Yes, their only disadvantage is lower power density (which sort of goes
long with the longer half life).
On 3/1/21 4:04 PM, Michael Kelly (Redacted sender mskellyrlv for DMARC)
wrote:
Northrop Grumman makes a whole range of pulse-tube cryocoolers for space applications, and have been developing them as electric generators when run in reverse. They have no moving parts (well, no parts that move very far), and last forever. https://rps.nasa.gov/internal_resources/160/ <https://rps.nasa.gov/internal_resources/160/>
And, yes, Americium 241 is back in production (big time). It would provide a more level power output in RTG applications, given a half-life ~> 5 times that of Pu 238.
On March 1, 2021 at 10:47 AM, William Claybaugh <wclaybaugh2@xxxxxxxxx> wrote:
Rand:
Yep, but that does not justify ignoring the best answers.
Bill
On Mon, Mar 1, 2021 at 8:24 AM Rand Simberg <simberg@xxxxxxxxxxxxxxx <mailto:simberg@xxxxxxxxxxxxxxx>> wrote:
Bill, you're the one who started this topic as a "home-built
space mission."
On 3/1/21 7:18 AM, William Claybaugh wrote:
Rand:
They don't last as long and NASA Gleen's Stirling power systems
are (ground) qualified for 20 years.
Bill
On Mon, Mar 1, 2021 at 8:02 AM Rand Simberg
<simberg@xxxxxxxxxxxxxxx <mailto:simberg@xxxxxxxxxxxxxxx>> wrote:
You could buy one from the UK. They've started making them
out of Americium.
On 3/1/21 6:55 AM, William Claybaugh wrote:
Rand:
I think an efficient RTG is required and that will mean USG
involvement in what likely wants to otherwise be a
privately funded activity.
Bill
On Mon, Mar 1, 2021 at 7:47 AM Rand Simberg
<simberg@xxxxxxxxxxxxxxx <mailto:simberg@xxxxxxxxxxxxxxx>>
wrote:
That begs the question of why it would be either big
budget, or done by
NASA. :-)
On 2/28/21 10:00 PM, Henry Spencer wrote:
> On Sat, 27 Feb 2021, Robert Steinke wrote:
>> imparting about... 15km/s if the back of my
envelope is
>> correct. That's a whole lot for a chemical
rocket...
>>
>> That close to the sun it should be easier to do high
thrust solar
>> thermal.
>> Wikipedia says Isp up to 1000 seconds so the mass
ratio would need to be
>> ~4.5. Use a drop tank for boiloff so the burn
starts out with a full
>> tank.
>
> Unfortunately, that Isp requires LH2, and after circa
a decade in
> space (out to Jupiter and back), almost certainly it
will all be gone.
>
> There are ways of storing LH2 for years, in
principle, e.g. active
> refrigeration, but it's beyond today's state of the
art, and I believe
> Bill is hoping for a relatively low-cost mission.
>
> (A big-budget planetary mission isn't going anywhere
unless you can
> convince a Decadal Review to make it their first
priority, which isn't
> going to happen for this. Smaller efforts can
sometimes do end runs
> around the traditional process, but ill-defined costs
and risks from
> techological pioneering are just what you don't want
if you're trying
> to convince people to stick their necks out in support.)
>
> Henry