Well, considering the infrastructure required to produce the fuel on site, swap out components and the vast amount of time needed for the spacecraft to travel between locations, I highly doubt this would be a better approach than sending spacecraft with a limited lifetime to a limited set of destinations.
Drop refueling, unlimited lifetime and changing out equipment, and we're already there. Dawn is orbiting its second destination. New Horizons is moving towards its second target. Kepler and Pioneer are still gathering data that was not part of their original mission.
The biggest problem is equipment eventually breaking down, like reaction wheels (Kepler, Dawn) and fuel valves (Juno), followed by fuel eventually running out.
Metal fueled vacuum arc thruster burning iron asteroids may be possible.https://iepc2017.org/sites/default/files/speaker-papers/paper_kuehn_iepc2017_0.pdf
Also, having a "stupid" (no scientific instruments), simple tank station satellite (probably on Sun orbit) could be the source of refueling. Quote from: high road on 06/03/2018 11:12 amDrop refueling, unlimited lifetime and changing out equipment, and we're already there. Dawn is orbiting its second destination. New Horizons is moving towards its second target. Kepler and Pioneer are still gathering data that was not part of their original mission.Exactly, I totally agree. This was the original source of this idea. These probes demonstrate, that additional results can be achieved over the original plans, and also, that could remain functioning for a long period in the space environment.Based on these, the next logical step could be making multi mission probes, than going on, step by step and eventually reaching the described fleet of long fife, multipurpose exploration crafts.I think, this will be a longer process, and will be done gradually. What I was interested in was, if this idea is known already, did somebody think about it, and at the current technological level, what are the biggest barriers.
If we want real long operation time, probably the best energy source is the solar panels (even though, this restricts the operation zone).
Sorry, my fault, I was not specific enough. Of course when I wrote about tank station, I meant it being in a proper orbit not"far" (deltaV) from the probes it is serving.
Quote from: jee_c2 on 06/11/2018 06:53 am... tank station, being in a proper orbit not"far" (deltaV) from the probes it is serving.Still not really viable. Too much propellant would be wasted to rendezvous with the tank station.
... tank station, being in a proper orbit not"far" (deltaV) from the probes it is serving.
Quote from: Jim on 06/11/2018 01:30 pmQuote from: jee_c2 on 06/11/2018 06:53 am... tank station, being in a proper orbit not"far" (deltaV) from the probes it is serving.Still not really viable. Too much propellant would be wasted to rendezvous with the tank station.Probably, you are right. It depends on the "distance" of the two spacecrafts. It really narrows down the range of usability of such a solution. May be even to zero. I think, one application could be (if) the asteroid belt. There should be more tank stations, serving a lot of probes , which could make standard examinations, measures on the asteroids for mapping the belt for later mining activities.. I try to write a simplified simulation to find out the numbers.It looks like, we should rather think about some propellent less drive like solar sail or Mr.Zubrin's dipol drive.. which also add more restrictions off course.
There have been proposals for a "grand tour" of the main asteroid belt, like Dawn, but doing flybys of many asteroids instead of going into orbit. Fuel needed for dV changes can be kept low by using the asteroids' gravity to adjust the orbit. I thought it was a great idea, though the proposal to fly by many of Jupiter's trojans (the LUCY mission) was selected instead. Similar to your thoughts, I think.