Tag: Spaceflight

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!

Ingenuity, the remarkable helicopter drone which forms a part of NASA’s Mars 2020 mission, has made its last flight and is now officially “retired” – and with full honours. Whilst very much an experimental vehicle, the craft achieved far more than the teams responsible for developing and building it and for operating it could ever have hoped for – and in doing to, the helicopter caught the imaginations of people around the world.

The vehicle’s remarkable history started in 2012 when the then director of NASA’s Jet Propulsion Laboratory (JPL) , Charles Elachi, met with members of the Autonomous Systems Division (ASD). They persuaded him that a concept study for aerial rover vehicles in support of surface missions on Mars had merit to the point where although NASA senior management had no interest in such a project, he used his influence to get the team sufficient funding for an initial design to be produced.

This demonstrator proved so impressive to NASA management that it was agreed the project should receive further funding to allow several engineering models to be built – even though there was still no mission on which any developed aircraft could join. It was not until March 2018, with the engineering models showing genuine promise for real flight capabilities on Mars that it was agreed that the helicopter project should go ahead – and should be flown as a part of the up-coming Mars 2020 rover mission, which was itself already at an advanced stage of development.

This resulted in a crash course of design and development – from engineering demonstrator to full-blown, mission-ready vehicle in just two years, including a deployment system which would allow the helicopter to be stowed against the rover’s belly and deployed from there once on the surface of Mars.

Originally called the Mars Helicopter Scout, the inclusion of the helicopter in the Mars 2020 mission angered some in the NASA hierarchy – and within the rover team itself. Jennifer Trosper, Perseverance’s mission systems development manager and project manager stated her belief that such were the capabilities of the rover’s autonomous driving system, it would simply outpace the helicopter, rendering any idea of the latter being a useful scout moot.

To help counter such opposition, the scope of the helicopter’s mission was intentionally limited. Named Ingenuity, as suggested by (then) schoolgirl Vaneeza Rupani as a name for the rover, it was related to the role of technology demonstrator and its mission initially limited to a 30-day period at the start of Perseverance’s time on Mars in order to limit any impact on the rover’s mission in having to sit by and observe what was expected to be a maximum of five flights. Even so, opponents of the helicopter’s inclusion in the mission remained vocal in their objections.

I have personally been opposed to it because we are working very hard for efficiencies and spending 30 days working on a technology demonstration does not further those goals directly from the science point of view [this] helicopter is a distraction from the priority scientific tasks, unacceptable even for a short time.

– Mars 2020 chief scientist Kenneth Farley voicing misplaced antagonism toward Ingenuity

This opposition is why Ingenuity’s project lead, MiMi Aung and her little team – who initially were not even awarded space in the Mars 2020 mission control room, but had to operate out of a meeting room they converted into their own operations centre – were so determined to see Ingenuity not only fulfil its initial primary mission but to exceed all expectations, even if it meant aggressively pursuing goals and extending flight parameters to a point of putting their little craft at risk.

The first opportunity for the team to prove their vehicle came on April 19th, 2021, almost two months after the mission had arrived within Jezero Crater, and almost two weeks after Ingenuity had successfully deployed onto the planet’s surface. In the intervening period, the helicopter’s electrical system had been charged and tested, the twin sets of contra-rotating blades unlocked for their stowed position and run through a series of ground tests – some of which didn’t quite go to plan –, with a finally high-speed test of the rotors being carried out 2 days prior to the first flight, confirming the motors could safely power the blades to their required 2400 rpm.

The first flight was brief: a simple lift-off to 3 metres above ground, then an axial rotation of around 90º prior to a descent and landing – simple, that is, until you consider that Ingenuity was attempting to take flight at within an atmosphere with a density equivalent to that of Earth’s at 34,000 metres (112,000 ft) – well above the capabilities of any Earth-based rotary craft.

The remaining four test flights came rapidly thereafter, initially testing the craft’s ability to transition from a hover to horizontal flight (covering 4 metres in its second flight, then just 3 cm shy of 100 metres in its third, before smashing its planned maximum horizontal flight capability (160 m) by covering 270 metres in its fourth flight prior to a more modest 130m in the final test flight). By this time, opposition to the helicopter’s presence on the mission was rapidly thawing, and continued operations were given the green light – providing they did not impeded on Perseverance starting into it primary mission of investigation and exploration.

This mission extension period saw the helicopter move from being a technology demonstrator to being more of a general testbed aircraft which could also gradually take up the mantle of its intended role as a scout for the rover. In this capacity it gradually flew flights of both longer duration (the longest being 169.5 seconds in August 201), and greater distance (peaking at 709 metres in a single flight on April 8th, 2022). But the end of 2022, Ingenuity was largely operating in support of Perseverance, not only keeping up with the rover in defiance of Trosper’s prediction, but also actually increasing the effectiveness of the rover’s autonomous driving capabilities by providing the mission team with data which allowed them to more efficiency plan routes wherein the rover could more easily navigate for itself, reducing the punctuation of drive, stop, survey and allow the drive team to plan and upload new instructions then drive, stop, survey and allow the drive team to plan and upload new instructions, common to a lot of the rover’s initial explorations.

