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sevenperforce

Space Tugs for fun and profit!

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Mostly profit.

Thinking about the SES-9 mission and the idea of having a propellant depot in space with a tug to pull satellites into their desired orbit. Having an active propellant depot in orbit would be fantastic in terms of generally expanding our access to space, but unless it would be profitable, no one would ever do it.

So...under what circumstances would an immediate-term (e.g., within the next five years) propellant depot and space tug system be profitable?

Let's assume that the project would be undertaken by an independent private company rather than NASA. Let's assume it's not SpaceX or another current launch provider. Your primary customers would be comsat companies who choose to pay you some stated fee to tow their satellites into a desired orbit, though you could also potentially give the ISS boosts.

You need at least one space tug -- probably several, to maximize your profit and to lower launch costs. Each tug needs solar panels, ion engines, a grappling or towing mechanism, and the ability to refuel in space (either by mating to disposable propellant capsules or by transferring propellant to an onboard tank. You'll probably want to buy two Falcon Heavy launches to start -- one for as many space tugs as you can fit, and one for your initial propellant depot. You'd then re-launch a Falcon Heavy each time you needed to top-up your propellant depot.

Would anyone actually buy your services? How many comsat companies would say, "Hmm, instead of giving my satellite an engine and fuel tanks to push it into the desired orbit, I'll just pay these folks, and so I can make my satellite a little bigger and give it more capacity"? And would you be able to have low enough prices to actually save them money? 

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Within 5 years, isn't possible. It takes more than that to design and build any spacecraft. Even more for an advanced concept such as this.

To be undertaken by a private corporation requires a market for frequent launches. The market simply isn't large enough to support a high-frequency infrastructure such as this. And a tug for boosting comsats would be a very different design from tug for boosting the ISS, because the docking and thrust requirements would be completely different. It would also have to be in a totally different orbit.

Comsats need engines for station-keeping. Adding a little extra fuel and tankage is cheaper than adding a docking system, and paying extra for a tug service. Especially as your tug is going to have to be overengineered and carry twice the dV that a good old disposable Fregat or Ariane ESC upper stage has. And you also need to add the extra launches that carry the propellant for the tugs. 

 

Edited by Nibb31

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I don't really see the benefit unless we have reusable ships and probes making regular trips between Earth and other solar system destinations.

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41 minutes ago, Nibb31 said:

To be undertaken by a private corporation requires a market for frequent launches. The market simply isn't large enough to support a high-frequency infrastructure such as this. And a tug for boosting comsats would be a very different design from tug for boosting the ISS, because the docking and thrust requirements would be completely different. It would also have to be in a totally different orbit.

Yeah, inclination changes take too much dV to be useful, even with ion engines.

42 minutes ago, Nibb31 said:

Comsats need engines for station-keeping. Adding a little extra fuel and tankage is cheaper than adding a docking system, and paying extra for a tug service. Especially as your tug is going to have to be overengineered and carry twice the dV that a good old disposable Fregat or Ariane ESC upper stage has. And you also need to add the extra launches that carry the propellant for the tugs.

That's what I was thinking -- it isn't cost-effective because you already have the station-keeping capabilities. 

Are there any sorts of scenarios where it would be cost-effective?

20 minutes ago, Mitchz95 said:

I don't really see the benefit unless we have reusable ships and probes making regular trips between Earth and other solar system destinations.

That would be a much bigger project than a comsat tug.

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Isn't this a specialized use of what Orbital is planning?  To repair satellites, they pretty much need to at least get there with nearly the same sized rig.  I'd wouldn't at all be surprised if they announced they could do such a thing (ferry to and from LEO-GTO).  Of course, Orbital might be going with a one-shot plan (or simply take a slow mosey around equatorial GTO (anything else would require a ton of delta-v.  On second thought, I really expect the equatorial GTO plan.  Maybe a follow-up bird might have the delta-v you need for such a thing).

