Is any of the technology in stargate possible?

[thekillman]

And it's not even a matter of speed. We barely know what we are doing with interplanetary travel, we aren't even that good at orbital travel!!! Until manned spaced flight is as available and frequently used as atmospheric flight is, I don't think we are ready to seriously talk about interstellar travel.

We can imagine. As early as the later half of the 1800's people imagined interplanetary travel. That didn't become a reality for over 100 years. Actually, scratch that. Manned interplanetary travel doesn't and has never existed. The moon doesn't count. Talk about trying to run before you even know how to walk.

It'll never be that cheap. It's a matter of energy budgets.

Still, yea we're basically using stone tools when it comes to putting stuff in space. I don't get people who put up the "we're not going to space anymore" whine because now companies have put up a great interest in space. We simply need infrastructure in space to do stuff. Imagine what life would be like without pump stations. That's what space travel is like. Until we can put the equivalent of gas stations in space, we're not going to spread among the stars.

After all, Low Earth Orbit is halfway to any place in the solar system.

[aretood2]

It'll never be that cheap. It's a matter of energy budgets.

Still, yea we're basically using stone tools when it comes to putting stuff in space. I don't get people who put up the "we're not going to space anymore" whine because now companies have put up a great interest in space. We simply need infrastructure in space to do stuff. Imagine what life would be like without pump stations. That's what space travel is like. Until we can put the equivalent of gas stations in space, we're not going to spread among the stars.

After all, Low Earth Orbit is halfway to any place in the solar system.

Refueling stations would be a huge help. Orbital stations that can be a link between space ships and habitats and the Earth. Ships dock at the stations which have shuttles to run supplies and personal back and forth. That would make orbital settlement much more practical. That we can do within our lifetimes. We can also set small temporary outposts on the Moon and if we are lucky, On mars that will behave like the ISS does now. Purely scientific and exploratory. Until we have a good orbital infrastructure, planet and lunar colonization can never be anything more (Or space mining).

I believe that as soon as that infrastructure is secured, private companies will be able to set up a mining system in space that would then allow private transport companies to thrive, and cause a growth in private exploratory endeavors. But all of that takes time, lots of time. And space is really really big. I don't think people realize how big it is. I mean....it's huge (And that's just to the moon).

[thekillman]

I believe that as soon as that infrastructure is secured, private companies will be able to set up a mining system in space that would then allow private transport companies to thrive, and cause a growth in private exploratory endeavors. But all of that takes time, lots of time. And space is really really big. I don't think people realize how big it is. I mean....it's huge (And that's just to the moon).

Space is big, yes. The main thing is going to be the setup of a fuel depot at the Earth-moon Lagrange point (EML). Depending on how rich the moon is in water, it should be fairly doable to build a couple of mining robots that can land on the moon, drill up some ice and transport it to EML. There, a large array of solar panels (a couple of times the size of the ISS' array) provides the power to crack the ice to oxygen and hydrogen. As hydrogen inevitably leaks, it will require planning and not just cracking a ton of water in advance. The mining ship (i'll call it a mosquito) refills at EML and makes another trip to the Moon. Alternatively, ice asteroids (if they're present around earth) may also be preferable targets. Eventually we'll probably move a much bigger ice asteroid into EML and have millions of tonnes of propellant ready but for now, even a few tonnes will do.

From there on, any spaceship can easily refill in space and go to mars (or anywhere) at a vastly reduced cost. After all, earth to orbit is halfway to anywhere in the solar system.

If we can then build a small base on the moon with the ability to process aluminium we may be able to create basic structures in space.

But all of that takes time, lots of time.

if we can build stuff in space (anything, really) then the cost can go down. Then, in stead of sending stuff up there in one go, we can actually build stuff meant to be in space and meant to stay in space. No more need for expensive heat shields, structural requirements for atmospheric reentry or engines with a thrust-to-weight ratio bigger than 1.

[jmoz]

Spoiler:

Space is big, yes. The main thing is going to be the setup of a fuel depot at the Earth-moon Lagrange point (EML). Depending on how rich the moon is in water, it should be fairly doable to build a couple of mining robots that can land on the moon, drill up some ice and transport it to EML. There, a large array of solar panels (a couple of times the size of the ISS' array) provides the power to crack the ice to oxygen and hydrogen. As hydrogen inevitably leaks, it will require planning and not just cracking a ton of water in advance. The mining ship (i'll call it a mosquito) refills at EML and makes another trip to the Moon. Alternatively, ice asteroids (if they're present around earth) may also be preferable targets. Eventually we'll probably move a much bigger ice asteroid into EML and have millions of tonnes of propellant ready but for now, even a few tonnes will do.

