Category: Other Worlds and Tech

For the last few years, and as news arises, I’ve been covering the ambitious plans developed by a team at the Applied Physics Laboratory (APL) of Johns Hopkins University (JHU) to send a flying rover vehicle to Saturn’s largest moon, Titan.

The mission, using a octocopter called Dragonfly has been in development for several years, being formally greenlit for full-scale development by NASA earlier in 2024 (see: Space Sunday: flying on Titan; bringing home samples from Mars), after initially selecting it for evaluation and conceptual development as a part of the space agency’s Frontiers programme in 2019.

The idea of sending a flying – or at least floating, as proposals have also included the potential use of balloons to explore Titan from within it dense atmosphere – has been around for some time. In fact,  Ralph Lorenz, of JHU/APL, one of the proposers of the mission, first considered using rotary craft on Titan back in 2000. His idea then was to use a battery-powered rotor craft equipped with a radioisotope power source.

That vehicle would spend the daylight hours on Titan (equivalent to 8 terrestrial days) in flight or carrying out surface science. during the hours of darkness (again, lasting the equivalent of 8 terrestrial days), the vehicle would sit on the ground and use the radioisotope to both keep itself warm and recharge the batteries.

It is to this idea that Lorenz returned whilst having dinner with Jason W. Barnes of University of Idaho in 2017, with the two of them agreeing to work on a baseline proposal for a large rotorcraft capable of  flying on Titan. Together, they formed a nucleus of a team of scientists largely from APL’s staff of space scientists, including Elizabeth “Zibi” Turtle, who would be the mission’s principal investigator, as well as expertise from both NASA and other universities and space science institutes such as Malin Space Science Systems (MSSS), another long-time NASA partner.

Their initial proposal was published in 2018, and pretty much laid out the entire concept. Put before NASA for consideration, the proposal went through a series of changes prior to acceptance as a Frontiers mission. Initially targeting a 2027 launch, the mission was hit (like most things) by the COVID 19 pandemic, with all parties agreeing to push back the launch until July 2028.

These delays actually pushed the Dragonfly mission outside of the parameters of the Frontiers guidelines – missions under its auspices are supposed to be developed and flown for no more that US $1 billion (including all launch operator costs); currently, Dragonfly is expected to hit a total cost of around $3.35 billion throughout its lifetime. In all, the primary mission is expected to last some 10 years, 3.3 years of which will by at Titan.

But why go so far and at such cost in the first place? Well, as I noted back in April:

Titan is a unique target for extended study for a number of reasons. Most notably, and as confirmed by ESA’s Huygens lander and NASA’s Cassini mission, it has an abundant, complex, and diverse carbon-rich chemistry, while its surface includes liquid hydrocarbon lakes and “seas”, together with (admittedly transient) liquid water and water ice, and likely has an interior liquid water ocean. All of this means it is an ideal focus for astrobiology and origin of life studies – the lakes of water / hydrocarbons potentially forming a prebiotic primordial soup similar to that which may have helped kick-start life here on Earth.

As both the Huygens lander and Cassini probe showed, Titan is similar to the very early Earth and can provide clues to how life may have arisen on Earth; it is also an aerodynamically benign world. Its dense atmosphere (around 1.45 times that of Earth’s) is ideally suited to the use of rotary vehicles – considered superior to balloons, dirigibles and aircraft because their ability to hover in place whilst carrying out ground observations and their VTOL (vertical take-off and landing) capabilities mean that can easily set down for surface science activities / at the onset of night. Further, Titan has low gravity (around 13.8% that of Earth) and little wind, making automated flight a lot easier.

Most crucially of all, flight allows the vehicle to move with relative ease between locations of interest for study, even if they are geographically widespread, separated by distances (and potential obstacles) a surface rover might find insurmountable.

Of course, we’re all now familiar with the idea of helicopter drones flying on other worlds, courtesy of NASA’s plucky little Ingenuity on Mars. However, The Dragonfly vehicle is something else all together. For a start, it is the size of a small car, and is expected to have an all-up mass of  around 450kg. A good portion of that will be taken up by its Multi-Mission Radioisotope Thermoelectric Generator (MMRTG), its large lithium-ion battery system and its four electric motors, each driving two pairs of 1.4 metre diameter contra-rotating rotor blades.  When flying, the vehicle will be able to reach speeds of up to 36 km/h, with a maximum airborne time of 30 minutes at that speed.

