[AR] Re: Successful Launch Of SS-520
- From: Henry Spencer <hspencer@xxxxxxxxxxxxx>
- To: Arocket List <arocket@xxxxxxxxxxxxx>
- Date: Sat, 3 Feb 2018 18:27:05 -0500 (EST)
On Sat, 3 Feb 2018, John Dom wrote:
3 kg highly eccentric orbit sat.
The highly elliptical orbit is unsurprising for the first launch of an
all-solid launcher. LEO orbit insertion is terribly sensitive to small
errors in the delta-V of the final stage, so if you want to be sure the
payload will stay up long enough to be verified, you use a light payload
that will give a rather high apogee -- that way you don't care too much
just *how* high the apogee is.
Especially so if orbit insertion is at low altitude and so the perigee is
going to be quite low. With perigee below 200km, probably neither the
payload nor the final stage will stay in orbit very long -- air drag at
perigee will bring down their apogees quickly, particularly since small
objects have high surface area per unit mass.
As you can see SS-520 is by a wide margin the smallest (publicly
confirmed) rocket to reach orbit. A full 6.75 meters _shorter_ than
Lambda-4S and only 2.6 tonnes at liftoff. It's tiny.
A quarter the mass of Lambda-4S and 3/4 the length of Black Arrow (the
former record holders in those categories, discounting the faint
possibility that Project Pilot reached orbit) is definitely impressive.
Its only payload was a single 3U cubesat. If you want to know what a
minimal cubesat launcher design might look like, this is it.
However, if you want to know what a commercially successful minimal
cubesat launcher might look like, this probably isn't it. :-) At the very
least, they need to get the perigee up some. Precise control of apogee
(which almost certainly means a liquid trim stage a la Electron), and a
12U or at least 6U payload, would also help.
Henry
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