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I propose a science satellite concept for gas giants: The
satellite dips into, say, Jupiter's
atmosphere at each perijove, to gather detailed data on
the atmosphere and climate.
Obviously this will incur aerodynamic drag losses, so
these are compensated for by collecting
some of the atmosphere
and using it as propellant. After
being collected by a scoop, either it
will be heated by a nuclear reactor or decay (thermal
ramjet) or the hydrogen component of
the atmosphere will be fused with itself (Bussard
ramjet), and then ejected out the back of the
satellite. If it's a thermal ramjet, the heat used can be
waste heat from the RTG or reactor (which I
assume the satellite will have, solar panels not being
very useful out near this solar system's gas
Jupiter's atmosphere, for reference, is 86% by number
The advantage of this over using stored propellant is that
the propellant is unlimited, and thus
the number of orbits achievable is unlimited by
propellant. (It will still be limited by decay of
other components such as nuclear fuel, electronics
exposed to strong magnetic fields, etc., but
those things can probably more easily be made to last
For anyone unfamiliar with the concept [notexactly, Oct 24 2016]
Prior art: satellite that orbited within Earth's atmosphere, with an ion engine to offset drag [notexactly, Oct 24 2016]
Some discouraging light math
Apparently this is not likely to be very feasible anytime soon, and would probably be a struggle to fease even with nuclear rocket technology, because your exhaust velocity has to be greater than your orbital velocity. (Not my questionI don't participate in Stack Exchange stuff.) [notexactly, Jul 13 2019]
On the other hand, ESA seems to think an air-breathing electric thruster might be feasible
They've tested one, anyway. [notexactly, Jul 13 2019]
Helium burning to carbon [Voice, Jul 14 2019]
||I have since realized that this might be more suited to gas
harvesting applications than scientific applications. For
example, most of the rest of Jupiter's atmosphere is helium.
We happen to not be able to hold onto our helium here on
Earth, so we will eventually need another source of it. This
type of spacecraft could then be used to collect helium from
||Aye aye skipper. We'll try full ahead.
||I think the expression is "go with throttle-up."
||// we will eventually need another source of it. //
||The main exhaust product of a fusion reactor is Helium. Build fusion powerplants, stuff in Deuterium, get lots of energy and the Helium is a bonus .. There's no downside !
||I thought one of the benefits of fusion was that it used very
little fuel, and therefore produced very little helium, for a
given amount of energy output?
||Then treat the helium as the "product " and use the "spare" energy to extract CO2 from your atmosphere (possibly via a biomass route) and reduce it to carbon - amorphous, or crystalline.
||Graphite blocks have all sorts of uses too.