Obviously, given the distances between Earth and Saturn / Titan render two-way real-time communications impossible without considerable lag, the vehicle will be equipped with a fully autonomous flight and navigation system capable of flying it along a selected flight path, making its own adjustments to account for local conditions whilst in flight, and with sensors capable of recording potential points of scientific interest along or to either side of its flight path, so the information can be relayed to Earth and factored into planning for future excursions. Flights over new terrain will likely be of an “out and back” scouting nature, the craft returning to its point of origin, allowing controllers on Earth to plan follow-up flights to locations where they might wish to set down and carry out ground-based science studies.

In terms of the latter, the vehicle will carry a number of science instruments, including two coring drills and hoses mounted within is landing skids, allowing it to gather tailings from the moon’s regolith and surface for on-board analysis by the vehicle’s on-board laboratory.

Most recently, as well a working on the full-scale development of the vehicle, APL has also been carrying out further tests with a half-scale flight-capable model, which has been used for the last year to help test and refine flight systems and avionics.  This has seen the vehicle put through its paces at near-to-ground flight tests and at reasonable altitudes (but not as high as the four kilometres maximum ceiling the full-size version is expected to operate at during deployment!

In particular, this works builds on work carried out inside a special wind tunnel at NASA’s Langley Research Centre during 2023, which was used to simulate the aerodynamic loads that would likely be placed on the vehicle’s rotors and motors during a wide range of flight operations – ascending, descending, hovering – allowing engineers to determine things like the amount of rotor pitch required during different types of flight operations, providing data which can be fed into the final design requirements for the actual vehicle.

Much of this testing has been around flight hardware redundancy – APL plan to have the vehicle capable of sustained flight even if one set of rotors fails  or even a motor supplying power to two sets of rotors dies. These tested have also allowed for direct assessment of the vehicle’s handling and determining where the centre of mass / centre of gravity should be placed (remembering that the drum-like thing at the back of the vehicle is a nuclear generator and all its associated shielding) to ensure good flight handling across a range of dynamic flight situations.

Also, on November 25th, 2024, NASA confirmed that  SpaceX Falcon Heavy launch vehicle will be used to send Dragonfly on its way to Saturn. This caused some mis-reporting (notably among SpaceX fans) that the mission is somewhat a NASA / SpaceX venture, or has only been made possible by SpaceX, with some SpaceX-biased commentators going to so far as to call the decision “unexpected”. However, Falcon Heavy is the only launch vehicle currently certified for launching NASA high-value missions – particularly those carrying an MMRTG; United Launch Alliance (ULA) having retired both of its certified launch vehicles – Atlas and Delta –  and have yet to achieve the required NASA certification with their Vulcan-Centaur (as is the case with Blue Origin’s New Glenn). As such, and with the prohibitive cost of using NASA’s own SLS rocket, Falcon Heavy has been the only real contender for the job.

At a cost of US $256.6 million, the contract to launch Dragonfly is significantly more than the $178 million NASA paid for the launch of the equally complex Europa Clipper, and the $117 million for the launch of the Psyche mission (although admittedly, that was agreed in 2020), both of which utilised Falcon Heavy. What was new with the announcement was the selected launch window and flight trajectory. The mission is slated to launch some time between July 5th and July 25th, 2028 (inclusive), in a window that will require the vehicle to make a fly-by of Earth in order to acquire the velocity required to reach Saturn in 2034. In this, the flight does differ from the originally planned 2027, which would likely have included a flyby of Jupiter, rather than Earth; however, for the 2028 launch, Jupiter will not be in a position to provide a gravity assist, hence the use of Earth, marking the mission as the first dedicated mission to the outer solar system to not use Jupiter in this way.

Progress MS-29 Update

In my previous Space Sunday update, I covered the detection of a “toxic smells” within the Russian section of the International Space Station (ISS), requiring the atmosphere throughout the station to be scrubbed. The first outlet to cover the news – as it was breaking – was the  highly-reliable Russian Space Web, operated by respected space journalist and author, Anatoly Zak, and it was through that source I first read of the situation.

During the past week other outlets have taken up the story, but it is Anatoly who continues to lead with updates. While there was no immediate danger to any of the ISS crew, the hatches to the Progress vehicle were sealed and the atmosphere throughout the station scrubbed – on the international side of the station, the use of the Trace Contaminant Control Sub-assembly (TCCS) system was imitated after NASA astronaut Don Petit reported a “spray paint-like” smell in the Node 3 module of he station.

