If we’re ever to make regular journeys from Earth to Mars and other far-off destinations, we might need new kinds of engines. Engineers are exploring revolutionary new technologies that could help us traverse the Solar System in much less time.
Because of the orbital paths Mars and Earth take around the Sun, the distance between them varies between 54.6 million km and 401 million km.
Missions to Mars are launched when the two planets make a close approach. During one of these approaches, it takes nine months to get to Mars using chemical rockets – the form of propulsion in widespread use.
That’s a long time for anyone to spend travelling. But engineers, including those at the US space agency (Nasa), are working with industrial partners to develop faster methods of getting us there.
So what are some of the most promising technologies?
Solar electric propulsion
Solar electric propulsion could be used to send cargo to Mars ahead of a human mission. That would ensure equipment and supplies were ready and waiting for astronauts when they arrived using chemical rockets, according to Dr Jeff Sheehy, chief engineer in Nasa’s Space Technology Mission Directorate.
With solar electric propulsion, large solar arrays unfurl to capture solar energy, which is then converted to electricity. This powers something called a Hall thruster.
There are pros and cons. On the upside, you need far less fuel, so the spacecraft becomes lighter. But it also takes your vehicle longer to get there.
“In order to carry the payload we’d need to, it would probably take between two to 2.5 years to get us there,” Dr Sheehy tells the BBC.
“For the kinds of outposts we’d need to build on Mars for crews to be able to survive for months, and the vehicles, you’d need a lot of cargo.”
Aerojet Rocketdyne is working on a Hall thruster for the Gateway, a proposed space station in lunar orbit.
“Solar is the best because we know we can scale it up,” Joe Cassidy, executive director of Aerojet Rocketdyne’s space division, explains.
“We’ve already got these flying today on communications satellites. The power level we fly at today is 10-15kW (kilowatts), and what we’re looking to do with the Gateway is to scale it up to something greater than 50kW.”
Mr Cassidy said Aerojet Rocketdyne’s Hall thruster will be much more fuel efficient than a liquid hydrogen and oxygen rocket engine.
But a good way to make access to space cheaper would be to have fewer launches, he explains.
“I think that solar electric propulsion is very good technology, using xenon as the propellant. But the two major drawbacks are the amount of time it takes to get there, and the size of the solar arrays,” says Tim Cichan, a human spaceflight architect at aerospace giant Lockheed Martin.
Dale Thomas, a professor and eminent scholar in systems engineering at the University of Alabama in Huntsville (UAH) concurs.
“Solar electric works well for smaller payloads, but we’re still having trouble getting it to scale,” he tells the BBC.
He thinks it could become an important alternative technology if the technical challenges can be solved. But for now, he says, there are other better options, such as nuclear thermal electric propulsion.
Nuclear thermal electric propulsion
Another idea is to use chemical rockets to lift off from Earth and to land on Mars. But for the middle part of the journey, some engineers propose using something called nuclear thermal electric propulsion.
Astronauts could be sent to the Gateway in Nasa’s Orion capsule. The Orion crew capsule would then dock with a transfer vehicle.
Once Orion has been connected to the transfer vehicle, a nuclear electric rocket would be used to get the crew capsule and the transport module to Mars, where they link up with a Mars orbiter and lander, which are waiting in Mars’ orbit.
In a nuclear thermal electric rocket, a small nuclear reactor heats up liquid hydrogen. The gaseous form of the element expands and shoots out of the thruster.
“If we can cut transit time [to Mars] down by 30-60 days, it will improve the exposure to radiation facing the crew,” says Mr Cassidy. “We’re looking at nuclear thermal as a key technology because it can enable faster transit times.”
Dale Thomas, together with UAH, has a study contract with Nasa to design a space rocket featuring a nuclear thermal engine. He thinks nuclear thermal electric is the closest new engine technology to being ready for use.
“Some of the trajectories we run in my lab, we can get the transit time down to three months, which is still a very long journey, but it’s about a third of the time that chemical propulsion requires to get us there,” he says.
