What will China’s space station mean for international cooperation? The problems of space debris. Small rocket launches redux. Mark Williamson reports from the 66th International Astronautical Congress, held in Jerusalem.
The in-orbit neighbourhood watch scheme
In many communities, when new neighbours move in it is customary to pop round and welcome them. When the China National Space Administration (CNSA) starts building its space station in low Earth orbit in 2018, will US astronauts pay a visit from the International Space Station?
It seems unlikely. The ISS and China Space Station (CSS) could coexist for a decade, but Nasa is a US government agency obliged to follow government policy, so Chinese astronauts are not welcome on the ISS. And that, in a nutshell, is why China has developed its own space station.
Once again, American fears about technology transfer have resulted in China developing its own equivalent technology. So where does this leave international cooperation in space?
If we take at face value what CNSA head Xu Dazhe told the 66th International Astronautical Congress (IAC) in Jerusalem this October, the future is bright. “China supports international cooperation in all areas of space and is fully open to whoever is interested”.
Zhou Jianping, chief designer of the China Manned Space Programme, added substance to the rhetoric by revealing that cooperation agreements with Esa and Roscosmos had already been signed and China was “in discussion” with the United Nations. The broad objectives of the CSS mission, Zhou explained, were to build a national space laboratory and encourage international and regional cooperation. More specifically, he announced that an expanded station could host modules from other nations, manned by foreign crews and supplied by their own spacecraft. If this transpires, it could make the CSS the new de facto international space station.
After launching its first astronaut, Yang Liwei, in October 2003, China followed the typical path of longer missions, larger crews and more complex technical demonstrations such as docking. This led to the launch in September 2011 of the Tiangong-1 space laboratory, which welcomed its first crew in June 2012. At the IAC, Zhou confirmed that Tiangong-2 will be launched in 2016 to continue China’s development of manned spaceflight techniques, including in-orbit propellant resupply and other preparations for the CSS.
The CSS itself will have three main modules: a core and two for experiments. Zhou’s team plans to launch the core in 2018 and complete the basic station in orbit by 2022. He explained that Experimental Module I and II would allow a crew of up to six to perform “science, applications and technical demonstrations” for at least 10 years, the station’s design lifetime. Moreover, the baseline station could be expanded to six modules, the additional three supplied and crewed by foreign nations, and joined in orbit by a free-flying space telescope that would be able to dock with the CSS for maintenance. Zhou gave precious little detail on the telescope – not even the fundamental dimension of its main mirror – but this will doubtless be released in due course by an appropriate CNSA official. Unless the money runs out and the free-flyer is cancelled.
This begs the question of how real the CSS programme itself is, but western observers should not be fooled by the parlous state of Chinese public relations. Once details of launch vehicles, launch sites and launch dates are announced at an international event such as IAC, we may be assured that they are officially planned, funded and almost certain to go ahead. China has so far not adopted the western habit of announcing PowerPoint stations and paper satellites that never see the light of day.
According to Zhou, the CSS core module will be launched by a Long March 5B, from the newly developed Wenchang Satellite Launch Centre on Hainan Island, to a 340-450km orbit at a 42-43° inclination. The ISS orbits at an average height of 400km and an inclination of 51.6°. The orbital altitude of both stations is dependent on friction with the Earth’s upper atmosphere, which varies with atmospheric density (itself affected by solar activity).
So, even though the stations will orbit in different planes, there will be times when their orbital heights become close, and two points where those orbits cross. The issue of collision in orbit is real, with a probability dependent on cross-sectional area. Thus two large space stations (the ISS is as big as a football pitch) are more likely to collide than two relatively small satellites (which has occurred).
However, it is extremely unlikely that the stations would be allowed to move close enough for their occupants to discern their shapes, let alone to collide.
Nasa flight rules for the ISS already stipulate what it refers to as a ‘pizza box’ and others might call a cordon sanitaire around the station. Its dimensions of 50km by 50km by 1.5km provide a safety zone for the ISS, in that any spacecraft or piece of orbital debris predicted to pass within that zone effectively triggers an alarm. Depending on the situation, flight controllers can then decide whether to move the station slightly to avoid the object or instruct the astronauts to shelter in a more protected part of the station or head for the ‘lifeboat’ return capsule.
So far so good, but you don’t have to see many space movies for the question of mutual rescue capability to spring to mind. The UN Rescue Agreement of 1968 requires that “States shall take all possible steps to rescue and assist astronauts in distress and promptly return them to the launching State”.
