences Cygnus automated resupply vehicle delivering supplies and equipment to the ISS. If all goes according to plan, the Cygnus vehicle will release the little satellite into its own orbit, where it will remain for 6 months.

Called LignoSat-2, the vehicle is roughly the size of a cubesat – no more than 10cm on a side. Its primary purpose will be to test a number of factors in the use of wood which could dramatically change the design of such small satellites, which are growing increasingly popular in a growing number of roles. For example, wood can be penetrated by electromagnetic waves, so delicate and awkward elements of a satellite – sensors and antennae – could be mounted inside the satellite’s overall structure, helping to protect them whilst simplifying the overall design of the vehicle.

The overall durability of wood will also be monitored, as will be the eventual destruction of the satellite, the majority of which should burn-up “cleanly” in the atmosphere at the end of the mission, leaving only minute amounts of trace particulates.

One of the missions of the satellite is to measure the deformation of the wooden structure in space. Wood is durable and stable in one direction but may be prone to dimensional changes and cracking in the other direction.

– Koji Murata, LignoStella Space Wood Project

The LignoSat project is not the only team to consider the use of wood in satellites. Working entirely independently to them, a consortium of researchers and businesses out of Finland, supported by the European Space Agency (ESA) and Rocket Lab were developed a similar project with a cubesat built primarily out of plywood and called WISA Woodsat.

Heavily promoted and slated to fly in 2022, the project as (and still is) billed as the “world’s first wooden satellite”. However, since mid-2022 the project has been stalled, with no website updates or further information from ESA since April of that year.

Medical Crystals Grown in Space

One of the major promises of near-Earth space operations has long been that of leveraging the micro-gravity environment in the manufacture of ultra-pure drugs and the components used within them. Multiple experiments in this regard have been carried out over the decades, using facilities on space stations such as Mir and the ISS, or aboard the space shttle when it flew the European Spacelab, and so on.

Now a US company is looking to take matters a stage further – and have just successfully recovered their first attempt.

Varda Space Industries is a relative new US start-up which has grand designs on microgravity manufacturing involving pharmaceuticals, fibre optics and computer chips. And they’ve moved fast. In 2021 the company purchased three Photon satellite buses from Rocket Lab to provide power, propulsion and navigation capabilities for the company’s “Winnebago” automated production satellites, the first of which – Winnebago-1 (W-1) – launched in June 2023, as a payload within a SpaceX Falcon 9 Transporter rideshare launch.

Originally, the craft was supposed to spend three months in orbit, growing exceptionally pure, “near-perfect” crystals used in an anti-viral medication called Ritonavir, a highly active antiretroviral therapy (HAART). The selection of a pharmaceutical product for the first Winnebago  mission as this is seen as the largest market which might benefit from the benefits of microgravity production techniques. However, the capsule remained in orbit far longer than intended, thanks to the US Department of Defense (DOD), having originally agreed in principle to allowing Varda to use its Utah Test and Training Range (UTTR) as their landing site, withdrew that permission after the mission had been launched.

Thus began a multi-month series of negotiations involving the DOD, the Federal Aviation Administration (FAA), Varda and Rocket Lab to try and reach an agreement on the use of UTTR to recover the capsule. So protracted did this became that Varda, rather than lose their product, actually started looking at overseas recovery options such as the Koonnibba Test Range in Australia.

On February 14th, however, the required agreement to use UTTR was reached and the FAA expedited granting Varda a licence to carry out a controlled re-entry into, and descent through, Earth’s atmosphere. As a result, on February 21st, 2024, Varda were finally able to bring their W-1 mission home on February 21st, 2024.

After the Photon buss had been used in a de-orbit manoeuvre, the capsule containing the automated manufacturing plant successfully re-entered the atmosphere and deployed its main parachute, touching down within the UTTR at 21:40 UTC in February 21st, marking the second time the range has been used for the recovery of space science capsules – the first being NASA’s OSIRIS-REx capsule, bringing samples from asteroid Bennu back to Earth for analysis.