Boeing is not so keen on nuclear thermal propulsion, because it worries about the effects a nuclear reactor might have on astronauts.
Mr Thomas disagrees: “This is a common misperception. The hydrogen propellant is a great radiation shield.
“The crew will be at one end of the vehicle, and the engine at the other end. As such, preliminary estimates show that the crew will get more radiation dosage from cosmic rays than from the nuclear thermal engine.”
However, he admits one downside of the technology is the inability to easily test it on Earth.
But Nasa is designing a ground test apparatus that scrubs the exhaust to remove radioactive particles – making ground tests possible.
Electric ion propulsion
Another idea is electric ion propulsion. These generate thrust by accelerating ions – charged atoms or molecules – using electricity.
Ion propulsion is already being used to power satellites in space. But they produce only a low thrust – more like the power of a hairdryer – and therefore have a low acceleration. But given time, they can reach high speeds.
Ad Astra says it is working on a type of thruster called the Vasimr that uses radio waves to ionise and heat a propellant and then a magnetic field to accelerate the resulting soup of particles – the plasma. The Vasimr is designed to produce much more thrust than a standard ion engine.
The electricity needed can be generated in different ways. But for sending humans to Mars, the team wants to use a nuclear reactor. The Vasimr would use solar electric for smaller payloads.
Ad Astra’s president and chief executive Franklin Chang Diaz, who is a former Nasa astronaut, says crewed missions need to get to Mars in less than nine months, ideally.
Going to the Red Planet is much harder than going to the Moon, he says.
“The solution is to go fast,” Mr Chang Diaz tells the BBC. “For a spacecraft that would weigh 400-600 metric tonnes, with a power level of 200 MW (megawatts), you can get to Mars in 39 days.”
Dale Thomas believes scaling up the Vasimr will be difficult, like going from the power of a lawnmower to a space rocket. But the technology does show promise.
“If, or perhaps I should say, when Ad Astra can solve the technical challenges of Vasimr, it does appear to be the best choice for electric propulsion at the human-ferrying spacecraft scale,” Mr Thomas says.
“The physics says that it should work. However, I must point out that Vasimr is still under development in the laboratory; it’s a long way from being flight-ready at any scale.”
Mr Chang Diaz doesn’t see a problem with scaling up, it’s just that there’s currently no market for a 10MW engine, so Ad Astra is sticking with 200kW.
“We have a market for the 200kW engine, there’s a lot of activity in low-Earth orbit and near the Moon to move cis-Earth satellites,” says Mr Chang Diaz.
Lockheed Martin also thinks the Vasimr is promising technology, but it is focusing on solar electric propulsion.
The case for chemical rockets
Although the new technologies are interesting, veteran space players Lockheed Martin and Boeing both think liquid chemical rockets need to be the bedrock of any human mission to Mars.
Lockheed Martin says we already have the technology we need to get to Mars, and chemical rockets are a proven technology that worked in all the Apollo missions.
“We already have the technology to get us to Mars today,” says Mr Cichan, the former system architect for Orion.
“There are some technical challenges, but it’s really about taking the technology we have, building the systems and gaining experience in flying in deep space that is the work ahead of us, as well as developing technology that will be groundbreaking in the future.”
Hydrogen upper stage launchers have been used since the 1960s, and they have a high success rate, he stresses.
“Nasa’s Space Launch System (SLS) has four liquid hydrogen and oxygen RS-25 rocket engines,” Rob Broeren, a Boeing rocket propulsion specialist tells the BBC.
“These are shuttle heritage engines, and the advantage of the RS-25’s is that they’re well proven, high-reliability engines.
“The nice thing about going with highly proven technologies is that you have full confidence that they definitely work. With new technologies, they sound good on paper, but when it comes to implementing them, you will run into issues that will delay you.”
When will we get to Mars?
A recent study by the Science and Technology Policy Institute (STPI) found that it was unlikely for human missions to Mars to follow Nasa’s timetable and begin in 2033.
