Space Sunday: radiation, rings and pollution

Missions like Elon Musk’s hopes for Mars need good radiation protection for crews – and NASA is working to bring this about. Credit: SpaceX

I’ve written several times about the risk radiation poses to dee space missions; particularly Galactic Cosmic Rays (GCRs), the so-called “background radiation” left over from the big bang. As I’ve noted, while solar radiation – up to and including Solar Particle Events (SPEs or “solar storms”) can be reasonably well dealt with, on account of the particles being relatively low-energy – 13 centimetres (5 inches) of water or similar liquid – is pretty good protection against the primary radiation threat of SPEs, for example – GCRs are far harder to deal with.

However, there are materials which can block them. Again, I’ve written about Hydrogenated boron nitride nanotubes (BNNTs). These are something being developed by NASA’s Langley Flight Centre in Virginia; extremely flexible, they can be used in the construction of key elements of space vehicles – walls, floors, ceilings, for example – and can even be woven into a material used as a lining in space suits to protect astronauts.  Similarly, borated polyethylene – already used for radiation shielding in nuclear reactors aboard US naval vessels, medical vaults and linear accelerators, among other applications – offers a means to provide primary radiation protection within the structure of space vehicles.

However, these are only effective in stopping primary radiation damage – that is, damage cause by the direct impact of radiation on living cells. A far, far greater risk people in deep space will face is from so-called secondary radiation,  particularly in the case of GCRs.  simply put, when a GCR particle collides with another, it sends energetic neutrons, protons and other particles in all directions, which can collide with others. It’s like a bullet striking something and scattering shrapnel, potentially doing damage to a lot of cells if they strike a living body. The problem here is that the more material used to block the effects of primary radiation damage, the more the risk of secondary radiation damage is increased.

Materials such as BNNTS and borated polyethylene could be used for surface vehicles and equipment as well

This means that there is unlikely to be a single solution to the issue of radiation exposure on deep space missions such as to Mars. Which is why scientists aren’t looking for one. NASA, for example has been conducting research into technologies such as BNNTs and magnetic shielding for space vehicles for over a decade. The latter, if possible, would use a magnetic field around a space vehicle to protect the crew, much as Earth’s magnetic field protects us. The problem here is that such systems currently require huge amounts of electrical power and can add a significant amount of mass to a space vehicle.

Another avenue of research being investigated is the use of pharmaceuticals as possible radiation inhibitors. Drugs such as potassium iodide, diethylenetriamine pentaacietic acid (DTPA) and the dye known as “Prussian blue” have for decades been used to treat radiation sickness. The theory is now that they could be used as part of a preventative regime of preventative treatment for astronauts on deep space missions.

The whole subject of radiation protection has become a focus in light of NASA’s “new” directive to return humans to the Moon and also because of Elon Musk’s determination to send humans to Mars, possibly as early as the mid-2020s. Because of this, NASA has been highlighting its research into radiation exposure management of late, which also includes solar weather forecasting (to help warn crews in deep space about the risk of SPEs, etc.), and in looking at 20+ years of orbital operations aboard the shuttle ISS and Russia’s MIr space station. All of this is leaving some at NASA feeling very positive about efforts to send humans beyond Earth orbit, as Pat Troutman, the NASA Human Exploration Strategic Analysis Lead, stated in a NASA press statement on the matter:

Some people think that radiation will keep NASA from sending people to Mars, but that’s not the current situation. When we add the various mitigation techniques up, we are optimistic it will lead to a successful Mars mission with a healthy crew that will live a very long and productive life after they return to Earth.

Whether progress on all fronts will be sufficiently advanced to encompass something like Elon Musk’s aggressive approach to human missions to Mars remains to be seen. However, with the “new” directive for NASA to return humans to the Moon, there’s a good chance we’ll see some of the current initiatives in radiation protection bearing fruit in the next few years.

The Risk Posed by Tiangong 1

Tiangong 1 (“Heavenly Palace 1”), the first Chinese orbital facility has been creating some sensationalist headlines of late.  Launched in 2011, the facility saw two crews spend time aboard it, prior to it being run on an automated basis from 2013. On March 21st, 2016 the Chinese Manned Space Engineering Office announced that they had disabled the facility’s data service in preparation for shifting their focus to the (then) upcoming Tiangong 2 facility and in allowing Tiangong 1’s orbit to decay so it would burn-up re-entering the upper atmosphere.

