Extreme metamaterial solar sails as proposed here have the potential to shift the paradigm of space exploration enabling numerous low cost and high-speed missions to be launched anytime and anywhere. Such sails could gain accelerations over 60AU/yr when coupled to low mass spacecraft and dive to extreme proximity to the sun (just 2-5 solar radii). This velocity is 20 times more than Voyager 1. This NIAC challenges the limits of materials, paving the way for the development of high endurance ultrathin film architectures that can handle extreme environments manifested by solar radiation and plasma in addition to providing spacecraft control. Our technology enables reaching Jupiter in 5 months, Neptune in 10, surpassing Voyager 1 in 2.5 years and getting to the solar gravity lens location in just 8.5 years.
Artur Davoyan has a NASA NIAC grant and presented at TVIW.
In 2018, Artur also co-wrote on the materials for laser pushed Starshot missions.
Brian Wang is a Futurist Thought Leader and a popular Science blogger with 1 million readers per month. His blog Nextbigfuture.com is ranked #1 Science News Blog. It covers many disruptive technology and trends including Space, Robotics, Artificial Intelligence, Medicine, Anti-aging Biotechnology, and Nanotechnology.
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Or you could always accelerate outwards away from the sun, and perform flyby maneuvers around planets or moons to alter course back inwards.
small space craft = small antenna = small gain with low power transmitter. How do we plan to communicate with these starshot missions with tiny vehicles when they reach Proxima Centauri? We communicate with Voyager using a 70m dish on the ground and 3.7m dish on the vehicle to get a whopping 160 bits/s data rate. Maybe use the sail as a reflector? There are a lot more problems to be solved if you don’t just want to sail a small brick out of the solar system.
Not so much for acceleration, but in continue turning the craft back to the sun at distances when other sources of light are stronger than it. If not enough, May be a dedicated E-sail can be used in conjunction as long as it doesn’t slow the space craft. Of course reaching minimal interstellar speeds (6000 km/s ?) will take decades.
Yes, if you have two sources of light you can bounce between them and do a bunch of interesting things.
But I don’t think we’ve even contemplated sails big enough to get noticeable acceleration from star light.
One thing my equation above does let us to is look at the results from other stars.
If total kinetic energy is 2k.r/(x.c) where r is the distance at which we get the same radiation intensity as Earth orbit, k is that intensity in 1/sq.m and x is the fraction of k that our sail can start at without melting.
Then a much bigger, much brighter star… say Rigel, which is 200 000 times brighter than Sol.
Then the value of k would be sqrt (200 000) times 1 AU = 447
All other constants stay the same, so you get 15 x 447
6700 MJ per sq. m
WHich is 21 times the velocity.
Hmm… I had to take the square root twice there. That’s not what I expected. I’ll redo this math later when I’m not late for a meeting.
Thank for your very good explanation. I wish I had more patience to delve into the math. You are assuming here a sail that is only depended on the Sun. What if you have a sail big enough to use light from outer space to turn the vehicle back to the sun and maybe collect extra velocity along the way from interstellar light and the sun gravity and in addition use the planets for an extra turn? Then you will be able to return to Sun vicinity as many times as you want and have enough time to explore the Solar system and beyond throughout. Indeed, in every round the acceleration that you gain will be smaller as your bypass will be faster and perhaps will take longer to reach back to the Sun, but you have time in your hand as for the time being you don’t have other choices. Once you reach 6000 km/s, you can reach Alpha Centauri in 200 years and after that you can start star hoping, gaining more speed at every “stop” and along the way.
Yeah, you can keep going in a circle, until your velocity gets too high. Once you are at the escape velocity of the solar gravitation, you are going to leave the solar system. Turning the sail will add some sideways velocity, but you can’t come back and get more velocity than one pass from the nearest point to the sun you can’t stand, out until the sunshine dies away.
It’s probably just the integral of the solar radiation intensity from start to infinity, multiplied by the area of the sail. That’s your maximum kinetic energy. Plus or minus some gravitational effects, but if we are looking at even 0.1% of C then the gravitational effects are trivial.
