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Bill Nye's Solar Sail Could Revolutionize Space Travel
The Planetary Society's solar sail is another step closer to spending its days in the sun. The world's largest space-interest nonprofit has unveiled the LightSail-2, the successor to the original LightSail CubeSat (or cube satellite used for space research) that successfully deployed its solar sails in space eight months ago.
The LightSail's mylar solar sails span 32-square-meters and are designed to capture sunlight and convert its pressure to propel the spacecraft forward. Photo credit: Josh Spradling / The Planetary Society
In June 2015, the Planetary Society proved that flight by light could be possible when it unfurled a solar sail in low-Earth orbit, paving the way for a full-fledged solar sail flight in 2016.
Once this technology is perfected, the LightSail could revolutionize and significantly lower the costs of space travel. Instead of rocket fuel, future spacecraft can be propelled by a sail that captures and converts the sun's photons into pressure that propels the spacecraft forward, thus making it an "inexpensive, inexhaustible means of propulsion," as the project's successful Kickstarter campaign pointed out.
As Vox wrote, what makes this project even more interesting is that it's not funded by NASA or a private enterprise. If successful, the LightSail project will essentially democratize space travel, as it's being built by the citizen-funded Planetary Society and the 23,331 backers who collectively pledged $1,241,615 to bring this crowd-funded project to life.
“Our mission at the Planetary Society is to advance space science and exploration. That’s what we do. That’s the elevator speech,” Bill Nye, CEO of the Planetary Society, told Motherboard. “Empower the world’s citizens to advance space science and exploration to know the cosmos and our place within it.”
The latest mission is expected to launch sometime this Fall. The LightSail-2 will travel on Georgia Tech’s Prox-1 satellite on Elon Musk's SpaceX Falcon Heavy rocket.
Here's what will happen to the LightSail once it's in orbit, as Gizmodo reported:
The new light sail features four triangular sails, made of mylar, which combine to form a rectangular-shaped surface. Once the [three unit] cubesat reaches an orbital altitude of 500 miles (800 km), the sails will deploy, extending across a total area measuring 32 square meters. The main test goal will be to assess whether the solar sails are a viable form of spacecraft propulsion.
This animation shows how the LightSail-2 will deploy from the Prox-1 satellite:
The idea of solar sailing came decades ago from Planetary Society founders Louis Friedman, Bruce Murray and Carl Sagan, who even stopped by Johnny Carson’s The Tonight Show to explain the technology.
“[It] travels on the radiation and particles that come out of the sun, the wind from the sun," Sagan said. "Because it has a constant acceleration, it can get you around the inner part of the solar system a lot faster ... than the usual sorts of rocket propulsion.”
Nye told Motherboard that besides interstellar space travel, the solar sail can be used in various other ways, from monitoring solar weather to helping a satellite de-orbit:
You’re required to have your satellite deorbit in 25 years. That’s an international rule being informally embraced, and people are working on treaties to formalize it. Getting a spacecraft to come down when you want it takes either fuel or dumb luck. With a sail, you can create all this drag. For example, where the ISS is, there are still a few air molecules. So when you deploy a sail, the thing comes down a thousand times faster than otherwise. Satellite manufacturers could very reasonably meet the requirements by including a little drag sail.
This video shows a test deployment of the LightSail 2's sails at California Polytechnic State University in January:
The Planetary Society's digital editor Jason Davis explains what happened in the video:
Unsurprisingly, [the] deployment tests revealed minor issues that engineers...have spent the past few weeks working to resolve. The deployment motor hesitated several times, not unlike the way it did during LightSail 1 testing. There was a glitch with the spacecraft’s onboard cameras, which capture staggered images during the sail deployment sequence. And additional refinements are still being applied to the spacecraft’s communications and attitude control systems.
A second round of system testing is planned at Cal Poly. This will pave the way for a full, day-in-the-life test as soon as March, when the spacecraft demonstrates its core mission functions one final time on the ground.
You can read the history of the LightSail here and learn more about the project in this video below:
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A central player in the fight against the novel coronavirus is our immune system. It protects us against the invader and can even be helpful for its therapy. But sometimes it can turn against us.