From there on, any spaceship can easily refill in space and go to mars (or anywhere) at a vastly reduced cost. After all, earth to orbit is halfway to anywhere in the solar system.

If we can then build a small base on the moon with the ability to process aluminium we may be able to create basic structures in space.


if we can build stuff in space (anything, really) then the cost can go down. Then, in stead of sending stuff up there in one go, we can actually build stuff meant to be in space and meant to stay in space. No more need for expensive heat shields, structural requirements for atmospheric reentry or engines with a thrust-to-weight ratio bigger than 1.

I could foresee problems with unstable Lagrangian points further out with numerically calculated points of other n-body systems besides Earth, Moon, Sun. The spacecrafts would have to maintain real-time active control of thrusters doing minute stability maneuvers to keep them at those points. This would be further complicated if they are resource taxed. That's where Aretoo's time problem really comes in, how long between periods of resupplying.

The obvious solution would be to increase the frequency of transport/supply vehicles. As everyone knows, increasing frequency decreases period. This would require a well-developed transit system throughout space.

And I think that's where the real issue comes in: the building of such an infrastructure. It is unfortunate we currently live in a society driven by instant gratification and just general hedonism/narcissism. A few eccentric billionaires here and there aren't enough to start building such a complex and complicated infrastructure with their limited departments and group of people involved in all things space. It'd require a large scale cooperative effort that I just don't think humanity is currently capable of when they cannot even put together such an effort to smaller social issues.

[thekillman]

I could foresee problems with unstable Lagrangian points further out with numerically calculated points of other n-body systems besides Earth, Moon, Sun. The spacecrafts would have to maintain real-time active control of thrusters doing minute stability maneuvers to keep them at those points. This would be further complicated if they are resource taxed. That's where Aretoo's time problem really comes in, how long between periods of resupplying.

The obvious solution would be to increase the frequency of transport/supply vehicles. As everyone knows, increasing frequency decreases period. This would require a well-developed transit system throughout space.

And I think that's where the real issue comes in: the building of such an infrastructure. It is unfortunate we currently live in a society driven by instant gratification and just general hedonism/narcissism. A few eccentric billionaires here and there aren't enough to start building such a complex and complicated infrastructure with their limited departments and group of people involved in all things space. It'd require a large scale cooperative effort that I just don't think humanity is currently capable of when they cannot even put together such an effort to smaller social issues.

There's no need for a massive infrastructure to make space profitable. Near-earth refills would already be a huge leap for anyone even remotely interested in space travel. Earth to LEO is already halfway to anywhere in the solar system delta-V wise, so a LEO (or near-LEO in case with an EML refill station) refill station would already be a stellar improvement. Any mission becomes a ton easier if we can refill in orbit.


Secondly, there already are companies out there that intend to operate in space. There's again no need to run before we can walk. We're in the stone age of space travel, and an orbital depot, some basic mining and rudimentary orbital construction would be an instant upgrade to the Roman age, to stick to analogies. It doesn't require exceptional money, time or effort to do this.


Maybe by the turn of the century we get to a point where a massive infrastructure can be made, but so far if we can just fill up our craft in orbit it'll be a huge leap for spacefaring mankind.

[jmoz]

What? Delta-V wise? Are you talking about changing thrust? Just because you're in a position of exerting massive thrust doesn't mean you have the capacity to do so propellant-wise. I think you're overestimating the capacity of our propellant systems. That's why we use slingshot maneuvers using gravity of planets and other spatial bodies.

And I agree with you about the setting up of refuel stations and baby steps. But we simply can't use just Lagrangian points and fuel to just send us across anywhere in the solar system. We need more of an infrastructure involving the other planets gravities, slingshot maneuvers, etc. We need more of an infrastructure unless we come up with a radically new propellant system capable of huge thrust.

I had this train system idea where we siphon off orbits of existing comets and asteroids and whatnot to set up constant orbits of space vehicles that act similar to trains on fixed tracks but in space. People and supplies would be analogous to people boarding and departing trains to get places. But my idea is rudimentary and I don't have a clue on how to go about doing this siphoning thing.

