Mars in Three Days, or Maybe 30 Minutes

This is a bit off topic for us, but it’s certainly worth talking about. In London’s Daily Express we read NASA works on laser propulsion spacecraft which could get to Mars in THREE days. Here are some excerpts, with bold font added by us:

In its latest video blog – NASA 360 – the space agency describes a spacecraft which is currently being developed and would rely on a technology known to experts as “photonic propulsion” which would allow spaceships to explore space at 30 per cent of the speed of light.

The video is no big deal. It’s only 2 minutes long. Wikipedia had an article on Photonic laser thruster. Let’s stay with the Daily Express:

The potential spacecraft, which NASA admits is still in its infancy, would be able to reach such pace as when the particles of light that it emits are reflected against an object, it would give the spacecraft speed and momentum, gradually getting faster and faster. NASA scientists Phil Lubin said: “There are recent advances that take this from science fiction to science reality. There is no known reason why we can not do this.”

Very nice, but it’s rather like shooting an arrow. Once it’s launched, you lose control. How does such a ship slow down and land at its destination? And unless there’s a laser setup on Mars, how does it return? The article continues:

However, for any aspiring astronauts hoping to be one of the first to explore space at speeds which have never been reached by humanity before, you’re probably out of luck. A spacecraft with the potential to reach such speeds would need be designed with weight in mind, which is why Lubin and co are proposing making the ship wafer thin meaning that humans would be too heavy, but would be perfect for robots.

But wait — that news is dated 24 February. Today there’s more! London’s Daily Mail has this headline: Forget three days, now physicist behind radical laser propulsion system explains how we could get to Mars in 30 MINUTES. It says, with our bold font:

A small probe could get to Mars in less time than it takes to watch ‘Interstellar’. That’s according to physicist, Phillip Lubin, who recently outlined how a probe could reach the red planet in just three days. Now, Lubin says that time could be reduced to just 30 minutes by using extremely powerful lasers to propel a wafer-thin unmanned spacecraft.

Good grief! It takes light from the Sun (traveling at the speed of light, obviously) 8 minutes to get to Earth. The distance from Earth to Mars varies as the planets move around the Sun, but still, 30 minutes is fast! At their closest, the distance between Earth and Mars is 56 million kilometers. If that can be done in 30 minutes, the ship would be traveling at 112 million km per hour. Light travels at 1,079,252,848.8 km per hour. The ship would be moving at about 10% of lightspeed. Okay, let’s read on.

The UC Santa Barbara physics professor first unveiled his ‘directed energy propulsion’ concept at a Nasa Innovative Advanced Concepts (NIAC) symposium last October. He’s now followed up his comments with a detailed 52-page paper in the Journal of the British Interplanetary Society.

We can’t find the paper at that journal, but the Daily Mail provides a link to a pdf file you can read online: A Roadmap to Interstellar Flight. We haven’t read it yet. Back to the Daily Mail:

He claims that by firing a laser at a spacecraft, it would have the ability to achieve frictionless acceleration in space. That would allow it to reach a more than a quarter speed of light in just minutes. … ‘[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.’

Even the Daily Mail has noticed a couple of problems. They say:

There are some major flaws in Lubin’s plan, such as how such a fast-moving probe would slow down when it reached Mars. The difficulty of encountering space junk is a major problem. But according to Lubin, the accumulation of interplanetary dust won’t impact its speed.

But then the newspaper gets crazy: They mention time dilation:

The effect was shown in Christopher Nolan’s 2014 science film Interstellar, in which a group of astronauts fly into the center of a supernatural wormhole. As they move farther into the universe, the time they experience slows down. The same thing could happen to a crew if they were able to reach Mars in 30 minutes. While it would appear as if they only spent 30 minutes getting to the red planet, in reality decades would pass.

BWAHAHAHAHAHA! These are not difficult calculations. Relativistic effects don’t become significant until a ship is traveling faster than 50% of lightspeed. If a ship traveled at “only” a quarter of the speed of light, time dilation would be barely noticeable. Observers on Earth would see that the trip took 30 minutes, and it would seem like only 29.047 minutes to passengers on the ship. Not decades!

There’s more in both articles, but we’ve given you enough to mull over. If you have any thoughts, we’d like to hear them.

Copyright © 2016. The Sensuous Curmudgeon. All rights reserved.

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11 responses to “Mars in Three Days, or Maybe 30 Minutes

  1. I suspect that the Mail, in its typical rightwing-loony fashion, has gotten it all wrong again.

    There’s nothing theoretically wrong with the laser-propulsion/laser-sail idea for space propulsion. There’s a reasonable likelihood you could get a 10% lightspeed out of it . . . by the time, probably years after launch, your craft had reached the edge of the solar system. Since this is an investigative probe only, you don’t need to worry about slowing it down as, maybe fifty years later, it zooms through the Alpha Centauri system.

    In other words, if ever we divert sufficient money from abstinence education to interstellar probes, the laser sail is one of the options worth investigating.

    It’s not, of course, an option worth investigating if you want to get to Mars. Yes, you get get to Mars in 30 minutes if you were moving at 10% lightspeed from the moment you left earth orbit. But no one save a loony — or a Daily Mail reporter (quel difference?) or the chairmanships of the US Senate and House science committees — would assume this was possible.

  2. The idea has been around for some time. It is similar to solar sails, but being propelled by more concentrated light from a laser. Solar sails have been flown – the Japanese IKAROS is an example.

    Paul Glister has been blogging about this for years – see http://www.centauri-dreams.org

    What’s interesting is why has this come up now? Is NASA trying to find support (i.e. budget) to pursue this in the near future?

  3. Niven and Pournelle used that means of propulsion in the SF novel, The Mote in God’s Eye, written in 1974.

    Slowdown was accomplished by sailing very close to the sun at the destination system.

  4. SC:
    “Observers on Earth would see that the trip took 30 seconds, and it would seem like only 29.047 seconds to passengers on the ship. Not decades!”

    Don’t you mean minutes, not seconds?

  5. It would be very cool if this technology is developed into something viable. I’m not sure that’ll happen in my lifetime.

  6. retiredsciguy asks: “Don’t you mean minutes, not seconds?”

    Aaaargh! Well, at least it wasn’t a math error. All fixed now. Thanks.

  7. As they move farther into the universe, the time they experience slows down. … While it would appear as if they only spent 30 minutes getting to the red planet, in reality decades would pass.

    Their writer is all confused. If you do reach relativistic speeds, it has nothing to do with “moving farther into the universe”, and time dilation would not cause “decades to pass” for the crew or the earthbound observers (it’s not clear who is meant) at any speed. Even at the speed of light, the travellers reach Mars instantly and the rest of us see the journey taking approximately 12 minutes.

  8. Comments? Sure. I have a cousin in the physics department at UC Santa Barbara who will receive his PhD in July after 10 years of work post MS.

  9. longshadow

    v=at

    If that can be done in 30 minutes, the ship would be traveling at 112 million km per hour.

    That’s the average speed.

    1.12 10^8 km/s = a (3600*30 minutes)

    rounding off:

    1 x 10^8 km/s = a (~1 x 10^5 seconds)

    a = 1 x10^3 km/s^2 = 1 x 10^6 m/s^2

    g = ~10m/s^2, ergo a = 100,000g

    Seriously, they think they can use a laser to accelerate the spacecraft at a rate equal to 100,000 times the acceleration of gravity on earth?

  10. Stay with us, longshadow. I have a political post coming up.

  11. longshadow

    oops, the left side is km/hr, not km/second.

    So, my answer is off by a factor of 3600.

    a = ~3 x 10^8 g.

    30 million g’s, give or take.