A new technique to save aging satellites promises to save millions of dollars by extending the life of communications spacecraft. A process developed by researchers from Purdue University and Lockheed Martin has already saved $60 million for unnamed broadcasters by extending the service life of two communications satellites.
In a nutshell the technique works by applying an advanced simulation and a method that equalizes the amount of propellant in satellite fuel tanks so that the satellite consumes all of the fuel before being retired from service. Some aging communications satellites are each equipped with four fuel tanks. If one of the tanks empties before the others, the satellite loses control and should be decommissioned, wasting the remaining fuel in the other tanks.
Communications satellites, which are maintained in proper orbit about 22,500 miles above Earth by firing small rocket thrusters, must be replaced shortly before they run out of fuel, researchers said in a paper published in the most recent Journal of Spacecraft and Rockets. Enough fuel must remain to get the satellites out of orbit to make room for their replacements.
The Purdue and Lockheed Martin engineers not only determined precisely how much fuel remained in each tank, but they also used a technique to "rebalance," or equalize, propellant levels in all of the tanks. The engineers kept the twin satellites operating an additional six months, which translates into about $60 million in revenue for the broadcast companies that owned the satellites said Steven Collicott a Purdue professor of aeronautics and astronautics in a statement.
Adjusting the levels of fuel in an orbiting satlite is no simple task. The problem's complexity is illustrated by the level of skills needed, said Collicott, adding that most researchers involved in such work have doctoral degrees in aerospace engineering.
The research paper details two portions of the work needed to accomplish the fuel equalization: how to perform the "thermal gauging" that determines how much propellant is contained in the tanks, and then how to accomplish the rebalancing.
"It took a year and a half of thermal pumping, carried out at different times, to accomplish the rebalancing," Yendler said. "We were really excited to see that we could take our new propellant-gauging method to provide this lifetime maximization in satellites that were never designed to have anything like this done to them."Communications satellites cost about $100 million and sometimes as much money to launch them into a geosynchronous orbit. They generally have a 15-year lifetime, bringing in $5 million to $10 million a month in revenue.
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Another Thought
Having a single tank which feeds all the thrusters, would solve the problem in the most simplest way, without requiring advanced simulation and aerospace engineering.
Dr. Abraham
And that didnt even require you to have a doctorate degree...lol
reason for multiple tanks
A single tank would solve the fuel balancing problem, but there may be other reasons to divide the fuel among multiple tanks.
Multiple tanks give redundancy. If one of four tank gets stuck closed or leaks out its fuel, you still have 75% of your original fuel load remaining. If one of one tanks fails, your mission is over.
There may also be a fit issue. It might be easier to fit four small tanks within the confines of the satellite bus than is is to fit one large tank. The equipment area of the satellite bus is pretty crowded.
If one tank is empty, it's
If one tank is empty, it's mission over. Read the article. Same thing as having one tank stuck, so that's not a valid argument. 3/4 working tanks is just as good as 0/1 working tank.
reasons for multiple tanks
With the exception of a few satellite models (some of which use monopropellant technology and some use ion propulsion technology), most newer three axis communications satellites use bi-propellent propulsion technology for stationkeeping operations - that is, they use both a fuel and an oxidizer and mix them together in the thrust chamber of the thrusters. Because the fuel and oxidizer form a chemical reaction when mixed, the two are kept in separate tanks until they are used. This is why no one uses a single tank.
There are multiple reasons for having four tanks instead of two tanks in a bipropellant propulsion technology system. One of which is redundancy and the other is for maintaining mass properties especially during transfer orbit operations. If you have only two tanks - one containing oxidizer and the other containing the fuel, and if one of the valves happens to leak, it would deplete the propellant. The remaining half of the propellant in the other tank, even if it is full, has nothing to react with, and thus the satellite thruster is unable to generate any thrust.
And the consumers??
Do we get a price break or is this just forwarded to the shareholders??
SOLAR POWER!!!!!!!!!!!!
Why are we still using fuel for these satellites. The new ones should start taking advantage of the gains in the solar panel energy producing market. I am just taking a guess here that since it is up in space it just might........get a little sun from time to time. It is also a little closer then us down here as well. My car has a very rundamentory fuel gauge that works well for me. I wonder if the car manufacturers should employ aerospace engineers. That would only bring the price of a car up an extra $10,000.00.
RE: Solar Power
Newton's second law: For every action there is an equal and opposite reaction.
In order for satellites to move around, thrusters are required to provide reaction mass. You can have all the solar panels in the world but the electricity provided would not move anyhting in a vacuum.