Moving Phobos to join Deimos for single moon.

[barycenter]

With current technology, could humans move Phobos to join with Deimos to create a single Mars moon? Move moon as a whole/cut it up and move it in peices, etc.

 

[DaveC426913]

With current technology, could humans move Phobos to join with Deimos to create a single Mars moon? Move moon as a whole/cut it up and move it in peices, etc.

1] Why?
2] Depends on what you mean by current technology. With current technology, we could build a superhighway around the equator, but it would break the budget of a passel of large countries.

 

[Drakkith]

It is within current scientific and technological understanding. We understand the math and have the technology to apply a force to the moon, arguably it is possible to apply enough to move it. However as Dave pointed out, the cost would be simply enormous.

 

[DaveC426913]

The challenge would be delivering enough fuel there for the delta-v (.5km/s) of an asteroid-sized (10^15kg) object.

 

[Drakkith]

Yep. I wonder how much fuel that would take for something akin to a hundred plus Saturn V rockets...just to throw out something.

 

[DaveC426913]

Yep. I wonder how much fuel that would take for something akin to a hundred plus Saturn V rockets...just to throw out something.

Deimos masses about as much as a million Pyramids of Cheops or a billion Saturn Vs.

 

[Drakkith]

Deimos masses about as much as a million Pyramids of Cheops or a billion Saturn Vs.

Sorry, I meant how much fuel would be required if we use something akin to 100 saturn V's to provide the force to move the moon. IE bolt these massive engines to it and fire em up!

 

[DaveC426913]

Sorry, I meant how much fuel would be required if we use something akin to 100 saturn V's to provide the force to move the moon. IE bolt these massive engines to it and fire em up!

Yeah, I know. My point was that it doesn't really matter what you use to provide the thrust - you could use one Saturn or a hundred (it would just be faster). The thing that is immutable is the mass to be moved times the change in velocity.

And.

One must not forget that we'll have to carry all our fuel with us (no on-site mining - current technology, remember), which means we'll need fuel to move that fuel. And fuel to move the fuel to move the fuel.

What ends up happening is that you need, like 95% of your fuel just to get your fuel to the target, leaving only 5% left to do any work. So, since you have a fixed amount of work to do, you work backwards from that, meaning you need to bring 20 times more fuel than you thought you needed.

Someone more number-savvy than me could work this out on the back of a napkin.

 

[Drakkith]

Yep. Where is the star ship Enterprise when you need her...

 

[Ryan_m_b]

Even if we could move the moons do we have the technology to safely combine them together? It might be simpler to imagine mining one of them into powder and dumping this into the other moon.

 

[sophiecentaur]

Even if we could move the moons do we have the technology to safely combine them together? It might be simpler to imagine mining one of them into powder and dumping this into the other moon.

The same amount of energy would be needed, though.

 

[Ryan_m_b]

The same amount of energy would be needed, though.

That's fine, I was just wondering if it was more practical.

 

[D H]

It is within current scientific and technological understanding. We understand the math and have the technology to apply a force to the moon, arguably it is possible to apply enough to move it. However as Dave pointed out, the cost would be simply enormous.

Just because we understand the math and physics does not mean we have the technological understanding. Example: We have a very good idea of the mechanism by which the Sun produces energy and we have very good measurements of how much energy the Sun is producing. That we do have that knowledge does not mean we have the technological understanding of how to build an artificial Sun that produces that amount of energy.

 

[DaveC426913]

Just because we understand the math and physics does not mean we have the technological understanding. Example: We have a very good idea of the mechanism by which the Sun produces energy and we have very good measurements of how much energy the Sun is producing. That we do have that knowledge does not mean we have the technological understanding of how to build an artificial Sun that produces that amount of energy.

Perhaps true, but what about an example more relevant to the scenario? What's not doable?

Actually, I know what's not doable. Logistics. It would be the largest project ever undertaken by man, and it wold be a massive team of people, and they would be orders of magnitude farther from Earth than any human has ever been. And, as with fuel, so it is with people. 95% of people and survival resources might result in 5% of the people and the resources left over to actually do the work.

Where would they live? Not on the Moon... where would their air, food and water and building materials come from?

So, the project itself has just seen a 20-fold increase in size. And again, we need fuel to transport all that, which means we reapply the 20-fold factor to the fuel. Which means we now need 400 times more fuel than we originally anticipated.

