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?
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.
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.
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...
If it does not it helps prove a lack of a market, while still helping to further automated refueling, that’s 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.
Quote from: SpacexULA on 09/25/2011 04:43 pmGood 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...
Quote from: DarkenedOne on 09/24/2011 12:53 pmIncorrect. 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.
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.
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.
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.
ElectrostaticIf 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 thrusterElectrothermalThe 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 thrusterElectromagneticIf 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
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.
A little though issue with Xenon-fueled SEP: Xenon is scarce and expensive http://www.thespacereview.com/article/602/1QuoteWoodcock 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.
Is the depot in LEO?