Whilst there were some problems encountered with flight software and concerns over motor and rotor performance in the face of slowly decline electrical power generation, overall, Ingenuity proved remarkably robust and capable of exceeding many of the parameters originally set to safeguard it. On October 2023, for example, it achieved an altitude of 24 metres (79 ft) above the ground – over double the 10-metre maximum originally envisioned as its operational ceiling – and this during a time when several flights exceeded that limit. It also withstood the ravages of Martian winter with its harsh cold weather, as well as the challenge of seasonal dust storms.

Nevertheless, it was acknowledged that the longer the mission went on, the greater the risk of something happening that could unexpectedly curtail flights. And at the start of 2024, these risks were made manifest.

By this time Ingenuity was operating over what the flight team called “difficult” terrain. To explain: Ingenuity’s flights are entirely autonomous. They are planned on Earth in terms of timings, direction, altitudes, etc., together with waypoints – static ground features and rocks the helicopter can be told to identify using its navigation cameras, and use to make changes in direction or its orientation and as reference points for landing.

However, since its 68th flight, Ingenuity has been flying over terrain where such definable waypoints are few and far between. On the helicopter’s 71st flight – which took place on January 6th, 2024 – this sparseness of waypoints resulted in Ingenuity becoming confused as to where it was and where it was going, triggering automatic a landing. Unfortunately, it seems one of the rotors suffered a very slight deformation on touch-down, as revealed in post-flight images the helicopter took of its own shadow – a trick the flight team had long used to help assess Ingenuity’s status after each flight when Perseverance was too far away to provide suitable images.

As a result, it was decided that prior to continuing in its scouting mission, Ingenuity should complete a straight up-and-down hop to test the rotor systems. This took place on January 18th, 2024 and initially looked to be successful: the rotors spun up to speed, and the helicopter rose to 10 metres and then descended for a landing. However, as I reported in my previous Space Sunday update, communications abruptly cut-off when it was still around a metre off the ground, and took a little while to restore.

Once communications had been recovered, the helicopter was ordered to again image its own shadow to help in the assessment of its overall condition as the flight team went back through the flight data to try to determine what caused the communications drop-out. In one of the the returned photos, the shadow of a rotor blades clearly shows its end has suffered damage, appearing broken and buckled.

This image suggests that at some point Ingenuity ended up at an angle as it descended at the end of flight 72. Whether this was the result of the deformation in a blade seen at the end of flight 71 or has some other cause, is unknown. However, it is clear than whatever happened, it was sufficient to bring at least one blade tip in contact with the ground, even if for a fraction of a second, causing it noticeable damage.

Whether it was the sudden jolt which likely accompanied the impact which caused the drop in communications or whether there may have been a general electrical glitch which caused both the communications drop and the blade impact is currently the subject of JPL assessments of the flight data. But whatever the cause, and even if the damage is to the one blade-tip, it has put paid to Ingenuity’s ability to fly: the damaged blade will simply cause too much turbulence and vibration for the little helicopter to remain stable. Thus, the mission has been declared over and Ingenuity retired from active duty, an event marked with the release of a short video by NASA, celebrating the mission and its achievements.

And celebration is the right word. During its 32-month operational period, Ingenuity conclusively proved the viability and value of rotary drones on Mars operating in support of other missions. In doing so, it not only itself covered a horizontal distance of 17.242 km (reaching a maximum speed of 36 km/h during some flights) and clocking up a total of 2 hours 8 minutes and 55 seconds in the Martian air, it has successfully laid for foundation for future generations of automated and – come human missions to Mars – teleoperated drones on the Red Planet.

In additional to the “official” video, NASA JPL release a more personal video from some of the members of the Ingenuity team, allowing them to say some final words about the Little Helicopter That Could – And Did.

SLIM Landed… On Its “Head”

In my previous Space Sunday, as well as commenting on Ingenuity’s 72nd flight (which at the time had not been identified as terminating its flying career) I reported on Japan’s SLIM mission to the surface of the Moon, which had met with some mixed results.

As I noted in that report, SLIM – Smart Lander for Investigating Moon – had apparently successfully landed right on target to make Japan the fifth nation to have successfully landed on the Moon, but potentially incorrectly oriented for its solar array to capture sunlight and convert it into usable energy.

At the time of that article, it was unclear precisely what had happened to the lander. The telemetry received and broadcast during the livestream seemed to suggest it was upside down – which many saw as unlikely, particularly as the lander’s systems and science instruments did appear to be working. However, in the hours between touchdown and the lander being placed in a dormant mode as battery levels dropped to a critical level, some of the images returned by the lander seemed to back-up the livestream graphics portrayal that the lander was inverted.

