Pump fed rockets are normally higher diameter so the tank thickness is greater
despite the lower pressure. I assume the low tank thicknesses of smaller
pressure fed rockets is what is being referred to when saying that they are
fragile.
Zach Martinez
Sent from my iPhone
On Sep 2, 2016, at 16:49, Ben Brockert <wikkit@xxxxxxxxx> wrote:
150 psi pc pressure fed rocket tank still has a significant multiple of the
tank pressure in a pump fed rocket, so there's no reason for it to be
unusually fragile.
150 psi pc also isn't the lower limit for sea level operation, of course.
Ben
On Friday, September 2, 2016, George William Herbert
<george.herbert@xxxxxxxxx> wrote:
Bill is correct, but you get very fragile rockets and minimum gauge problems
this way.
Not impossible, just... Be careful.
Sent from my iPhone
On Sep 2, 2016, at 12:04 PM, William Claybaugh <wclaybaugh2@xxxxxxxxx>
wrote:
Zachary:
You can do as little as 50 psia against vacuum and 150 psia to sea level
air; look into Bob Truax's Sea Dragon work for reference.
That said, note that he was planning on using Lox / LH2 to recover the lost
Isp. But as a general rule mass fraction improves as the operating
pressure of a pressure fed liquid drops...and mass fraction has an
exponential effect on performance, whilst Isp is merely linear.
Bill
On Friday, September 2, 2016, Zachary Martinez <znm3m8@xxxxxxx> wrote:
Hello all,
Are there any issues operating at a relatively low chamber pressure for an
engine ~180-220psi other than the poor Isp. For a pressure fed rocket with
a relatively high thrust to weight ratio the benefits of using a lower
chamber pressure are really tempting, but I imagine there are some design
challenges that I am unaware of. My main concerns are difficult ignition
or possible flame out but I don't really know.
Thank you,
Zachary Martinez
Aerospace Engineering | Missouri S&T
