Author Topic: Fuel for Fuel depot  (Read 7297 times)

Offline A_M_Swallow

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Re: Fuel for Fuel depot
« Reply #20 on: 09/25/2011 02:58 PM »
Please explain to me how this scheme would work with an Ariane 5 carrying a payload to geosynchronous transfer orbit. How much propellant could it deliver to a depot? Where would the depot be located? What type of propellant would it be?

Propellant taken to geosynchronous transfer orbit probably wants taking all the way to geosynchronous orbit.  In GEO the main purpose of fuel is station keeping.  So the propellant is likely to be xenon (or argon).

Where as depots at LEO and Lagrange points are likely to sell high thrust fuels.

Offline douglas100

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Re: Fuel for Fuel depot
« Reply #21 on: 09/25/2011 03:45 PM »
Incorrect.  Once again you fail to consider that the fuel depot can make the orbital adjustments once in space as long as those orbital adjustments are small.  The launch window would be set by the primary payload.

I removed my original reply in favour of this.

The fact that the fuel depot can maneuver does not change the fact it dictates the length of the launch window.

Consider the following scenario: a commercial launch vehicle is going to deliver or pick up propellant (it doesn't matter which) at a depot in low Earth orbit before going on to place its primary payload in geosynchronous transfer orbit. The orbit of the depot is adjusted so that the time of launch for rendezvous is convenient for the customer's payload. Then the Range goes red for high upper atmosphere winds and the count is held. It is expected that in maybe half an hour or so that conditions will be favourable. During the hold the launch window for the depot is missed. (It will typically be only a few minutes.) Half an hour later the range is green. The payload is good to go (the launch windows for GTO launches can be over an hour) but in order to make the depot rendezvous the launch must be scrubbed. The tail is still wagging the dog.

I stand by my original assertion.

The depot system has to be set up first for non commercial uses (probably HSF) and then, maybe, there might be a case for commercial users.
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Offline douglas100

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Re: Fuel for Fuel depot
« Reply #22 on: 09/25/2011 04:21 PM »

Propellant taken to geosynchronous transfer orbit probably wants taking all the way to geosynchronous orbit.  In GEO the main purpose of fuel is station keeping.  So the propellant is likely to be xenon (or argon).

Where as depots at LEO and Lagrange points are likely to sell high thrust fuels.

I agree that xenon could be needed in geosynchronous orbit. Whether there is a market for it is a different matter.

I also agree with your second point. This is of course where the ULA architecture originally suggested depots should be located for HSF.
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Offline SpacexULA

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Re: Fuel for Fuel depot
« Reply #23 on: 09/25/2011 04:43 PM »
I agree that xenon could be needed in geosynchronous orbit. Whether there is a market for it is a different matter.

I also agree with your second point. This is of course where the ULA architecture originally suggested depots should be located for HSF.

Good thing about a xenon depot is the pathfinder depot could also be an operational one.  Send the depot up with an orbital express type vehicle to test dock with in 3-4 times, then just let it sit in orbit with the offer of free xenon to anyone who designs their spacecraft to take it from the depot.

Don't think a xenon depot is going to have a problem station keeping for 10-20 years :)
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Offline douglas100

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Re: Fuel for Fuel depot
« Reply #24 on: 09/25/2011 06:05 PM »

Good thing about a xenon depot is the pathfinder depot could also be an operational one.  Send the depot up with an orbital express type vehicle to test dock with in 3-4 times, then just let it sit in orbit with the offer of free xenon to anyone who designs their spacecraft to take it from the depot.

Don't think a xenon depot is going to have a problem station keeping for 10-20 years :)

Good points. But so little xenon is needed for station keeping you wonder if you could possibly make a profit by selling it in GEO...
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Offline SpacexULA

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Re: Fuel for Fuel depot
« Reply #25 on: 09/25/2011 08:10 PM »
Good points. But so little xenon is needed for station keeping you wonder if you could possibly make a profit by selling it in GEO...

If it does not it helps prove a lack of a market, while still helping to further automated refueling, thatís still a win-win.  So if no one takes you up on the offer so be it, not THAT much more money is lost than your standard unmanned science mission, but on the other hand that depot could provide some interesting business models.