Tiangong 1. Credit: CMSE

The time-frame from re-entry was predicted to be late 2017 / early 2018. However, around the time Tiangong 2 was launched the Chinese space agency admitted they’d lost attitude control of the laboratory, so they could no longer orient it as it orbits the Earth. As a result, the facility has been under scrutiny from Earth by individuals and groups monitoring the rate of its orbital decay.

One of these observers is astrophysicist Jonathan McDowell of Harvard university. In early October he released a statement which indicated that as a loss of attitude control, increased friction has resulted in a sharp decline in Tiangong 1’s altitude to the point where it had reached the point were atmospheric drag now could see the vehicle re-enter the Earth’s atmosphere in the next few months. He also noted – accurately – that some elements of the 8.5 tonne vehicle could survive re-entry and reach the surface of the Earth (something the Chinese have always noted).

Unfortunately, his report led to some sensationalist responses from portions of the media. For example, one UK media tabloid blasted: “Out-of-control space station to smash into Earth THIS MONTH…and it could hit ANYWHERE. … A MASSIVE space station is hurtling towards Earth!” (block capital their own, not mine); other newspapers also highlighted the upper-end of the risk posed by the vehicle’s re-entry.

Needless to say such reports wildly over-egg the situation. The reality is that Tiangong’s orbit carries it over vast swathes of ocean and large areas of sparsely populated land. As such, while there is a risk of parts of the station reaching the ground, the chances of them hitting a populated area are remote. In this, Tiangong reflects the US Skylab mission in 1979 and the Russian Salyut 7 / Cosmos 1686 combination of 1991. Both of these where much larger than Tiangong 1 (77 tonnes and 40 tonnes respectively), both made an uncontrolled re-entry, and in both cases, wreckage did not cause loss of life.

A Dwarf Planet with a Ring

Haumea is a dwarf planet located beyond Neptune’s orbit. Referred to as a trans-Neptunian object (TNO), this egg-shaped object was a source of its discovery in 2004/5. Originally the discovery was announced by Mike Brown, Chad Trujillo and David Rabinowitz.

However, José Luis Ortiz and Pablo Santos-Sanz of the Instituto de Astrofísica de Andalucía, Spain, filed a claim based on observations they made in 2003. Initially, this led Brown e al to concede the discovery to Ortiz and Santos-Sanz. However, it later transpired Ortiz and Santos-Sanz had accessed Caltech observing logs remotely, looking at when and where Brown was looking with his telescopes. While initially denying they’d done so, Ortiz and Santos-Sanz later admitted what they had done, while claiming they were only seeking confirmation of their findings. As a result, the discovery of Haumea has never officially been awarded to either Brown et al or Ortiz and Santos-Sanz.

I mention this because Ortiz and Santos-Sanz are now responsible for leading observations of Haumea which has resulted in the discovery that the dwarf planet has two small companion moons and a ring of material surrounding it, making it the first trans-Neptunian object found to have such a ring.

An artist’s impression of Haumea and its moons. Credit: NASA

On January 21st, 2017, Haumea passed in front of a distant star, in an event known as an occultation. This can allow information about the object passing in front of the star  – such as its size, shape, and density — which might otherwise be difficult to obtain. The January 2017 event was the first such an occultation observed with Haumea.

“Twelve telescopes from ten different European observatories converged on the phenomenon,” said Ortiz reported. “This deployment of technical means allowed us to reconstruct with a very high precision the shape and size of dwarf planet Haumea, and discover to our surprise that it is considerably bigger and less reflecting than was previously believed. It is also much less dense than previously thought, which answered questions that had been pending about the object.”

The observation reveals the egg-shaped Haumea measures 2,320 km along its largest axis, compared to previous estimates had put this at some 1,960 km, and has a rotation period of 3.9 hours – far less than any other body in the Solar System. Ortiz states that the data he and Santos-Sanz put together shows the newly discovered ring lies on the equatorial plane of the dwarf planet and has a 3:1 resonance with respect to the rotation of Haumea. That is, the ring rotates around Haumea three times slower than the dwarf planet rotates around its own axis.

