Aerospace & Aviation
¨ How do you accomplish making a rocket soar?
¨ How are rockets compared to the speed of sound?
¨ Why does ice form on the outside of rockets?
¨ What propellants should I use for my homemade rocket?
¨ Did Auk XXXI break the sound barrier?
¨ Which speed of sound reference
is used during a rocket launch?
¨ When do the Delta II boosters ignite?
¨ What is venting from the Delta II booster stage?
¨ Precipitation on the Delta rocket camera during Mars launch
¨ Why do we use nautical miles in spaceflight?
¨ How do the Delta II booster rockets
jettison?
¨ How are calculus and differential
equations applied to rocketry?
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QUESTION:
How do you accomplish making a rocket soar?
ANSWER from Mike Bastoni
on 22 September 2005:
Hi...it's certainly easier to make a rocket soar then it is to make a Dinosaur......I
had to write that, it just seemed like too much fun.
I think another way to make a rocket sore
is to smack it on the booster with a launching pad...oh oh, I'd better
quit now with the humor.
Any way I'm not exactly certain what you
mean...but if you're asking how to make a rocket fly...that's fairly
easy. Here is an experiment you can do to get a sense of how
a rocket engine moves a rocket.
Ask your phys-ed department for a small
to medium size medicine ball or weighted exercise ball. Sitting
on a skateboard (remember sit don't stand) try and throw the weighted
exercise ball as hard as you can in the direction you are facing...if
all goes well the ball will move away from you and you will move
in the opposite direction away from the ball...
If the skateboard had perfect wheels and
bearings, with no frictional forces acting on them, the product of
the balls mass x the velocity it was thrown at, would be equal to
the product of the mass of you, and the skateboard times the velocity
that you move away from the ball.
Rocket engines work in a similar fashion...hot,
presurized gases exit the rocket engine nozzle. Although the
hot pressurized gases have very little mass...they exit extremely
fast.
The product of their relatively small
mass, times their relatively high velocities creates a force we call
thrust. The thrusting force is described by a measure we call
the total impulse. The total impulse is the product of the
thrusting force (measured in lbs or Newtons) times the burn time
of the engine.
It is this total impulse that gets the
rocket up to speed. With model rockets the burn time is very
short, on the order of .3 - 1.2 seconds on average and the maximum
thrust force is around 3-8 lbs. On the shuttle, the burn times
are many times longer and the thrusting forces are insanely high. Somewhere
in the order of 3 x 10^7 pounds for the main engines and boosters
combined.
Here is a link to a web site with a great
rocket altitude prediction simulator...I use it in class every year.
http://webalt.markworld.com/webalt.html
We use it to play rocket golf. A
game where we try and land rockets with specially modified Estes
A8 rocket engines inside hula hoops at ranges of 200 - 300 feet!
Hope this helps to get you thinking about
rockets...spend some time tonight cruising the web and using search
engines like Google and Yahoo and keywords like rocket engines, rocket
thrust, and space shuttle thrust..
Enjoy
Mike Bastoni
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QUESTION:
How are rockets compared to the speed of sound?
ANSWER from Homer Hickam
on 1 September 2005:
I believe you are asking whether rockets can go as fast as the speed of sound
which is around 700 miles per hour. The answer is yes and some rockets
can go much faster. For instance, rockets that put satellites into orbit
go 25 times faster than the speed of sound!
But not all rockets have to go fast. Some
rockets, such as those used for fireworks during celebrations, go
very slow. You can even watch them from launch all the way
until they shower the sky with sparkles. You should also look
up how sound works and why it goes as fast as it does. For
instance, do you know that sound goes faster in water than it does
in the air? You should ask your science teacher to explain
sound and sonic waves to you.
Homer Hickam
[Editor's Note: Be sure to read some of
Homer’s books about rockets including: The Rocket Boys, The
Coalwood Way and Back to the Moon. The first two
are memoirs; the last one is a fictional story.]
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QUESTION:
In the movie Apollo 13 when the rocket takes off, ice chunks are seen falling
off. The movie takes place in Florida where it is at least 80 degrees
F so where did this ice come from?
ANSWER from Dean Davis
on 16 February 2005:
The Apollo Saturn V rocket used a cryogenic (super cold) mixture of Liquid
Hydrogen (LH2) propellant & Liquid Oxygen (LOX) oxidizer as its rocket
fuel, like the Space Shuttle External Tank (ET).
This rocket fuel is much colder than outside
ambient (normal temperature) air, so it tends to condense on the
outside of the rocket (like water droplets on the outside of a Coke
can after taking it out of the refrigerator on a hot day). This
typically occurs near fueling vents where it turns to frost and ice. During
liftoff, these chunks of frost and ice fall off.
It is currently believed that this ice
problem combined with poorly designed foam insulation on the outside
of the Space Shuttle External Tank resulted in damaging the Columbia's
forward wing edge Thermal Protective System and caused the destruction
of the last Shuttle during reentry into the Earth's atmosphere.
