Design of a rapid transit to Mars mission using laser-thermal propulsion • Hacker News Board

Re: Design of a rapid transit to Mars mission using laser-thermal propulsion

#91

Post by Valgrim » Thu, Feb 17, 2022, 6:51 PM UTC

bdamm wrote: post #6

We must go to Mars, if only to convince people on Earth that there really is no second planet.

As far as we know, humanity is the only example of the universe becoming aware of itself.

As far as we know, there isn't / hasn't / won't be anybody else out there, ever.

Until we know better, any other presumption must be rejected as wishful thinking.

What we DO know is that the conditions that can support life (and consciousness) on Earth rely on an incredibly fragile balance, especially on cosmic timescales.

Maybe there's no second planet like earth, but we have a lot to learn if we are to prevent the absolute extermination of consciousness in the universe, so we better get on with it, and fast.

Sure we may debate on how we try to achieve this: should we get on the Moon, on Mars, in space habitats, make earth resistant to cosmic catastrophes, transfer our consciousness into computers or teach machines to become conscious in our place?

But debating this is actually moot. Billions of people. Massive parallelism. We've been working on all those fronts now for decades, and there's progress.

Right now, a company making cheap steel rockets is on it's way to crack cheap space travel. That's a pretty good step for all humanity, in my opinion.

Re: Design of a rapid transit to Mars mission using laser-thermal propulsion

#92

Post by nine_k » Thu, Feb 17, 2022, 6:52 PM UTC

revicon wrote: post #18

bbojan wrote: post #5

Earlier quoted context omitted.

The Moon has very little hydrogen, carbon and nitrogen, which Mars has in abundance. These are very important elements both for biology and chemistry. E.g. if you want to have a self-sufficient colony outside Earth, you could do it on Mars but not on the Moon. Mars could be terraformed (in theory); the Moon never could.

With no magnetosphere would there even be a point to terraforming?

A strategically placed powerful magnet outside Mars can protect from the solar wind. There is an orbit that places the orbiting body always on the line between Mars and Sun. Place a superconducting magnet there that generates a few Tesla. Due to the distance from the planet, even though the magnet will deflect more distant particles to relatively small angles, this should still be enough to keep Mars completely in the "shadow".

Of course you'll have to and solar-powered thrusters to keep it on the orbit, and fly regular missions to replenish fuel in the ion drives. But thil looks doable even with today's level of technology, given enough money.

Re: Design of a rapid transit to Mars mission using laser-thermal propulsion

#93

Post by signatoremo » Thu, Feb 17, 2022, 6:53 PM UTC

gambiting wrote: post #47

dahfizz wrote: post #31

Earlier quoted context omitted.

Why did Homo Erectus leave Africa? Why did early humans cross the land bring into the Americas? What could have possibly possessed the aborigines to cross the ocean to Australia? Because its cool. Because its interesting. Because it is baked into our monkey brains to want to explore. If people want to push the frontier, why are you such a grump about it?

I'm positively certain that in all of your examples people have pushed into new areas because of food, to find new land to live on, to find riches, to find the promised land or other mythological reasons. Somehow I don't imagine aborigines crossing the ocean because "it's cool". You know what we're going to find on Mars? Rocks. A whole lot of radiation. No breathable atmosphere and freezing temperatures. Imagine the…

> I'm positively certain that in all of your examples people have pushed into new areas because of food, to find new land to live on, to find riches, to find the promised land or other mythological reasons

First of all, you can’t be positively certain of those. We don’t have access to the reasoning of why the Vikings decided to cross the Artic to America, or Polynesians crossing the Pacific.

Second of all, let’s say they did go to look for food. Are you sure they ran out of land to grow food, or forest for hunting that they had to look for new land? The answer is quite resounding no. Likewise, we don’t have to exhaust all of the resource on Earth before exploring other planets.

Finally, what were those mythological reasons you listed there, if not the desire of human being to explore?

