Getting into space isn’t easy, and for every proposal that has made it off the ground, there are more proposed solutions, false starts, and batshit crazy ideas that didn’t.

One of my favorites is a proposal currently in development of attempting to get an orbiter around Neptune with a propulsion system so incredible that it uses sunlight bouncing off of Venus as an autoclave. Read this description from reader shortyoh, who notes that he actually worked on this project, and you’ll see what I mean.

It has not made it off the ground yet, even 20+ years later - but they’re still talking about it.

So here’s the catch:

1) Boosters are expensive. The heavier your payload, the bigger the booster. You want as small a booster as possible.

2) The further you want to go, the more change in speed you’ll need, and the more fuel you’re going to need - fuel demand is exponential with your change in speed, so while a change of 5000 m/s might take 250 kg of fuel, a change of 10000 m/s might take 1000 kg of fuel. That’s a reason why payloads are expensive per pound - because for each pound of payload, you’re carrying a lot of fuel - and a lot of fuel simply to boost fuel up to speed, too.

3) Going to Neptune takes a lot of change in speed

4) The normal method for deep space, chemical thrusters with nuclear power, is unpopular because of cost and perceived danger.

5) Without nuclear, you need batteries or fuel cells (HEAVY = nope) or solar

6) At Neptune, you need 1000 square meters of solar cells to produce the same power as you get from 1 square meter at Earth. Even at Jupiter, you’re only about 15% of the way there, but your power production is already down over 96%.

Now solve the problem. Get to Neptune with solar power, even when there’s seemingly no solar power to be found.

And do it cheap.

The solution? We had (and most of the basic idea still stands) a gigantic inflatable solar mirror to concentrate the sun’s rays. You could even harden the thing so it wouldn’t be susceptible to damage. That was big, but cheap and compact for launch. It allowed us to use much smaller areas of solar cells (which are $$$$$$)... AND it allowed us to use very little power for data transmission (the sun and the earth are approximately in the same location when you get far enough away, and a mirror makes a pretty good antenna, too).

Then to get the whole thing there, we pulled in ion thrusters. Yes, they do exist. The nice thing is their specific impulse is MUCH higher than a chemical thruster, so you need less fuel mass. And since that’s exponential, there’s less mass still. All of a sudden, we were back to a bargain basement Delta II booster and the mission was affordable.

They just had to figure out how to get an ion thruster to last several years of constant use, because accelerating with one is kind of like trying to move a 747 with the engine out of a Peel P50.

And that’s not all! Here’s where Venus-as-a-heat-reflector comes in.

You want to know the real batshit crazy part? Our proposal didn’t have any radioisotopes - pure solar power with Xenon gas as the “propellant” for the ion thruster.

Without radioisotopes, our inflatable mirror was bigger. MUCH bigger. And here’s where it gets really crazy - one part I didn’t mention - to keep that inflated for years, we had to harden it. The proposed solution at the time? Make the inflatable structure out of a composite material, only without the resin. Inject the resin into the structure with the air you use to inflate it, and it will naturally permeate into the composite. But you still have to bake it. The proposal for that was that you set the trajectory the wrong freakin’ way from Neptune, and actually go in to Venus first. You use Venus for a gravity assist (which meant that the whole transit time was actually faster than trying to go straight out to Neptune), and as you get near to Venus, you inflate the structure and use the more intense heat from the sun plus the radiation coming off the surface of Venus as your autoclave (without Venus’ radiation, you risk uneven curing).

That, to me, really made the whole thing batshit crazy. I just wish I had been the one to think up that lunatic plan.

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That is completely and utterly bonkers.

But I’m sure that you’ve heard of an even more incredible space program that didn’t happen.

Note: I’m not talking about science fiction here. I’m talking about space programs proposed, developed, and researched by actual space organizations with an intention of trying them out.

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Leave your wildest proposal below.

Photo Credit: NASA (It’s always good when a map has an arrow pointing ‘To Neptune’ on it.)

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Contact the author at raphael@jalopnik.com.