Persephone Pluto Orbiter Options

[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.

[stevesliva]

I wanted to see if you recalled correctly, because I myself could not recollect this:
https://hackaday.com/2018/09/11/do-space-pr...-space-weather/

[HSchirmer]

I wanted to see if you recalled correctly, because I myself could not recollect this:
https://hackaday.com/2018/09/11/do-space-pr...-space-weather/

In 2013, they figured launch shaking or radiation.

Launch damage or radiation are most likely causes, says CEO of reaction wheel company
https://spectrum.ieee.org/tech-talk/aerospa...ght-have-failed

By September 2017 they had research and published a paper

CONCLUSIONS
The anomalous friction increases and failures of ITHACO RWAs on the FUSE, Kepler and other spacecraft are the result of the space environment, and likely space charging. This is based on strong statistical correlation of events with geomagnetic storms, and simultaneity of events on different RWAs during geomagnetic storms. Duplication of friction events in the laboratory by applying small voltages across the rotating bearings supports this conclusion. Finally all metal ball bearing control wheels for satellites may be similarly impacted as discussed, when operated in these adverse space weather conditions
http://esmats.eu/esmatspapers/pastpapers/p...2017/bialke.pdf

About a year later that led to a Youtube episode on reaction wheels that has about 700,000 views.

https://www.youtube.com/watch?v=KibT-P...re=emb_imp_woyt[/url] ]

Time to put up some cubesats for small scale testing of different types of bearings.

Hard Disk Drive Based Reaction Wheels for CubeSat Attitude Control
August 2017 DOI: 10.2514/1.A33866
https://www.researchgate.net/publication/31...de_Control#read