How to make space exploration profitable.

[gomipile]

You need to slow them down a *lot*. To get from Mars orbit down to Earth orbit requires about 2.9km/s delta-V, and that just gets the asteroid to Earth--you need to do another manoeuvre once it gets there in order to capture it, else it'll just swing right back out to Mars again. Anything beyond Mars orbit (e.g. most asteroids) will take more delta-V than that.

As far as the engineering goes, that's not a problem because Earth has an atmosphere to use for aerobraking. However, I admit that aiming an asteroid within 100 km of Earth at solar orbital speeds might present some public relations challenges.

[halfeye]

But they need to be positively huge to have an impact on anything happen, and they get the most traction moving away from the sun. I guess you could drag one behind an asteroid like a drag parachute, tipping it slightly towards the sun, pulling outwards to slow down, but it's going to take a while. Fuel cost for that stage is minimal, I'm just unsure of all other costs.

There's a thing called tacking, sailors do it all the time. The thrust from a light sail is quite small, but it's continuous, which is a huge difference, once they're off Earth, most rockets burn for seconds, minutes tops, I don't think any rocket has ever burned contiuously for an hour, there just isn't enough fuel to do that.

[Kato]

Not sure how serious you are..
I mean, sure, you can just drop it anywhere on Earth / we're pretty good at orbital calculations by now but if you want to do this in a way that gets you profit and not a massive lawsuit you don't want to play space billard from the asteroid belt to here.
I cannot provide any numbers but I think 'slowing it down and dropping it towards Earth' is WAY harder than it sounds.

What do you think is the profit margin for cleaning up space junk in leo?

[halfeye]

Not sure how serious you are..

Personally, I am very sure that light sails are the propulsion of the future, at least within solar systems, it's free acceleration. I am pretty sure space mining is a bust, I don't think it's going to be profitable.

I mean, sure, you can just drop it anywhere on Earth / we're pretty good at orbital calculations by now but if you want to do this in a way that gets you profit and not a massive lawsuit you don't want to play space billard from the asteroid belt to here.
I cannot provide any numbers but I think 'slowing it down and dropping it towards Earth' is WAY harder than it sounds.

It's not going to be easy, but with lightsails it's not impossible. Even with lightsails I don't think it will be profitable.

What do you think is the profit margin for cleaning up space junk in leo?

At this point negative, it's a cost. If someone put up a big enough bounty it would be doable, but at this point it would purely be a cost.

[wumpus]

People keep saying it's difficult to move asteroids to Earth. It's not trivial, but it's a lot easier than people seem to think, the Earth is in the plane of the Ecliptic, and so, approximately, are the asteriods. The asteroids are in higher orbits, so you need to slow them down a bit, but then if you get it right, they will just drop down towards Earth's orbit, and if you hold them in a slightly higher orbit until the Earth comes by, then you can drop them into an orbit near Earth, and then catching them is a matter of getting the approach right. I think we really ought to avoid anything Chicxulub big while we're practicing.

For propulsion I favour solar sails myself, They're as near to a free lunch as we're going to get.

My point (ion or sails) is not that it is difficult (or particularly expensive to launch a craft capable of doing so), just that it is *slow*. And as long as time is money, slow is expensive.

There's a thing called tacking, sailors do it all the time. The thrust from a light sail is quite small, but it's continuous, which is a huge difference, once they're off Earth, most rockets burn for seconds, minutes tops, I don't think any rocket has ever burned contiuously for an hour, there just isn't enough fuel to do that.

Only if you claim that ion propulsion is "not a rocket". NASA's Dawn probe fired its ion drive for months at a time (it had to, the thing has next to zero thrust) and had a total delta-v of 11km/s (*after* being launched past escape velocity [~12km/s]. That's essentially impossible for a chemical rocket). I think the motor was tested for *years* of continuous use.

[gomipile]

Personally, I am very sure that light sails are the propulsion of the future, at least within solar systems, it's free acceleration.

Not entirely free. There is the cost of maintaining/replacing the sail. Hopefully lightsails will be as good of a deal as sailing with the wind on our oceans is. As long as you don't care too much about speed, they'd be the cheapest way to get around.

[halfeye]

My point (ion or sails) is not that it is difficult (or particularly expensive to launch a craft capable of doing so), just that it is *slow*. And as long as time is money, slow is expensive.