There might be a number of possible explanations for the ring. It could be the remnants of a collision with another object, for example, or it could be dust and particles thrown off of Haumea as a result of its high rotational period. However, the most intriguing aspect of the discovery is that it opens the door for other small bodies to have rings – and if they do, they may also have other unexpected characteristics.

Virgin Boss Not to Fly “In Six Months”

Virgin Galactic founder Richard Branson most likely won’t be going to space in the next six months, despite his recent comments on the subject.

On October 12th, 2017, Virgin Galactic president Mike Moses indicated that while the company plans to have one of its SpaceShipTwo suborbital vehicles reach altitudes of more 80 km (50 mi) above Earth’s surface within the next three months, it’s unlikely that passengers — including Branson — will be on board a vehicle in less than half a year.

SpaceShipTwo VSS Unity, rolled-out on February 19th, 2016. Commercial tourist flights are due to commence in 2018

Branson made his comments on October 2nd at a the Nordic Business Forum in Helsinki. In responding to questions on his comments while at the International Symposium for Personal and Commercial Spaceflight (ISPCS) in New Mexico, Moses said, “Richard always poses a challenge. He likes to push very hard … But three months is about right. We hope to be in space by the end of this year. He’s a little bit further away [from a flight] than that.”

Virgin Galactic has been conducting glide tests with the VSS Unity for the last several months, and plan to commence powered flights, testing the vehicle’s rocket motor expected to begin in the very near future. “We’re going to do the powered program just like we did the glide program,” Moses said. “The first thing you want to do is kind of predict what you’re going to see, fly it, make sure you got what you thought so you know that your prediction for the step after that is right. We’ll take our time with it … We’re going to fly when we’re ready.”

Unity is currently the only SpaceShipTwo vehicle in operation, but Virgin Galactic is in the process of building two more of the craft, each of which will operate numerous times, flying up to six tourists or scientific experiments on sub-orbital flights. Around 700 tickets as US $250,000 each have been pre-sold  to customers, and Virgin Galactic has frozen sales of further tickets pending commercial flights commencing.

ESA Launches Advanced Air Pollution Monitoring Satellite

The European Space Agency (ESA) has launched the most advanced air-pollution-monitoring satellite ever built, with the mission of mapping the global distribution of dangerous air pollutants.

Sentinel-5P lifted-off from the Russian Plesetsk Cosmodrome on October 13th, 2017. It forms a part of the European Union’s Copernicus programme, the world’s largest Earth-observation mission, which  now consists of six satellites in orbit. Sentinel-5P  is the first to focus on measuring the chemistry of Earth’s atmosphere in unprecedented detail.

“Having Sentinel-5P in orbit will give us daily and global views at our atmosphere with a precision we never had before,” Josef Aschbacher, ESA’s director of Earth-observation programs, said in a statement.

An artist’s impression of the Sentinel-5P. Credit: ESA/ATG medialab

In particular,  Sentinel-5P carries an instrument called Tropomi, the TROPOspheric Monitoring Instrument. This is a spectrometer designed to measure a wide range of pollutants in the atmosphere, including nitrogen dioxide and sulphur dioxide, which come from the burning of fossil fuels, as well as carbon monoxide, formaldehyde.

Thanks to Tropomi’s high-resolution monitoring capabilities, scientists will be able to understand in detail how air pollution spreads in the atmosphere, see what the most important sources of air pollution are and identify accumulation hotspots. Tropomi will be especially important for monitoring of methane, a greenhouse gas that is 28 times more potent in warming the planet than the more known carbon dioxide.

Emitted from agricultural source, such as cow manure, as well as from oil and gas exploration, methane is of great concern to the climate research community. While emissions of carbon dioxide have been flattening out over the past few years, emissions of methane keep rising sharply, according to recent studies.

Sentinel-5P will help scientists to comprehensively understand the composition of the atmosphere, including the extent and impact of pollution on weather, climate, and the environment.

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