In Anatoly’s most recent update in the story, he confirmed that after recycling the atmosphere in the Progress vehicle, the hatches had been reopened between it and the Poisk module against which its docked and off-loading of supplies had commenced. Anatoly also noted the the current working hypothesis from Roscosmos is that the smell did not originate from within the Progress MS-29 vehicle.

Instead, the Russian space agency believe the smell came from within the docking mechanism on the Poisk module. The Russian docking mechanisms include fuel lines for both off-loading hypergolic propellant supplies from a newly-arrived resupply vehicle carrying them, and to transfer propellants to Soyuz vehicles to “top off” the tanks of their thrusters prior to making a return to Earth.

Because of this, and while docking operations involving Progress and Soyuz are automated, after any departure from the Russian section of the ISS, ground control should perform a purging of the inner chamber of a docking mechanism to ensure any leak of hypergolic propellant that have been in the feed lines at the time which might otherwise be contained within the chamber is removed. This appears not to have been done following the departure of the last vehicle to use this particular docking port, Progress MS-27, potentially leaving traces of highly toxic propellant caught between the newly-arrived MS-29 and the interior of the Poisk module, releasing them into the latter when the inner hatch was opened.

China’s space programme is perhaps the most aggressive in the world in terms of ambitions and speed of development. In the last two decades, the country has been embarked on one of the most forward-thinking human spaceflight programmes, quickly moving from two small orbital laboratories to a fully-fledged space station whilst setting its eyes firmly on the Moon. At the same time, it has shown itself to be the equal of both the United States and Europe in the field of robotic exploration of the Moon and Mars, whilst also seeking to match the United States in pioneering the use of uncrewed reusable vehicles.

Most notably in this latter regard has been the Shenlong orbital vehicle, which I first wrote about in 2023, and which completed its second 200+ day orbital mission September 2024. Whilst not as long in duration as those of America’s X-37B, which it matches in terms of size and secrecy, Shenlong could be broadly as capable. And it will soon be joined by a second Chinese automated spaceplane, one with a similar purpose to America’s upcoming Dream Chaser vehicle.

Called Haolong, this new vehicle is one of two finalists in an 18-month selection process initiated by the China Manned Space Engineering Office (CMSEO) to determine the next generation of resupply vehicles intended to support the country’s Tiangong space station. In May 2023, CMSEO sought proposals from government agencies and China’s growing private sector space industry for vehicles capable of delivering a minimum of 1.8 tonnes of materiel to the Tiangong space station at a cost of no more than US$172 million per tonne. From the 10, in September 2023 four were selected to move forward to a more intensive design and review phase lasting just over a year, with the potential for two of them to be picked for full vehicle development.

On October 29th, 2024, the winning proposals were announced, with the Haolong spaceplane immediately gaining the the most interest due to its nature and the fact it was heavily promoted at China’s annual Zhuhai Air Show, complete with videos showing it in operation and images showing the full-size proof-of-concept development model.

Haolong’s development is being undertaken by an unlikely source: the Chengdu Aircraft Design and Research Institute, operated by the state-owned Aviation Industry Corporation of China (AVIC). Neither Chengdu, which is largely responsible for military aircraft development, nor AVIC has been involved in space vehicle development until now. At a length of 10 metres and a span of 8 metres with its wings deployed, Haolong is very slightly longer and wider than America’s Dream Chaser (9 metres long with a 7-metre span). Like the American vehicle, Haolong is designed to be vertically launched via a rocket, its wings folded to fit within a payload fairing, ready to be deployed once it reaches orbit and separates from its carrier rocket.

Exactly what to overall payload capability for the vehicle might be is unclear; Chengdu have only confirmed it will be able to lift the required 1.8 tonnes to orbit. This is less than one-third the total load carried by the current automated (and completely expendable) Tianzhou resupply vehicle, which can carry up to 6 tonnes to orbit – a capacity Dream Chaser can match.

However, given Haolong’s size and pressurised cargo space – coupled with the fact that the CMSEO requirement included a provision the new resupply vehicles can dispose of / return to Earth up to 2 tonnes of waste / materiel – it would seem likely Haolong’s all-up payload capability is liable to be above the 1.8 tonne minimum should it ever be required to fly heavier loads. 

