A tugboat for satellites

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The competition heats up: An Israeli start-up is building a satellite tugboat that could be used to move stranded satellites to their proper orbits.

The planned satellite, once built and deployed, should be able to rendezvous with in-orbit satellites and propel them into new orbits, give them course corrections, or steer them towards what’s known as the “graveyard orbit” – a decommissioned satellite graveyard some 300km above their usual height of 36,000 kilometers over the equator. This fuel saving can extend a communications satellite’s life.

The company says its tugboat design could be a possible solution to two stranded Galileo Project satellites, now in possibly unusable orbits following a launch malfunction over the weekend.

The spacecraft would use an ion engine for propulsion.



  • Competential

    Geopositioning satellites are not in GEO, they are in MEO which is about 10,000 km lower altitude and also in very different inclinations from the equator. And the failed two Galileo are obviously somewhere far from there. How many tons of fuel does it carry in order for their “micro-satellite” to perform such huge maneuvers? And what universal satellite construction standard is there in place today for the “tugboat” to be able to grab any satellite?

    The usual old problems with this concept remain unanswered. This won’t fly!

  • Competential

    The 2 Galileo satellites where misplaced by 1 km/s. That’s a quarter of the delta-v from LEO to Mars. And their mass is 675 kg each, almost three times that of this tugboat. Pie in the sky!

  • Tom Billings


    Let’s see, …..Assume an ISP of only 5,000, …that’s an exhaust velocity of 49,000m/sec.


    m(i)/m(f)= 1.02
    m(f)/m(i)= .97
    m(f)=m(i)x .97


    M(f)= 906kg

    propellant expended= 925-906= 19kg

    assume tug has a mass ratio of .5

    125kg/19kg= 6 missions to move GPS satellites

    Capital=$25 millions

    This seems to work out well, since the value of an unlaunched GPS satellite is several times the $25 millions capital cost for the tug. I think they could get their capital back in one mission. Of course, as the little cubesats start being used more they will also find specific ones needing a nudge, which is also a market.

    So, what’s the problem???

  • Edward

    Tom, the problem is that the article states the intended orbit for the tug is GEO, not the 50 degree orbital plane that the stranded satellites are in, so you need to factor in the plane change to get to the plane of the first of the lost Galileo satellites. That delta V, by my quick back of the envelope calculations (where is my slide rule when I need it?), is about 8,000 km per hour (around 2,000 m/sec, twice your calculation).

    Then there is the fuel expenditure to reach the first satellite, put it into orbit (including another 5 degree orbital plane change, 1,000-ish km per hour, or 300-ish m/sec), go back to the second, put it into orbit, then maybe return to GEO (another 8,000 km per hour).

    That’s a lot of delta V.

    I agree that a rescue tug may be less expensive than rebuilding and relaunching two more satellites, but it may be better to rescue these satellites with a specifically assigned and launched tug. If a tug were launched into the current orbit, the delta V is relatively small (compared with the above scenario) to rescue these satellites.

    If the tug has leftover fuel after the rescue, it could be used at the end of the satellites’ lives to put them into their graveyard orbit, which makes this a two-fer. They could earn a lot of money on this one mission alone.

    I found nothing on their website about fuel capacity or ISP, so it all looks theoretical (or hypothetical). I will bet that they quickly decide to refuel their tugs (probably less expensive than replacing the whole tug when it runs out of fuel).

    Competential asked: “And what universal satellite construction standard is there in place today for the ‘tugboat’ to be able to grab any satellite?”

    There is a standard sized “launch ring” on the bottom (apogee thruster end) of many satellites. These are used to mate with the launch vehicle, and could be used for a tug to dock with the satellite.

    I see a host of other problems to overcome, such as the center of mass of the satellite/tug system being above the tug, but these problems *can* be overcome. It reminds me of the scene in “Apollo 13” in which Jim Lovell has the same problem controlling the Apollo/LEM combination from the LEM, which was never intended for that job.

    As with Lovell, I suspect that Effective Space Solutions will have a learning curve early in their operations. No one has done this before, but many have talked about it. I wish them luck, it is about time someone tried this solution.

  • DK Williams

    If the misplaced satellite is rotating rapidly, it would prove difficult to capture if at all. I didn’t see mention of what launch vehicle they intend to use. I wish them success, but too risky for my venture capital (that is, if I had any).

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