Laser Launch into Orbit
Another great resource for hypothetical space stuffs (with math!) is Atomic Rockets / Project Rho, here's some of their articles on laser propulsion: https://www.projectrho.com/public_html/rocket/enginelist.php
Electric propulsion using high power laser beaming makes way more sense outside the atmosphere for non-launch use cases, where thrust requirements to achieve desired delta-V usually aren't measured in kN and the mission longevity implied by higher Isp matters so much more and there isn't a pesky atmosphere in the way of power beaming or any concern about accidentally ablating airliners.
Numerous startups are tackling the power beaming issue with relatively short timelines and in some cases a lot of funding, but the scale of what's actually been publicly demonstrated with lasers is unimpressive...
I think they’ll have a hard time pushing that much energy through the atmosphere without striking a plasma. Indeed, at least one of the concepts relies on striking a plasma in atmospheric gas by reflecting and focusing the incident radiation.
Laser retro-propulsion seems interesting for landing space-mined materials on earth. The obvious (to me) way to do that is to wrap the mined material in a vague lifting-body shape of metal or maybe just slag, thick enough that after it ablates away there's still enough to be economical (to be clear there's at least a couple major options: high value payload wrapped in low-value vehicle, or big aerodynamic blob of low-mid value material, with more options in between). But if you have a big laser you can shine at it to slow it down, maybe you could get away with a lot less sacrificial material.
>Using a 700 Isp laser-thermal engine on the lower stage of a 50 ton rocket requires more than 2 GW of laser power to lift off the launch pad. Accounting for inefficiencies, between 5.5 and 18GW of electrical power has to be fed to the launch facility.
Oh that's all?
And you're going to avoid having to spend $600 billion on the equivalent of four Ōi Nuclear Power Plants by wishing a practically impossible flywheel proposed as an exercise in engineering optimism over 30 years ago into existence?
Sweet!
To put less than the payload of a single Falcon Heavy into space?
Why build one when you can have two at twice the price!
edit: forgot the 90s were 30 years ago.....
Cool ideas. Unclear how practical any of it is (how many gigawatts is that laser producing?) but cool nonetheless. Perhaps this kind of research will be driven be the value of the space industry, which is rapidly proving itself to consumers.
> Naturally, a rocket going into space cannot carry along an electrical wire to the ground to deliver energy.
I’ve been wondering about this actually. (Please keep an open mind if responding)
In theory if we used a high enough voltage. Possibly in the megavolt range we could have a very lightweight wire. And if we could turn that directly into heat on the rocket without even needed equipment to step it down.
I don’t see why we couldn’t have long wires. At least 20 miles and use it as a low speed first stage.
About 20 years ago, I briefly considered what it would take to use heliostats focussed on a heat exchanger to the same effect.
The mistake I made then was thinking fuel was expensive, so I assumed similar performance to existing rockets as if I was using it to superheat cheap water to the combustion temperature of hydrogen-oxygen — the problem with this being that it's pumping the equivalent of the entire electrical power demand of the United Kingdom into an engine the size of a truck for 6 minutes without it exploding.
(Similarly, it's possible to push against Earth's magnetic field but if you use copper the resistive losses will vaporise you launch vehicle. And you can make a much stronger artificial field on the ground, but the way magnetic fields reduce with distance means the current loop on the ground has to be significantly larger than CERN's LHC).
> Fibre lasers, where hundreds of tiny beams are joined through optical fibres into a larger beam
I'm no laser expert, but this doesn't seem right to me.
I'm still surprised no billionaire has latched onto this as their passion project.
This book outlined a whole space colonization effort from soup to nuts:
RIP Jordin Kare.
An extended family member worked on using lasers to launch payloads to orbits. [0]
Here's a quick video demonstrating the technology, using lasers to lift a small prototype several meters, back in, what I believe is the 90s: https://www.youtube.com/watch?v=i81f3LifpWY
[0] https://en.wikipedia.org/wiki/Leik_Myrabo