But even if this isn’t the case, Haolong still scores over Tianzhou, as it’s all-up mass is expected to be less than half that of the older vehicle, potentially enabling it to be launched by a selection of Chinese rockets rather than being restricted to the expensive Long March 7. It could, for example even come to be launched atop the semi-reusable Long March 2F (if this enters production), or the rumoured semi-reusable variants of either the Long March 8 or long March 12B, as well as the expendable versions of Long March 2.

Details of the second vehicle to be selected, the Qingzhou cargo spacecraft, are somewhat scant, including its overall reusability. However, it will be launched via the upcoming Lijian-2 rocket being developed by CAS Space. The latter is commercial off-shoot of the Chinese Academy of Sciences, so technically its use as the launch vehicle for a space station resupply craft marks the first time a commercial entity will participate directly in China’s national space programme.

Long March 9: China’s Answer to Starship / Super Heavy?

Also present at the Zhuhai Air Show were further models of China’s in-development super heavy launch vehicle, the Long March 9 (Changzheng 9 or CZ-9) booster, together with the first models of China’s answer to (or near-clone of, if you prefer) the SpaceX Starship vehicle.

First announced in 2011, Long March 9 has been through a number of iterations and design overhauls. As first envisaged, the vehicle would comprise a 10-metre diameter core stage supported by up to four 5-metre diameter liquid-fuelled boosters (essentially Long March 10 first stages), giving it the ability to lift an upper stage with a payload capacity up to 140 tonnes to low-Earth orbit (LEO). With minor variations, this remained pretty much the baseline design until around 2019.

A substantial redesign then appeared in 2021. This saw the elimination of the strap-on boosters and the first stage diameter increased 10.6 metres. To compensate for the loss of the strap-on boosters, the first stage of the vehicle had its original four engines replaced by 16 kerosene / liquid oxygen (LOX) motors, each one generating some 300 tonnes of thrust at sea level, allowing it to haul up to 160 tonnes of payload up to LEO.

Then in 2022, the decision was made to make the first stage of the rocket reusable. The LOX / kerosene motors were swapped for 26 of the more efficient YF-135 methane / LOX motors, the exact number compensating for the reduction in overall thrust. However, as 26 main engines required an 11-metre diameter first stage to fit them and their additional propellants, the design was then scaled back to keep the 10.6 metre diameter, and the number of motors reduced to 24 first stage engines. A further change at this point small the vehicle’s optional third stage increased in diameter from 7.5 metres to 10.6 metre as well, unifying all three stages.

This design carried over to 2023, where it was displayed at that year’s Zhuhai Air Show. However, the engine configuration had again changed for the first stage, with 30 of the more compact YF-215 motors now being used. In this configuration, Long March 9 was touted as being capable of delivering somewhere over 100 tonnes but less than 160 tonnes of payload to LEO in a two-stage variant and between 35 and 50 tonnes of payload to the Moon in a 3-stage version.

Also revealed at the 2023 Air Show were drawings of CALT’s take on the SpaceX Starship. At the time, the idea was defined as a “possible” iteration of the Long March 9 design, and unlikely to be ready for use – if pursued – until the 2040s. However, at the 2024 Air Show held in early November, it was clear CALT is invested in making a fully reusable Long March 9 launch system; on display were a set of models, one showing the Long March reusable first stage with the “starship” vehicle sitting on top of it, with two smaller models showing the “starship” vehicle on the lunar surface and a Long March 9 first stage resting on its “catch gantry” at the end of a flight.

According to CALT representatives at the show, work has now commenced on fabricating the first Long March 9 test vehicle, indicating the core design for the rocket’s first stage is now largely finalised, and the focus will initially be on developing this and the expendable second and third stages, with the first launch of an integrated rocket targeted for 2030. However, the representatives also indicated that the development of the reusable upper stage vehicle is seen as more integral to China’s lunar aspirations, and that they are looking to introduce it possibly as soon as the mid-to-late 2030s.

While making no secret of the fact they are directly emulating SpaceX with their design, CALT noted their vehicle would be more flexible in its application. As well as being able to deliver 100 tonnes to LEO, it was suggested it will be able to deliver smaller payloads to other orbits – such as MEO, GEO, GTO and SSO, and deliver as much as 50 tonnes to TLI, all apparently without the need for on-orbit refuelling (which Starship currently requires in all these cases).

