A new orbital moon station could take us to Mars and beyond. Here’s how

An artist's conception of the Phoenix Mars Lander on the Red Planet. Image: NASA/Getty.

The dream of a human habitat in orbit about the moon came a step closer on 27 September, when NASA and the Russian space agency (Roscosmos) signed up to a common vision for future human exploration. The project, a follow-up to the International Space Station (ISS), involves a facility placed in orbit somewhere between the Earth and the moon – a region known as cis-lunar space. Seen as a stepping-stone on the way to deeper space exploration, it has been dubbed the Deep Space Gateway, DSG.

NASA’s new heavy-lift rocket, the Space Launch System, which is still in development, will enable the construction of DSG. It will be supplemented by Russia’s less-powerful Proton-M and Angara rockets. However, it is misleading to portray this as a purely Russia-US partnership, because the three other ISS partners (the European, Japanese and Canadian space agencies) are highly likely to be involved too.

Since Apollo 17 came back from the moon in 1972, no human has ventured further from home than “low-Earth orbit”, an altitude of only 400km in the case of the ISS.

The International Space Station passing over part of the western Mediterranean in 2009. Image: NASA.

The ISS began construction in 1998 and has been continuously occupied by (usually) six crew since November, 2000. Previously planned to last until 2020, the project has been extended until 2024 and could be eked out longer. However it is ageing – and many would argue that it should have already been replaced. It has cost somewhere in the region of $150bn. That isn’t cheap, but, to put it into context, it works out as about the same as what humanity has frittered away on buying lipstick over the same 20-year period.

We can expect a comparable or larger price tag for the DSG, which is due to begin to be assembled in the mid-2020s, assuming that NASA can get its heavy-lift Space Launch System ready in time despite a precarious funding situation.

Orbits

The DSG derives its name because its position beyond the deepest part of Earth’s gravity well, the strongest part of the Earth’s gravity field, which means you need less energy to launch a mission from there. That makes it a great staging post for departure of human expeditions to the lunar surface and more distant destinations such as Mars. It could also act as a receiving facility for initial examination (and quarantine, for planetary protection purposes) of samples brought back from Mars or other bodies.

A NASA Orion craft brings a crew to the Deep Space Gateway in lunar orbit (artist’s impression). Image: NASA.

Unlike the ISS, the DSG would not be continuously inhabited. Current plans call for one annual 42-day visit by a four-member crew, at first. When unoccupied, instruments on the DSG could continue to collect useful scientific data, especially when close to the moon. It won’t be placed into a low lunar orbit, but into special points in space such as where the gravitational attraction between the Earth and moon are balanced. This allows it to follow a “near rectilinear halo orbit” (see video below). From the moon’s point of view, the DSG would repeatedly sweep low over one pole, offering great opportunities for scientific measurements.

The ‘Near Rectilinear Halo Orbit’ and other animations.

At other times the DSG may sit further from the moon, in a halo orbit about a position on the moon-Earth line known as the L₂ Lagrange point. The balance of gravitational forces here makes it possible to “park” a spacecraft to make observations.

However, these orbits are only quasi-stable, so some adjustments would be necessary to maintain the DSG in these configurations without floating away elsewhere. The Canadian Space Agency has suggested the use of a solar sail to do most of the work, rather than using thruster fuel. I think that is a great idea, because solar sails, which get a push from radiation pressure, have not yet been trialled adequately to test their potential – so this is an opportunity to assess how to best work them. Apart from their use in manoeuvring around the solar system, solar sails may one day propel probes to the nearest stars.


The competition

The DSG is all still a very long way from reality. However it is a logical next step after the ISS – and any long-term multinational cooperative enterprise in space has to be a good thing, given the bickering between nations going on down here on Earth. It may not lead us very quickly to Mars though – government-funded projects are often cash-strapped, meaning the plans could lag behind private enterprise efforts such as Elon Musk and his super-heavy-lift Interplanetary Transport System, or BFR.

This is only Musk’s first step. Speaking at the International Astronautical Congress in Adelaide, he revealed his own ambitious plans for a lunar base followed by rockets to Mars by 2022.

The ConversationWhichever way it comes about, it would surely be inspiring to see astronauts travelling beyond low Earth orbit again. A refurbishable platform such as the DSG somewhere near the moon would offer many ways to study both the moon (personally I’d like to mount an X-ray spectrometer on the DSG to map the distribution of the chemical elements across the lunar surface) and the interaction between Earth and the sun.

David Rothery is professor of planetary geosciences at The Open University.

This article was originally published on The Conversation. Read the original article.

 
 
 
 

To beat rising temperatures, Vienna launches a network of 'Cool Streets'

A Vienna resident cools off at one of the city's new Cool Streets installations. (Courtesy Christian Fürthner/Mobilitätsagentur Wien)

Over the past several months, Austria has recorded its highest unemployment rate since World War II, thanks to the economic aftermath of the Covid-19 pandemic. With no job or a suddenly smaller income – not to mention the continued threat of the virus – many Viennese will opt for a staycation this summer.  