Wonder how much some sat companies would pay to have a Micro-Sat in GEO that can fly out to bird and effectively hit it with a ball pen hammer to see if it wakes up, or change it's orbit slightly (without refueling the actual spacecraft).

There have been less intersting science missions.
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Offline douglas100

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Re: Fuel for Fuel depot
« Reply #26 on: 09/25/2011 09:08 PM »

If it does not it helps prove a lack of a market, while still helping to further automated refueling, thatís still a win-win.  So if no one takes you up on the offer so be it, not THAT much more money is lost than your standard unmanned science mission, but on the other hand that depot could provide some interesting business models.

Wonder how much some sat companies would pay to have a Micro-Sat in GEO that can fly out to bird and effectively hit it with a ball pen hammer to see if it wakes up, or change it's orbit slightly (without refueling the actual spacecraft).

There have been less intersting science missions.

Something along these lines was proposed by Orbital Recovery eight years ago. Their vehicle was bigger and probably cost a lot more than a microsat. They don't appear to be around any more.

Inspection/refueling of comsats is up to the owners, I suppose, and whether a market exists is up to them.
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Offline A_M_Swallow

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Re: Fuel for Fuel depot
« Reply #27 on: 09/25/2011 09:08 PM »

Good thing about a xenon depot is the pathfinder depot could also be an operational one.  Send the depot up with an orbital express type vehicle to test dock with in 3-4 times, then just let it sit in orbit with the offer of free xenon to anyone who designs their spacecraft to take it from the depot.

Don't think a xenon depot is going to have a problem station keeping for 10-20 years :)

Good points. But so little xenon is needed for station keeping you wonder if you could possibly make a profit by selling it in GEO...

The main alternative to refuelling a satellite is to replace the satellite.  A two year extension on a satellite with a planned 10 year life could be worth
(2/10)*(cost of new satellite)
including both assembly and launch costs

It may even be worth the satellite operator paying more if the replacement is 3 years late.

The other possible customers need to raise out of fuel satellite(s) to a graveyard orbit.

Offline DarkenedOne

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Re: Fuel for Fuel depot
« Reply #28 on: 09/25/2011 11:02 PM »
Incorrect.  Once again you fail to consider that the fuel depot can make the orbital adjustments once in space as long as those orbital adjustments are small.  The launch window would be set by the primary payload.

I removed my original reply in favour of this.

The fact that the fuel depot can maneuver does not change the fact it dictates the length of the launch window.

Consider the following scenario: a commercial launch vehicle is going to deliver or pick up propellant (it doesn't matter which) at a depot in low Earth orbit before going on to place its primary payload in geosynchronous transfer orbit. The orbit of the depot is adjusted so that the time of launch for rendezvous is convenient for the customer's payload. Then the Range goes red for high upper atmosphere winds and the count is held. It is expected that in maybe half an hour or so that conditions will be favourable. During the hold the launch window for the depot is missed. (It will typically be only a few minutes.) Half an hour later the range is green. The payload is good to go (the launch windows for GTO launches can be over an hour) but in order to make the depot rendezvous the launch must be scrubbed. The tail is still wagging the dog.

I stand by my original assertion.

The depot system has to be set up first for non commercial uses (probably HSF) and then, maybe, there might be a case for commercial users.

I see where the problem is here.  Your analysis would hold for some sort of integrated approach, which is not what I originally proposed.

When secondary payloads, like university cubesats, are carried on rockets like the Araine V, the rocket does not go alter its trajectory in any fashion nor do they alter launch times of the $140 million dollar rocket in order to accommodate the $10,000 dollar cubesats.  What they will do is simply deploy the satellite somewhere along the route.  At that point if the cubesat has its own propulsion it can make the orbital adjustments needed to reach its own orbit.

That is the arrangement I am talking about.  The rocket will not alter its course, nor change its launch times in order to accommodate the refueling spacecraft.  The upper stage with the satellite will not accompany the refueling spacecraft on its way to the depot.  The refueling spacecraft will simply be ejected somewhere along the way then use its own propulsion to make the adjustments to the orbit.