There's also the issues of long term space travel for humans and radiation shielding and just general living conditions for such things. All of this would be part of the large infrastructure problem I'm talking about.

[thekillman]

What? Delta-V wise? Are you talking about changing thrust? Just because you're in a position of exerting massive thrust doesn't mean you have the capacity to do so propellant-wise. I think you're overestimating the capacity of our propellant systems. That's why we use slingshot maneuvers using gravity of planets and other spatial bodies.

And I agree with you about the setting up of refuel stations and baby steps. But we simply can't use just Lagrangian points and fuel to just send us across anywhere in the solar system. We need more of an infrastructure involving the other planets gravities, slingshot maneuvers, etc. We need more of an infrastructure unless we come up with a radically new propellant system capable of huge thrust.

I had this train system idea where we siphon off orbits of existing comets and asteroids and whatnot to set up constant orbits of space vehicles that act similar to trains on fixed tracks but in space. People and supplies would be analogous to people boarding and departing trains to get places. But my idea is rudimentary and I don't have a clue on how to go about doing this siphoning thing.

There's also the issues of long term space travel for humans and radiation shielding and just general living conditions for such things. All of this would be part of the large infrastructure problem I'm talking about.

uhm i am confused about what you precisely mean.

Thrust actually doesn't really matter. this may seem weird, but it's not. We need a large amount of thrust to get off the earth, because we need to fight gravity. However once in freefall in space, we can apply however little thrust for however long we want to get where we want. That's why ion engines are even a thing.

Now, the reason why even a basic orbital depot is useful is because to launch a kilogram of fuel, you need an amount of fuel, and that fuel needs fuel etc. If you can launch a spaceship with it's space stage almost completely dry, one could save many tonnes of additional fuel. That fuel gets added in space. But to get from, say, the moon to earth, the Delta V cost is much less than to lift it from earth. So despite the fact that the fuel comes from many thousands of kilometers further away, it's actually cheaper to do. Not to mention that since the thrust/weigth ratio doesn't need to be greater than 1 in space, one could resort to MUCH more efficient engines than the horribly inefficient chemical engines we use. Like, ion engines. Even though the journey may take 5-10 times as long, the vastly reduced cost for fuel pays for the extra spaceships needed.

[thekillman]

Just to be on the safe side:

delta v comes from the Tsiolkovsky rocket equation. it is:

Delta V = Ve*Ln(R)

Where:

Delta V = change in velocity [m/s]
Ve= exhaust velocity [m/s]
ln = natural logaritm
R = mass fraction (how much kilogram propellant per kilogram ship)

Thus, the actual mass of the ship is of no importance. For as long as you carry the same ratio of fuel to ship, it could be a cubesat or a Death Star, you can make the same changes in speed.

The not-so-unimportant implication is this:

in the case of a multi-stage ship, the upper stages count as "payload". every kilogram you save there, saves a LOT more. It's a logarithmic fuction.

Assuming a rocket with Ve= 3500 (kerosine-oxygen), a ship with 4000 kg propellant and 1000 kg payload (mass ratio of 4). The payload is a secondary stage.

dV= 4852 m/s

(since the payload is a ship with identical properties, the total dV is twice this)

Assuming the top stage has an identical mass ratio (4), and is launched dry, we get a payload of (1/4) * 1000) = 250kg.

R then becomes: 4000/250 = 16

dV= 3500 * ln(16)= 9704m/s

or 2x greater DeltaV for the bottom stage. Total dV is thus 9704+4852 m/s.

Reversely, we know that the payload is 250kg. The mass ratio thus needs to be:

dV= 4852
Ve=3500
R= 4.
(obviously).

With 250 kilograms to lift, that becomes 4*250 = 1000 kg fuel.

So what does that mean? That by launching the top dry, we can save 3000kg of fuel.

The other number here, Ve or exhaust velocity is why ion engines are useful. Since a destination can be defined by it's deltaV, sending an ion-powered rocket to the moon is much more efficient than sending a chemical-powered rocket to the moon as its exhaust velocity is much higher. Interestingly, if the deltaV you need is equivalent to the exhaust velocity, the mass ratio will be e (=2.7 something). If the deltaV is twice the exhaust velocity, the mass ratio needs to be e^2 or about 7.4. Simply put, greater exhaust velocity means more ship and less fuel.

