Date: 13th May
2007
Location: Workshop
Conditions: Pleasant
since it was indoors.
Rockets:
(click the name for rocket details)
|
Name |
Capacity |
Notes |
|
Acceleron III |
24.75
L |
A new rocket expanding on
Acceleron II's capacity. It is also our first
two stage rocket booster. |
Team Members at
Event:
GK and PK
Development
Now that Acceleron (I and II) has
successfully flown 16 missions we are ready
to start adapting it to its intended purpose
- adding a staging mechanism so that it will
be able to release a sustainer to reach
higher altitudes. Booster Upgrade
We disassembled Acceleron II this week
and extended each of the segments by another
2L bottle. This makes the total capacity of
the booster around 25L.
As always we pressure tested each
assembled segment to make sure all the new
joints were sealing well. The first segment
held just fine, but when we were filling the
second segment, the segment let go at one of
the couplings at around 40psi. There was a
pretty loud boom in the workshop but luckily
only the nosecone got a little crushed.
We've seen this once before, and we had
kind of suspected it because we only used
normal bottle caps, instead of the longer
thread ones. Due to the coupling and washer
there just isn't enough thread left with a
normal cap. We will go back and replace the
caps for the new extensions so that does not
happen again. The dummy payload will be
replaced by a new payload pod that will
house the flight computer, camera, parachute
and staging mechanism actuator. The staging
release is mounted just above the pod. The
pod will also be used to support the
sustainer and protect the payload contents
from the spray during separation. We have
also replaced the central pipe with a longer
one to account for the extra bottle and the
new pod being attached. Staging Mechanism
After much consideration we decided that
the staging mechanism will be based on a
Gardena release mechanism rather than a
crushing sleeve.
The reasons for going with the Gardena
mechanism are:
- The sustainer can be released exactly
when needed, rather than when the pressure
drops inside the main booster as with a
crushing sleeve.
- All our existing nozzles will fit the
sustainer.
- We know that the Gardena mechanism can
hold relatively high pressures up to at
least 220+ psi. We want to be able to
retain the design once we start
reinforcing the bottles.
- The crushing sleeve method doesn't
lend itself very well to the construction
of CD nozzles, which we plan to revisit
especially with the sustainer.
We have manufactured most of the air
supply components of the staging mechanism
that allows pressurised air to go from one
of the booster segments into the
sustainer. The air hose fitting in the
bottle cap looks a little complicated, but
it includes a non-return valve, as well as
allowing the air hose to swivel so it
doesn't twist when we need to take the cap
off to fill the segment with water. We
removed the spring from the Gardena
mechanism and we will add a small latch
that will keep the release closed until
the flight computer determines when the
best time is to release it. The release
will be actuated by a small RC servo
motor. The force to pull back the Gardena
attachment will be provided by a number of
rubber bands.
We will publish the full technical
drawings once the system is completed and
we know it works.
|
