Iâd like to point out a fatal flaw in saying launching gold is not worth the money: you donât have to LAUNCH gold, you just have to return it. If you can harvest enough gold to pay for the equipment and the launch of said equipment, thatâd be what you need.
Edit: SpaceX Dragon can return 3,000kg, which comes out to about 123m USD, if Google didnât lie to me about goldâs value per kg.
Edit 2: Since the mining/refinement equipment wonât have to return, I wonder how many empty dragons could be launched simultaneously. Or, more likely, a custom built rig to return even more each time.
[quote=âRed_Syns, post:793, topic:445â]
Iâd like to point out a fatal flaw in saying launching gold is not worth the money: you donât have to LAUNCH gold, you just have to return it.[/quote]
Ignoring the issues of getting the mining and refining gear to the asteroid in the first place, and ignoring the need to automate the entire process, the return vehicle needs to get to the asteroid. It needs fuel to get there and fuel to stop and fuel to get back. As soon as you do that, the costs explode. Each lot of fuel is cargo for the trip that gets the return vehicle wherever itâs going. DeltaV to chase down the asteroid, deltaV to stop at the asteroid, deltaV to return to Earth. Atmosphere to stop at Earth - whew. The resulting rocket launch would be the size of a Saturn V. Just for one return. That means that youâre effectively launching the gold; its mass is trivial compared to that required for fuel.
However, if you can mine and refine fuel at the same asteroid, then youâve eliminated the need to send return fuel. But a metallic asteroid isnât likely to also contain useful volumes of volatiles. So youâve got to mine another asteroid to provide fuel for the return vehicles.
On top of that, if you can make return vehicles at the asteroid, then youâve got a huge win, but youâve got to include automated fabrication in the machinery that you send out to the mining asteroid (youâll still have consumables like parachutes and electronics, but theyâll be dramatically lower mass than entire fueled capsules). Perhaps you just fabricate a simple shell of nickel-iron that ablates as the unit reenters the atmosphere. For all I know, the capsule can use that heat to smelt the ore being deorbited.
Ultimately, the costs of doing industrial scale asteroid mining are so high, and the technology is so unknown at this point that weâre not going to see anything serious for at least another 50 years. What we may see is some significant samples returned by commercial companies that will sell those as extremely-high-end vanity items. How about a gold ring set for a married couple that came from the famous asteroid that is the only asteroid ever to be mined? Only $1,000,000. Those rings would be as famous as the Hope Diamond.
I maintain that the most cost-effective solution for asteroid mining (with Earth as a destination, instead of, say, ISRU or space-to-space industry) is to simply break it in smaller and somewhat shield-shaped chunks, maybe heat them up a bit to harden them, and simply drop them somewhere in a desert for further mining.
I mean, what could possibly go wrong?
A space elevator would be ideal for not only ship building but returning material from space, especially gold. 
SeeâŚwe did go to the moon.
take my hand Zen we fly together.
Iâve actually considered the same thing, considering that smaller pieces could be dropped in relatively risk-free. I assume bigger = more cost efficient, so itâd be a matter of figuring out how large you could go without causing huge problems, especially if you had a large lake (artificial or not) to target.
While thatâs true, you have to launch the equipment to gather it and return it first. That still has a cost and currently they are prohibitly enormous.
Let me give you an example: 123m is what you get back in gold. Letâs assume Falcon 9+ dragon can rendezvous with an asteroid(it canât). Falcon 9 costs 60 mil and some change to launch. That leaves 60 mil to manufacture a never before tested mining method that can remotely and autonomously extract and store ore. All of this has to weigh practically nothing due to the fact that once dragon is fully laden it will need to deorbit itself.
Performing a quick bit o math with a 4 ton dragon + 3 tons o goldâŚahh we need to decide on an engine. The f9 second stage which canât operate beyond GEO, or dragon 2 hypergolic superdracos.
The first had a vacuum ISP of like 320 I think, the later is around 280.
Lastly, we need to know how much dV we need to deorbit. Iâm going to assume our craft is on Earth escape which requires about(bit more) 3km/s of dv from Leo. For simplicity well stick with 3.
With that, you can solve for the amount of fuel needed to deorbit
DV = gISPln(m0/m1)
We need to solve for m0 - m1 to find the amount of propellant necessary. Iâm on mobile so this really sucks.
Dv=3000
G=9.81
ISP= 320 or 280
M0 = 7
So solve for m1 and subtract 7 and thatâs it. Iâd wager itâs a fair bit of propellent that isnât possible to store on the dragon alone, and that the second stage canât have in reserve(if it could make it that).I wanted to go through this math to show its not as simple as picking a vehicle and say letâs try this. The physics of this are hard to begin with and economics make it even harder.
The point Iâm trying to make is that using any current tech itâs not economically feasible because not only do the craft to actually mine not exist, the cost of launching with current pricing isnât profitable. Thereâs no way you can mine 3 tons of gold and return for less than 120 million, right now.
Not only that once youâve launched something into orbit, itâs more valuable staying there. Leaving the gravity well is the most expensive thing humanity can spend itâs resources on. If Earth were a bit larger, the atmosphere a bit thicker, it would be nearly impossible to reach orbit without highly efficient engines(think nuclear or antimatter).
To expand on my original point in another post about the economics of a Martian colony, now youâre leaving two gravity Wells. Itâs not going to be profitable. Peroid. Not for a long time because costs must drop.
This isnât a business venture itâs a charity case to ensure the survival of humanity.
To reply to others, I read the responses yesterday but I remember agreeing with JB and thinking he has the right ideaâŚwhatever it was.