Even so, it was not until the two tiny rovers  – LEV-1 (for “lunar excursion vehicle”) and LEV-2, released by the lander shortly before touch down – reported in that the status of the lander could be confirmed. After establishing contact with Earth with LEV-1 acting as a relay for LEV-2  (also called “Sora-Q”), the rovers returned images of their immediate surroundings before being tasked with making their way over to the lander and imaging it; and both return some remarkable shots of the lander sitting on its head, one of its descent engine nozzles pointing up into the lunar sky.

It’s not clear exactly what occurred, but JAXA – the Japan Aerospace Exploration Agency – believes one of the lander’s decent engines failed during landing, causing it to touch-down harder than intended and then toppling over as a result of landing on a slope, or possibly the off-axis thrust from the remaining descent engine cause it to flip over following initial ground contact.

As I previously noted, mission operators had hoped that as the lunar day progressed, the Sun would move into a position where light would strike SLIM’s solar array and perhaps furnish it with power. The images from the LEV rovers have confirmed this is indeed possible – the array is facing west, and so will encounter sunlight the the Sun moves towards the local horizon. However, given that nightfall commences of February 1st/2nd, and the lander is not equipped to withstand the harsh night-time lunar temperatures, SLIM may only have a couple of days in which to resume gathering data, even if it can be revived. Even so, the fact that the lander has gathered and returned images and data post-landing, and its two little rovers are operational means this mission can still be counted a success.

The first all-European crewed space mission is currently underway at the International Space Station (ISS) – albeit through the auspices of two US-based companies and NASA.

The Axiom AX-3 mission lifted-off from Launch complex 39A at Kennedy Space Centre, Florida at 21:49 UTC on January 18th, carrying a crew of four aboard the Crew Dragon Freedom. As its name suggests, the mission is the third crewed flight to the ISS undertaken on a private basis by Axiom Space, utilising the launch capabilities of the SpaceX Falcon 9 booster and Crew Dragon capsule.

Delayed by 24 hours to allow for additional pre-flight checks, the launch was perfect, carrying mission commander and former NASA astronaut Michael López-Alegría, representing Spain, his nation of birth (he holds dual Spanish and American citizenry), vehicle pilot Walter Villadei of the Italian Air Force, making his first fully orbital flight into space, having previously flown as a member of Italy’s sub-orbital flight with Virgin Galactic, and mission specialists Marcus Wandt, a reservist in the European Astronaut Corps, and Turk Alper Gezeravcı who becomes his country’s first astronaut.

Following launch, the Falcon 9’s first stage made a successful landing at Cape Canaveral Space Force Base south of Kennedy Space Centre, whilst the dragon went on to a successful orbital insertion and separation from the booster’s upper stage, to start a 36-hour gentle rendezvous with the ISS, the Crew Dragon gently raising its orbital altitude to match that of the ISS before closing to dock with the station.

The latter took place at 10:42 UTC on Saturday, January 20th, 2024, when Freedom latched on to the forward docking port on the station’s Harmony module and pulled into for a hard dock. 90 minutes later, with post-flight checks completed and the AX-3 crew able to change from their pressure suits to less restrictive flight wear, the hatches between station and capsule were opened, and López-Alegría led his crew out to be greeted 7 members of ISS Expedition 70.

The mission – which is due to last some 14 days at the station – marks the sixth orbital flight for López-Alegría. He first flew in 1995 on the second mission of the US microgravity laboratory, a research module carried within the payload bay of the space shuttle prior to the development of the ISS.  He subsequently flew on STS-92 and STS-113 whilst the ISS was being constructed, prior to serving as ISS mission commander for the Expedition 14 rotation in 2006-2007. He also served as the head of NASA’s ISS Crew Operations office (1995-2000) and is also a former NASA aquanaut, serving on the first NASA Extreme Environment Mission Operations (NEEMO) crew aboard the Aquarius underwater laboratory, in October 2001. Having joined Axiom in 2017, he first flew aboard Crew Dragon in the AX-1 mission in April 2022.

The remaining three AX-3 crew are all orbital rookies making their first stay in space. However, their presence on the ISS means that the station now has its largest ever international crew, with two US citizens, three Russians, a Dane, and a Japanese astronaut making up the ISS expedition crew.

We’ve got so many nationalities represented on board, and this is really symbolic of what we’re trying to do to open it up not only to other nations, also to individuals to researchers to continue the great work that’s been going on onboard the ISS for the last two decades plus.

– Michael López-Alegría

While aboard, Ax-3 crewmembers will live and work alongside the station’s current residents, performing experiments and research started with the first two Axiom missions, with a focus on human spaceflight and habitability in microgravity environments, a goal very much in keeping with international research on the station and of particular interest to Axiom Space, which plans to operate its own orbital facilities, initially docked their own modules with the ISS prior to separating them to become a dedicated orbital facility when the ISS is decommissioned in 2030.