Following touchdown, the capsule was subject to analysis and cooling prior to being harnessed to a helicopter for transfer to a Varda receiving station where it could be opened in suitable lab conditions, and the crystals produced initially assessed.

From there, the Ritonavir vials onboard the spacecraft will be shipped to our collaborators Improved Pharma for post-flight characterisation. Additionally, data collected throughout the entirety of the capsule’s flight — including a portion where we reached hypersonic speeds — will be shared with the Air Force and NASA under a contract Varda has with those agencies.

– Varda statement

No information has been given on the next Varda mission, called Winnebago-2, or its likely payload.

A recent comment on Space Sunday, from Gwyneth Llewelwyn concerning the concept of space elevators got me thinking as to whether or not I should cover this idea in a little more detail – or as much as I can in under 2,500 words! So here we go.

For those unfamiliar with the concept, a space elevator is a proposed means of payload transfer (cargo and people) between Earth and geostationary equatorial orbit (GEO – 35,786 km) by means of large scale transport units called “climbers” moving up and down a cable system generally referred to as a tether. Such a system would, it is claimed, make routine, shirt-sleeve access available to everyone, and would reduce the cost of payloads from the current average of around US $12,125 per kg to as little as US $200 per kg and without the need for all that tedious mucking about with cylindrical things using propellants with a propensity to go BANG! in unwanted ways if given the chance.

The concept actually dates back as far as 1895, when the “grandfather of modern rocketry”, Konstantin Eduardovich Tsiolkovsky (1857-1935) was inspired by Eiffel’s tower in Paris. He calculated that any object carried up a tower reaching as far as GEO would acquire sufficient horizontal velocity during its ascent so has to remain in orbit on reaching 35,786 km altitude and being released.

Tsiolkovsky’s idea was more an exercise in mathematics and orbital mechanics than an actual design proposal; even the title of his paper on the subject was Day-Dreams of Heaven and Earth. He was well aware that any tower built from the ground up would increase in mass to a point where it could no longer support itself and so collapse under its own weight long before reaching any significant altitude.

However, with the arrival of the space age, the concept was reborn, thanks to Yuri Nikolaevich Artsutanov (1929-2019). He actually never heard of Tsiolkovsky’s paper, although he was similarly aware that building up was a non-starter, so he came up with the idea of building down – starting from GEO and using a tensile structure.

He first published his idea in 1959, outlining how a large space station in GEO could be used as an “anchor point” for two cables – one going towards Earth, and the other on the opposite side of the station to counter the mass of the first cable, helping to keep the station in place and, once the Earth cable was anchored to the planet, act as a counterweight to maintain tension throughout the structure.

In writing his paper, Artsutanov also calculated that in order to maintain a constant stress throughout its length, aiding its stability and strength, the cable extending down to Earth would need to tape as it descended, becoming gently narrower and narrower. Thus, he laid the foundations for what has become the most recognised concept for building a space elevator.

Unfortunately, Artsutanov’s work didn’t reach an audience outside of the former Soviet Union until the mid-1960s. By that time, and quite independently, similar proposals for a tensile space elevator had by written by David Edward Hugh Jones (1938-2017) in the UK (1964) and by US engineers J.D. Isaacs, A. C. Vine, H. Bradner and G. E. Bachus in 1966 (although they called their idea the “sky hook”), which led to Artsutanov’s ideas passing largely uncredited until the late 1970s, when his paper finally gained the international recognition it deserved.

Only of the key points of the tensile system has is its potential flexibility of use, as identified and proposed by numerous researchers over the past 60 years. For example, if a waystation were to be built some 8,900 km above the Earth as the tether descended, it would have a gravity environment equivalent to that of the Moon, while a second waystation built some 3,900 km altitude would have a gravity environment equivalent to Mars. These could thus be used as training facilities for crews heading for the Moon and Mars, allowing them to acclimatise to the lower gravity environments.