An example situation will play out as follows.  DirecTV buys a launch to GTO on the Ariane V for a satellite with a mass of 6000kg.  Since the Ariane V is capable of launching 10500 kg into GTO, the DirecTV company has 4500 kg of capacity it has no use for.  Refueling company A comes in and offers to buy the 4500 kg of extra capacity for half price.  DirecTV accepts because its better to then letting the capacity go to waste.  The rocket launches at the optimum time and trajectory for the DirecTV satellite.  Both the refueling spacecraft and the DirecTV satellite are carried into orbit by the rocket's upper stage.  The refueling spacecraft is released early before the upper stage achieves GTO.  The DirecTV satellite continues on carried by the upper stage into GTO.  The refueling spacecraft then uses its own propulsion system and a bit of the fuel its carrying to travel to the depot.


Offline mlorrey

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Re: Fuel for Fuel depot
« Reply #29 on: 09/26/2011 02:20 AM »

Good thing about a xenon depot is the pathfinder depot could also be an operational one.  Send the depot up with an orbital express type vehicle to test dock with in 3-4 times, then just let it sit in orbit with the offer of free xenon to anyone who designs their spacecraft to take it from the depot.

Don't think a xenon depot is going to have a problem station keeping for 10-20 years :)

Good points. But so little xenon is needed for station keeping you wonder if you could possibly make a profit by selling it in GEO...

The depot belongs in the gravitational wells that GEO satellites all drift toward. They expend significant propellant over time keeping themselves in their assigned slots in GEO, if you were unaware of this, google "zombiesat" for stories about one sat that lost maneuvering ability last year. So a depot in the gravity well wont spend much xenon to stay where it wants to be anyways, the other satellites will move there to refuel naturally.
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Offline MP99

Re: Fuel for Fuel depot
« Reply #30 on: 09/26/2011 07:00 AM »
The refueling spacecraft is released early before the upper stage achieves GTO.  The DirecTV satellite continues on carried by the upper stage into GTO.  The refueling spacecraft then uses its own propulsion system and a bit of the fuel its carrying to travel to the depot.

Is the depot in LEO? [The refueller is dropped before GTO, and only uses "a bit of the fuel" to reach the depot.]



An example situation will play out as follows.  DirecTV buys a launch to GTO on the Ariane V for a satellite with a mass of 6000kg.  Since the Ariane V is capable of launching 10500 kg into GTO, the DirecTV company has 4500 kg of capacity it has no use for.  Refueling company A comes in and offers to buy the 4500 kg of extra capacity for half price.

Or is it in GSO? [That "4500 kg" is capacity to GTO.]

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Online Archibald

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Re: Fuel for Fuel depot
« Reply #31 on: 09/26/2011 07:15 AM »
A little though issue with Xenon-fueled SEP: Xenon is scarce and expensive

http://www.thespacereview.com/article/602/1

Quote
Woodcock describes a hypothetical SEP system for orbit-raising of heavy loads. This reference utilizes a payload of 50 mT driven by a 500 kW solar electric propulsion system with a specific impulse of 2000 sec. The trip time (up) is 240 days and (down) is 60 days. The required amount of xenon (Xe) propellant per transfer is 41.2 mT. According to estimates on the Internet, world production of Xe is presently 10 x 106 liters/yr = 53 mT/yr. Thus, one transfer would require approximately the present annual world production of Xe. Furthermore, Xe presently costs about $10/liter so the cost of Xe for one orbit transfer could be $100M. While it may be possible to increase world production significantly, recent articles on anesthesiology suggest difficulties.

Fortunately not all SEP systems use Xenon - or rare gases, I'm not sure Argon is much an improvment.

By contrast there is ammonia a plenty - arcjets thrusters have lower specific impulse but higher thrust; and most of the electrothermal or electromagnetic thrusters as listed by wikipedia also works with ammonia (yes, I did search beyond wikipedia).

Quote

Electrostatic

If the acceleration is caused mainly by the Coulomb Force (i.e application of a static electric field in the direction of the acceleration) the device is considered electrostatic.

    * Electrostatic ion thruster
    * Hall effect thruster
    * Field Emission Electric Propulsion
    * Colloid thruster

Electrothermal

The electrothermal category groups the devices where electromagnetic fields are used to generate a plasma to increase the heat of the bulk propellant. The thermal energy imparted to the propellant gas is then converted into kinetic energy by a nozzle of either solid material or magnetic fields. Low molecular weight gases (e.g. hydrogen, helium, ammonia) are preferred propellants for this kind of system.

