Author Topic: Photonic Propulsion to Mars in 3 Days  (Read 6287 times)

Offline Proponent

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Re: Photonic Propulsion to Mars in 3 Days
« Reply #20 on: 03/01/2017 08:56 AM »
He claims he can accelerate a 100 kg probe to 0.3 c in 10 minutes.  By my rough calculation, that's an acceleration of over 15,000 G's.

It's 100 kg to Mars in three days; that corresponds to a speed of much less than 0.3c.  No mass is quoted for the probe to be accelerated to 0.3c.

Online rdheld

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Re: Photonic Propulsion to Mars in 3 Days
« Reply #21 on: 03/01/2017 11:28 AM »
What spacecraft can stay intact and fucntional after a 15K g acceleration period?

Offline IRobot

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Re: Photonic Propulsion to Mars in 3 Days
« Reply #22 on: 03/01/2017 12:50 PM »
All of these mega projects (mega-laser, space elevator, etc) are doomed to fail because of initial investment cost and the huge risk of being technologically surpassed before they have return of investment.

The path forward is to use existing technology and cut down costs by organizational measures. Basically what SpaceX is doing and what others are starting to do (ULA, Arianespace, etc).

Of course, keeping an eye for technologies reaching a useful readiness level and that can be employed on small scale.

Offline jstrout

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Re: Photonic Propulsion to Mars in 3 Days
« Reply #23 on: 03/01/2017 01:40 PM »
It's 100 kg to Mars in three days; that corresponds to a speed of much less than 0.3c.  No mass is quoted for the probe to be accelerated to 0.3c.

In the , he says: "It takes us about 10 minutes to get to 30% of the speed of light.  ...We could propel a 100 kg craft to Mars in a few days."

It's this "10 minutes to get to 30% the speed of light" figure that I was reacting to.  Now it's possible the "3 days to Mars" is referring to a completely different flight profile (it's not even mentioned in the paper I could find), but from the juxtaposition in the video, it sure sounds to me like he's talking about the same thing.

Offline KelvinZero

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Re: Photonic Propulsion to Mars in 3 Days
« Reply #24 on: 03/02/2017 03:56 AM »
https://www.extremetech.com/computing/162322-mit-creates-the-first-perfect-mirror

Im not sure if that is actually perfect, but that is what would make the idea interesting to me. Light is about the most inefficient way of pushing something. If you had perfect mirrors it would be the perfect way of pushing something. You just have one mirror on a heavy object like the moon, the other on your vehicle, trap some photon energy between the mirrors and after billions of reflections it would pretty much all end up as kinetic energy on your vehicle.

If there is such a thing as a truely perfect mirror, you could also understand it not heating up.

Online john smith 19

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Re: Photonic Propulsion to Mars in 3 Days
« Reply #25 on: 03/22/2017 11:11 PM »
What spacecraft can stay intact and fucntional after a 15K g acceleration period?
Pretty much the same kind of tech that's used to developed GPS guided naval artillery shells at something like 15 000g's.

It's not impossible but it's not easy.
"Solids are a branch of fireworks, not rocketry. :-) :-) ", Henry Spencer 1/28/11  Averse to bold? You must be in marketing."It's all in the sequencing" K. Mattingly.  STS-Keeping most of the stakeholders happy most of the time.

Online MATTBLAK

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Re: Photonic Propulsion to Mars in 3 Days
« Reply #26 on: 03/22/2017 11:50 PM »
What spacecraft can stay intact and fucntional after a 15K g acceleration period?
Let alone the crew! Even accelerating at a constant 1/10th of a G or similar after achieving Earth escape would give outstanding performance to anywhere in the Solar System.
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Offline Proponent

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Re: Photonic Propulsion to Mars in 3 Days
« Reply #27 on: 03/23/2017 09:12 AM »
In the , he says: "It takes us about 10 minutes to get to 30% of the speed of light.  ...We could propel a 100 kg craft to Mars in a few days."

It's this "10 minutes to get to 30% the speed of light" figure that I was reacting to.  Now it's possible the "3 days to Mars" is referring to a completely different flight profile (it's not even mentioned in the paper I could find), but from the juxtaposition in the video, it sure sounds to me like he's talking about the same thing.

That is very confusing, but "30% of the speed of light"  and "3 days to Mars" have nothing to do with each other.  It takes light 8 minutes to cover 1 AU, so at 30% of the speed of light it would take about half an hour to cover 1 AU.  Even when Mars, about 1.5 AU from the sun, is on the opposite side of the sun, the travel time would be less than an hour and a half.
« Last Edit: 03/23/2017 09:15 AM by Proponent »

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