Oh, did I mention we have to get all those people back home? Another 20-fold increase.

(There' s a reason why our current trips to Mars only send about a ton of payload, only send robots that don't need survival resources, and only send them on a one way trip.)

 

[Ryan_m_b]

And, as with fuel, so it is with people. 95% of people and survival resources might result in 5% of the people and the resources left over to actually do the work.

Where would they live? Not on the Moon... where would their air, food and water and building materials come from?

Totally agree. Sticking with the stipulation that we can only use current technology there's no way this would be a manned mission. It would have to be robotic with delayed telepresence.

 

[D H]

Totally agree. Sticking with the stipulation that we can only use current technology there's no way this would be a manned mission. It would have to be robotic with delayed telepresence.

That's not feasible, either. This simply isn't feasible, period, using current technology, or anything remotely resembling current technology.

 

[DaveC426913]

That's not feasible, either. This simply isn't feasible, period, using current technology, or anything remotely resembling current technology.

The issue at-hand is the subtle distinction between technological capability and logistical capability.

Enough Saturn V's with enough fuel* attached to Deimos would indeed move it. But the OP probably didn't realize how incredibly difficult that would be to achieve.




* actually, even this is beyond us. We do not have the technology to store more than one or two SaturnVs worth of LOx and LHi at a time. You'd need something that would store thousands and thousands of SaturnVs-worth of fuel and a continual pump system to feed the rockets.

 

[D H]

* actually, even this is beyond us. We do not have the technology to store more than one or two SaturnVs worth of LOx and LHi at a time. You'd need something that would store thousands and thousands of SaturnVs-worth of fuel and a continual pump system to feed the rockets.

Exactly. Just because we know how to do X does not mean we know how to do 10*x, let alone 10⁶*X. Technology oftentimes does not scale.

 

[Drakkith]

What do you mean Dave? Would it not be possible to simply make a lot of storage tanks?

 

[DaveC426913]

What do you mean Dave? Would it not be possible to simply make a lot of storage tanks?

How long can LOx and LHi be stored? (Hours.)
How will we get it there? How will we store it for years in-transit?
How will we route it to the rockets?
Where will the power come from to refrigerate it?
etc.
etc.

 

[Drakkith]

I didn't realize you couldn't store Lox for more than a few hours.

 

[Lsos]

Everybody seems to to have forgotten about the 5000 or so megatons of nuclear weapons we have lying around. That said, I'm sure we have means and the know-how to do this thing.

 

[sophiecentaur]

I suspect that storing Lox in space may not be as difficult as storing it on Earth. A few layers of reflective screens between the tank and the Sun (andEarth) would put it in a 'deep space' situation as far as far as balancing absorbing and radiating energy are concerned.
I still think the project would be a wasted exercise. The resources would be better spent on food!

 

[DaveC426913]

Everybody seems to to have forgotten about the 5000 or so megatons of nuclear weapons we have lying around.

No we haven't. They're a drop in this bucket.

Did I not mention that Deimos masses as much as a million Pyramids of Cheops? Now accelerate that by .5km/s.

 

[DaveC426913]

I suspect that storing Lox in space may not be as difficult as storing it on Earth. A few layers of reflective screens between the tank and the Sun (andEarth) would put it in a 'deep space' situation as far as far as balancing absorbing and radiating energy are concerned.

Again: current technology. We don't have that technology.

 

[sophiecentaur]

Again: current technology. We don't have that technology.

?? Reflecting screens?


Are we after a soft landing or a good old collision? There would be a significant difference in the energy needed in each case.

 

[DaveC426913]

?? Reflecting screens?

Do you seriously think it's that simple?

All right. How did all that LOx and LHi get into space in the first place, such that all you need to do is wrap some foil around it?

Are we after a soft landing or a good old collision? There would be a significant difference in the energy needed in each case.

How would a collision controllably accelerate Deimos to combine with Phobos? Again, seems easy to say, till you start thinking through the deets.

 

[Lsos]

No we haven't. They're a drop in this bucket.

Ok I'm not so sure that it's possible. But still, I wouldn't say a drop in a bucket...not 5000 megatons.

 

[sophiecentaur]

Do you seriously think it's that simple?

