[AR] Re: How Many Us ?
- From: Henry Spencer <hspencer@xxxxxxxxxxxxx>
- To: Arocket List <arocket@xxxxxxxxxxxxx>
- Date: Tue, 12 Mar 2019 19:55:02 -0400 (EDT)
On Tue, 12 Mar 2019, Robert Steinke wrote:
I've wondered why the 8U form factor hasn't been more popular? It would
satisfy the "closer to spherical" criteria. Is it just that 3U got more
popular than 2U and larger sizes got based on that?
Early on, the emphasis was on 1U birds for students, and all this
multi-cube stuff was seen as something that would be done rarely and so
didn't really need careful thought.
The original P-POD deployer was designed around the idea of bulk launches
and therefore naturally was built to accommodate more than one cubesat.
Somewhat arbitrarily -- don't recall ever hearing a specific rationale --
it held two rows of three cubes each. This made it trivial to replace two
cubes with a 2U or three with a 3U, and the partition between the two rows
was non-structural, so if you removed it, you could fit a 6U. And there
was no obvious growth path beyond that.
When people started trying to do real payloads, surprise surprise they
needed more volume, and they went to 3U and sometimes 6U. The emphasis on
those sizes in the market has pushed later deployer designs to be
compatible with them, so everything had to be 3U long, and the obvious
next step after 6U was a 12U deployer that could carry four 3U or two 6U
or a single 12U. Even that's been a long time coming.
Our Generic Nanosatellite Bus actually is roughly an 8U, and there are a
dozen or so of those in orbit now (with real payloads for paying
customers). But we build our own deployers, including provisions for
predeployed appendages, so exact compatibility with cubesat form factors
and cubesat deployers wasn't an issue.
Henry
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