Ships motor across the oceans slowly, but they're the preferred way of transporting most goods.

Only if you claim that ion propulsion is "not a rocket". NASA's Dawn probe fired its ion drive for months at a time (it had to, the thing has next to zero thrust) and had a total delta-v of 11km/s (*after* being launched past escape velocity [~12km/s]. That's essentially impossible for a chemical rocket). I think the motor was tested for *years* of continuous use.

If I'd heard about that (entirely possible) I'd forgotten. I would hope that light sails could do better than that.

Not entirely free. There is the cost of maintaining/replacing the sail. Hopefully lightsails will be as good of a deal as sailing with the wind on our oceans is. As long as you don't care too much about speed, they'd be the cheapest way to get around.

No, you're right, you do have to pay for the sails, as is usual for sails.

[factotum]

Ships motor across the oceans slowly, but they're the preferred way of transporting most goods.

"Slowly" is relative here. Even the slowest freighter would be able to go entirely round the world in two or three months. It would take decades to perform all the manoeuvres needed to move your asteroid around using a light sail. Oh, and also, ships are only preferred for transporting goods because of money, again--you *could* transport the same cargo by air as you send by ship, but you'd have to send thousands of planes where a single ship could do the job, so the ship is the cheaper option even though it's slower.

[Lvl 2 Expert]

Or, in historic context: investors in European sailing ships to Asia had to wait up to about 7 years for their profits. One year there, one back, five in between to do some local runs to pump up the profits. It wasn't a particularly great investment because of both this delay and the risk, which is why when the volume of trade became large enough traders started companies, so people could invest in just sort of the average results. I'd say seven years is a good benchmark for our puroses. Plenty people with lots of money to invest will figure they have more than seven years to live. If the expected payout is good enough it's worth it. If it takes three times as long it gets seriously questionable.

[Fat Rooster]

Maybe more recent context is worth considering too. The value of significant dot com business is astounding, and sometimes they are floated having not ever returned a profit.


Markets are not scared of long term investments, even risky ones. The value of an investment is determined by the returns compared to other investments, and they are surprisingly low. Investors dying before it matures is not as much of a problem as you might think, because the value of their investment will have been increasing as it got closer to maturity. They can cash that in any time.

An interesting thing happens when we consider the viability of metal return missions. Metals like platinum, iridium, and gold are investments in their own right, and operate in the same market as all other investments. We can directly compare the cost of a mission to return some metals to a future option on those metals to see whether it is viable, because market effects cancel. That would give a figure of about $300-$400 million for a 10 ton return mission of those 3 metals over any timescale.

[wumpus]

Not sure how serious you are..
I mean, sure, you can just drop it anywhere on Earth / we're pretty good at orbital calculations by now but if you want to do this in a way that gets you profit and not a massive lawsuit you don't want to play space billard from the asteroid belt to here.
I cannot provide any numbers but I think 'slowing it down and dropping it towards Earth' is WAY harder than it sounds.

What do you think is the profit margin for cleaning up space junk in leo?

It also requires you to know exactly what the weight and outer envelope of the returning vehicle. Constructing this (especially assuming that the exterior presumably comes from Earth) would almost certainly kill your profits. I'd assume that you would shave the asteroid until it was the shape you wanted (possibly with some ballast corrections) and then send it off to land in the Outback, Mohave, or similar.

Ships motor across the oceans slowly, but they're the preferred way of transporting most goods.

If I'd heard about that (entirely possible) I'd forgotten. I would hope that light sails could do better than that.

No, you're right, you do have to pay for the sails, as is usual for sails.

Sails still exist, but few people are outfitting container ships with sails (although modern "sails" have been researched in the last few decades). Granted, the fuel they do use can be really nasty.

[LordEntrails]

An interesting thing happens when we consider the viability of metal return missions. Metals like platinum, iridium, and gold are investments in their own right, and operate in the same market as all other investments. We can directly compare the cost of a mission to return some metals to a future option on those metals to see whether it is viable, because market effects cancel. That would give a figure of about $300-$400 million for a 10 ton return mission of those 3 metals over any timescale.

So since we know launch costs are $60-100 million, and vehicle development is easily upwards of $200 million (and more likely a non-orbital launch and deep space craft with return capabilities is more likely in the $1-2 billion range), at least for the foreseeable future it is not economically viable.