In addition, the AX-3 crew will conduct research into AI and human health – the mission includes an experiment from Turkey called Vokalkord, which uses AI algorithms to diagnose several dozen diseases by analysing a cough or someone’s speech -; experiments with high-strength alloys, with implications for in-space construction and assemblies as well as other biology and physics-related work.

China’s SpaceX? Sort-of, But Not Exactly

A glance at the image above might initially suggest it is one from the history books: an early flight test of the Falcon 9 reusable first stage out of SpaceX’s flight test centre at McGregor, Texas. However, the landscape isn’t entirely in keeping with that of McLennan and Coryell counties, Texas, whilst a closer look at the booster might reveal something of the truth, thanks to the large red flag painted thereon.

The craft is in fact the Zhuque-3 vertical take-off, vertical landing unit 1 (VTVL-1), a test article developed by Chinese private sector launch start-up Landspace. It is intended to pave the way for a semi-reusable launch vehicle called Zhuque-3 (“Vermillion bird-3”), which is intended to have the same overall launch capabilities as Falcon 9 (up to some 21 tonnes to low-Earth orbit (LEO) when flown fully expendable, and between 12.5 and 18.4 tonnes when the first stage is to be re-used). However, to call it an outright “Falcon 9 clone”, or a “copy” of SpaceX’s work would not be strictly accurate.

Whilst there is much about Falcon 9 which likely influenced the Zhuque-3 design, the fact is that its looks are as much about the old axiom, form follows function, as much as any “copying” of SpaceX; the overall design and appearance of the booster and its landing legs are simply the result of their form being the most logical to meet the requirements of their functionality (hence why, in aircraft design, for example, vehicles designed for a specific task by different nations can often end up appearing quite similar, even if not direct copies).

Similarly, and while SpaceX fans have pointed to Landspace also “copying “SpaceX in the use of stainless steel for the rocket and the use of methlox – liquid methane/liquid oxygen – engines (all of which are used by SpaceX in their Starship / Super Heavy combination), the fact is that the Chinese commercial space sector has been dabbling in methlox propellants since around 2015, pre-dated Starship development, whilst the use of stainless steel in the Zhuque-3 rocket is perhaps more the result of Landspace already having experience in fabricating rocket cores out of it via their operational Zheque-2 launch vehicle than any attempt to copy someone else’s work. While also is not to say that SpaceX haven’t cut a path that other companies around the world can follow.

The first (expendable) launch of Zhuque-3 is expected in 2025, and will mark a further expansion of China’s commercial space sector, in which Landspace is just one of a number of companies developing or operating launch systems and developing semi-reusable launchers. Just how much competition there is already in the market is perhaps illustrated by the fact that some news agencies reported on the Zhuque-3 test flight by using video footage of the second test carried out by China’s iSpace company of their Hyperbola-2 VTVL test vehicle, which took place in December 2023!

Such is the broad and rapid pace of reusable booter development in China’s commercial space sector, footage similar to this video showing the first VTVL test of the iSpace Hyperbola-2 booster VTVL test article (and which I covered at the time), was mistakenly used by some news outlets to report on the January 19th Zhuque-3 VTVL test. Video credit: iSpace via SciNews

Overall, the Chinese commercial market is as richly diverse as the developing commercial space sector in the US, and with China enjoying good trade relations with a number of Asian countries looking to develop space-based capabilities, there is good potentially for interest in using these vehicles to gain something of an international footprint.

Three Mini Mission Updates

Peregrine Mission One

Astrobotic’s Peregrine Mission One (aka Peregrine or Peregrine One), is now officially over. As I’ve previously reported, the NASA-funded private mission to put a lander on the surface of the Moon under the agency’s Commercial Lunar Payload Services (CLPS) programme, got off to a flying start with a January 8th, 2024 ride to TLI (trans-lunar injection) aboard the maiden flight of United Launch Alliance’s Vulcan Centaur rocket. However, some time after the separation of the lander from the rocket’s Centaur upper stage, a propellant leak occurred which resulted in the lander entering an uncontrolled tumble, shifting it away from its rendezvous with the Moon and starving it of the propellants needed to make a landing even if it could get there.

On January 14th, the lander crossed the orbital path of the Moon, and shortly after that, gravity took over and started pulling it back towards Earth. As a result, on January 18th, 2024, the craft re-entered the atmosphere over the South Pacific, where it proceeded to burn-up. However, analysis of data returned by the craft as it headed back to Earth revealed a possible cause of the propellant system failure, as related by Astrobotic CEO John Thornton during a press briefing on January 18th:

The valve separating the helium and oxidiser in the lander’s propulsion system did not re-seal properly. This allowed a rush of helium to enter the oxidiser tank, raising the pressure to the point where the tank ruptured.