Given the constraints on Nasa’s budgets, STPI thinks it is much more likely that we will leave for Mars in 2039, though the White House wants the US space agency to explore the Moon first by 2024, under its Artemis programme.
Dr Paul Dimotakis, John K Northrop professor of aeronautics and professor of applied physics at the California Institute of Technology (Caltech) is sceptical of the new technologies, and even chemical propulsion.
“I personally have not seen answers to technical questions of how to have enough chemical propulsion to last the long trip. It’s not known for a hydrogen-oxygen rocket to last longer than six months,” he says.
“We do not have a technical solution that addresses all the issues. Plus, someone has to demonstrate this before we send humans to Mars, and all of these things do not correspond to Nasa’s timetable.”
'Extreme planet' orbits star in three Earth days, has temperatures of 3120 degrees Celsius – CTV News
Research on data from a new satellite is revealing strange new details about one of the “most extreme planets” in our known universe, and the blue, oddly-shaped star it orbits.
WASP-189b is 322 light years away from Earth in the constellation of Libra, has a permanent dayside and night side, and takes less than three Earth days to fully orbit its star — far faster than our 365 days.
“It is 20 times closer to [its star] than Earth is to the Sun,” Monika Lendl, lead author of the study from the University of Geneva, said in a press release.
WASP-189b is a gas giant, but it’s not any old gas giant. It is around one and a half times as large as Jupiter, and is part of a group called “ultra-hot Jupiters,” which are gas giants that are much larger and hotter than any planet we see in our solar system.
And this planet is even hotter than most other ultra-hot exoplanets scientists have identified. A paper published in the Astronomy & Astrophysics journal last week which detailed the new research described WASP-189b as “one of the most highly irradiated planets known thus far.”
It not only orbits incredibly close to its star, but the star itself, known as HD 133112, is one of the hottest stars we know of that has its own planetary system, at around 2,200 degrees Celsuis hotter than our Sun.
“Because it is so hot, the star appears blue and not yellow-white like the sun,” Willy Benz, professor of astrophysics at the University of Bern and head of the CHEOPS consortium, said in the release.
The dayside of the WASP-189b — the side that faces the star — is roughly 3,400 Kelvin, which is more than 3,120 degrees Celsius. It’s so hot that if there were iron present in the planet’s makeup, it would be gaseous.
In our solar system, the way that our planets spin while they rocket around the sun in their orbit gives them a night and day and allows multiples sides of the planet to get some face time with the sun. This isn’t the case for planetary objects like WASP-189b.
“They have a permanent day side, which is always exposed to the light of the star, and, accordingly, a permanent night side,” Lendl explained.
These details were discovered using data from the CHaracterising ExOPlanets Satellite (CHEOPS), the first European Space Agency (ESA) mission dedicated solely to extra-solar planets. The mission was launched in partnership with Switzerland, and benefitted from contributions from numerous European countries.
The satellite, with its mounted telescope, was launched in December of 2019, and has been orbiting 700 km above Earth ever since. Unlike many previous exoplanet-focused missions, CHEOPS is not interested in identifying new exoplanets, but was designed to peer closely at systems where we already knew an exoplanet is present.
Exoplanets — or extrasolar planets — are planets orbiting stars outside of our solar system, and because they’re so far away, we identify them not by finding a coloured speck in the sky, but by measuring dips in the light from stars.
When a star dims, it means something has passed in front of it, blocking some of the light from reaching the Earth. Using this “transit method,” researchers can figure out how large exoplanets are, how big or long their orbit is, and even what materials they are likely composed of.
There is also a change in light when a particularly bright planet goes behind its star, something called an “occultation.”
“Only a handful of planets are known to exist around stars this hot, and this system is by far the brightest,” Lendl said in an ESA release. “WASP-189b is also the brightest hot Jupiter that we can observe as it passes in front of or behind its star, making the whole system really intriguing.
“As the planet is so bright, there is actually a noticeable dip in the light we see coming from the system as it briefly slips out of view.”
While CHEOPS was pointed at WASP-189b, cataloguing all of its strange properties, researchers discovered that the star was unusual for more than just its bright blue colour.