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I don't think there will be much demand for tug hauling sattelites LEO->GEO or anything. But fuel depot… yes. If you could somehow refill alive GEO sats and deorbit/graveyard dead ones, that would probably extend service life of many sats considerably. Developing such system is not going to be easy however.

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4 hours ago, sevenperforce said:

Mostly profit.

Thinking about the SES-9 mission and the idea of having a propellant depot in space with a tug to pull satellites into their desired orbit. Having an active propellant depot in orbit would be fantastic in terms of generally expanding our access to space, but unless it would be profitable, no one would ever do it.

So...under what circumstances would an immediate-term (e.g., within the next five years) propellant depot and space tug system be profitable?

Let's assume that the project would be undertaken by an independent private company rather than NASA. Let's assume it's not SpaceX or another current launch provider. Your primary customers would be comsat companies who choose to pay you some stated fee to tow their satellites into a desired orbit, though you could also potentially give the ISS boosts.

You need at least one space tug -- probably several, to maximize your profit and to lower launch costs. Each tug needs solar panels, ion engines, a grappling or towing mechanism, and the ability to refuel in space (either by mating to disposable propellant capsules or by transferring propellant to an onboard tank. You'll probably want to buy two Falcon Heavy launches to start -- one for as many space tugs as you can fit, and one for your initial propellant depot. You'd then re-launch a Falcon Heavy each time you needed to top-up your propellant depot.

Would anyone actually buy your services? How many comsat companies would say, "Hmm, instead of giving my satellite an engine and fuel tanks to push it into the desired orbit, I'll just pay these folks, and so I can make my satellite a little bigger and give it more capacity"? And would you be able to have low enough prices to actually save them money? 

I would use large VASMIRs and launch 3 ion tugs. Then, after sending satellites from LEO to GEO via space tugs, I would slowly aerobrake back to base, or use propellant if needed more quickly.

4 hours ago, Nibb31 said:

Within 5 years, isn't possible. It takes more than that to design and build any spacecraft. Even more for an advanced concept such as this.

To be undertaken by a private corporation requires a market for frequent launches. The market simply isn't large enough to support a high-frequency infrastructure such as this. And a tug for boosting comsats would be a very different design from tug for boosting the ISS, because the docking and thrust requirements would be completely different. It would also have to be in a totally different orbit.

Comsats need engines for station-keeping. Adding a little extra fuel and tankage is cheaper than adding a docking system, and paying extra for a tug service. Especially as your tug is going to have to be overengineered and carry twice the dV that a good old disposable Fregat or Ariane ESC upper stage has. And you also need to add the extra launches that carry the propellant for the tugs. 

 

Well, Vivisat is reboosting GEO sats via attaching to their apoapsis engine an using it as a makeshift docking port. ION engines will likely need less fuel, enough to justify this, if your LEO to GEO mission is not time critical.

3 hours ago, sevenperforce said:

Yeah, inclination changes take too much dV to be useful, even with ion engines.

That's what I was thinking -- it isn't cost-effective because you already have the station-keeping capabilities. 

Are there any sorts of scenarios where it would be cost-effective?

That would be a much bigger project than a comsat tug.

Well, LEO>GEO do not need inclination changes, so there's that....

49 minutes ago, radonek said:

I don't think there will be much demand for tug hauling sattelites LEO->GEO or anything. But fuel depot… yes. If you could somehow refill alive GEO sats and deorbit/graveyard dead ones, that would probably extend service life of many sats considerably. Developing such system is not going to be easy however.

That's what OrbitalATK is planning on doing now.

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My way to make money in space related to the OP will be with a "fuel depot" of 10000 Tons from a capture asteroid.