All right. How did all that LOx and LHi get into space in the first place, such that all you need to do is wrap some foil around it?

How would a collision controllably accelerate Deimos to combine with Phobos? Again, seems easy to say, till you start thinking through the deets.

No, I'm not taking it at all seriously. I'm just commenting on isolated points.
No one insisted that the final orbit should be the same as the original, did they? The energy required would be less if the orbit could change. Still a barmy project, though.

 

[DaveC426913]

Ok I'm not so sure that it's possible. But still, I wouldn't say a drop in a bucket...not 5000 megatons.

I'll leave it to some math buff to guess how much bomb megatonnage can be converted to useful momentum, then we can simply divide that by a thousand billion tonnes of Moon moving at .5km/s.

 

[Drakkith]

Everybody seems to to have forgotten about the 5000 or so megatons of nuclear weapons we have lying around. That said, I'm sure we have means and the know-how to do this thing.

I've been purposely leaving them out, as most people have a huge issue with them.

 

[Ryan_m_b]

Would nuclear explosions actually help? Could it be controlled enough and could enough energy be provided?

EDIT: for clarity I mean with the weapons we have

 

[Lsos]

Honestly I really don't know. I really don't even know how a nuclear explosion works in a vacuum. Is there a fireball? Is there a shock? Is it just a bright flash of light and heat?

Since it's in space, I imagine the moon wouldn't be blown to bits unless the explosion happened inside of it. If we blew it up close to the moon, it would probably heat up/ vaporize the surface, resulting in a makeshift rocket?

I do know that the stockpile we have has enough energy to at least give the thing a proper nudge. There's a few ideas on how to go about delivering this nudge, and in this discussion we shouldn't be constrained to talking about only the stockpile we have. Surely more could be built/ modified with the idea of controllably moving a moon (and not uncontrollably moving a city).

 

[sophiecentaur]

Ideally, you'd insert it under the surface, opposite to the direction you wanted it to go. Then a small amount of mass would be ejected in one direction and the moon would go in the opposite direction. (Conservation of momentum / Newton III). Using some of the moon's mass in that way would be better value. The exact depth etc would depend on the energy and the 'rate' of its production (i.e. Power), I think.

 

[DaveC426913]

Ideally, you'd insert it under the surface, opposite to the direction you wanted it to go.

Current technology... We don't have robotic moon-mining tech yet.

Using some of the moon's mass in that way would be better value.

How much Moon would be left when we're done? How much would be dust in orbit, waiting to pulverize anything in its way?

 

[sophiecentaur]

Why are we being drawn to this thing like moths to a flame? It's towwwtally crazy from beginning to end.
I don't think you'd need to bury it very far - would a spade be 'current technology'?

 

[DaveC426913]

Why are we being drawn to this thing like moths to a flame? It's towwwtally crazy from beginning to end.

Because we like discussing stuff academically.

The question is: 'what technology don't we have'? Not 'how hard is it'?

I don't think you'd need to bury it very far - would a spade be 'current technology'?

1] What is the point in burying it 2 metres deep?
2] We don't have the technology to send a man, let alone hundreds, to Mars.

 

[sophiecentaur]

Because we like discussing stuff academically.

The question is: 'what technology don't we have'? Not 'how hard is it'?
1] What is the point in burying it 2 metres deep?
2] We don't have the technology to send a man, let alone hundreds, to Mars.

I'm not sure that the above comments are mutually compatible.
Either, we don't have the technology now so - end of conversation or what technology would we need? In which case, moon mining is as likely a scenario as are rockets to take the stuff there.

"Academically" is a good thing to aim at but I haven't seen many quoted figures on this thread. Engineering matters always should involve figures to establish possible feasibility. So is this thread really academic or just Buck Rogers and a bit of fun? (Not that it would matter)

 

[DaveC426913]

I'm not sure that the above comments are mutually compatible.
Either, we don't have the technology now so - end of conversation or what technology would we need? In which case, moon mining is as likely a scenario as are rockets to take the stuff there.

When someone first raised the idea of using nukes, there was no assumption that they had to be accompanied by humans.

"Academically" is a good thing to aim at but I haven't seen many quoted figures on this thread. Engineering matters always should involve figures to establish possible feasibility. So is this thread really academic or just Buck Rogers and a bit of fun? (Not that it would matter)

The question is straightforward: what technology are we missing?