Re: Design of a rapid transit to Mars mission using laser-thermal propulsion

#94

Post by nine_k » Thu, Feb 17, 2022, 6:58 PM UTC

kitsunesoba wrote: post #81

jmyeet wrote: post #2

Sure let's continue unmanned exploration of Mars but manned exploration let alone colonization makes absolutely zero sense. mars is nothing more than a further, more annoying version of the Moon. Similar gravity, less sunlight (ie further from the Sun), communication latency (~10 minutes vs 1.5 seconds), no magnetosphere (just like the Moon so you'll probably need to live underground) and just enough atmosphere to pr…

> mars is nothing more than a further, more annoying version of the Moon. I would say the opposite. Compared to the Moon, Mars has: - A day-night cycle more suited to humans that’s nearly identical to that of Earth (Moon colonies will need to be in polar areas to avoid long stretches of no sunlight) - A more temperate climate with less dramatic temperature swings - Gravity likely high enough for most processes and ma…

Another downside of Mars is its having relatively less sunlight. You'll need quite significantly more solar panels to harvest enough power.

Even if Mars has enough uranium and thorium, it'll be quite a long time before mining and enriching it would be locally possible so as to power a nuclear reactor. Local production of solar panels looks a bit more feasible.

Re: Design of a rapid transit to Mars mission using laser-thermal propulsion

#95

Post by signatoremo » Thu, Feb 17, 2022, 6:58 PM UTC

gambiting wrote: post #49

ericmay wrote: post #29

Earlier quoted context omitted.

Why do anything?

This is a very flippant comment, but I will try to respond anyway - we simply haven't achieved a post scarcity society yet. Maybe we will at some point, but we just aren't there yet. So right now our time, money and natural resources are quite simply limited. So maybe it's not that we shouldn't have a base on Mars - it's just that maybe that shouldn't be the first step in human habitation in space.

How long do you think until we can set up a base on Mars? Let alone other planets in the Solar system? 50 years, 100 years at the very least. If we don’t get started now, when will be the right time?

We flew to the Moon 50 years ago, logically there would have been human on Mars by now. That didn’t happen, so the next best time is as soon as possible. Like now.

As for limited resources, how much money do you think we spend for space exploration? We waste a lot more money and resource for other things. We should cut down those instead. Let’s take a trivial example. Do you think gaming is a waste of resource? Why don’t we cut down gaming?

Re: Design of a rapid transit to Mars mission using laser-thermal propulsion

#96

Post by nine_k » Thu, Feb 17, 2022, 7:06 PM UTC

revicon wrote: post #85

I haven't seen it mentioned in this thread, but a much easier place to colonize is the atmosphere of Venus. There's a band of altitude in Venus's atmosphere where it's equal pressure to earth and you'd be able to get out and walk around with a simple oxygen mask. Huge blimps could suspend colonies in this zone (think Bespin from Star Wars). Interesting stuff, more info: https://bigthink.com/hard-science/how-to-coloni…

Depending on what you mean by "colonize".

To place a permanent habitat that depends on all solids to be delivered from Earth, certainly.

To build something that can grow and develop based on local materials, hardly,

I'd say that the most interesting idea would be to grow single-celled organisms which would be able to proliferate in the Venusian atmosphere at these altitudes, completely airborne, and form large reflective clouds to help cool down the planet. Or maybe, help condensate the existing clouds and render the atmosphere transparent, again cooling down the planet.

Re: Design of a rapid transit to Mars mission using laser-thermal propulsion

#97

Post by ben_w » Thu, Feb 17, 2022, 7:09 PM UTC

0_____0 wrote: post #90

ben_w wrote: post #46

Earlier quoted context omitted.

Nuking the core is neither sufficient nor necessary for the magnetosphere. Not sufficient because all of the nukes together are orders of magnitude too little to melt it, not necessary because a spinning ball of liquid metal is a really inefficient way to make a magnet. IIRC one of the plans for an artificial magnetosphere for Mars only needed a 1 GW supply to the magnetic coil.