How to do it:
1) search a perfect asteroid (at least 75% ice) close to 22m of diameter who also need the less amount of deltav to be capture using gravity assist from the moon and earth.
2) gather investors (promise of profit) and international government support (asteroid impact defence program)
3) sent a probe using ion propulsion for the asteroid encounter, probe payload will be 200kg of reflective paint to spray the asteroid and a small nuclear reactor that it will melt the ice and will be used as propellant to capture the asteroid, with the help of extra pipes (as RSC) it will be possible to control direction and rotation.
4) The parking orbit would be elliptical from LEO to pass GEO, you install a big inflatable tank in which you store the water and extra tanks to store hydrogen and oxygen.
5) You can sell the propellent or orbital momentum with a tether system, in which sats will stole kinetic momentum to the asteroid to reach geo.
6) You can use this asteroid as kinetic mass to hit other asteroids that menace earth, or just to provide a fast service propellent to sent heavy nuclear weapons to hit the asteroid menace..  Nuclear weapons can release more energy, but you need to detonate first the weapon and most of that energy is waste it.

You can sell close to 7000 tons in propellent just with a 22m asteroid, this would require 175 falcon heavy launches.
Even if something happen and this asteroid fall into earth, is small and mostly ice, it will break in the atmosphere.

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3 minutes ago, AngelLestat said:

My way to make money in space related to the OP will be with a "fuel depot" of 10000 Tons from a capture asteroid.

How to do it:
1) search a perfect asteroid (at least 75% ice) close to 22m of diameter who also need the less amount of deltav to be capture using gravity assist from the moon and earth.
2) gather investors (promise of profit) and international government support (asteroid impact defence program)
3) sent a probe using ion propulsion for the asteroid encounter, probe payload will be 200kg of reflective paint to spray the asteroid and a small nuclear reactor that it will melt the ice and will be used as propellant to capture the asteroid, with the help of extra pipes (as RSC) it will be possible to control direction and rotation.
4) The parking orbit would be elliptical from LEO to pass GEO, you install a big inflatable tank in which you store the water and extra tanks to store hydrogen and oxygen.
5) You can sell the propellent or orbital momentum with a tether system, in which sats will stole kinetic momentum to the asteroid to reach geo.
6) You can use this asteroid as kinetic mass to hit other asteroids that menace earth, or just to provide a fast service propellent to sent heavy nuclear weapons to hit the asteroid menace..  Nuclear weapons can release more energy, but you need to detonate first the weapon and most of that energy is waste it.

You can sell close to 7000 tons in propellent just with a 22m asteroid, this would require 175 falcon heavy launches.
Even if something happen and this asteroid fall into earth, is small and mostly ice, it will break in the atmosphere.

You still don't want it in Earth Orbit due to a fear of asteroids. Keep it in high Lunar Orbit, it doesn't need much more delta V.

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My nuclear tug has 4 nukes and 4 aerospikes (for extra thrust) it's cool, but runs out of fuel pretty fast... And weighs more than the payload 95% of the time

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2 hours ago, fredinno said:

You still don't want it in Earth Orbit due to a fear of asteroids. Keep it in high Lunar Orbit, it doesn't need much more delta V.

The Chelyabinsk meteor that crash in the atmosphere above that city, was of similar size, but its speed was much higher that is why when it broke it took almost no time to be destroy, and was that explosion what cause all the damages, if it would be burn over a major time frame which also divide the shock wave over a major area, it would not cause any damage.
Is still risky.. but if the final burn approach gives you a periapsis that will be over oceans, then you reduce even more the risk.
The benefit of a elliptic orbit which periapsis is close to LEO, is that you reduce a lot your deltav requirements to capture the asteroid, and you can later sale that kinetic energy pushing sats and ships to higher orbit without even waste your 7000 tons of propellant. 

Other space tug system can use this fuel depot, if you plan to have a colony in mars or venus, you can have a similar asteroid (fuel depot) there providing propellent and kinetic energy.

2 hours ago, max_creative said:

My nuclear tug has 4 nukes and 4 aerospikes (for extra thrust) it's cool, but runs out of fuel pretty fast... And weighs more than the payload 95% of the time

heh, I guess you have a lot of room to improve.

