USC undergraduate rocket propulsion lab has test fired a solid-rocket
they intend to use for an attempt at a flight to suborbital space:
https://mach5lowdown.wordpress.com/2018/02/26/graveler-ii-stats/
The USC rocket has about half the total impulse of the SpaceLoft and
GoFast rockets that went to suborbital space. Then we may estimate the size
of the USC rocket as a ca. 100 kg propellant load. But like the SpaceLoft
and GoFast rockets uses carbon fiber for the rocket motor casing to
approximately double the mass ratio. So it may indeed have sufficient
delta-v for the suborbital flight.
But this amateur effort reminded me of the Maverick Civillian Space
Foundation. They instructed high school and university students in building
a two-stage APCP rocket to reach 100,000 feet. This rocket used three
clustered motors for the first stage and one motor for the second stage.
The total propellant load was about 200 kg, like the SpaceLoft and GoFast
suborbital rockets.
All four of the Maverick Civillian Space Foundation motors had a ca. 50 kg
propellant load. However, it used aluminum casings as indicated in this
video:
California Academy of Math & Science Explorers Program - The Rocket Project.
https://www.youtube.com/watch?v=MutkJ0HKyA8
This reduced the mass ratio and therefore the delta-v possible. BUT
suppose the Mavericks used also carbon fiber casings for the 3-cluster
first stage? Then the first stage alone might have sufficient delta-v for a
suborbital space flight, as it would be larger than the USC rocket at a ca.
150 kg propellant load. You might want to use a fiberglass or carbon fiber
cylindrical tube covering for the 3-clusters though for aerodynamics
reasons, as it would be traveling faster than the Mavericks original
version not having to carry the heavy upper stage.
You would have to get the carbon fiber casings however. The USC team build
their own carbon fiber winder. But one could be purchased for ca. $3,000
from the X-winder company.
It maybe though you want to use all four of the Mavericks motors clustered
together. This would give a rocket of the same propellant size as the
GoFast and SpaceLoft suborbital rockets. You would still need to give the
motors carbon fiber casings.
Bob Clark
On Tuesday, October 3, 2017, Robert Clark <rgregoryclark@xxxxxxxxx> wrote:
The group Maverick Civilian Space Foundation has instructed both
university and high school students in building their own high power
experimental rockets.
Under supervision of the groups professional rocket engineers, high school
students were able to build a rocket to reach 100,000+ feet altitude and
Mach 2.8 velocity:
California Academy of Math & Science Explorers Program - The Rocket
Project.
https://www.youtube.com/watch?v=MutkJ0HKyA8
The rocket featured two stages with a 3-core cluster first stage. The
total propellant load was 500 lbs. of APCP propellant, which the students
mixed themselves.
We can estimate how much delta-v would be required of an additional third
stage to be able to reach the Karman line of 100 km altitude. The original
rockets max. altitude of 100,000 feet is about 30,000 meters. So the third
stage fired at apogee would be required to achieve an additional 70,000
meters. Then use the equation relating velocity and altitude to get:
v = sqrt(2*70000*9.81) = 1,170 m/s.
The 30,000 meter altitude of third stage firing would mean the air drag
is minimized and the few seconds duration of firing would mean the gravity
drag is minimized, so this should be close to the needed delta-v to
actually reach the 100 km altitude.
As before with the estimate of a third stage added to the USC rocket, use
for the vacuum Isp of the third stage that of commercial ground-launched
APCP motors of ca. 260 s to input into the rocket equation. Then with the
mass ratio in the range of 2.5, such as with the Cesaroni motors, these
motors could receive a delta-v of 2,600ln(2.5) = 2,380 m/s, well above the
needed delta-v to reach the Karman line.
Again, these would be straight off-the-shelf motors for the third stage,
no carbon fiber casing, or lengthened vacuum-optimized nozzle required. But
since the students did mix their own propellant they could certainly make
their own small third stage for the purpose.
Bob Clark