Performance of electrothermal systems in terms of specific impulse (Isp) is somewhat modest (500 to ~1000 seconds), but exceeds that of cold gas thrusters, monopropellant rockets, and even most bipropellant rockets. In the USSR, electrothermal engines were used since 1971; the Soviet "Meteor-3", "Meteor-Priroda", "Resurs-O" satellite series and the Russian "Elektro" satellite are equipped with them.[5] Electrothermal systems by Aerojet (MR-510) are currently used on Lockheed-Martin A2100 satellites using hydrazine as a propellant.

    * DC arcjet
    * microwave arcjet
    * Pulsed plasma thruster

Electromagnetic

If ions are accelerated either by the Lorentz Force or by the effect of an electromagnetic fields where the electric field is not in the direction of the acceleration, the device is considered electromagnetic.

    * Electrodeless plasma thruster
    * MPD thruster
    * Pulsed inductive thruster
    * Helicon Double Layer Thruster
    * VASIMR
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Offline douglas100

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Re: Fuel for Fuel depot
« Reply #32 on: 09/26/2011 08:30 AM »

I see where the problem is here.  Your analysis would hold for some sort of integrated approach, which is not what I originally proposed.

An example situation will play out as follows.  DirecTV buys a launch to GTO on the Ariane V for a satellite with a mass of 6000kg.  Since the Ariane V is capable of launching 10500 kg into GTO, the DirecTV company has 4500 kg of capacity it has no use for.  Refueling company A comes in and offers to buy the 4500 kg of extra capacity for half price.  DirecTV accepts because its better to then letting the capacity go to waste.  The rocket launches at the optimum time and trajectory for the DirecTV satellite.  Both the refueling spacecraft and the DirecTV satellite are carried into orbit by the rocket's upper stage.  The refueling spacecraft is released early before the upper stage achieves GTO.  The DirecTV satellite continues on carried by the upper stage into GTO.  The refueling spacecraft then uses its own propulsion system and a bit of the fuel its carrying to travel to the depot.

In the example you give, the refueling spacecraft is released early before the upper stage achieves GTO. That is impossible with the current Ariane since the HM-7B engine in the upper stage is not restartable.

And even if you could do that, the depot, by virtue of the Ariane's launch trajectory, would be in an orbit with a low inclination which could not be reached by a Proton launched from Baikonur, certainly not one carrying a commercial payload.

And my point is that the devil is in the details. You have proposed a generic idea. You haven't said where the depot will be located, what propellant will be used, who the customers will be. You were right to say I was thinking of depots as an integrated system. That's the only way it could work.

You'll notice the recent discussion has been about refueling operations in GEO. That's because that's where most current commercial traffic goes. Let's move on.
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Offline Tass

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Re: Fuel for Fuel depot
« Reply #33 on: 09/27/2011 10:43 AM »
A little though issue with Xenon-fueled SEP: Xenon is scarce and expensive

http://www.thespacereview.com/article/602/1

Quote
Woodcock describes a hypothetical SEP system for orbit-raising of heavy loads. This reference utilizes a payload of 50 mT driven by a 500 kW solar electric propulsion system with a specific impulse of 2000 sec. The trip time (up) is 240 days and (down) is 60 days. The required amount of xenon (Xe) propellant per transfer is 41.2 mT. According to estimates on the Internet, world production of Xe is presently 10 x 106 liters/yr = 53 mT/yr. Thus, one transfer would require approximately the present annual world production of Xe. Furthermore, Xe presently costs about $10/liter so the cost of Xe for one orbit transfer could be $100M. While it may be possible to increase world production significantly, recent articles on anesthesiology suggest difficulties.

Fortunately not all SEP systems use Xenon - or rare gases, I'm not sure Argon is much an improvment.

Of course argon is an improvement. It makes up almost a percent of the atmosphere. It costs on the order of dollars per kilogram.

Offline savuporo

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Re: Fuel for Fuel depot
« Reply #34 on: 10/01/2011 09:28 PM »

Is the depot in LEO?

There is one in LEO right now. Depot fans, meet Zarya, a fully functional propellant depot which has been circling overhead since 1998

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