This knowledge actually helped in securing the lander’s final demise: by characterising the nature and direction of the leak, together with the rate of loss of remaining gases, flight engineers were able to put the lander into a more controlled entry into the atmosphere, pushing itself farther over the South Pacific to avoid the risk of any components surviving re-entry from falling over land masses.

Despite the loss, Astrobotic remain upbeat about their next lunar mission – again supported by NASA – which will hopefully see the company’s Griffin lander deliver NASA’s VIPER rover to the Moon in 2024.

 Japan’s “Sniper” Achieves Lunar Landing But Not Without Issues

Meanwhile, Japan became the 5th country to successfully land a spacecraft on the Moon when their Smart Lander for Investigating Moon (SLIM)  touched-down near Shoji Crater close the Moon’s equator at 15:20 UTC on January 19th, 2024 (00:20 on January 20th, Tokyo time).

Launched in September 2023 alongside Japan’s X-Ray Imaging and Spectroscopy Mission (XRISM), SLIM – nicknamed “Moon Sniper” – took a leisurely trip to the Moon, spiralling slowly away from Earth to enter lunar orbit on Christmas Day 2023, orbiting the Moon at an altitude of just under 600 km. The orbit was then eased down to around 50 km, and than further reduced to a point just 20 km above the lunar surface, where the descent proper began, curving the lander in towards its target zone. At 5 km above the Moon, the descent became vertical, with livestream telemetry showing everything to be spot-on.

At 50 metres above the surface, the vehicle translated in flight, moving horizontally to position itself directly over a pre-planned landing point, before descending to a successful soft-landing. It was this final manoeuvre which formed one of the key goals for the mission. Usually, landing zones for robot vehicles are planned well in advance and encompass  elliptical areas around 10 km wide and a couple of dozen in length. However, SLIM carried modified facial recognition software which allowing it to monitor its descent and adjust its position autonomously by matching surface features scanned by its cameras with high-resolution images of the landing site stored in its navigation system. At 50 metres, the craft was able to confirm its desired landing point – an area just 100 metres across by contrast to normal landing zones and then manoeuvre itself to a landing with it.

But while the landing was successful, it became clear something was wrong; there was no sign that the battery system powering the craft was receiving energy from the lander’s solar array. After investigating the issue for a number of hours, engineers at the Japan Aerospace Exploration Agency (JAXA) concluded that while SLIM had landed within the desired zone, for some reason its wasn’t correctly oriented for its solar array to receive sunlight, leaving it trapped on battery power, which would expire within hours.

Prior to completely exhausting the battery, attempts were made to put the lander in a dormant mode, the hope being that as the Moon moves in its orbit over the next few days, sunlight will fall onto the lander’s solar array, and power will start to be generated, allowing to to wake itself up and start surface operations.

While both of the mini-rovers – LEV-1 and LEV-2 are thought to have successfully reached the surface of the Moon, at the time of writing, their status is unknown.

Even if the lander cannot recover itself with the aid of sunlight, SLIM is a very successful mission: demonstrating the means to make landings on other bodies with near pinpoint accuracy will be of vital importance in unfolding efforts to explore and develop the Moon and to further explore Mars both robotically and (eventually) with human missions.

Ingenuity Suffers Communications Glitch

NASA’s Mars Helicopter Ingenuity completed its 72nd flight on January 18th, 2024, but not without incident. Lifting-off from sand dunes some 800-900 metres from the Mars 2020 rover Perseverance, the helicopter was engaged in a brief “pop-up” test flight intended to see it climb vertically to 12 metres altitude, hover, and then descend back to a landing.

Telemetry received via the rover indicated that the first elements of the flight were successful – but all contact was lost during the descent phase. For a time it was unclear if the use was a communications drop-out, or something more drastic, and with Perseverance out of direct line-of-sight with the helicopter, determining which was initially difficult.

In recent flights Ingenuity has been ranging ahead of the rover, acting as an airborne scout for possible driving routes. At the end of its 71st flight, the helicopter suffered a slight issue, causing a premature landing somewhat further than planned from the rover; as a result this flight was to confirm all flight systems and software were operating nominally, prior to resuming normal operations and allowing the helicopter to come back closer to the rover.

Following the loss of signal, telemetry was reviewed to see if it revealed any indication of a serious issue and possible vehicle loss. None was found, so engineers determined it was likely a comms problem and ordered Perseverance to change its communications parameters and lengthen the time periods it listens for Ingenuity’s transmissions.

As a result, in the early hours of January 21st (UTC), communications were once again established, allowing more data on the final phase of the flight to be relayed to Earth for study. Currently, Ingenuity remains grounded, and mission planners are considering ordering Perseverance to drive a point where it can see Ingenuity to allow for a visual inspection of the helicopter.

On Monday January 8th, 2024 United Launch Alliance completed the maiden launch of their Vulcan Centaur rocket with complete success, silencing critics and demonstrating that the caution and most recent delays around the launch (outside of those coming from the payload side) were worth it.