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QUESTION:
I am interested in rockets, electronics, robotics, physics and computers. I
have done some simple projects in robotics and they are capable of launching
simple rockets, but the rockets are not working well. One day one exploded
and I got injured. I want to know about easily available propellents
for making small rockets.
ANSWER from Dean Davis
on 9 October 2004:
While I strongly encourage you to continue your rocket experiments, I suggest
that you work in partnership with an experienced, responsible, adult partner
and that you employ the utmost safety. Make sure your launch site is
away from air traffic, and a safe distance from homes, schools and businesses. It
really concerns me that your rocket exploded and you got hurt.
I highly recommend that you use commercial
rocket engines and rocket kits available from most hobby shops. Estes
Model Rockets (www.estesrockets.com) is one of the most experienced
and well known companies in this field. You can purchase a
24-rocket engine Blast-Off Flight pack from them and experience a
full day of rocket launches without worry about the rocket exploding
and hurting you.
Dean Davis
Senior Principal Scientist/Engineer
Boeing
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QUESTION:
This afternoon I just finished Rocket Boys. I love it! I think it is amazing
that you got all that help from residents of Coalwood. I'm just curious,
did Auk XXXI break through the sound barrier? I'm also amazed that
you could make such a powerful propellent out of zinc dust and pure alcohol.
ANSWER from Homer Hickam
on 25 September 2003:
Thank you for your note. If you liked Rocket Boys, you're in luck. There
are two more books in what I call the Coalwood Trilogy. The Coalwood
Way is another story of the Rocket Boys, a Christmas story, that I left out
of the first memoir. Sky of Stone is the true sequel to the book. It
is being developed into a Hallmark Hall of Fame television movie but I recommend
reading the book. Books are always better than movies. As to your
question on the last Auk, it did indeed go supersonic less than a second after
launch. Zinc dust and sulfur with an alcohol binder is a very powerful
propellant if you know how to handle and pack it. The secret to our success
in rocketry, however, were the finely machined DeLaval nozzles produced by
the mine machine shop experts that were then lined with a ceramic coating. As
for a career path, I like to say I wanted to be an engineer but I HAD to be
a writer. Thank goodness, I got the chance to follow both passions. For
more information on all this, check out http://www.homerhickam.com/
Homer Hickam
Retired Aerospace Engineer
Writer
Alabama, USA
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QUESTION:
When the Delta reaches "Mach 1", what is the Mach number relative to? Since
Mach is defined as v(object)/v(speed of sound), which speed
of sound is the rocket velocity using?
ANSWER from Dean Davis
on 4 August 2003:
The term Mach is a measure of speed with respect to the speed of sound. 760
mph is the speed of sound (Mach 1) at Standard Temperature and Pressure (STP)
(32 degrees F at sea level), while at 40,000 ft and the same temperature the
speed of sound is 660 mph.
The speed of sound is a relative measure
named after the Austrian Physicist Ernst Mach who measured sounds
speed in various mediums, temperatures and pressures. Sound
moves faster in higher density mediums such as water than in lower
density mediums such as air. Air which is the medium of interest
in the Delta case is just the earth's standard atmosphere.
Dean Davis
Aerospace Engineer
Boeing
Washington, D.C.
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QUESTION:
When MER-B launched on July 7th, the countdown went to T-7 and halted. I
thought that the booster rockets had started to ignite when the countdown was
halted. It might have been my imagination as I was anticipating seeing
them fire. So, my question is, at what point in the countdown do the
booster rockets on the Delta II ignite?
ANSWER from Dean Davis
on 2 August 2003:
Delta Boosters use solid propellant, which cannot be shut down once they are
started and they ignite at T-Zero, liftoff. So, it probably was your
imagination, for once the boosters lift-off the Delta either launches or explodes.
Dean Davis
Aerospace Engineer
Boeing
Washington, D.C.
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QUESTION:
Watching the MER-B rover launch on TV, I saw these white jets of smoke emanating
perpendicularly from the booster stage of the Delta II during tanking procedures
through till launch. What is being vented out? Is it a deliberate
jetting or does the wind just making it stream out that way?
ANSWER from Dean Davis
on 13 July 2003:
The venting you observed on the Delta 2 was probably caused by condensation
from the Liquid Oxygen (LOX) oxidizer which is loaded into the first stage. This
oxidizer provides oxygen to the RP1 fuel for this stage. Because the
LOX is much colder than ambient air temperature it condenses with air on contact
during fueling and forms harmless water vapor.
It just looks like deliberate jetting,
it is just natural venting of condensation. If it is not properly
vented the resulting condensation will result in a thick layer of
ice forming on the outside of the launch vehicle, which could be
very bad.
By the way, these super-cold cryogenic
oxidizers and fuels which are used on the Atlas, Space Shuttle, Centaur
Upper Stage and certain Delta stages are not used on most launch
vehicles. Solid-propellent rocket engines have their oxidizer
embedded in their fuel mixture grains, whereas other liquid-chemical
rockets, such as the Titan use highly-toxic hypergolic monomethyl
hydrazine & dimethyl tetroxide fuel and oxidizer combinations
which ignite upon contact.