At the same time, last year, Austria’s capital experienced 39 days with temperatures of over 30°C (86°F), one of its hottest summers in history according to the Central Institute for Meteorology and Geodynamics.

Climate experts expect a similarly sizzling 2020 season, and city officials are now doubling down on efforts to combat the heat by launching a “Cool Streets” initiative as well as a new, state-of-the-art cooling park.

“As the city councilwoman in charge of climate, it is my job to ensure local cooling,” Vienna’s deputy mayor Birgit Hebein proclaimed at the opening of one of 22 new “Cool Streets” on 22 June.

“In Austria, there are already more heat deaths than traffic fatalities,” she added.

Hebein was referring to the 766 people the Austrian Agency for Health and Food Security included in its 2018 heat-associated mortality statistics. The number was up by 31% compared to 2017, and in contrast to the 409 people who died in traffic collisions the same year.

The project includes 18 temporary Cool Streets located across the city, plus four roads that will be redesigned permanently and designated as “Cool Streets Plus”.

“The Plus version includes the planting of trees. Brighter surfaces, which reflect less heat, replace asphalt in addition to the installation of shadow or water elements,” said Kathrin Ivancsits, spokeswoman for the city-owned bureau Mobilitätsagentur, which is coordinating the project.


Vienna's seasonal Cool Streets provide shady places to rest and are closed to cars. (Petra Loho for CityMetric)

In addition to mobile shade dispensers and seating possibilities amid more greenery provided by potted plants, each street features a steel column offering drinking water and spray cooling. The temporary Cool Streets will also remain car-free until 20 September.

A sensor in the granite base releases drinking water and pushes it through 34 nozzles whenever the outside temperature reaches 25°C (77°F) . As soon as the ambient temperature drops to 23°C (73°F), the sensor, which operates from 10 a.m. to 8 p.m., turns off the water supply.

The sensors were included in part to allay concerns about legionella, a pathogenic bacteria that can reproduce in water.  

“When the spray stops, the system drains, and therefore no microbial contamination can develop,” said Dr. Hans-Peter Hutter, deputy head of the Department of Environmental Health at the Center for Public Health at Medical University Vienna, in a televised interview.

Hutter also assured the public that there is no increased risk of a Covid-19 infection from the spray as long as people adhere to the one-meter social distance requirement.


But Samer Bagaeen of the University of Kent's School of Architecture and Planning notes that air cooling systems, like the ones used in Germany at abattoirs, have been found recently to be a risk factor for Covid-19 outbreaks.

“The same could be said for spay devices,” he warned.

Vienna’s district councils selected the 22 Cool Street locations with the help of the city’s Urban Heat Vulnerability Index. The map shows where most people suffer from heat by evaluating temperature data, green and water-related infrastructure, and demographic data.

“Urban heat islands can occur when cities replace the natural land cover with dense concentrations of pavement, buildings, and other surfaces that absorb and retain heat,” as the US Environmental Protection Agency states.


A rendering of Vienna's planned park featuring a Coolspot, which is scheduled to open in August. Click to expand.
(Courtesy Carla Lo Landscape Architecture)

Vienna’s sixth district, Mariahilf, is such an area. The construction of the capital’s first “Cooling Park”, a €1 million project covering the 10,600 square-metre Esterházypark, is designed to provide relief. 

Green4Cities, a centre of excellence for green infrastructure in urban areas, designed the park’s main attraction, the “Coolspot”. The nearly 3.40-metre high steel trellis holds three rings equipped with spray nozzles. Textile shading slats, tensioned with steel cables, cover them.

The effects of evaporation and evapotranspiration create a cooler microclimate around the 30 square-metre seating area, alongside other spray spots selectively scattered across the park.

The high-pressure spray also deposits tiny droplets on plant and tree leaves, which stimulates them to sweat even more. All together, these collective measures help to cool their surroundings by up to six degrees.

The landscape architect Carla Lo and her team planned what she calls the “low-tech” park components. “Plants are an essential design element of the Cooling Park,” Lo says. “By unsealing the [soil], we can add new grass, herbaceous beds, and more climate-resistant trees to the existing cultivation”.

Light-coloured, natural stone punctuated by grass seams replaces the old concrete surfaces, and wooden benches meander throughout the park.

Living near the park and yearning for an urban escape close by, Lo says she’s motivated to ensure the park is completed by mid-August.

“If we don't do anything, Vienna will be another eight degrees Celsius hotter in 2050 than it already is,” Hebein said.

Vienna recently came in first in the World's 10 Greenest Cities Index by the consulting agency Resonance.

“There is no one size fits all on how cities respond to urban heat,” says the University of Kent’s Bagaeen, who points out that Vienna was one of the first European cities to set up an Urban Heat Islands Strategic Plan in 2015.

In the short term, prognoses on the city’s future development may be more difficult: Vienna votes this autumn.

Petra Loho is a journalist and photographer based in Austria.