We don't need to assign numbers to know that we don't have the technology to house the town of technicians required to move it manually. (And ou're right. If we did supply numbers, this would be a very short thread.) So now we're exploring methods that could be done remotely. Just for fun.

 

[sophiecentaur]

Yes - I get it.
I have the same with 'role playing' exercises in the work place, though. I never know when to be really in role or just to be realistic.

But if we were going to be letting off nukes all over that little moon, would anyone ever want to go there later?

But, why are we discussing this particular exercise at all? I would have thought that a much more interesting and relevant question to discuss would be what to do about a rogue asteroid on collision course with us. A very similar problem and it could actually have relevance this very afternoon!

 

[DaveC426913]

But if we were going to be letting off nukes all over that little moon, would anyone ever want to go there later?

True. An issue for the OP. He didn't say anything about it being usable afterward...

But, why are we discussing this particular exercise at all? I would have thought that a much more interesting and relevant question to discuss would be what to do about a rogue asteroid on collision course with us.

Yawn. Been hashed out a million times.

And the distances involved dramatically narrow down the solutions using current technology.

 

[sophiecentaur]

And the distances involved dramatically narrow down the solutions using current technology.

NASA would even be pushed to get to the ISS without some help.

 

[barycenter]

1] Why?
2] Depends on what you mean by current technology. With current technology, we could build a superhighway around the equator, but it would break the budget of a passel of large countries.

Answer: Why?
1) To give NASA a large goal that doesn't require the negative PR of human loss.
2) To give NASA the time to formulate a plan, practice, and create the tools necessary to move an asteroid or comet when it is on a collision course with Earth (The Universe: Season 3, Ep.6 - Deadly Comets and Meteors)
3) I'm working on a Theory that will help humans colonize Mars but needed to know if moving Phobos as a whole was feasible or if it needed to be taken apart.

 

[barycenter]

Totally agree. Sticking with the stipulation that we can only use current technology there's no way this would be a manned mission. It would have to be robotic with delayed telepresence.

Do you believe some sort of large focused nuclear explosion could exert enough force to move Phobos into a higher orbit without shattering it? Or would a small oscillating force over a long period of time be a better approach? Any possibility of making fuel from Phobos itself?

 

[D H]

Answer: Why?
1) To give NASA a large goal that doesn't require the negative PR of human loss.

Without that human element NASA will go the way of the British space agency.

2) To give NASA the time to formulate a plan, practice, and create the tools necessary to move an asteroid or comet when it is on a collision course with Earth (The Universe: Season 3, Ep.6 - Deadly Comets and Meteors)

The delta-v needed to move an asteroid or comet off a collision course with the Earth is much, much smaller (many orders of magnitude smaller) than is the delta-v needed to make Phobos collide with Deimos. If you want to make that a gentle collision so that they become a single moon you will need to more than double that already huge delta-v. This is not a realistic goal.

3) I'm working on a Theory that will help humans colonize Mars but needed to know if moving Phobos as a whole was feasible or if it needed to be taken apart.

Time to go back to the drawing board.

 

[barycenter]

The delta-v needed to move an asteroid or comet off a collision course with the Earth is much, much smaller (many orders of magnitude smaller) than is the delta-v needed to make Phobos collide with Deimos. If you want to make that a gentle collision so that they become a single moon you will need to more than double that already huge delta-v. This is not a realistic goal. Time to go back to the drawing board.

So you don't believe humans could move an asteroid to avoid hitting Earth?

Phobos and Deimos wouldn't have to join overnight, just make enough of an alteration in the direction of Phobos to travel faster than Deimos is traveling away from Mars, like Earth's moon is currently doing. Eventually Phobos will catch up to Deimos (5,10,15 years). This way while NASA is not around, the work can accomplished without our constant intervention.

The farther away from Mars Phobos traveled, the more attraction Deimos would have on Phobos (and vice versa). They would eventually create a single moon, and a single unified force of tidal friction on Mars.

 

[Ryan_m_b]

So you don't believe humans could move an asteroid to avoid hitting Earth?