How does our immune system react to the coronavirus?<p>The coronavirus is — like any other virus — not much more than a shell around genetic material and a few proteins. To replicate, it needs a host in the form of a living cell. Once infected, this cell does what the virus commands it to do: copy information, assemble it, release it.</p><p>But this does not go unnoticed. Within a few minutes, the body's immune defense system intervenes with its innate response: Granulocytes, scavenger cells and killer cells from the blood and lymphatic system stream in to fight the virus. They are supported by numerous plasma proteins that either act as messengers or help to destroy the virus.</p><p>For many viruses and bacteria, this initial activity of the immune system is already sufficient to fight an intruder. It often happens very quickly and efficiently. We often notice only small signs that the system is working: We have a cold, a fever. </p>
Is there an immunity? How long does it last?<p>The good news is that it is very likely there is an immunity. This is suggested by the proximity to other viruses, epidemiological data and animal experiments. Researchers <a href="https://www.biorxiv.org/content/10.1101/2020.03.13.990226v1" target="_blank">infected four rhesus monkeys,</a> a species close to humans, with SARS-CoV-2. The monkeys showed symptoms of COVID-19, the disease caused by the coronavirus, developed neutralizing antibodies and recovered after a few days. When the recovered animals were reinfected with the virus, they no longer developed any symptoms: They were immune. </p><p>The bad news: It is not (yet) known how long the immunity will last. It depends on whether a patient has successfully developed neutralizing antibodies. Achim Hörauf estimates that the immunity should last at least one year. Within this year, every new contact with the virus acts as a kind of booster vaccination, which in turn might prolong the immunity.</p><p>"The virus is so new that nobody has a reasonable immune response," says the immunologist. He believes that lifelong immunity is unlikely. This "privilege" is reserved for viruses that remain in the body for a long time and give our immune system a virtually permanent opportunity to get to know it. Since the coronavirus is an RNA (and not a DNA) virus, it cannot permanently settle in the body, says Hörauf.</p><p>The Heidelberg immunologist <a href="https://www.klinikum.uni-heidelberg.de/immunologie/immunologie" target="_blank">Stefan Meuer</a> predicts that the novel coronavirus will also mutate like all viruses. He assumes that this could be the case in 10 to 15 years: "At some point, the acquired immunity will no longer be of any use to us because then another coronavirus will return, against which the protection that has now been formed will not help us because the virus has changed in such a way that the antibodies are no longer responsible. And then no vaccination will help either."</p>
How can we take advantage of the antibody response of the immune system?<p>Researchers are already collecting plasma from people who have successfully survived an infection with SARS-CoV-2 and are using it to treat a limited number of patients suffering from COVID-19. The underlying principle: <a href="https://www.dw.com/en/coronavirus-drugs-can-antibodies-from-survivors-help/a-52806428" target="_blank">passive immunization.</a> The studies carried out to date have shown positive results, but they have usually been carried out on only a few people.</p><p>At best, passive immunization is used only when the patient's own immune system has already started to work against the virus, says Achim Hörauf: "The longer you can leave the patients alone with the infection before you protect them with passive immunization, the better." Only through active immunization can one be protected in the long term. At the same time, it is difficult to recognize the right point in time.</p><p>PCR (polymerase chain reaction) tests are currently used to find out whether a person is infected with the coronavirus. With the help of PCR, it is not possible to tell whether or not there is reproducible viral RNA; it is just a proof of whether the virus is still present, dead or alive. A PCR test cannot tell us whether our immune system has already intervened, i.e. whether we have had contact with the virus in the past, have formed antibodies and are now protected. Researchers are therefore working on tests that check our blood for the presence of antibodies. They are already in use in Singapore, for example, and are nearing completion in the USA. With the help of these tests, it would finally be possible to gain an overview <a href="https://www.dw.com/en/corona-confusion-how-to-make-sense-of-the-numbers-and-terminology/a-52825433" target="_blank">of the unclear case numbers.</a> In addition, people who have developed antibodies against the virus could be used at the forefront of health care, for example. An "immunity passport" is even under discussion.</p>
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Why do people react differently to the virus?<p>While some people get off with a mild cold, others are put on ventilators or even die of SARS-Cov-2. Especially people with <a href="https://www.dw.com/en/coronavirus-who-is-particularly-at-risk-and-why/a-52710881" target="_blank">pre-existing conditions</a> and older people seem to be worst-affected by the virus. Why? This is the hottest question at the moment.</p><p>It will still take a very, very long time to understand the mechanistic, biological basis for why some people are so much more severely affected than others, virologist Angela Rasmussen told <em>The Scientist</em>. "The virus is important, but the host response is at least as important, if not more important," her colleague Stanley Perlman told the magazine.</p><p>Stefan Meuer sees a fundamental survival principle of nature in the different equipment and activity of our immune systems: "If we were all the same, one and the same virus could wipe out the entire human species at once. Due to the genetic range, it is quite normal that some people die from a viral disease while others do not even notice it. "</p><p>Achim Hörauf also suspects immunological variants that could be genetically determined. Since interstitial pneumonia is observed with the coronavirus, the focus is probably on an overreaction of the immune system. However, it is also possible that each person affected may have been loaded with a different dose of the virus, which in turn leads to different outcomes. And finally, it makes a difference how robust the body and lungs are: Competitive athletes simply have more lung volume than long-time smokers. </p>
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