Although the ISS is funded until 2024, technical reviews have suggested that it could easily operate until 2028, ten years after the core of the CSS is planned for launch. So there could be a decade of co-existence, and at least potential mutual support.
Apart from the usual legal and policy agreements, the show-stopper is the incompatibility of docking mechanisms. Asked whether China would subscribe to the international docking standard being developed by ISS partners, Zhou seemed unsure. “It’s possible”, he said. “Some details need to be discussed”. Which is a way of saying ‘it’s above my pay-grade’.
While it seems illogical to have two space stations that can’t exchange crews even if lives are at stake, the fact remains that the barriers against international docking standards have been built in America, not in China, and will require a good deal of political will to resolve.
The first notable cross-border manned mission was the Apollo-Soyuz Test Project of 1975, when Russian and US astronauts performed a historic ‘handshake in space’. A special adapter allowed the Apollo capsule to dock with the Soyuz. Later political accords led to Russia’s critical involvement with the ISS – so critical that Soyuz became the only way for American astronauts to access the station. Cooperation was alive and well.
The ISS has been permanently occupied for 15 years, but none of the 220 people from 17 nations that have served on it have been Chinese. One could surmise that had the US agreed to cooperate with China, there would be no plans for a China Space Station today. At IAC, Nasa administrator Charles Bolden acknowledged the prospect of the USA being left out of future international space collaboration: “We will be on the outside, looking in,” he said.
If the docking standard fails to become universal, Bolden’s fear may become the literal fate of Nasa’s astronauts.
Private sector steps up in the space debris race
Space debris, whether from exploded satellites or dropped astronaut tools, has been a recognised hazard in low Earth orbit for many years. Even the International Space Station is manoeuvred several times a year to avoid potentially damaging collisions. But so far the world’s space agencies have failed to fund and field a debris removal demonstrator mission.
Frustrated by the lack of government initiatives, a Singapore-based private-sector company called AstroScale announced its own plans to clear up space debris at this year’s IAC in Jerusalem, Israel, even renting exhibition space to market its proposals.
According to marketing manager Yasunori Yamazaki, the concept involves “a mother spacecraft carrying one or more deorbiters equipped with a disc covered in a silicon adhesive compound” which allows the deorbiter to attach itself to the debris object. The spacecraft fires its thrusters and drags the debris down to allow atmospheric friction to burn up the conjoined objects.
The job of convincing space players – from government departments to commercial entities – that orbital debris was an issue of concern has been a decades-long process. October 1993 saw the establishment of the Inter-agency Space Debris Coordination Committee (IADC) by the space agencies of America, Europe, Japan and Russia, with the intention to “exchange information” on research activities, “facilitate opportunities” for cooperation, “review” progress and “identify debris mitigation options”.
This has led to a lot of studies. Indeed, the French space agency CNES has studied potential solutions since at least 2000. According to Christophe Bonnal, deputy technical director at CNES, the preferred solutions for what protagonists call ‘active debris removal’ (ADR) include robotic arms that grab the offending object, harpoons or hooks to snag the debris and ‘capture nets’.
Methods such as these are generally recommended for so-called ‘non-cooperative targets’, but others, such as probe-and-drogue docking mechanisms, can be ‘designed into’ more cooperative targets. Another concept involves unreeling a tethered mass from a satellite, which generates electrodynamic drag in the Earth’s magnetic field to increase the orbital decay rate. There are almost as many ideas as there are proposers, but so far no hardware.
In June 2014, Nasa adopted a policy to support development of ADR technology with Technology Readiness Levels (TRL) 1 to 4, which stops short of technology demonstration at TRL 5 or 6. As Nasa spokesman Joshua Buck put it: “At present, there is no viable technological or economically affordable approach that is sufficiently mature to justify technology demonstration”.
It is in this context that AstroScale decided, when it was founded in 2013, to make a leap of faith and industrialise the process in the commercial arena with private-sector funding.
AstroScale’s Yamazaki confirmed to E&T that the company, which has a manufacturing facility in Tokyo, has raised $7.7m for the first phase of its plans. This includes “the development of IDEA-1, our sub-millimetre-sized-debris tracking satellite,” he said.
