John Strickland has some suggestions for in-LEO transportation:
One of the features of the original space station and shuttle concept was a space tug. The concept was called the S.T.S: (Space Transportation System), which would have allowed access to other locations in LEO (in the same or similar orbital plane) from the station. Such a tug would be able to capture large payloads, either modules or large cargo containers, and deliver them safely back to the station. The tug was originally in the post-Apollo plans, but by the mid-1970’s, like many critical components of the current Station, such as the Large Centrifuge Facility, it got chopped by budget cuts and budget overruns of other parts of the shuttle program, leaving just the Shuttle. Thus this component was lost long before the 1984 Reagan Space Station proposal. We still only have two components of what was intended to be a three-component system.
There were a few half-hearted attempts over the years to restore it (e.g., the Orbital Maneuvering Vehicle, which Marshall screwed the pooch on with, among other things, stupid requirements), but this hasn’t really been a serious discussion at NASA in decades. Yet it’s a key piece of the architecture for both LEO and BEO ops (a BEO version could be similar to the LEO one, except with larger tank or propulsion kits). And it’s all enabled by gas stations, of course. And these are all issues that Constellation, with its “let’s do Apollo again” mindset, completely ignored.
Sounds similar to the Russian concept of the Parom Orbital Tug
http://www.russianspaceweb.com/parom.html
The ARDV-Tugs for the Flagship Technology Demonstrations in FY2011 seem like a good evolutionary approach to space tugs:
http://www.nasa.gov/pdf/458813main_FTD_AutomatedAutonomousRendezvousAndDockingVehicleOverview.pdf
Tugs may make sense going from LEO to GEO but in LEO they are of low value.
Even at the same inclination it takes a long time to get plane changes,
depending upon impulse used. If you have a nuke, sure, it
works but with a chemical storable it’s a tough case.
What about ion engines?
the FTD SEP sounds relevant for beyond LEO destinations.
http://www.nasa.gov/pdf/458818main_FTD_SolarElectricPropulsionStage.pdf
it’s all enabled by gas stations
Everything becomes a tug once you’ve got refueling. With the OMV they intended for the shuttle to bring empty fuel tanks back to earth for refilling.
Can the Falcon9 second stage achieve a stable LEO orbit of its own independent of the Dragon?
That is: One of the most interesting features of the DIRECT plan to me was how the upper stage was a significant slice of a ‘gas station’. Missing was the essential sunscreen, and cryogenic maintenance gear. But the -tanks- were up.
Could Falcon9 second stage reasonably manage something similar?
Al
No, it won’t restart.
jack, you wrote:
Even at the same inclination it takes a long time to get plane changes, depending upon impulse used.
It takes even longer to get plane changes when you can’t make them. There’s also a possible market of rescuing satellites that are in a bad insertion orbit (commonly due to a premature engine cutoff). It might be worth a few tens of millions of dollars to launch a tug which would push a billion dollar satellite into a better orbit.
You also wrote:
No, it won’t restart.
While SpaceX’s current Merlin and Kestrel engines aren’t designed to restart, it’s worth noting that their smallest engine, the Draco is restartable. The Draco is a hypergolic engine while its big brothers are kerosene/LOX. There are some other differences (particularly, no regenerative nozzle) so it’s not clear whether they can scale Draco up.
While SpaceX’s current Merlin and Kestrel engines aren’t designed to restart
Not even for flights to GTO?
Sigh, of course the SpaceX engines are restartable.
While SpaceX’s current Merlin and Kestrel engines aren’t designed to restart, it’s worth noting that their smallest engine, the Draco is restartable.
I don’t know where you got your information but it’s wrong. From SpaceX’s Falcon 1 page:
A single SpaceX Kestrel engine powers the Falcon 1 upper stage. A highly reliable and proven TEA-TEB pyrophoric system is used to provide multiple restart capability on the upper stage.
From their Falcon 9 page:
A single Merlin engine powers the Falcon 9 upper stage with an expansion ratio of 117:1 and a nominal burn time of 345 seconds. For added reliability of restart, the engine has dual redundant pyrophoric igniters (TEA-TEB).
They demonstrated restart on the Falcon 1 second stage on Flight 4 and perhaps Flight 5.
Add a manipulator arm and refuel DragonLab and you’ve got a tug. They definitely demonstrated restart on flight 4 and I expect they will announce restarts on this latest once they put out an update.