It is spinning so rapidly that it is actually thicker at the equator, distorting the shape itself.
“The star itself is interesting — it’s not perfectly round, but larger and cooler at its equator than at the poles, making the poles of the star appear brighter,” said Lendl. “It’s spinning around so fast that it’s being pulled outwards at its equator! Adding to this asymmetry is the fact that WASP-189 b’s orbit is inclined; it doesn’t travel around the equator, but passes close to the star’s poles.”
This misaligned orbit implies that the planet had been formed further away from the star, and then been somehow pushed closer to it. Lendl suggested that this could mean the planet had interacted with other planets, or even other stars that had changed its orbital path.
According to the research, the planetary and star system is fairly young, which means researchers will be able to use this system to track the “atmospheric evolution of close-in gas giants.”
The new research is exciting to scientists not only for what it reveals about this planet and star, but for what it reveals about the telescope that provided such clear information.
“This first result from Cheops is hugely exciting: it is early definitive evidence that the mission is living up to its promise in terms of precision and performance,” Kate Isaak, CHEOPS project scientist at ESA, said in the ESA release.
Researchers point out in the paper that CHEOPS allowed them to refine and correct the size of the planet, which had been estimated incorrectly years earlier when the exoplanet’s existence was discovered by telescopes on the ground on Earth.
The paper concludes that the levels of the precision in the data shows that CHEOPS will be an invaluable tool in studying more exoplanets.
“We are expecting further spectacular findings on exoplanets thanks to observations with CHEOPS,” Benz said. “The next papers are already in preparation.”
Buried lakes of salty water on Mars may provide conditions for life – MENAFN.COM
(MENAFN – The Conversation) In 2018 a team of Italian scientists announced to the world that there was a lake on Mars . Using satellite radar data, the team detected a very bright area approximately 20 kilometres across located about 1.5 kilometres deep under the ice and dust of the south polar cap.
After analysis, they concluded that the bright area was a subglacial lake filled with liquid water. The discovery raised some fundamental questions.
Was this the only lake hidden beneath the ice on Mars? How could liquid water exist in the extreme cold of the Martian south polar region, where the average surface temperatures are lower than -100 °C?
After acquiring additional satellite data, my colleagues and I have discovered three more distinct ‘lakes’ near the one found in 2018 and confirmed that all four bodies contain liquid water.
Read more: Mars: mounting evidence for subglacial lakes, but could they really host life?
How can we see lakes under the ice on Mars?
The radar sounder MARSIS (Mars Advanced Radar for Subsurface and Ionosphere Sounding) is one of eight instruments on board the European Space Agency orbiter Mars Express. This scientific spacecraft has been circling the red planet since December 2003.
The orbiting radar directs radio ‘chirps’ toward the planetary surface. These signals are partly reflected back by the surface, and partly penetrate deeper, where they may be absorbed, scattered, or reflected back to the radar. Liquid water reflects radar signals better than many other materials, so the surface of a body of liquid water shines brightly in a radar image.
Radar sounders are used on Earth to detect subglacial lakes in Antarctica, Greenland and Canada. Here, a technique called radio-echo sounding (RES) is commonly used to analyse the signals.
There are some obvious differences between how radar sounding is used on Earth and on Mars. For a start, MARSIS operates from altitudes between 250 km and 900 km above the surface, it has a 40-metre long antenna, and it operates at much lower frequencies (1.8-5 MHz) than Earth-based radar sounders.
These differences meant we had to do some work to adapt standard radio-echo sounding techniques for use with signals from MARSIS. However, we were able to analyse data from 134 MARSIS tracks acquired between 2010 and 2019 over an area 250 km wide and 300 km long near the south pole of Mars.
In this area, we identified three distinct bright patches around the lake already ‘seen’ in 2018. We then used an unconventional probabilistic method to confirm that the bright patches really do represent bodies of liquid water.