If the lack of refuelling is accurate, then it suggests CALT are considering different internal layouts for their “starship”, such as utilising payload space for additional propellant tanks to enable their vehicle a wider range of operational capabilities; however, until CALT are more forthcoming on exactly how they envisage vehicle operations to work, this is purely speculative.

Reaction Engines in Administration

Reaching orbit using rockets – even reusable ones – is a costly business.  Rockets require complex, high-performance (and costly) motors, have to carry a lot of propellants to feed them, and require a lot of specialised infrastructure to operate them. Because of this, one of the holy grails of access to space has been the SSTO – single stage to orbit – vehicle; a craft capable of taking off in a manner akin to that of an aircraft, reaching orbit and then returning to Earth and again landing like a conventional aircraft.

In the 1980s, Britain in particular worked on an SSTO concept called HOTOL (Horizontal Take-Off and Landing), an uncrewed vehicle roughly the size of an MD-80 airliner. It would have utilised a unique air-breathing engine underdevelopment by Rolls Royce (the RB-545) to carry up to 8 tonnes of payload to orbit , using the air around it as an oxidiser for its rocket motors, mixing it with on-board supplies of liquid hydrogen until the atmosphere became too rarefied for this, and the engines would switch to using on-board LOX with the liquid hydrogen. But despite initial government backing, interest from the European Space Agency and the United States, HOTOL floundered and ultimately died in 1989, and Rolls Royce shelved development of the RB-545.

Undeterred by this, one of HOTOL’s originators, Alan Bond, co-founded Reaction Engines Ltd (REL), a company dedicated to developing both a new air-breathing engine to supersede the RB545 and a new SSTO spaceplane to use it. The motor, called SABRE (Synergetic Air Breathing Rocket Engine) and the vehicle, called Skylon, have been in development ever since, with SABRE in particular seeing much progress and both national and international interest. In fact, as recently as 2019, things looked remarkably rosy for SABRE and Reaction Engines.

This is why the announcement that REL had entered administration, with all staff laid-off, is deeply saddening. An eight-week process has commenced to either restructure or sell the company; if neither proves viable, it will enter liquidation and all assets sold-off. No formal reason for the company’s failure to continue to gain funding has been given; however, it has been suggested that the fact SABRE and Skylon would only be able to operate from specially reinforced runways, rather than any suitably-equipped airport facility, may have been a contributing factor.

NASA and Roscosmos at Loggerheads over ISS Leak

For the last five years the International Space Station (ISS) has been suffering from an atmospheric leak within one of its oldest modules, the Russian Zvezda Service Module. Launched in 2000 as the third major element of the space station, Zvezda is actually approaching its 40th birthday, the core frame and structure having been completed in 1985 when Russia was still engaged in its Mir space station programme.

As such, the unit is well beyond its operational warranty period, and since 2019, the short airlock tunnel connecting the Zvezda’s primary working space with the aft docking port has been suffering an increasing number of microscopic cracks that have allowed the station’s atmosphere to constantly leak out. Whilst the overall volume of atmosphere lost is small, by April 2024 it had reached a point where attempts to patch some of the cracks were made. While this did reduce the amount of air being lost for a short time, the volume has once again be rising of late.

Whilst the leaks are still far short of being any risk to the station’s crew, NASA and Roscosmos cannot reach an agreement on either their root cause or their potential to become a significant hazard. Roscosmos remains of the opinion that the cracks are purely down to thermal contraction as the module expands and contracts as it passes in and out of the Sun’s light and heat, and therefore no different to the thermal wear on all other parts of the station.

However, while agreeing agreeing thermal expansion and contraction has a role to play in the leaks, NASA does not agree that it is the only cause. Instead, they see the continued use of the aft docking port – primarily used to receive Progress resupply vehicles – as putting additional stress on the tunnel’s walls, and this, couple with the aging of the module in general and the thermal expansion / contraction is causing the cracks. What’s more, NASA is concerned that if use of the after docking port continues, it is elevating the risk of a high-rick failure within the tunnel which could seriously compromise station operations.

Given this, NASA would like to see Roscosmos discontinue the use of the docking port – which Roscosmos argues is not necessary. While both agree the issue is unlikely to result in a complete and catastrophic failure within the tunnel culminating in a lost of the station as a whole; NASA engineers and mission controllers are concerned that any failure within the tunnel could impact operations throughout the station. As such, they have ordered the hatch between the Russian elements of the ISS and the US / international modules to be kept closed other than during crew passage between the two sections of the station.