Lift-off came at 07:18 UTC as the four Blue Origin BE-4 motors of the 62-metre tall vehicle’s core stage ignited together with the two solid rocket boosters strapped on either side of it, lighting up the sky at Cape Canaveral Space Force station as the rocket climbed into a pitch-black sky. At 2 minutes into the flight, their job done, the solid rocket boosters shutdown and separated, leaving the rocket’s core to continue to power it upwards for a further three minutes before its liquid propellants were expended, and it separated to fall back into the Atlantic Ocean. The Centaur upper stage coasted for some 15 seconds before igniting it own pair of RL-10 motors in the first of three burns to place the vehicle and its payload into a trans-lunar injection (TLI) orbit and the first phase of what was hoped would be a looping trip to the lunar surface.

As I’ve previously noted, Vulcan Centaur is slated to replace ULA’s Atlas and Delta workhorses as a highly-capable, multi-mission mode payload launch vehicle in both the medium and heavy lift market places. Initially fully expendable, the vehicle may evolve into a semi-reusable form in the future, ULA having designed it such that the engine module of the core stage could in theory be recovered. It is also intended to become a human-rated launch vehicle. The Centaur upper stage is also designed with enhancement in mind, with ULA indicating that future variants might be capable of orbiting on an automated basis as space tugs or similar, once in orbit.

Whilst the vehicle carried a critical payload, the flight was actually regarded as a certification flight rather than an operational launch; one designed to gather critical performance and other data on the rocket which can be feed back into any improvements which might be required to make the vehicle even more efficient, etc.

A second certification flight is due to take place in April 2024, again with a critical payload – this one in the form of Sierra Space’s Dream Chaser cargo vehicle Tenacity, the first in a number of these fully reusable spacecraft which will help to keep the International Space Station (ISS) supplied with consumables and equipment, as well as helping in the removal of garbage from the station and the return of instruments and experiments to Earth.

While the launch of the Vulcan Centaur was a complete success – doing much too potentially boost ULA’s position as it seeks a buyer – the same cannot be said for its primary payload, which now looks set to make an unwanted return to Earth.

Peregrine Mission One (or simply Peregrine One), was to have been America’s first mission to land on the surface of the Moon since Apollo 17 in 1972. Financed in a large part via NASA’s Commercial Lunar Payload Services (CLPS) programme, this mission is nevertheless regarded as a private lunar mission, carrying some 20 experiments and instruments allowing it to operate in support of NASA’s broader lunar goals.

At first everything seemed to be going well with the mission. The lander rode the Vulcan Centaur to orbit before it powered-up its own flight systems and ‘phoned home to say it was in good shape. Then, some 50 minutes after launch, and the Centaur upper stage having completed its final burn to set the lander on its looping course to the Moon, Peregrine One separated from its carrier.

All appeared to go well in the hours immediately following separation, but following an attitude adjustment, telemetry started being received suggesting the craft was in difficulties and was unable to correctly orient itself. It was not initially clear what was wrong with the lander, and in an attempt to find out, Astrobotic – the company responsible for designing and building it – ordered camera mounted on the lander’s exterior to image its outer surfaces for signs of damage. The very first image returned showed an area of the craft’s insulation around the propulsion system – required to make the descent and soft-landing on the Moon – had suffered extensive damage, with propellants leaking into space from around it.

This, coupled with the telemetry gathered from the lander caused Astrobotic to determine that one of the vehicle’s attitude control system (ACS) thrusters was still firing well beyond expected limits, most likely due to a failed / stuck valve, placing the vehicle in an uncontrollable tumble.

If the thrusters can continue to operate, we believe the spacecraft could continue in a stable sun-pointing state for approximately 40 hours, based on current fuel consumption. At this time, the goal is to get Peregrine as close to lunar distance as we can before it loses the ability to maintain its sun-pointing position and subsequently loses power.

– Astrobotic statement, Monday, January 8th

Initially, it had been hoped that the craft would still reach the Moon and make what is euphemistically called a “hard landing” (that is, crash into it) around the time of the planned landing date of February 23rd, engineers having calculated that by then, even if the rete of propellant loss slowed over several days and ceased, the craft would have insufficient reserves to make a controlled landing. However, by mid-week it was clear even this would not be the case; the leak had put Peregrine One on a much more direct path towards the Moon’s orbit than had been intended such that on January 12th, an status update from the company noted:

Peregrine remains operational about 238,000 miles from Earth, which means we have reached lunar distance! Unfortunately, the Moon is not where the spacecraft is now, as our original trajectory had us reaching this point 15 days after launch, when the Moon would have been at the same place.

