[AR] Re: hovering rocket vertical position control
- From: Jonathan Goff <jongoff@xxxxxxxxx>
- To: arocket@xxxxxxxxxxxxx
- Date: Tue, 17 Feb 2015 16:17:38 -0700
Ben,
Agreed. If you're just trying to test out the control laws, a ducted fan
system makes a lot of sense. And if you use counter-rotating blades, you
can cancel out the torques so it behaves more rocket-like.
~Jon
On Tue, Feb 17, 2015 at 4:09 PM, Ben Brockert <wikkit@xxxxxxxxx> wrote:
> It was a Haskel, and I'm working with another one again now to run up
> some tanks to ~5000 psi with nitrogen. (This year I had a part I
> designed proof tested to 9000 psi, which is my new personal record.)
>
> Air at 100 psi is a boring utility gas, air at 2500 psi is getting
> into the realm of scary oxidizers. There's a lot of potential energy
> in there and you need to be cleaning for oxidizer service or you'll
> unleash the chemical energy too.
>
> If you google nitrous pump you can get an air-powered booster that
> will pump anything to 1500 psi for $800. Funnily enough they're
> shipped with seal materials that aren't nitrous compatible.
>
> I would absolutely do a ducted fan 'rocket' before doing a cold gas
> rocket. The cold gas one requires many of the complexities of a liquid
> rocket but flight time is terrible.
>
> Ben
>
> On Tue, Feb 17, 2015 at 5:18 PM, Jonathan Goff <jongoff@xxxxxxxxx> wrote:
> > Yeah, we had one of the Haskel gas boosters. It looks like you can pick
> > something up on ebay for ~$1500 or less.
> >
> >
> http://www.ebay.com/itm/Hydraulics-International30-30-Air-Driven-Gas-Booster-Paintball-Scuba-/371245373173?pt=LH_DefaultDomain_0&hash=item566ff2d6f5
> >
> > Looks like with that you could get up to 3500psi of air or more with a
> > reasonable compressor feeding it.
> >
> > ~Jon
> >
> > On Tue, Feb 17, 2015 at 3:10 PM, Jonathan Goff <jongoff@xxxxxxxxx>
> wrote:
> >>
> >> I can't remember. I think we had an industrial one. Can't remember what
> >> flow rate it was designed for.
> >>
> >> Jon
> >>
> >> On Feb 17, 2015 2:37 PM, "Lars Osborne" <lars.osborne@xxxxxxxxx> wrote:
> >>>
> >>> What kind of booster did you use at Masten?
> >>>
> >>> There are industrial pressure boosters, which are in the $3000 range,
> >>> and I found a manually operated one for paintball, which is $700. I am
> >>> wondering if there is a sweet spot for low flow rate boosters, but
> >>> automatically reciprocating.
> >>>
> >>> Thanks,
> >>> Lars Osborne
> >>>
> >>> On Tue, Feb 17, 2015 at 1:25 PM, Jonathan Goff <jongoff@xxxxxxxxx>
> wrote:
> >>>>
> >>>> George,
> >>>>
> >>>> If you're doing that, and want more than a few seconds of flight,
> you'll
> >>>> likely need to go to higher pressures than a normal air compressor
> can go
> >>>> to... But there are those differential piston gas pumps we used at
> Masten to
> >>>> take low pressure helium and boost it back up to enough pressure to
> refill a
> >>>> T-bottle.
> >>>>
> >>>> ~Jon
> >>>>
> >>>> On Tue, Feb 17, 2015 at 12:35 PM, George Herbert
> >>>> <george.herbert@xxxxxxxxx> wrote:
> >>>>>
> >>>>> For (very) short flights, compressed air rockets using COTS tanks
> >>>>> (like, standard propane bottles) give you more rocket-like behavior
> and are
> >>>>> still darn cheap. Air compressor, tank, compressed air "throttle"
> valve,
> >>>>> whatever thrust vector you want to employ.
> >>>>>
> >>>>> They even really are a rocket - it's just rare to see cold gas
> >>>>> thrusters these days.
> >>>>>
> >>>>>
> >>>>> George William Herbert
> >>>>> Sent from my iPhone
> >>>>>
> >>>>> > On Feb 17, 2015, at 9:26 AM, Nate Vack <njvack@xxxxxxxxxxxxxxxx>
> >>>>> > wrote:
> >>>>> >
> >>>>> >> On Mon, Feb 16, 2015 at 5:18 PM, <rsteinke@xxxxxxxxxxx> wrote:
> >>>>> >>
> >>>>> >> What have other people done? Are there other ideas?
> >>>>> >
> >>>>> > If you're looking to actually build a thing and test your stuff,
> you
> >>>>> > might do well with model rotorcraft; IIRC, Paul Breed tested a lot
> >>>>> > with helicopters. Quadrotors could reasonably approximate
> >>>>> > multi-engine
> >>>>> > rockets, and you could probably build a single ducted-fan design
> that
> >>>>> > would hover, too.
> >>>>> >
> >>>>> > Moving to actual rocket hardware will still involve some surprises,
> >>>>> > of
> >>>>> > course. But crashing a $500 model is... cheaper than crashing a
> >>>>> > rocket.
> >>>>> >
> >>>>> > -n
> >>>>> >
> >>>>>
> >>>>
> >>>
> >
>
>
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