The In-situ Debris Environmental Awareness satellite is “the first sweeping satellite [designed] to collect data on the size, mass and speed” of this small-scale debris in low Earth orbit which “cannot be tracked using existing technologies”, according to the company. Yamazaki also confirmed that IDEA-1 is “on track and will be launched in the second half of 2016” on a Russian launch vehicle.
The second phase is the construction and deployment of an actual debris removal mission towards the end of 2017. The spacecraft, called ADRAS-1 (for Active Debris Removal by AstroScale), will comprise “a mothership called the mother and a catcher satellite called the boy,” said Yamazaki.
As might be expected, ADRAS is a fairly small satellite (60×60×100cm with a mass of about 100kg) and will be able to capture and deorbit only relatively small spacecraft, but that is the purpose of a demonstrator. Design details are sparse, but the company has published images of a box-shaped mothercraft releasing a hexagonal ‘boy’ powered by solid propellant thrusters. This catcher satellite is equipped with a circular disc mounted on a ‘gimbal assembly’ to provide a degree of manoeuvrability for the adhesive-coated disc which, it is hoped, will attach itself to non-cooperative targets.
Pressed for details of this all-important coating, Yamazaki was unhelpful: “we will share more at the right time”, he said. Asked about the advantages of the adhesive over the types of capture mechanism used by other proposed systems, he said: “Among the various advantages... it is a simple solution, which has minimal mechanical movement and thus a lower probability of mechanical failure.”
As for the disadvantages, such as trying to grab a thermal blanket that could tear, he admitted that “not all surfaces may be compatible with our adhesive”. However, he added, “we have a solution for this challenge... which we will share at the right time”.
Although it’s true to say that no-one has presented actual flight hardware for a debris removal mission, AstroScale does not have the field entirely to itself and will ultimately have to compete if ADR enters the commercial marketplace. For example, the German Aerospace Centre, DLR, has announced plans to launch its robot-arm-equipped Deutsche Orbital Servicing Mission (DEOS), which includes a debris removal demonstration, in 2018.
Less certain is a proposal from Switzerland’s École Polytechnique Fédérale de Lausanne with the optimistic name of Clean Space One, which is designed to catch a cubesat with a conical net and remove it from orbit.
Return of the Rockoon?
Back in the 1950s, space scientist James Van Allen and co-workers developed a method for launching a small rocket from a balloon, which effectively replaced the first stage of classical rocket flight. They called it a ‘rockoon’.
Now, zero2infinity, a small company based in Barcelona, Spain, is hoping to transform the launch industry for small payloads to low Earth orbit by updating this retro-technology with its Bloostar system. At €4m to launch a 150kg payload, it could be the affordable launch solution that aspiring ‘New Space’ companies have been calling for.
Speaking at the International Astronautical Congress (IAC) in Jerusalem this October, CEO José Mariano Lopez Urdiales reassured his audience that Bloostar was “not reinventing the wheel, just making it turn the right way”. The rocket itself is a short, squat vehicle comprising three stages stacked more like a Russian doll than a conventional launch vehicle. The first stage has six methane/oxygen engines developing 15kN of thrust apiece, while the second and third stages are powered by smaller 2kN engines. Asked about the status of engine development, Urdiales said, “We have already built up our first liquid rocket engine, flown our liquid tank in the stratosphere and made multiple equipment validations in real conditions above 30km”.
The concept involves carrying the rocket to an altitude of about 20km, which means that its engines can be optimised for near-vacuum operations and avoid the issues of maximum dynamic pressure (Max-Q). The rockoon assembly would be launched from the sea, which is cheaper than renting land-?based facilities, said Urdiales; and because the balloon platform is lighter once the rocket is released, it “goes higher and acts as a telemetry relay platform”.
Technical journalists at the IAC press conference quizzed the team on a number of issues and they denied suggestions that the 90-minute balloon ascent to 20km would allow too much of the cryogenic propellant to ‘boil off’ prior to engine ignition. Urdiales claimed that “boil-off is relatively small”, not even enough to warrant carrying propellant to “top-off the tanks”. And as for winds aloft, he said this is not seen as a problem. “Gimballing and throttling [the engines] can correct for winds.”
Clearly, the Bloostar concept is not going to replace conventional rockets that deliver multi-tonne satellite payloads to geostationary orbit, but it could be the answer for the burgeoning number of cubesat designers looking for affordable rides to lower altitude orbits; a single Bloostar launch could carry several such payloads under its 2.3m3 fairing.
Four test flights are planned from the Canary Islands, with future progress dependent on funding.