[AR] Re: Roll control...
- From: Henry Spencer <hspencer@xxxxxxxxxxxxx>
- To: Arocket List <arocket@xxxxxxxxxxxxx>
- Date: Thu, 7 Jun 2018 00:19:18 -0400 (EDT)
On Wed, 6 Jun 2018, Henry Vanderbilt wrote:
Let's see, a two-tube minimum core still needs two-axis gimballing on
each tube, but no longer needs any separate roll control. On three or
four tubes, you can steer with only one-axis gimballing - but, question
for the floor, can you then also do roll control with just one-axis
gimballing? I don't see how just now...
Easy: rather than gimbaling each engine in and out from the vehicle
centerline, instead gimbal at right angles to that, along the
circumference. That's what Black Knight and Black Arrow, the British
peroxide/kerosene rockets, did. To steer, you gimbal opposite engines
together; to control roll, you gimbal opposite engines in opposite
directions. It does mean that you can't pack the engines together quite
as tightly, i.e. you need smaller nozzles or a bigger vehicle base.
With single-axis gimbaling, apart from having half as many gimbal
mechanisms, you can run propellant feeds in along the axis to use rotary
joints instead of flexible lines, and you can put the gimbal axis roughly
at the center of mass of the engine to minimize gimbaling forces and
inertia effects. (Black Knight/Arrow did both.)
Henry
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