Thereâs a reason this stuff hasnât been done. Itâs hard and expensive. Any other combination and it would have been done already.
Edit: reread the other posts, I pretty much reiterated with scattered thoughts what JB said.
Double edit: I realized I never summarized the AMA and Iâll get to that tomorrow when I get home.
'Course, that all assumes a mission would need to take the fuel to get back with it when mining from asteroids; and that the initial investment in infrastructure wouldnât continue generating income past its first delivery. Spacecraft tend to be mobile. Why stop at one asteroid when it could mine several?
Iâve read this a few times and Iâm afraid I still donât understand*. Are you saying you donât need fuel to get around? Without fuel youâre going nowhere.
*before morning coffee
Edit: Post coffee:
Iâm still confused, but maybe weâre starting with different initial conditions. Iâm thinking about the near future. What could be possible with current launchers and the ones slated to to launch soon⢠as well as the technology thatâs available to us. This means that the spacecraft we do have or can manufacture is pretty well understood and we have no exotic forms of propulsion so we still bow to the tyranny of the rocket equation. Barring use of massive spacecraft that make use of their sheer size to get around it(which is a double edged sword and still cannot be even be manufactured let alone launched) I just donât see it happening in the near term <40-50 years. (Speculation)This is about the time it will optimistically take, assuming a successful initial Mars colony, for the forcing function of a colony to start returning the first big technological improvements in space travel.
Iâve mentioned it earlier, this is not feasible or economical until we have a radical shift in paradigm of space travel. Iâm not saying it wonât happen because I know it will, but I have a feeling the method we choose to mine asteroids will be different than anything we can speculate here because we donât have the political will or technology available to us that we will in 50 years. We can armchair spacecraft using current restrictions and armchair debate them to the death and how they could perform but ultimately arenât an efficient way to do it. Then we can armchair ideal spacecraft and possibly talk about their restrictions and the obstacles to their development.
A few things need to happen, both technologically and politically, for space mining to really lift off. If you want, we can talk about what needs to happen, but saying we can just mine more asteroids before returning the payload isnât really a solution and just creates more of an issue for the spacecraft. You can thank the rocket equation for that.
Yes, you must be very clever. Yesterday I discovered that gog.com began to have official Russian support.
No, Iâm saying you can get/make fuel in the same place you get whatever valuable resource youâre looking send back to earth.
Gotcha! I wasnât sure.
That proves difficult because if youâre at a metallic asteroid, itâs difficult to find organic material and/or water. Plus, youâre now carrying around all of the heavy equipment and the necessary form of power generation to refine it all, increasing the mass of your spacecraft and the amount of propellant you need to create in the first place.
I just reading up on the MCT/ITS and it would require 1700 tons of water to fully fuel that sucker. Granted, itâs payload capacity is in the hundreds of tons, but thatâs not trivial. Whatâs more, is the amount of CO2 that is sucked out of the Martian atmosphere which is necessary carbons for methane. That wonât happen on an asteroid. Furthermore, is the fact that this process requires something like 90 GWh of power to produce. Pretty sure thatâs ignoring the power required to actually mine the ice. Thatâs a lot of power for 1 spacecraft. The very same ITS is planning to have 200 KWh of panels. Thatâs 6 orders of magnitude more powerâŚand also an unfair comparison because you donât need all 90 GWh at once, but I just wanted to compare.
Iâm not saying itâs impossible, Iâm just saying there are a lot of untested components and as is itâs difficult to do in a place where the resources are readily available(Mars). Doing the same process while asteroid hopping is going to prove much more challenging.
Funnily enough, I think the easiest way to mine asteroids with current day tech is to just redirect them to the Antarctic. It allows us to easily mine whatever it was, and itâs a far simpler payload to send to an asteroid. Itâs way way way easier to send an engine and a lot of propellant somewhere than a complicated mess of dependencies with many failure modes. Itâs also much cheaper to mass produce.
Interesting read.
The Future of Rockets: Q&A With Air Force Rocket Labâs Shawn Phillips - space.com
Researchers install a solid rocket motor into an AFRL Rocket Lab altitude chamber at Edwards Air Force Base in California.
Credit: U.S. Air Force Research Laboratory
So I got some questions if a few of you wonât mind answering, revolving around rocketry itself. Anyone that can provide any input would be greatly appreciated.
If the âfuel adds weight which needs more fuelâ problem means rockets already require 20 times as much weight in fuel as the payload just to get into low earth orbit, would a slightly larger planet mean civilizations canât get to space? What size planet is the limit? Iâm less interested in something like, what the Space Shuttle can do on a brown dwarf, and more interested in whether we are lucky to be able to get into space at all. It seems like the planet wouldnât need to be significantly larger before itâs heavy enough to rule out conventional rocket solutions completely, but I wouldnât know where to start with even âback of the napkinâ math.
Feel free to correct the â20 time the weightâ figure (itâs my napkin calculation based off the Saturn V).
I donât mean this to claim alternatives to a conventional rocket are impossible.
Another thing Iâve been playing with this question:
Iâve been reading and processing material (as a hobby) about how rocket engines work. Not having a solid background in mechanics or physics, Iâve had a few questions. Iâve understood where the third Law of Motion and Conservation of Momentum apply, but I donât understand the pressure related aspect of such engines. Iâve seen that depending on what altitude you mean to use it, you have to elongate the nozzle so that the pressure reduces as much as possible until at the end of the nozzle, it is equal to the external pressure. But I would think that to increase the speed of the exhaust gas, one would need high pressure gas so that it wants to go even faster out of the engine?
Also I donât really understand the need for pressurizing the gas before the combustion chamber⌠is it to help combustion? To reduce the size/weight of the combustion chamber?