NASA Starts The Week With A Commercial Launch From Virginia
NASA Sends New Research on Orbital ATK Mission to Space Station
“Astronauts soon will have new experiments to conduct related to emergency navigation, DNA sequencing and ultra-cold atom research when the research arrives at the International Space Station following the 4:44 a.m. EDT Monday launch of an Orbital ATK Cygnus spacecraft. Cygnus lifted off on an Antares 230 rocket from NASA’s Wallops Flight Facility in Virginia on Orbital ATK’s ninth cargo mission under NASA’s Commercial Resupply Services contract. The spacecraft is carrying about 7,400 pounds of research equipment, cargo and supplies that will support dozens of the more than 250 investigations underway on the space station.”
Actually, this post should read “Orbital ATK Sends New NASA Research to the Space Station” – ISS resupply is a commercial service even if SpaceX isn’t doing it.
I think the coolest aspect of this mission is that they plan to boost ISS using this Cygnus. Been a while since a US vehicle has done that.
When oh when are they going to install a tether system so they can get a boost for ‘free’ when they depart?
Do we actually know enough about “tether-tech” to attempt it in this case?Transferring momentum is intriguing but as far as I have learned much basic-level research remains, no?
The last thing I read on the subject was a 2009 book by vanPelt (I think) so maybe more has been done since then.
I’d have to say no. I think he’s talking about an electrodynamic tether, not a momentum transfer device.
For momentum transfer (lowering something, like a capsule going back to Earth and then it), you could probably do something. It would a short-duration use and there wouldn’t be any need for a maneuver during the procedure. But I don’t know how much a a boost you’d get per drop.
For an electrodynamic tether, you’d have the cable extended all the time. By running current through it, you get a constant but small acceleration (from a current flowing across the Earth’s magnetic field.) I don’t think something like would be a good idea for ISS. Most of the potential problems and unknowns could be dealt with since it wouldn’t be a critical system. If it doesn’t work they could still go back to using rockets.
What I don’t like is the dynamics of firing a rocket with the cable deployed. That could include the ~ 1m/s maneuvers they occasionally do to avoid orbital debris. I’m trying to imagine the bending, oscillations and wobbling that would produce, and I don’t like the image in my head. Things like that have been done before, on spacecraft with long (>100 m) wire antennas. But those are spinning spacecraft with the cable under tension from the centrifugal force. A cable off ISS would only be under tension from the much weaker gravitational tides.
You should read comments more carefully, fcy. I was speaking precisely of momentum transfer, hence the reference to the departure of the cargo ships. E-D tethers are a different ball of twine, as it were.
TSS-1 demonstrated the inherent stability of a space tether, and with TSS-1R demonstrated the viability of tether deployment (and with -1, retrieval) algorithms, not to mention off-nominal control strategies. TSS-1R unintentionally demonstrated the basic physics of the momentum transfer technique (The satellite got a 60 nmi altitude boost.). Better, more robust tethers have been designed and I believe proto-typed if not outright manufactured.
The most significant challenge would be management of the tether at separation, but there are a number of ways this could be done…including use of other already-flown disposable tether designs more simple than the TSS reel system. If the tether were to separate at the ISS top end and fly away with the departing spacecraft, the hazard to the ISS would be almost nil (this, too, was demonstrated most robustly by TSS-1R).
As for fcy’s worry about the firing of rockets with a deployed tether, yes…a concern. But, again, both the TSS missions exercised DTOs which proved the viability of firing rockets while attached to a tether (as did Gemini XI & XII)…and TSS-1 had to do so dramatically when the tether reel jammed multiple times…the contingency response procedures worked as advertised.
The option is more viable than many folks think. The real (or should I say reel) question is whether the down-mass is sufficient to make it worthwhile to ISS. How big a boost each end-mass gets depends on its distance from the combined system’s center of gravity. The departing cargo ships would get lots of de-boost (saving them propellant, meaning more potential up-mass at least) but the ISS probably wouldn’t get much at all. The idea made more sense when we had heavier spacecraft (i.e., shuttle-orbiters) bringing up the cargo.
But this is the sort of thing that ISS should be testing out on a regular basis for the sake of pushing the tech…but I fear NASA management has been just a tad afeared of tethers ever since TSS.
Based on time and distance from my home these are the only launches I have a shot at seeing live. Made it down for one, wasn’t able to this time. Hope they keep it up so I get another chance to get down to Wallops Island again for a launch.