Phobos and Deimos wouldn't have to join overnight, just make enough of an alteration in the direction of Phobos to travel faster than Deimos is traveling away from Mars, like Earth's moon is currently doing. Eventually Phobos will catch up to Deimos (5,10,15 years). This way while NASA is not around, the work can accomplished without our constant intervention.

The farther away from Mars Phobos traveled, the more attraction Deimos would have on Phobos (and vice versa). They would eventually create a single moon, and a single unified force of tidal friction on Mars.

I think this is a vastly simplistic model. Trying to boost Phobos's orbit would require precise control to avoid it loosing energy and crashing into Mars, assuming you could actually manage to get them into the same orbit and close together you still have the problem of how to safely combine them. They aren't made out of play-doh! Two moons closing together at the speeds that they will would cause them to shatter.

 

[SpectraCat]

So you don't believe humans could move an asteroid to avoid hitting Earth?

Phobos and Deimos wouldn't have to join overnight, just make enough of an alteration in the direction of Phobos to travel faster than Deimos is traveling away from Mars, like Earth's moon is currently doing. Eventually Phobos will catch up to Deimos (5,10,15 years). This way while NASA is not around, the work can accomplished without our constant intervention.

The farther away from Mars Phobos traveled, the more attraction Deimos would have on Phobos (and vice versa). They would eventually create a single moon, and a single unified force of tidal friction on Mars.

This is all about tides? Phobos and Deimos are *tiny* 6 or 7 orders of magnitude smaller than our own moon (in terms of mass). I doubt they would have much effect on tides, certainly not nearly as much as the effect of the moon on earth, even if they were somehow combined.

 

[D H]

So you don't believe humans could move an asteroid to avoid hitting Earth?

I said nothing of the sort. Moving an asteroid off a collision course with the Earth is a trivial task compared to moving "Phobos to join with Deimos to create a single Mars moon".

Deimos would make for an extremely large asteroid. Phobos: Absolutely huge. Making Deimos merge with Phobos is an impossible task given our current technology. Making Phobos merge with Deimos? Please! Assume we have some Saturn V style rockets (specific impulse = 4130 m/s) attached to Phobos. The amount of energy needed just to move Phobos as described is on the order of 10²² joules, or 1000 times the total electrical energy produced by the US per year. This completely ignores the energy needed to move the fuel and oxidizer to Phobos. The task is impossible not only with current technology, it is impossible given any reasonable extrapolation of technology. (Suppose we have a flux capacitor (1.21 gigawatts). In fact, suppose we have half a million flux capacitors at hand. You would have to run those half a million flux capacitors continuously for almost a year to produce the energy needed here.)

Moving an asteroid off a collision course with the Earth is indeed trivial in comparison. The required delta-v is many orders of magnitude smaller than that required to move Phobos, and the mass of a typical near Earth object is also many orders of magnitude than that of Phobos. (Phobos is huge).

Phobos and Deimos wouldn't have to join overnight, just make enough of an alteration in the direction of Phobos to travel faster than Deimos is traveling away from Mars, like Earth's moon is currently doing. Eventually Phobos will catch up to Deimos (5,10,15 years). This way while NASA is not around, the work can accomplished without our constant intervention.

Wrong. A tiny nudge to Phobos is going to change its orbit a tiny bit. Phobos' orbit has a semi major axis of 9,377.2 km; Deimos' is 23,460 km. Do the math. The minimal delta-V to accomplish this desired merger is attained by a Hohmann transfer, 417.5 m/s to start the transfer, 330 m/s to finish it, or 747.5 m/s total. Using thrusters with a 4130 m/s specific impulse, having fuel continuously transferred to Phobos, ignoring the energy needed to accomplish this fuel supply, and ignoring gravity losses due to continuous thrust, this 747.5 m/s delta-V translates to 1.65×10²² joules. Continuous thrust would only serve to increase the energy required.

 

[DaveC426913]

3) I'm working on a Theory that will help humans colonize Mars but needed to know if moving Phobos as a whole was feasible or if it needed to be taken apart.

This little tidbit may have slipped under the radar, yet it seems to be the driver for the entire thread.

If I had to guess, you're thinking about combining the two Moons in the hopes that it will give Mars some sort of tidal effect?

1] Many orders of magnitude too small.
2] Tides will not make Mars habitable.
3] Read Arthur C. Clarke's The Sands of Mars where they made Mars habitable by setting Phobos on fire.