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Just now, AngelLestat said:

The Chelyabinsk meteor that crash in the atmosphere above that city, was of similar size, but its speed was much higher that is why when it broke it took almost no time to be destroy, and was that explosion what cause all the damages, if it would be burn over a major time frame which also divide the shock wave over a major area, it would not cause any damage.
Is still risky.. but if the final burn approach gives you a periapsis that will be over oceans, then you reduce even more the risk.
The benefit of a elliptic orbit which periapsis is close to LEO, is that you reduce a lot your deltav requirements to capture the asteroid, and you can later sale that kinetic energy pushing sats and ships to higher orbit without even waste your 7000 tons of propellant. 

Other space tug system can use this fuel depot, if you plan to have a colony in mars or venus, you can have a similar asteroid (fuel depot) there providing propellent and kinetic energy.

heh, I guess you have a lot of room to improve.

It is mostly useless I use it for not a lot of stuff and takes a 1250 ton launcher to get into orbit, but who doesn't love explosions? :P

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Also, the refueling station in an elliptical orbit is a good idea. When it passes, say 100 km you can load on cargo like a lander, then go flying out to the mun and do a small burn, use a gravity assist and and you get a low delta-v, low part count, reliab- wait a second... less parts = smaller explosions! ;.; although it is a very good idea AngelLestat I'm going to try it (after I make the diamond back jr)

Edited by max_creative
Fixing some stuff

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Ok... The ssto blew up. Highest altitude was 2150 meters. I'm going to try that tomorrow because I have nothing better to do. (Other than sacrifice stuff to the kraken)

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19 hours ago, AngelLestat said:

The Chelyabinsk meteor that crash in the atmosphere above that city, was of similar size, but its speed was much higher that is why when it broke it took almost no time to be destroy, and was that explosion what cause all the damages, if it would be burn over a major time frame which also divide the shock wave over a major area, it would not cause any damage.
Is still risky.. but if the final burn approach gives you a periapsis that will be over oceans, then you reduce even more the risk.
The benefit of a elliptic orbit which periapsis is close to LEO, is that you reduce a lot your deltav requirements to capture the asteroid, and you can later sale that kinetic energy pushing sats and ships to higher orbit without even waste your 7000 tons of propellant. 

Other space tug system can use this fuel depot, if you plan to have a colony in mars or venus, you can have a similar asteroid (fuel depot) there providing propellent and kinetic energy.

heh, I guess you have a lot of room to improve.

But any refueling station will also have to be useful for LEO to GEO transfer. Making it in an ellipical orbit destroyed the purpose.

Also, when did I say the asteroid was dangerous? I said PUBLIC FEAR was the problem.

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2 hours ago, fredinno said:

But any refueling station will also have to be useful for LEO to GEO transfer. Making it in an ellipical orbit destroyed the purpose.

Also, when did I say the asteroid was dangerous? I said PUBLIC FEAR was the problem.

If you reach LEO and you want propellent, the main purpose of that need would not be to leave LEO?
So you use both, a tether for momentum exchange between the asteroid and the ship or sat.
The same tether can have a pipe to transfer the propellent at the same time.
It would not be like this example, but is kinda similar:  Min:2:52
 


Public fear can be managed if you have government support with the excuse that this asteroid can help the world in case you need to divert a biggest asteroid.

Edited by AngelLestat

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23 hours ago, AngelLestat said:

If you reach LEO and you want propellent, the main purpose of that need would not be to leave LEO?
So you use both, a tether for momentum exchange between the asteroid and the ship or sat.
The same tether can have a pipe to transfer the propellent at the same time.
It would not be like this example, but is kinda similar:  Min:2:52
 


Public fear can be managed if you have government support with the excuse that this asteroid can help the world in case you need to divert a biggest asteroid.

Yeah freakiing right. Good luck with that. People have been told vaccinations are not harmful since most people were born (and so have scientistists stating it is far less dangerous to take vaccines) but people STILL don't listen, and the measles researgence is evidence of it. Same with Chemtrails, Nuclear power plants and GMOs. You think people are going to listen that an asteroid over their heads is a good idea?

 

If so, you have too much faith in humanity. 

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