The space Tug

[Avron]

One item mentioned a few times is the concept of a space tug. I would guess that for the SDLV to be of use, a tug would be needed to "dock" componets launched via SDLV and other launch vehicles.

 Not only could it be used to dock components to the ISS but it could bring items to the ISS and provide station keeping, while the station arm grapples the componet. Assembly of larger space vehicle in orbit, could also do with a 'tug' or two.

I was wondering if there has been any official mention of such a tug and any plans on development?

Any ideas on what a space tug would look like? It capabilities?

[lmike]

If you look at this recently released ESAS slide: http://images.spaceref.com/news/2005/nas.esas.16.l.jpg , there is a planned service module+unpressurized cargo palette version of the LEO CEV (3rd from the left).  I believe that is the tug (if you delete the container and just leave the palette with the payload interface fixtures*).  However, it goes on top of the CLV and has a declared payload of 6MT.  I would think it could be adapted to be launched on the HLV however, and/or to meet up with the pre-launched payloads to be hauled.

*and add an SRM arm to it to grapple the payloads

[kraisee]

The SDLV 'Tug' is being folded into the design of the upper stage.

The upper stage itself will have a fully automated multiple-redundant RCS systems built in, which will allow it (and it's payload) quite a bit of manoeuverability.

And for lunar missions, remember that it has been designed to retain about 90-95 tons of propellant on board, after LEO injection, for use on the TLI burn to send everything moon-ward.   That's a LOT of fuel.

[lmike]

"The upper stage itself will have a fully automated multiple-redundant RCS systems built in..."  

Oh, this is a new development to me.  So it's going to be a 'smart' stage.  Thanks for sharing the info!  For some reason, I had the impression they'd launch the departure stage into a stable parking orbit, and then the lunar CEV's service module would be the one to do the approach, prox ops, and hook up to it for the moon flights.  Then, that's the heavy tug.

[AndyMc]

kraisee - 28/10/2005  12:43 AM

The SDLV 'Tug' is being folded into the design of the upper stage.

Hi,

Great news. Where did you get this info from? Is the first I heard of it, and makes perfect sense. Could it, or are there any plans to make it re-fuelable. It will need to be quite a sophisticated piece of kit if it is to remain in orbit any length of time. I guess the disposable stage used for TLI, would not have cryogenic cooling or the multi-redundant RCS, or will it?

Something like this was proposed for the OASIS project some years ago - the hybrid propellant module, though it had a seperate Chemical transfer module that contained the two engines. Perhaps some of these technologies will find their way into this upperstage design.

http://spacecraft.ssl.umd.edu/old_site/academics/484S03/oasis_docs/oasis_pics/
http://spacecraft.ssl.umd.edu/old_site/academics/484S03/

http://spacecraft.ssl.umd.edu/old_site/academics/484S03/oasis_docs/OASIS_FY01_FINAL.PDF
http://spacecraft.ssl.umd.edu/old_site/design_lib/OASISEXEC_97.pdf

[Avron]

Thanks.. good news...

Now I was hoping that the 'Tug' could be launched a little earlier and stay in orbit, so other options could be used to get  items launched.. maybe even use some commercial vendors to launch and 'dock' the tug with the component and move it to its station..

I guess that the SDLV upper stage could do the trick, so maybe it can be developed first and launched using a EELV/CLV (mass may be a problem) before the rest of the SDLV is developed to provide options before 2018.

[kraisee]

AndyMc - 28/10/2005  8:42 AM

kraisee - 28/10/2005  12:43 AM

The SDLV 'Tug' is being folded into the design of the upper stage.

Hi,

Great news. Where did you get this info from? Is the first I heard of it, and makes perfect sense.

...

Yes, it does make sence.   You don't want the the tiny CEV's RCS system being the only thing available to reposition the entire 100+ tons of Earth Departure Stage & propellant, Lunar Surface Access Module, CEV CM and SM in preparations for the TLI to go to the moon.