Similarly a waystation built on the counterweight tether at a distance of 23,750 km from Earth would mean that any satellites or craft released from it would have insufficient velocity to maintain a stable orbit. Instead, they would spiral down towards Earth, gaining a small degree of angular momentum in the process, such that by the time they reached an altitude of 300-400 km, they would be moving at orbital velocity and remain there.

Further, if the counterweight tether was extended out to 100,000 km from Earth, it would provide points from which vehicles and payloads could be released with sufficient velocity to enter transfer orbits to the Moon or the L1 or L2 Earth-Sun Lagrange points; whilst those released from the end of the tether could be sent on their way to Mars and beyond.

All of these ideas helped promote the concept as both potentially viable and very desirable, and by the late 1970s, the idea of the space elevator was starting to enter public consciousness – helped, no doubt in part by science fiction authors like Arthur C. Clarke, who made the space elevator the nucleus for his 1979 novel The Fountains of Paradise (in fact Clarke became so enamoured with the idea, he wrote his own scientific paper on the subject, also published in 1979,entitled The Space Elevator: “Thought Experiment” or Key to the Universe?).

However, despite decades of research and ideas – and even s further resurgence of the idea in the last decade or so, the space elevator is still only a concept and despite predictions to the contrary, is likely to remain so for the foreseeable future.

This is because right now, we simply do not have a material with the necessary tensile strength / density ratio required for a space elevator to support both its own mass and the mass of anything built on it or travelling along it whilst also remaining somewhat flexible. This ratio has been calculated  as being 77 megapascal (MPa)/(kg/m³). By comparison, titanium, steel or aluminium alloys have a tensile strength / density ratio of just 0.2–0.3 MPa/ kg/m³ (and would result in a structure far too heavy and rigid even if they could be used), whilst Kevlar and carbon/graphite fibre are more flexible, lighter a, stronger and better suited – but still only have a ratio of 1.0–4.0 MPa/ kg/m³.

Much has been made of carbon nanotubes (CNTs) providing the solution. First invented in the early 1990s, these are tiny tubes about 100,000 times smaller than the width of a human hair with a huge amount of tensile strength for their mass (perhaps as much as 100 MPa / kg/m³. But there is a snag. Thus far, the longest researchers have been able to grow individual CNTS is just 50 cm, whilst CNT “forests” (hundreds of CNTs grown together so that they can be drawn out into a thread-like length (the idea being that the threads can then be woven together in increasing thickness to produce super-strong cables, as well as being used in other ways) haven’t exceeded 14 cm in length when drown out before they start to collapse. Thus, there is a long way to go before CNTs can be used to manufacture something as massive as a space elevator cable.

The reason the tether must be capable of flexing and moving is two-fold. Firstly, as climbers ascend and descend along the tether, they either gain or shed angular momentum. This means that an ascending climber will reach a point where its angular momentum is greater than that of the cable it is travelling along. As a result, a Coriolis force will be applied, causing the cable to bend to the west. Similarly, a descending climber will reach a point where its angular velocity is less than that of the section of tether it is travelling along, and the resultant Coriolis force with flex the tether to the east.

Whilst some of this flexing (and the oscillations it might induce in the entire structure) can be mitigated to some degree – the oscillations can be countered by placed the structure’s centre of mass somewhere above GEO, for example, whilst pairing-up climbers so that when one is ascending another of an identical mass is descending so that the forces they apply to the cables of the tether can cancel one another out to some degree – it will still be necessary for the tether to be able to bend, flex and sway (within reason!) in response to forces placed on it through the movement of climbers (as well as natural forces like winds).

The second reason for the tether being capable of movement is a matter of safety: much of the space it will be moving through is cluttered with thousands of satellites and millions of piece of space debris on 10 cm or grater in size. While collisions between such debris and space vehicles are rare, they do occur – so it is essential the tether has a means  – however limited – to avoid any debris large enough to be tracked (and thus risk significant damage on impact) and any satellites in orbit which cannot get out of its way should their orbits intersect with its passage through space.

