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https://www.yahoo.com/tech/could-spacec ... 30966.htmlTechnology
Could a spacecraft really make the journey to Mars in 30 minutes? One physicist says yes
Rick Stella,Digital Trends Fri, Feb 26 6:15 AM PST Comments Sign in to like Reblog on Tumblr Share Tweet Email
Aside from its extremely cold temperatures, unbearably thin atmosphere, and its all-around shroud of complete mystery; perhaps the biggest obstacle facing a journey to Mars is the sheer amount of time it would take to get there. Though exact timeframes tend to differ, a 260-day trip to the red planet seems the closest to a consensus among those knowledgeable of the journey, meaning it would take nearly nine months to reach its orbit. However, according to UC Santa Barbara physics professor Philip Lubin, by making use of directed energy propulsion (i.e. lasers) it might be possible to reach Mars in a fraction of the time it would take to watch The Martian.
While Lubin’s idea of a 30-minute trip to Mars first burst on the scene during a NASA Innovative Advanced Concepts (NIAC) symposium last October, the concept was featured by NASA 360 in a recent video. Though two-minute video hardly delves into the exact science of achieving such an endeavor, Lubin published a detailed, 52-page explainer in the Journal of the British Interplanetary Society. Amid the many paragraphs of scientific jargon, experimental equations, and detailed set of planning, Lubin maintains this isn’t some far-off idea, but rather, something that’s attainable this very second.
Artist rendition of laser propulsion
Artist rendition of laser propulsion
NASA 360
In essence, Lubin asserts that by firing a laser at a spacecraft, one would feasibly have the ability to speed that spacecraft to a significant fraction of the speed of light. What this means is that scientists would point a powerful, Earth-orbiting laser (think tens of gigawatts of power) at a spacecraft equipped with a laser sail. By focusing the beam squarely on the sail, the craft would have the ability to achieve frictionless acceleration in space, allowing it to reach a sizable percentage of the speed of light in a matter of minutes. Lubin’s theory trades fuel propellant for photonic propulsion and appears ready to take the EmDrive head-on.
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“As an example, on the eventual upper end, a full-scale (50-70 GW) DE-STAR 4 — Directed Energy System for Targeting of Asteroids and Exploration — will propel a wafer scale spacecraft with a one meter sail to about 26 percent the speed of light in about 10 minutes,” Lubin says, “[it would] reach Mars (1 AU) in 30 minutes, pass Voyager 1 in less than 3 days, pass 1,000 AU in 12 days and reach Alpha Centauri in about 15 years.”
But how close is this to the truth?
Like any announcement of this nature, the immediate response to Lubin’s claims was first met with overwhelming excitement and pure awe. Of course, figuring out a legitimate way to turn a 260-day journey into a 30-minute jaunt deserves all the attention it gets. However, there are heaps of speed bumps Lubin can’t just chalk up as plot holes like Christopher Nolan and Interstellar. To Lubin’s credit, he’s addressed a number of the most critical questions posed by his more eagle-eyed followers. Because deciphering a 52-page scientific journal isn’t always the most appealing way to pass the time, here are a few problems facing this innovative theory and how Lubin’s attempting to solve them.
How would the craft slow down?
This is perhaps the most pressing question facing Lubin’s theory, one even he admits is a “very difficult challenge.” If a spacecraft (with or without astronauts) ends up reaching anywhere near 26 percent the speed of light (roughly 174.3 million miles per hour) slowing that craft to enter the orbit of Mars would take a sizable dissipation of energy.
Lubin poses such solutions as using a star’s photon pressure or harnessing stellar wind, however, he quickly points out that none of these options appear up to the ultimate task. Moreover, he admits that comprehensive trials and simulations are required before a suitable solution will be discovered.
What about all that space junk?
