[AR] Re: Radian One spaceplane
- From: Henry Spencer <hspencer@xxxxxxxxxxxxx>
- To: Arocket List <arocket@xxxxxxxxxxxxx>
- Date: Sat, 22 Jan 2022 23:17:23 -0500 (EST)
On Sat, 22 Jan 2022, Uwe Klein wrote:
Separation is two jobs:
* You have mechanical release
some contrived mechanical device
pyro release ( bolts, cutting charge, ... )
Georg Tiesenhausen (one of the last of von Braun's team) said once that
which you got depended on who you hired for the job. :-) Hire an
aerospace engineer, and you got a pyro system. Hire a mechanical
engineer, and the result was a mechanical system... like the Saturn V's
pad hold-down system, which he designed.
Mechanical releases, typically with pneumatic actuation, actually have a
considerable history, and work fine if designed properly. They may be a
bit heavier than a pyro system -- pyros do have the advantage of producing
a lot of force from a lightweight actuator.
* separation of the (created) bodies by introducing some impulse.
working on one or both bodies
spring ( works on both bodies due to reaction forces)
thruster ( only one item is moved.)
Gas pistons are another option, and I think that's what SpaceX is using.
In principle you could just pressurize the interstage volume -- which
would help stiffen it against loads too -- and let that push the two
stages apart.
Mind you, as several launcher operators have found out, there can be
trouble if your separation impulse isn't big enough. Especially since big
liquid-fuel engines can produce non-trivial thrust for a surprisingly long
time after official cutoff, so the lower stage that's about to be
discarded can still be effectively under power... Avoiding this is one
advantage of "fire in the hole" staging (ignite before release).
In extreme cases, you can even exploit "fire in the hole" to *accomplish*
release: the solid motors in the Jupiter-C upper stages were fast-burn
high-thrust types, and ignition of each stage simply sheared the pins
holding it to the previous stage.
Henry
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