South Korea Successfully Tests Solid-Fuel Sat Launcher

[26C.Z969]

https://english.chosun.com/site/data/html_dir/2023/01/03/2023010301226.html

South Korea has successfully tested a four-stage solid-fuel
space rocket, the Defense Ministry said Monday.

The craft's second test flight last week was intended to
check separation of the second, third and fourth stages
as well as ignition and combustion of each engine.

In the first test last March, the Agency for Defense
Development succeeded only in testing combustion of the
second-stage engine.

But last Friday the agency successfully tested propellant
combustion, fairing separation, rocket separation, upper-stage
rocket attitude control and the separation of a dummy satellite.

. . .

Interesting. Solid-fuel rockets are quite uncommon for
launching satellites. Not sure why FOUR stages, perhaps
they have problems fabricating very large fuel castings.

The small 4th stage IS liquid ... they need the ability
to throttle to achieve precise orbital insertion.

Projected orbits are about 500km. A "small" radar-sat
is expected to be the first real payload later this year.

I always wondered if the shuttle SRBs could have been
used to launch sats ... add a smallish 2nd stage on top.
The STS boosters might have similar uses. You could even
cluster them, kinda like Musk's "heavy".

It has been revealed that the Saturn-V program had a
shadow - based in the Everglades - which was designing
a solid-fuel version of the booster ... just in case.
They apparently got pretty far along too - but the
ultimate product was buried under the floor once the
Saturn was proven trustworthy.

Solid fuel has advantages and disadvantages. Liquids
can deliver a little more result per pound ... but
they are also plumbing nightmares and require very
dangerous cyrogenics that always risk sending volatile
fumes that could cause huge trouble in various ways.
Indirectly, the second shuttle crash was because of
the cyrogenics ... causing exterior ice to form.
THE disadvantage of solids is, of course, that once
you light 'em up you're along for the full ride.
Making large flawless fuel castings is another issue.

In any case, wouldn't HURT to think whether we can
leverage existing/tested SRBs for launching small
sats & microsats for cheap. Of course NASA (and its
contractors) never seem to like the word "cheap" :-)