Force is radiation energy divided by the speed of light E/c
Radiation is just k/x^2 so the integral is just k/x.c
x2 for a reflection
k is the sunshine intensity at unit distance, so if we use AU we get k is 1500 W/sq.m
If we start at say… 0.1 AU, then the integral from 0.1 to infinity is 2x15000x1.5E11/c (the last bit to convert it to metres)
so 4.5E16/c or 15 MJ per square metre (assuming perfect sail, no losses)
A 1 gram per sq. m sail is therefore going to have
15 000 000 is 1/2 m v^2
v is 173 km/s
But the mass has no effect on the kinetic energy, that’s just 15 MJ/sq.m. Doesn’t matter if your sail is nanogram graphene or a tonne of steel. The tonne will be going much slower, and take much more time to accelerate, but the final kinetic energy is the same.
Directing the solar sail itself in an angle toward the sun that will keep the vehicle in Sun orbit?
Captions? Ah, because of that ridiculous accent?
Seriously, how do you pronounce lasers as “laysourrs”
You don’t.
You could definitely do some good old-fashioned gravity slingshot work around Jupiter to go back sunwards and get more energy.
But this only works at 10s of km per second at most. Once you get faster than that there is nothing in our solar system that has enough gravity to do a u-turn around.
Maybe there is an orbit that can keep it for than one circle around the sun and accelerate it to a higher speed.
Laser pulse fusion technology would be easier.
Seems like a boundary for thought experiment would be “something of a wash” condition of simple circular orbit with sail tilt of 45 deg, so vector slowing equals vector outwards, normal to each other. Total force will always be normal to sail. Question is whether the load approaches escape velocity *as* it slows to 0 angular v. If it is equal, which I will guess “true” as I am trying to get a gut feeling for this rather than *the Math*, it ends up motionless at an infinite distance. I’m going to announce this is independent of sail thrust/mass of load!? Given this set-up, the description of this process as “tacking” makes sense, as the sail has to be tilted more away from the light, so slowing is more than pushing away. This lessens the sail effective area, but gets the job done eventually, much like a sailboat squeezes against water to shoot somewhat into the wind. Again, won’t help interstellar, but the gravity/orbit balance is the main factor in asteroid mining, and can be manipulated with lightsails.
The low thrust has been known all along, and is dealt with by Drexler. It is certainly part of the trade off between time and expense. I tend to think in terms of ratios rather than absolute amounts, so am skeptical that a lightsail solution that would be best at one small size would not be better at larger sizes. Aerobraking works with mass brought in by either method, but may be easier to temporarily detach the lightsail than make the mass driver able to sustain the air, or detach. If no aerobrake, more advantage to lightsail, which will increase with delta-v and distance increase. Another notion is that a large O’Neill Settlement can hang motionless on light pressure anywhere *in* the Solar System up to 10 times the distance of Neptune, in any direction, and have plenty of energy collected too, with lightsail weighing 10% of total. But clearly, the market will look at each need. Another consideration would be to avoid comparing apples and cats as the mass driver solution may be far smaller than thought if it can go as slow, so to speak, as the lightsail. The idea of the Solar Wind particles being deflected with charged sheets may be better than both at these non-interstellar speeds. Fixed mass drivers and/or rotovators would soon be set up for moving a steady stream of materials. I wanna go!
Honestly, it’s probably because he is running low on subject matter. Only by virtue of how MUCH he covers and how often he does so[weekly].
Another problem with solar sails that GoatGuy hasn’t addressed is their very small thrust. You’d need really enourmous sails to move large masses in a reasonable amount of time. Remember that for asteroid mining, we’re talking about thousands to millions of tons of payload, per delivery. And time does matter when you’re dealing with commercial shipments.
For asteroid mining, you have a bunch of not-particularly-useful stuff that you can fling out the back. If you have an Isp in the 1000-10000 s range, the delivered mass fraction can be over 80% (even as high as 95%). You don’t need the 30 million s Isp of a solar sail. Remember that for any given power, the higher the Isp, the lower the thrust. So a solar-powered mass driver with an Isp of 3000 s would give you ~10000 times more thrust than a solar sail of the same size (neglecting conversion losses; more realistically, closer to x1000).