– Astrobotic statement, Friday, January 12th

However, the one “good” piece of news through the week was that as time progressed, the propellant leak deceased, and some steps to help stabilise the vehicle – and maintain its orientation to the Sun such that its solar arrays could continue to received energy and power the vehicle’s systems – could be taken. These in turn allowed a number of the experiments on the lander to be powered-up. While they are not operating in their intended modes (or location), it is hoped that they will still be able to gather data on the radiation environment in interplanetary space around the Earth and the Moon.

The most recent projections from Astrobotic (January 14th) suggest that as the Lander has in sufficient velocity to complete escape Earth’s gravity well, it will likely start to “fall back” to Earth in the coming weeks, and orbital mechanics being what they area, most probably slam into the upper atmosphere and burn-up.

Given Peregrine One’s involvement in the CLPS programme, NASA has been monitoring the Peregrine One situation closely, and on January 18th the agency and Astrobotic are due to convene a telecon in order to review Astrobotic’s efforts to recover the craft and what they have learned. In the meantime, agency officials have noted that the failure of Peregrine One to successfully achieve a lunar landing will not in any way impact CLPS.

Artemis 2 and 3 Slip

On January 9th, 2024, NASA announced America’s return to the Moon with crewed missions at the head of Project Artemis is to be further delayed.

In the announcement, made in part by NASA Administrator Bill Nelson, it was indicated that the upcoming Artemis 2 mission around the Moon and back, and intended to take place in November 2024, will now not take place before September 2025. Meanwhile, the first US crewed mission to the surface of the Moon will now occur no sooner than September 2026.

The reasons given for the delays relate most directly to Artemis 2. In particular, there are a number of new systems and capabilities in development as a part of the overall Artemis programme which are now far enough along that it makes sense to delay Artemis 2 to leverage them, as they offer increased safety at the pad and prior to launch – such as improved means for crew egress from the launch vehicle in an emergency, and faster propellant loading capabilities.

Another cause for the delay is on-going concerns about the performance of the ablative heat shield on the Orion Multi-Purpose Crew Vehicle (MCPV). Whiles the shield did its job and protected the unscrewed capsule of Artemis 1 during its passage back into the Earth’s atmosphere at the end of that mission in November 2022, it still showed signs that rather than charring in place, some of the material actually peeled away from the vehicle as it charred, which is not supposed to happen.

Finally, concerns have recently been raised about the electrical system managing the crew abort system rockets, designed to haul the Orion capsule and its crew clear of the SLS rocket if the latter suffers a serious failure during the initial ascent to orbit. As a result, further tests have been requested on that system.

I want to emphasize that safety is our number one priority. And as we prepare to send our friends and colleagues on this mission, we’re committed to launching as safely as possible. And we will launch, when we’re ready.

– Jim Free, NASA’s Associate Administrator

The announcement was, oddly, seen as a cause for vindication among some SpaceX fans – the private launch company has been cited as a potential reason for delaying the Artemis 3 programme, given they are still a long way from demonstrating they have the ability to supply NASA with an operational lunar landing vehicle and the means to get it to lunar orbit.

However, even the addition of a further 11 months to the Artemis schedule still leaves SpaceX with precious little time to achieve those goals in a manner which meets NASA’s safety requirements. As such, the concerns about SpaceX being able to meet current Artemis time faces, as highlighted (again) in 2023 by the US Government Accountability Office (which has an uncannily accurate eye for predicting programme slippages and their causes) still remain valid.

Continue reading “Space Sunday: lunar losses and delays; strings and rings” →

For 40 years, the European Space Agency (ESA) has been at the forefront of space innovation and exploration – although its work and contributions have oft been overshadowed by those of NASA and Russia -, and that drive to innovate is set to continue through the next decade and beyond.

To demonstrate this, on January 3rd, 2024, ESA issued a video showcasing upcoming projects and innovations which will help define the future of crewed and uncrewed voyages into orbit which are being driven from with Europe, either as direct ESA projects, ESA partnerships or ESA-supported private ventures. In particular, the 2:32 minute video (including end credits) showcases the following projects and launch vehicles:

• 0:26: Space RIDER:  (Reusable Integrated Demonstrator for Europe Return) – a small-scale reusable lifting body supported by an expendable service module and capable of delivering 600 kg of payload to low-Earth orbit on missions of up to 2 months at a time. Payloads are intended to be experiments and science instruments, which the vehicle returns to Earth at the end of a mission. Designed to be launched atop ESA’s Vega-C launch vehicle, Space Rider will land horizontally, gliding to a landing under a parafoil, and the vehicle’s qualification flight is expected to take place in 2025.

• 0:33: Prime Micro-launcher – a UK-led (by Orbex) private sector launcher designed to leverage the growing cubesat market, and deliver up to 150 kg of payloads to 500 km Sun-synchronous orbit (SSO), primarily from the UK’s SaxaVord Spaceport in the Shetland Isles, and potentially from Portugal’s Azores International Satellite Launch Programme (ISLP) facilities, currently being developed on the island of Santa Maria.
• 0:44: Skyrora XL – a UK-developed 3-stage vehicle designed to place up to 315 kg into a 500 SSO from the UK’s SaxaVord Spaceport. Skyrora will be powered by its own in-house developed engines, including the Skyforce-2 70 kN motor, which is the focus of the video, and which uses liquid kerosene created from waste plastic as its propellant.