It’s no secret that there are loads of space junk not just orbiting Earth, but hurtling through the universe. So while achieving a fraction of light speed certainly saves on the amount of time it takes to travel from point A to point B, it’s likely that even a tiny object could lead to a catastrophic event. Perhaps the chances of actually hitting something in the 30 minutes it takes to get to Mars are low, but the possibility remains and NASA (or any other space agency, for that matter) won’t take a chance on “perhaps.”
Lubin vaguely addresses this quandary, bringing up the eventual accumulation of interstellar and interplanetary dust and its effect on the craft. After showing off the equation he used to calculate the possible amount of dust accumulate, Lubin concludes that “the total energy of impacts is negligible to the kinetic energy of the wafer.” He continues by saying “it is NOT negligible in total energy delivered to the wafer (i.e. damage to the wafer) but it is not all delivered at once and the face on case is the worst case.” In other words, a small accumulation of dust won’t significantly impact the KE of the craft nor does Lubin think it will damage it.
A real-time look at objects currently orbiting Earth
A real-time look at objects currently orbiting Earth
Stuff in Space
Obviously, this only tangentially addresses the larger concern of space junk though if something of this magnitude were to move forward with production, this will undoubtedly be one of the first problems solved. Solutions such as an ablation shield or magnetic field could be possible resolutions, however, the inherent speed could be affected by the addition of anything other than what Lubin originally stated.
Would time dilation have a significant effect?
In director Christopher Nolan’s 2014 science fiction opus Interstellar, a group of astronauts perilously make a jump to a far off galaxy by willingly flying into the center of a seemingly supernatural wormhole. As they traverse to a far-reaching outpost of the universe, the time they experience begins to drastically slow compared to what’s being experienced on Earth. As the film enters its final act, Matthew McConaughey’s character is eventually reunited with his daughter aboard a massive space station. Though McConaughey has yet to age much more than a few years (roughly the length of his galaxy-spanning mission), his daughter has lived a full life, has a head of gray hair, and is on the edge of succumbing to old age.
Sure, this series of events happened in a big-budget Hollywood film, but time dilation isn’t just some far-fetched film industry plot piece; it’s a legitimate physical phenomenon. For instance, astronauts aboard the International Space Station experience time a bit slower than those on Earth, however, the effects are minimal. For any six-month stay on the ISS, astronauts effectively age roughly 0.005 seconds less than people on the ground.
A black hole in Interstellar
A black hole in Interstellar
Where time dilation would really begin to take effect is when something (or someone) starts traveling closer to the speed of light — i.e. Lubin’s directed energy propulsion theory. If a craft was actually capable of propelling a crew of astronauts at even 26 percent the speed of light, time dilation would have a notable effect on those involved. Though it likely wouldn’t mean that a crew would leave for Mars, get there in 30 minutes, and decades would pass, it would be significant in the fact that time dilation of that nature is unprecedented.
Lubin does point out that the first step (after years of training and simulations) is to use an unmanned probe, so manned missions are likely decades away. The paper acknowledges that the technology is completely scalable, so manufacturing a craft large enough to fit an astronaut (or three) isn’t out of the question. This would, however, affect the propulsion necessary to make the journey, which would also affect the amount of time it takes to get to Mars.
Can it work?
Compared to the controversial (yet similar) EmDrive technology, Lubin’s directed energy propulsion system is something scientists have the ability to physically test in real time right now. The professor even goes so far as to provide a necessary timeline for developing the tech, how technology would need to mature during the timeline, and a step-by-step breakdown of testing. Unsurprisingly, he’s incredibly fervent in his belief that this is something wholly attainable and that it deserves immediate scientific attention.
“This technology is NOT science fiction,” Lubin says. “Things have changed.”
Whether or not the theory gains traction is yet to be seen, but the fact it was picked up for a video series by NASA 360 certainly bodes well for its advancement. As NASA continues to move forward with its own plans on visiting the red planet, the topic of how to efficiently and effectively get there is likely to be a hot topic of discussion. If Lubin proves capable of filling all the sizable gaps in his method, perhaps this won’t be the only time the agency enjoys collaborating with him.
Posted: Wed Feb 24, 2016 12:33 pm