The Upper stage will thus be able to perform automated rendezvous even if there is no CEV or crew involved - and this will be very useful for sending automated craft to the moon and building things in LEO too - like a Mars spacecraft.

[realtime]

But this upper stage "tug" is designed to be expendable, yes?  If that's true then this is not a "tug", it is a disposable OMS, good for no more than the mission it launched on.

My definition of a tug is a spacecraft that is designed to stay on orbit and handle payloads from multiple launches.  It would contain a sophisticated OMS to allow it to dock with payloads and guide them to ISS or to rendezvous at assembly points.  It may (or may not) be refuelable on orbit.  To allow the tug to dock successfully, payloads would carry only a kick motor for circularization and a minimal RCS system to prevent tumbling.

Theoretically, this configuration would allow mission planners to throw "dumb" payloads into LEO and then maneuver the payload without the expense of certifying, boosting, and discarding a full-up OMS on every HLLV flight.

[AndyMc]

Hi,

It's well within the realms of possibility that there will be a tug version and an expendable version of the upper stage. There has  been plenty of research into cryo cooling done by NASA over the years. Where better to test it than in an unmanned vessel in LEO, before trying to rely on it for a 3 year round trip to Mars.

[Peter NASA]

AndyMc - 29/10/2005  2:50 PM

Hi,

It's well within the realms of possibility that there will be a tug version and an expendable version of the upper stage. There has  been plenty of research into cryo cooling done by NASA over the years. Where better to test it than in an unmanned vessel in LEO, before trying to rely on it for a 3 year round trip to Mars.

That is correct and these tug boats are an intriguing addition to the overall future planning.

[Avron]

realtime - 29/10/2005  1:57 PM

But this upper stage "tug" is designed to be expendable, yes?  If that's true then this is not a "tug", it is a disposable OMS, good for no more than the mission it launched on.

My definition of a tug is a spacecraft that is designed to stay on orbit and handle payloads from multiple launches.  It would contain a sophisticated OMS to allow it to dock with payloads and guide them to ISS or to rendezvous at assembly points.  It may (or may not) be refuelable on orbit.  To allow the tug to dock successfully, payloads would carry only a kick motor for circularization and a minimal RCS system to prevent tumbling.

Theoretically, this configuration would allow mission planners to throw "dumb" payloads into LEO and then maneuver the payload without the expense of certifying, boosting, and discarding a full-up OMS on every HLLV flight.

Thats what I had in mind for a Tug. Now what would prevent a SDLV upper stage from being launch into LEO an remain there for say a year, playing the roll of a Tug?

[FransonUK]

Anyone have an image of what a space tug would look like?

[nacnud]

This is Boeings first spacetug [astronautix], it seems like a very useful vehicle

The original BoeingSpace Tug design of the early 1970's was sized to be flown either in a singleshuttle mission or as a Saturn V payload. Optimum mass was found to be 20.6tonnes regardless. The Tug could be outftted with a variety of kits to serve inmany roles, including as a manned lunar lander. Aerobraking for recovery in lowearth orbit was considered for further study, but the baseline used RL10engines to brake into earth orbit for refurbishment and refuelling at a spacestation. All further work was cancelled by NASA in 1972, but resurrected as theaerobraking Orbital Transfer Vehicle in the 1980's.

http://www.astronautix.com/graphics/z/zstugmw.jpg" />
http://www.astronautix.com/graphics/z/ztugcrew.jpg" />

[nacnud]

Crap, I just added information on some other space tugs such as the TKS, Parom, the Turtle 2 OTV, Orbital recoveries Cone express, etc but the post didn't work. Still heres a pic of the proposed Parom next to the klipper, you'll have to google for the rest
http://uplink.space.com/attachments//364545-futureK2.jpg" />

[Tap-Sa]

This is Boeings first spacetug [astronautix]

Looks neat, but getting down to surface from the lunar version would be interesting.

"One small step for maAAAAAAAAANNN*THUMP*"