• 1:06: Isar Spectrum – a German-led project to develop a two-stage launch vehicle designed to deliver up to 1 tonne to LEO orbits out of Europe’s Spaceport at the Guiana Space Centre, Kourou in French Guiana, and up to 500 kg to SSO from the Andøya Spaceport, Norway.
• 1:26: second launch of Miura-1 – a Spanish-developed sub-orbital, reusable rocket system for flying experiments of up to 200 kg to altitudes between 80 and 110 km. The initial flight of the vehicle occurred in October 2023, but was only a partial success – range safety concerns limited the flight to less than 50 km altitude and the vehicle sank after splashdown, potentially due to its lower than intended altitude resulting in velocity-induced damage on impact with the sea. Once operational, Minura-1 will be Europe’s first fully-reusable launch vehicle and help pave the way for the Miura-5 orbit-capable launcher.
• 1:32: RFA-1 – a German-led project to build and fly a three-stage multi-role launch vehicle capable of delivering up to 1.6 tonnes to LEO, 1.35 tonnes to polar orbit or 450 kg to geostationary transfer orbit (GTO). The first orbital flight attempt is due to take place from the UK’s SaxaVord Spaceport in the summer of 2024.
• 1:52: Smart Upper Stage for Innovative Exploration (SUSIE) – potentially Europe’s most ambitious launcher vehicle development programme. A25-tonne lifting body intended to be launched atop the Ariane 64 booster, SUSIE – which is being developed for ESA by ArianeSpace – will be able to deliver either payloads of up to 7 tonnes to orbit when operating autonomously, or crews of up to five astronauts to orbital space facilities. The vehicle is intended to form the upper stage of the launch vehicle, requiring no fairings to protect it during orbital ascent. Following atmospheric re-entry, the vehicle will make a tail-first propulsive descent and landing in a manner akin to the DC-XA demonstrator vehicle, flown in the mid-1990s.

• Propulsion systems featured in the video include:
  • 0:40: M10 liquid methane-liquid oxygen motor currently being developed for use on ESA’s future Vega-E booster by Italy’s Avio aerospace company.
  • 0:50: Parafin-liquid oxygen hybrid propulsion – an in-development rocket motor by Germany’s HyImpulse, and designed to power the first and second stages of the company’s proposed SL1 launcher, designed to lift up to 500 kg to low-Earth orbit (LEO).
  • 1:44: Prometheus – a reusable methane-fuelled rocket motor, currently in development on behalf of ESA and intended to power a reusable test vehicle called Themis, starting in 2025. Both Prometheus and Themis are intended to pave the way for the semi-usable Ariane Next, which will replace Ariane 6 in the 2030s.

 Athena: a Space Engine in the Palm of Your Hand

One European innovation not featured in ESA’s video is the Spanish-developed Athena propulsion system. A palm-sized unit specifically designed to manoeuvre small satellites and cubesats once they are in orbit, thus helping them to become more flexible in the range of uses to which they might be put. And it does so in a highly innovative manner – via an electrospray.

An electrospray is an apparatus which uses and electrical current to disperse a liquid through an emitter. The idea itself is not new; its underpinnings were theorised in the 1960s by Sir Geoffrey Ingram Taylor, after whom the most ideal form the liquid is forced into under the influence of the electrical current – the Taylor cone – is named.

Electrosprays are used in a number of fields of science, and they have spurred the use of electrical currents to direct the thrust of cold gas thrusters on satellites However, what makes Athena (the name standing for Adaptable, THruster based on Electrospray powered Nanotechnology, rather than being drawn from mythology, as is the case with main space-related projects) so unique is a combination of its tiny size coupled with the use of a non-toxic propellant that does not require complex tank storage and pressurisation.

The system comprises a set of seven electrostatically charged thrust emitters, each about two finger tips across and containing an array of 500 pinhole-sized thrust ports each. A conductive salt is passed through these emitters, the electoral charge accelerating the particles and directing them into a cone of unified thrust which can be turned on and off by applying / removing the electrical current. The result is a set of tiny thrusters with practically no moving parts and a propellant which can be stored in a simple, compact container. This means that the overall mass of Athena thrusters and their propellant source is much lower than “traditional” cold-thrust systems, but they are capable of exceptionally fine control.

The current versions of Athena can be used on satellites of up to 50 kg, and can produce a sustained thrust of up to 20 m/s, if required. They are ideal for use on 10-cm-on-a-side cubesats, with the team bhind them hoping to scale them up for use with small Continue reading “Space Sunday: ESA’s future of spaceflight; Vulcan readies to fly” →