Note this:

A Hohmann orbit between two planets is guaranteed to take the smallest amount of deltaV possible. For the Terra-Mars Hohmann, deltaV is 5590 m/s.

Notice that the deltaV required to get into orbit is 11180 m/s while the Terra-Mars deltaV is only 5590 m/s. As Robert Heinlein noted, once one gets into Earth orbit, you are "halfway to anywhere."

That's where we put 1 and 1 together and make 2. Once you're in space, you've already paid a huge dV price (and with it, a ton of propellant). As the rocket equation shows, launching a ship dry vastly, VASTLY reduces the necessary propellant. The use of an orbital depot would easily slash prices.


FuelDepot.jpg

The above picture is what a dV map looks like. Note that it's in Km/s. The red lines indicate one-way aerobraking maneuvers

Note that earth to LEO is 9500 km/s (it takes more for geostationary). Look at the above numbers. My filled rocket has to ditch it's first stage (4852m/s) and then it's second stage (another 4852m/s) to get to space (total: 9704m/s). this is what we do today.

And my dry launch ship (the second calculated one)?

The first stage can go to space alone. ( 9704m/s). I made this up on the spot so it's not entirely perfect. However if we had an orbital fuel tank in LEO, this baby can go to EML1.

Moon to ELM1 is only 2.5km/s. The mass ratio with above engines then needs to be:

e^(6300/3500) = 2

the ship will bring the aforementioned 750 kg of fuel up. The ship itself will be the other 250 kg so the total payload is 1000kg.

Thats 2000kg of fuel to bring 750 kg of fuel into EML1. conversely, 4000kg of fuel couldn't lift a rocket from Earth to EML1. That and the above dry rocket example, it's clear that it's better to refuel a ship in EML1 than to send that same ship filled from earth up to the lagrangean point.


Now it would be even better if we could just build the rocket tanks on the moon. That way, the actual payload of the rocket (the tank) could be ejected into an aerobraking maneuver and made to dock with a LEO refill station. the actual ferrying rocket would simply refill on the moon's surface (where the fuel refinery would be).

[jmoz]

uhm i am confused about what you precisely mean.

Thrust actually doesn't really matter. this may seem weird, but it's not. We need a large amount of thrust to get off the earth, because we need to fight gravity. However once in freefall in space, we can apply however little thrust for however long we want to get where we want. That's why ion engines are even a thing.

Now, the reason why even a basic orbital depot is useful is because to launch a kilogram of fuel, you need an amount of fuel, and that fuel needs fuel etc. If you can launch a spaceship with it's space stage almost completely dry, one could save many tonnes of additional fuel. That fuel gets added in space. But to get from, say, the moon to earth, the Delta V cost is much less than to lift it from earth. So despite the fact that the fuel comes from many thousands of kilometers further away, it's actually cheaper to do. Not to mention that since the thrust/weigth ratio doesn't need to be greater than 1 in space, one could resort to MUCH more efficient engines than the horribly inefficient chemical engines we use. Like, ion engines. Even though the journey may take 5-10 times as long, the vastly reduced cost for fuel pays for the extra spaceships needed.

No, I know what the Hohmann maneuver is, hell we even proved why it is the most energy efficient method in astro. And I'm not arguing against fueling stations. And I'm not talking about just going to Mars, but even further out. I'm talking about spreading to the entire solar system. You will need to build an infrastructure, fueling stations and such. That stuff up to Mars has been calculated and done for years now.

To get further out, you have more bodies being introduced and more computations, making simple issues more complicated. Obviously, multi-staging is done for the efficiency but further multi-staging in space will require tanks (unless they haven't been disposed). You also have the issue of fuel needed for minute corrections or braking maneuvers which can add up for longer transfers. Lagrangian points come in handy then. It just becomes more complicated when going further out and requires a bigger infrastructure to maintain something within the span of a person's lifetime.

[destiny khan]

yes it is all possible if there was an ancient around...

[thekillman]

No, I know what the Hohmann maneuver is, hell we even proved why it is the most energy efficient method in astro. And I'm not arguing against fueling stations. And I'm not talking about just going to Mars, but even further out. I'm talking about spreading to the entire solar system. You will need to build an infrastructure, fueling stations and such. That stuff up to Mars has been calculated and done for years now.