Lowering the delta-v with aerobreaking would enable a larger returned mass fraction with a lower Isp, but even just 1000 tons of payload would still have a kinetic energy equivalent to ~10 kiloton of TNT, so it’s easier to increase the Isp a little. But 30 million s is too high for this application.
And furthermore, just was thinking about an elliptical starting orbit, where the slow down should be easier as the object is heading inward.
I’m just recalling K. Eric Drexler’s description of how to drop an elephant leg into the Sun, using his simple aluminized nothing lightsail concept. And there is no hurry, just letting the Sun gravity work once the orbit is *stopped* will get the stuff here eventually. The sails will be reusable, so they are cheap, which is a big advantage. Solar system distances and delta-vs (deltas-v?) greatly favor a non reaction mass device. The sail can be completely turned *off*, so gravity will win eventually, slowly.
A drink and a snack
His early stuff. Especially the Fermi paradox work. His more recent work I’m not such a big fan of
Do you show down?
Sure, except think about your vectors… when a sail’s whole face is normal-to-Sol, then 100% of the radiation falling on it either goes straight thru, unimpeded, or is reflected directly back at Sol. Each watt reflected back becomes 2 W of propulsive energy.
However, for any angle not normal to Sol, the reflected beam portion heads off at an angle of 2θ, or twice the not-normal angle. The resulting vector tho’, has the single θ angle. There remains an anti-Sol component, an one tangential to that either prograde (in the direction of a circular orbit, say) ore retrograde, against that circular orbit’s direction.
Retrograde would slow down the vehicle, nominally. Slowing down would ease it toward Sol. However, the anti-Sol vector continues to accelerate the vehicle outward. I don’t have the time to do the math, but I think it could be something of a wash … in terms of getting closer to the inner planets’ orbits.
⋅-⋅-⋅ Just saying, ⋅-⋅-⋅
⋅-=≡ GoatGuy ✓ ≡=-⋅
Isaac Arthur is a gem of youtube
The gravity of Sol will pull inwards if the sail slows the orbit around the Sun. This is true of any light sail, but is slow compared to interstellar needs. More like a conveyor belt from mine to processing plant, once started, slower is not a big problem.
I don’t think the expense is an issue, as much as “won’t accelerate in any direction except a modest angle away from Sol”. Now, if the mined asteroid group were to be between us and Sol say … then they could be critically useful.
⋅-⋅-⋅ Just saying, ⋅-⋅-⋅
⋅-=≡ GoatGuy ✓ ≡=-⋅
Good call. i regularly rail about ”come-on-just-round-it!” math.
In reading, it appears to be “accelerates in close proximity to Sol to an outward drift velocity of over 60 AU/a”.
But yah, you’re right. Misguided terminology-for-the-uncritical-masses.
⋅-=≡ GoatGuy ✓ ≡=-⋅
If you were new, I would have advised you to grab a sandwich, something to drink and turn on the closed captions 😉
Physics Error.
Acceleration 60AU/year
should be either 60AU/year^2
or
accelerate to a “VELOCITY” of 60AU/year.
Acceleration is a square in the denominator i.e. 9.8 meters per second per second.
You can round that up to 0.001c (besides, they say greater than 60 AU/year), which is 0.1% of c. Exactly as stated in the title slide. Mind you, this is still about 20 times faster than the Voyagers and New Horizons.
Yes – you can say that again! Luckily I’ve been following him since the beginning – I can’t imagine the panic attacks and addition issues I’d have had if I just found him now!
Anyone unfamiliar with Isaac Arthur is in for a treat!
Are these too expensive for *normal* stuff like mineral transport from asteroids, where there is less hurry?
60AU / year is only 0.00094875 C. Hmm, this tech could be useful for moving stuff around the solar system until we set up the Interstellar Laser highway as proposed by Isaac Arthur. https://www.youtube.com/watch?v=oDR4AHYRmlk They can reach upwards of 10% C, or eventually get to our neighbouring stars in 40 years instead of over 4000 with these solar sails.