We also obtained a much clearer picture of the shape and extent of the lake discovered in 2018. It is still the largest of the bodies of water, measuring 20 km across on its shortest axis and 30 km on its longest.
How could liquid water exist beneath the Martian ice?
The surface temperatures in our study area are around -110 °C on average. The temperatures at the base of the ice cap may be slightly warmer, but still way below the freezing point of pure water.
So how can bodies of liquid water exist here, let alone persist for periods of time long enough for us to detect them?
After the first lake was found in 2018, other groups had suggested the area might be warmed from below by magma within the planet crust. However, there is to date no evidence this is the case, so we think extremely high salt levels in the water are a more likely explanation.
Read more: What on Earth could live in a salt water lake on Mars? An expert explains
Perchlorate salts, which contain chlorine, oxygen, and another element, such as magnesium or calcium, are everywhere in the Martian soil. These salts absorb moisture from the atmosphere and turn to liquid (this process is termed ‘deliquescence’), producing hypersaline aqueous solutions (brines), which crystallise at temperatures far below the freezing point of pure water. Furthermore, laboratory experiments have shown that solutions formed by deliquescence can stay liquid for long periods even after temperatures drop below their own freezing points.
We therefore suggested in our paper that the waters in the south polar subglacial lakes are ‘salty’. This is particularly fascinating, because it has been shown that brines like these can hold enough dissolved oxygen to support microbial life.
Could conditions be right for life beneath the ice?
Our discoveries raise new questions. Is the chemistry of the water in the south polar subglacial lakes suitable for life? How does this modify our definitions of habitable environments? Was there ever life on Mars?
To address these questions new experiments and new missions must be planned. In the meantime, we are gearing up to continue acquiring MARSIS data to collect as much evidence as possible from the Martian subsurface.
Each new piece of evidence brings us one step closer to answering some of the most fundamental scientific questions about Mars, the solar system and the universe.
Read more: Mars: mounting evidence for subglacial lakes, but could they really host life?
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Scientists find evidence of multiple underground lakes on Mars – Yahoo News Canada
The team used data from a radar instrument on the European Space Agency’s (ESA) Mars Express spacecraft to investigate the planet’s southern polar region. Mars Advanced Radar for Subsurface and Ionosphere Sounding or MARSIS, as the instrument is called, is capable of sending out radio waves that bounce off materials on the planet’s surface. Different materials reflect those signals differently, and the same technique is used to find subsurface glacial lakes here on Earth.
Upon observing an area that’s around 75,000 square kilometers in size, they found locations that reflected those signals back in a way that indicates the presence of water trapped underneath a kilometer of ice. The main lake, the one discovered back in 2018, measures 30 kilometers or 19 miles across, while each of the three smaller lakes surrounding it are a few kilometers across.
<p class="canvas-atom canvas-text Mb(1.0em) Mb(0)–sm Mt(0.8em)–sm" type="text" content="While the scientists’ findings are promising, some experts still believe we won’t find lakes on the red planet at all. Jack Holt, a planetary scientist part of NASA’s Mars Reconnaissance Orbiter program, doesn’t believe there’s enough heat flow under the surface of the planet for water to remain liquid. And even if we do find liquid water under Martian ice, that won’t automatically mean we’ll also find life. See, the lakes have to be very salty to remain liquid, but their salt content must not exceed five times that of seawater to be able to support life. As John Priscu, an environmental scientist at Montana State University, told Nature:” data-reactid=”27″>While the scientists’ findings are promising, some experts still believe we won’t find lakes on the red planet at all. Jack Holt, a planetary scientist part of NASA’s Mars Reconnaissance Orbiter program, doesn’t believe there’s enough heat flow under the surface of the planet for water to remain liquid. And even if we do find liquid water under Martian ice, that won’t automatically mean we’ll also find life. See, the lakes have to be very salty to remain liquid, but their salt content must not exceed five times that of seawater to be able to support life. As John Priscu, an environmental scientist at Montana State University, told Nature:
“There’s not much active life in… briny pools in Antarctica. They’re just pickled. And that might be the case [on Mars].”
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