[X] My Assistant

[stevesliva]

From fall 2020 OPAG https://www.lpi.usra.edu/opag/meetings/opag2020fall/

Persephone:
https://www.lpi.usra.edu/opag/meetings/opag...Howett_6005.pdf

There is talk of extended missions out to 2079. Building cathedrals for our grandkids here...

[Steve G]

About that 27 years trajectory . . . That puts a lot of lifetimes to the wayside when it arrives. With a launch ten years from now, new and better rockets may be available, such as StaceX's Starship should it deliver to expectations, or even Blue Origin's New Armstrong (should it be ever come to pass). If launch costs are reduced by the new (reusable) space rockets along with the massive payloads they are advertising, you could conceivably launch it really fast with loaded with tons of fuel and jam on the breaks hard. That would cut trajectory significantly. Based on the cost per flight, SLS may not even be around by then.

[Explorer1]

If launch costs are reduced by the new (reusable) space rockets along with the massive payloads they are advertising, you could conceivably launch it really fast with loaded with tons of fuel and jam on the breaks hard. That would cut trajectory significantly. Based on the cost per flight, SLS may not even be around by then.

The trouble is, what sort of fuel will last long enough on the journey to still be available for a Pluto orbit insertion? Cryogenic fuels like liquid hydrogen tend to evaporate, don't they? Would solids be better (like for the Mars Ascent Vehicle being planned?)

[HSchirmer]

The trouble is, what sort of fuel will last long enough on the journey to still be available for a Pluto orbit insertion? Cryogenic fuels like liquid hydrogen tend to evaporate, don't they? Would solids be better (like for the Mars Ascent Vehicle being planned?)

IIRC, ESA has been looking at hydrogen peroxide monopropellant for attitude control thrusters; and New Shepherd used hydrogen peroxide and kerosene for their oxidizer and fuel. So some propellant combinations could do double duty.

With RTG supplying electric , more likely an ion drive for long term course correction, and reaction wheels for fine attitude control. Would need a battery to store power for fast slewing at encounter, so you might still need thrusters as a backup if the reaction wheels failed.

IIRC some papers found that eddy currents from solar storm could cause arcing across the bearings that chews them up and causes failure; but until somebody perfects and proves ceramic bearings work on reaction wheels, you'll have redundant systems.

[mcaplinger]

With RTG supplying electric , more likely an ion drive for long term course correction, and battery powered reaction wheels for attitude control

Persephone already uses electric propulsion, though the viewgraphs are not terribly clear about exactly how the orbit insertion works -- it takes almost 10 years between the KBO flyby and arrival at Pluto. If you want really fast transit times, electric probably won't help. But you are talking a lot more launch vehicle delta-V than anything available now.

Solids have no particular advantages over storable biprops. A solid motor was used for Magellan; it worked but would not be anyone's first choice.