There are other issues – location of the base station (most of the Earth’s equator is open ocean, after all), power requirements (which will be huge), and so on. However, none of these are actually insurmountable, so in the interests of brevity I’ll take them as read here.

All of which mean that, while the construction of a space elevator is not beyond the realms of possibility – technologies such as CNT production will improve, for example – it is not something we’re likely to see happen in the next few decades. Not that this has stopped some like Japan’s Obayashi Corporation from dreaming, as the video below demonstrates – just take the timeline with a pinch of salt!

But were a space elevator to be built, what would travelling it be like? Well, for a start you can forget the zooming ride depicted on the above video! Whilst being cost-effective means getting payloads to and from GEO as quickly as possible, there are actually limitations as to how fast climbers can realistically ascend / descend in order to avoid over-stressing the cables section they are travelling along.

Speed also needs to be limited to ensure passengers are not subjected to prolonged periods of excess of G-forces. As such, a speed of between 300-400 km/h has been suggested for climbers. Whilst this might sound fast, it actually means that a trip to GEO would take as long as crossing the Atlantic on an ocean liner – 4 to 5 days. Given this, climbers used for passenger operations will have to offer a range of passenger amenities – including the ability to move around relatively feely. All of which means climbers will be fairly substantial vehicles, even if only carrying a modest number of passengers – so forget the Disney-esque all sitting in a little capsule and watching Earth recede behind you and *ping* you’re there; riding a space elevator to GEO is liable to be quite the experience!

Which brings me to a final point in this rapid-fire run-down of the concept. And that’s the fact that perhaps the space elevator is best suited for use not here on Earth, but on Mars (as identified by Kim Stanley Robinson in his Mars trilogy). There are several reasons for this.

Mars’ gravity is 38% that of Earths. This means its equatorial orbit distance is just 17,032 km above the planet. These facts combine to mean that not only can a Mars space elevator be much smaller (or shorter, if you prefer) than one on Earth, it could be built out of existing materials – no need for exotic CNTs. That said, there are two slight hiccups with this idea. first, we have to actually get to Mars and reach a point in its development where a space elevator is warranted. Secondly, Mars’ inner moon, Phobos, orbits inside the planet’s equatorial orbit distance, crossing the equator every 5.8 hours. As such, it presents a significant threat to any space elevator, which must therefore have an ability to move itself aside on those occasions went it and Phobos would otherwise be occupying the same volume of space.

However, most intriguingly is an idea to use Phobos itself  – which is tidally locked with Mars, so always has the same side facing the planet) as the platform for a novel space elevator system. This would see two tethers built out from the Moon – one towards Mars and the other as the counterweight – to a distance of 6,000 km. This would place the end of the Mars-facing  tether just above the denser atmosphere of the planet, and travelling some 0.52 km/s fast that the planet is rotating. Craft could then be launched from Mars with a delta-V of just 1,872 km, much less than required to reach orbit, to dock with the tether as it skims around the planet, and / or landers could be dropped off to touch down without the need to slam into the atmosphere at Mach 25.

Meanwhile, the counterweight end of the tether would by moving at 3.2 km/s – just 1.8 km/s short of Mars escape velocity. So it could be used to start payloads on their way back to Earth with only minimal propellant needs at launch – or it could give a kick-start to crewed vehicles designed to rendezvous with a Mars cycler craft as it skips around the planet, allowing the crew to make a return to Earth aboard the cycler, again for far least propellant use than would be required with a launch from the planet’s surface.

Again, this is not intended to be an in-depth look at space elevators, so there are aspects I’ve not mentioned or glossed over to piece this piece to a reasonable length. However, if the subject is new to you, I hope this acts as a reasonable primer, and we’ll be back to the more usual format for Space Sunday next week!