The core nuking thing I pulled out of my ass but I guess it sounds serious given a sufficiently fantastical context. Doing a little more reading I came across the superconducting latitudinal "wrap the planet in a solenoid" thing, as well as magnets at L1 etc. I guess that's possible, but that's more of a 2000-years-out sort of set of ideas. There's a philosophical debate to be had about how far out humans should be t…

> 2000-years-out sort of set of ideas.

Nah, if we really cared we could do either in like a decade or two depending on the Starship timeline.

> If you build for tomorrow, you solve yesterday's problems. If you build for the next millenium, you solve nobody's problems.

Essentially agree; this is why I don’t buy into longtermism: https://kitsunesoftware.wordpress.com/2020/01/08/morality-th...

Re: Design of a rapid transit to Mars mission using laser-thermal propulsion

#98

Post by nine_k » Thu, Feb 17, 2022, 7:14 PM UTC

Let's not discuss our choice of nearby planets but the paper. It offers:

- A light-powered inflatable jet engine with an impressive Isp of 3000 s.

- A reusable acceleration block which is laser-powered relatively close to Earth, and then can return back to LEO and attach to another spacecraft.

- A way to shoot missions to other destinations using the same tech.

- An extreme aerobraking maneuver at Mars, because the acceleration block is not available for slowing down.

- A colossal 100 MW laser array on Earth, and the perils of atmosphere compensation. I hope in the future such an array would rather belong to LEO and be solar-powered.

Re: Design of a rapid transit to Mars mission using laser-thermal propulsion

#99

Post by gambiting » Thu, Feb 17, 2022, 7:18 PM UTC

signatoremo wrote: post #95

gambiting wrote: post #49

Earlier quoted context omitted.

This is a very flippant comment, but I will try to respond anyway - we simply haven't achieved a post scarcity society yet. Maybe we will at some point, but we just aren't there yet. So right now our time, money and natural resources are quite simply limited. So maybe it's not that we shouldn't have a base on Mars - it's just that maybe that shouldn't be the first step in human habitation in space.

How long do you think until we can set up a base on Mars? Let alone other planets in the Solar system? 50 years, 100 years at the very least. If we don’t get started now, when will be the right time? We flew to the Moon 50 years ago, logically there would have been human on Mars by now. That didn’t happen, so the next best time is as soon as possible. Like now. As for limited resources, how much money do you think we…

That's not my point, I think either I didn't explain myself properly or people are missing it. What I want to say is that currently we have very limited resources(on the planetary scale) - no we don't have to wait for post scarcity to try, but I just don't understand why we're trying for Mars first instead of the moon, which is simply more achievable, cheaper, and fulfils all the goals of getting kids and adults excited about science again.

Re: Design of a rapid transit to Mars mission using laser-thermal propulsion

#100

Post by 0_____0 » Thu, Feb 17, 2022, 7:23 PM UTC

ben_w wrote: post #97

0_____0 wrote: post #90

Earlier quoted context omitted.

The core nuking thing I pulled out of my ass but I guess it sounds serious given a sufficiently fantastical context. Doing a little more reading I came across the superconducting latitudinal "wrap the planet in a solenoid" thing, as well as magnets at L1 etc. I guess that's possible, but that's more of a 2000-years-out sort of set of ideas. There's a philosophical debate to be had about how far out humans should be t…

> 2000-years-out sort of set of ideas. Nah, if we really cared we could do either in like a decade or two depending on the Starship timeline. > If you build for tomorrow, you solve yesterday's problems. If you build for the next millenium, you solve nobody's problems. Essentially agree; this is why I don’t buy into longtermism: https://kitsunesoftware.wordpress.com/2020/01/08/morality-th...

If our species declared Total War Against The Lack of a Martian Magnetosphere, I could see that happening. However, that implies that our species are in a state of development and coordination that would largely obviate the existential need to create a "Planet B" as people imagine it.

Thanks for the link to the blog post, I enjoyed it.