Take a very light object, propel it with a laser source on Earth at a constant acceleration.

Can this object reach the Moon?

Could this be more reliable than a rocket? (supposing solar panel energy to power the laser.)

Yea the idea its use a constant thrust to get out the LEO and go on the the nearest corpus, and not accelerate to get escape velocity...

  • $\begingroup$ Reach the moon? Absolutely! Soft land it on? Not likely... $\endgroup$
    – PearsonArtPhoto
    Jun 9 '16 at 13:17
  • $\begingroup$ but what if stop accelerating it near moon? or put jet breaks in it? This could be more reliable than a rocket? $\endgroup$ Jun 9 '16 at 13:30
  • $\begingroup$ Momentum by a photon = hv, where h is the planks constant and 'v' is the frequency. this would be the base of further calculations that would include size of sail, mass of object, gravitational pull. $\endgroup$
    – Infi
    Jun 9 '16 at 14:03
  • $\begingroup$ Google laser propulsion. $\endgroup$
    – kim holder
    Jun 9 '16 at 14:04
  • 1
    $\begingroup$ More economical? No, at least not now. You need GW of power to run a laser capable of propelling a spacecraft at reasonable speeds, that's a million times more power than the ISS (largest orbiting object at the moment) has available. $\endgroup$
    – Hobbes
    Jun 10 '16 at 7:56

Theoretically it is possible to launch a spacecraft using a laser. In practice this is very hard to do and the technology is nowhere near being able to launch anything.

The problem you will have getting a very light spacecraft to the moon is gravity. You have to escape Earth's gravity and then negate the effects of the moon's. When you go to the moon from the Earth there is a point where the gravitational forces are exactly the same, called the neutral point. Once past the neutral point the moon's gravity is stronger and your probe will get pulled into the moon, and if you don't have some sort of propulsion to slow it down it will be drawn in faster and faster and impact on the moon.

If a very light spacecraft means no propulsion system then it's going to and make its own crater on the surface.

  • $\begingroup$ or we can let it in the neutral point wayting the outher parts of the craft... $\endgroup$ Jun 13 '16 at 14:18

I think by "Can this object reach the Moon?" you are asking the wrong question. In order for something to reach a given destination the only parameters are its velocity and the distance. Even something traveling only at 1mm/s could reach the moon eventually (or any other target in that matter).

However, if you look for example at the LightSail project from the Planetary Society, they are using the momentum of the photons that are coming from the sun. This gives them a rather "low" acceleration of a few mm*s^(-2) but since they don't need any propelant (or fuel) they can accelerate basically for an infinite amount of time, allowing them to reach much higher velociities (given enough time) than rockets relaying on some kind of fuel.

This makes something like the LightSail a very good alternative to rockets when you try to reach object further away, since a rocket would need a lot of fuel, while the light sail does not need any. However, for close targets like the moon, a rocket would be much faster and probably also more ecnomic.

With a laser stationed on earth you can increase the acceleration of the satelite that has a light sail by quite a bunch and therefor make it even a more viable alternative to classic rocket propulsion. But still for close targets like the moon rockets will probably be the best tech to go for in the near future.

Note that also the Starshot project plans on using lightsails with a stationary laser station on earth to accelerate their light sails to around 20% of light speed, with that we could reach alpha centauri in around 20 years, or pluto in only around a day!

  • $\begingroup$ the idea is if it is possible take off earth with it $\endgroup$ Jun 10 '16 at 14:33
  • $\begingroup$ No, that would be impossible (at least with current technology). The thing is in order to accelerate something with light, it needs a very low mass and a huge light sail. That is very bad aerodynamically speaking. Not to mention the air resistance would rip the sails apart at the speeds an object needs to achieve when on an escape trajectory. LightSails are only designed for environments without atmosphere. $\endgroup$
    – RononDex
    Jun 11 '16 at 8:27
  • $\begingroup$ yea but my question is that. I need a escape trajectory? I know this is not economic but if I can why not just propel it in a constante speed up util it get out earth gravit field? $\endgroup$ Jun 13 '16 at 14:17
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    $\begingroup$ if you launch it with a constant speed, that speed will get slower because the gravity pulls it down. What you probably mean is a constant acceleration? You will at least need to have a force of F = m * g upwards to keep it from falling backwards to earth. If you manage to increase that force it will eventually reach space yes, but that is extremely impractical $\endgroup$
    – RononDex
    Jun 13 '16 at 14:40

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