To get further out, you have more bodies being introduced and more computations, making simple issues more complicated. Obviously, multi-staging is done for the efficiency but further multi-staging in space will require tanks (unless they haven't been disposed). You also have the issue of fuel needed for minute corrections or braking maneuvers which can add up for longer transfers. Lagrangian points come in handy then. It just becomes more complicated when going further out and requires a bigger infrastructure to maintain something within the span of a person's lifetime.

sorry. i don't like it when people try to preach me about my own field of expertise, yet i just did the same to you.

It was hard to figure out what you meant exactly, so i took a more cautious road of explanation. However, i understand what you're saying now. Yes, i agree. Unfortunately (well, for large-scale solar system exploitation) there are plenty of low-hanging fruits that will be prioritized. E.g. mining the moon and easy-to-retrieve asteroids near earth will take precedence over say, the asteroid belt or mining Jupiter's moons. On the short term an EML1 fuel station is doable but once that's in place...well it makes space trips a lot easier but also far more profitable to do nearby e.g. the moon. I do agree that a full infrastructure would require a change of mind from relatively short term profit to thinking on the scale of such space missions which won't start to return a penny untill as much as a decade later. And that's for relatively close to earth.

Maybe the Singularity will change this, though i doubt it'll be Skynet. We've been indoctrinated too much by apocalyptic robot movies so that any serious attempt at a post-human machine would probably meet extremely strict regulation.

[jmoz]

sorry. i don't like it when people try to preach me about my own field of expertise, yet i just did the same to you.

It was hard to figure out what you meant exactly, so i took a more cautious road of explanation. However, i understand what you're saying now. Yes, i agree. Unfortunately (well, for large-scale solar system exploitation) there are plenty of low-hanging fruits that will be prioritized. E.g. mining the moon and easy-to-retrieve asteroids near earth will take precedence over say, the asteroid belt or mining Jupiter's moons. On the short term an EML1 fuel station is doable but once that's in place...well it makes space trips a lot easier but also far more profitable to do nearby e.g. the moon. I do agree that a full infrastructure would require a change of mind from relatively short term profit to thinking on the scale of such space missions which won't start to return a penny untill as much as a decade later. And that's for relatively close to earth.

Maybe the Singularity will change this, though i doubt it'll be Skynet. We've been indoctrinated too much by apocalyptic robot movies so that any serious attempt at a post-human machine would probably meet extremely strict regulation.

Guessing you're in aerospace engineering or some engineering, huh?

Yeah, they need a bigger infrastructure for further out and for that, you need a bigger form of cooperation down here on Earth. But they could definitely do a lot of the necessary groundwork portions on Earth, such as autonomous mining stuff or the whole manufacturing process in some semi-autonomous way. NASA has difficulty with just a basic rover for Mars and the like. There's also the issue of figuring out a way to build a self-contained environment or at least long-lived for the purposes of solar system exploration somehow.

[thekillman]

Guessing you're in aerospace engineering or some engineering, huh?

Yeah, they need a bigger infrastructure for further out and for that, you need a bigger form of cooperation down here on Earth. But they could definitely do a lot of the necessary groundwork portions on Earth, such as autonomous mining stuff or the whole manufacturing process in some semi-autonomous way. NASA has difficulty with just a basic rover for Mars and the like. There's also the issue of figuring out a way to build a self-contained environment or at least long-lived for the purposes of solar system exploration somehow.

Mechanical engineering.



I think the biggest problem above all is incentive. Near-earth refuelling makes sense. It then requires a place to get the fuel (or just ReMass) from. Well that makes operating near earth easier. Boost a nearby asteroid into an earth orbit, start mining it. Then what? rinse, repeat. There's no naquahdah or other macguffin to mine out there. As far as i know, anything we could want to mine, is mineable nearby. (in relative terms). Why bother building an infrastructure to go to Saturn or Pluto or Mercury when you could mine it nearby?


Things like orbital manufacturing would certainly help a lot, but this is also something you want to have close to the source. Maybe until we want to go to other stars via a laser-powered craft and need Mercury's abundant solar energy to go there, we will exploit further out planets.

[tpn]

self-replicating technology has already been created

[thekillman]

self-replicating technology has already been created

Not truly Universal stuff