Dean Davis
Aerospace Engineer
The Boeing Company
Washington, D.C.
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QUESTION:
During the launch of MER-A, at about T+15 through to T+30 seconds, there appeared
to be a splattering of a liquid onto the onboard camera. Was that
bychance the rocket going through the clouds?
ANSWER from Omar Baez
on 27 June 2003 on NASADirect!:
No, what we have is, if you notice the Delta II rocket before we tank it, it
is actually a nice teal blue color. When we tank it, it turns a nice
white frosty color, and there's a reason for that. We load the first
stage up with liquid oxygen, which is at minus 300 degrees Fahrenheit, and
we form a frost coating over the first stage, or ice actually. If you
look at the tape when it rolls initially, right at launch, you will notice
a lot of ice coming off. What's going on in that first couple of seconds
is, as we're rising, some of that frost on the launch tank is melting off and
that is the precipitation you see forming on the lens of the camera as it came
over the fairing on the first stage camera.
Omar Baez
Launch Director
Kennedy Space Center
Florida
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QUESTION:
How far into a mission is a spacecraft's distance calculated in "nautical
miles"? What is the reason for using the nautical mile?
ANSWER from Dean Davis
on 27 April 2003:
Nautical Miles are used by NASA because pilots and astronauts have used this
measurement in aviation since the Wright Brothers and this measurement originally
came from sailors who used it to navigate the seven seas.
Dean Davis
Aerospace Engineer
The Boeing Company
Washington, D.C.
ANSWER from Bob Raab on
28 April 2003:
Since it has been many years since I studied navigation in college ROTC I had
to search the web. I could put the answer in my own words and impress
you with my brilliance, but I'll be honest and give you this link. See "nautical
mile" at: www.unc.edu/~rowlett/units/dictN.html
Bob Raab
Retired Airline/Former Fighter Pilot
Southern California
ANSWER from Bob Mase on
21 May 2003:
For the interplanetary missions that JPL flies, we do not use nautical miles
at all. Only the launch vehicle contractor does to describe the flight
of the launch vehicle. Once the spacecraft is separated from the launch
vehicle (about an hour after launch), the spacecraft is on an interplanetary
trajectory, and no one uses nautical miles past that point. The use of
nautical miles is just an historic carryover from sea and air travel.
For more info on what a nautical mile
is refer to: http://www.howstuffworks.com/question79.htm
Also try: http://www.unc.edu/~rowlett/units/dictN.html
Bob Mase
Mars Odyssey Navigator
Jet Propulsion Laboratory
California
ANSWER from Omar Baez
on 7 June 2003 on NASADirect!:
That was a good one! I had to go do some research on that one and I spent some
time doing that. The reason we do it - humans are lazy. And the
Earth is composed mostly of bodies of water. And the way most charts
have been written down, has been a system of Mercator projections, that means
latitude and longitude. And the way that is broken up is into squares
over the Earth, a matrix of squares. Each one of those points inside
of those squares are divided into hours, degrees, minutes, and seconds. And
one minute in that Mercator projection system is equal to 60 nautical miles. So
the reason we use that is the charts are available, it's a system that's been
used for many years, all the folks doing navigation over the oceans have been
using it, the aviation industry uses it. And it was just easier to adopt,
and that's why we use it. But you could really use any other system -
you'd just have to chart things in that other system that you chose.
Omar Baez
Launch Director
Kennedy Space Center
Florida
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QUESTION:
When the Delta II rockets release the booster rockets, are first 3 ejected
and then the remaining 6 or are they released 3 at a time?
ANSWER from Omar Baez
on 7 June 2003 on NASADirect!:
I've got to take you back a little bit. The lights - there's nine solid
rocket motors on the Delta II. We light six of them on the ground. As
we're going through the atmosphere, we will expend those six solid rocket motors. Towards
the end of its life, we'll light the other three, making that total of nine. One
second after those last three are lit, we'll jettison three of the rockets. One
second later, we'll jettison three more of them. And during this time,
we'll be still flying on three of the air-lit solids for the next 65 seconds
after that point and then we'll jettison those.
Omar Baez
Launch Director
Kennedy Space Center
Florida
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QUESTION:
How are calculus and differential equations applied to rocketry?
ANSWER from Dean Davis
on 15 June 2003:
Calculus & Differential Equations are used continuously in rocketry to
perform a wide variety of calculations which require far more power than Alegbra
and Geometry alone provide. Some of the many rocketry problems which
require these mathematical techniques include propulsion analysis (which predicts
and computes rocket engine and fuel consumption), trajectory analysis (which
predicts and computes launch vehicle & spacecraft flight paths, downrange
stage impact sites, and reentry footprints), and astronautics analysis (which
predicts and computes orbital transfers).
Dean Davis
Aerospace Engineer
Washington, D.C.
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