Design a Mars Plane Forum
Questchat with Peter Gage, Andrew Hahn and Steve Smith
May 18 - 23, 2001
NASA Ames Research Center, Mountain View, CA
[ Susan/NASAChatHost - 0
- 11:30:04 ] Welcome to the Design A Mars Airplane Forum!
A forum is like a chat but not real time.
[ PeterGage - 10 - 11:36:43
RE: [RickyMcDermott] Hello. I am in High School now and I want to be an
astronautical engineer and design spacecraft when I am older. I know this
involves alot of math, but I am wondering what type is mainly used, and
Hello Ricky. Spacecraft designers do use a lot of math. Every kind of
math taught in high school is helpful. Simple algebra is used for relationships
between all sorts of components. Trigonometry is used when we define the
size and shape of a spacecraft or airplane. Calculus is used to model
spacecraft behavior. You may have heard of differential equations. They
are used to describe how structure deflects when load is applied, how
heat is distributed around the spacecraft, how the engine thrust will
change the path that the spacecraft travels, and all sorts of other details.
Statistics is used, too, especially for detailed design. All sorts of
tests are conducted on the ground and statistics is sued to predict the
reliability of all the spacecraft pieces. That helps us to gain gain confidence
that the mission will be successful. While math is essential for designers,
other subjects are important too. Designers have to write clearly and
concisely, to explain their ideas. They must give presentations and have
discussions with members of their team. Students who want to do engineering
should not concentrate only on Math and Science.
[ PeterGage - 11 - 11:45:38
RE: [AndrewLadd] Howdy. I am the
Andrew Ladd. When NASA sends a manned mission to Mars will they send an
airplane for the crew to use, and will it be similar to this one?
Howdy to the Andre Ladd! The first manned missions to Mars probably won't
use airplanes. It will be a huge achievement just to get people to the
surface of Mars at all, and they will have plenty to do in the vicinity
of the landing site. Transporting equipment to Mars is very expensive,
so only the most important things will be carried. Airplanes that can
transport people from place to place on Mars will probably need to wait
for much later missions. Airplanes that carry people would need to be
much bigger than the ones already designed, so they would probably look
[ Susan/NASAChatHost - 18
- 14:18:14 ]
RE: [Chase] i really like this website.it has stuff i want to know.
[ PeterGage - 19 - 19:59:10
RE: [Johnathan] How far can the plane go?
I think that if it has a long range and it finishes some important work
it should fly over the site where they think the Polar Lander is, to confirm
what happened. Because I have read that some people think they found it
intact on the surface, but its tough to tell for sure. Also it would just
be cool if they could fly over and take pictures of the Viking Landers
as well. You can get a good idea of how far the airplane travels by playing
with the Design an Airplane applet on the web site. The proposed flying
sites are far from where the Polar Lander is believed to be. But they
are sending more Mars satellites soon, with high resolution cameras, so
they may have a chance to see the landers.
[ PeterGage - 20 - 20:01:40]
RE: [Phil] Will the plane go by the face so we know its really an ancient
Phil, you've stumped me. I'm not expecting that they'll find many statues
on Mars. Whatever life might have been living there must have produced
different kinds of art!
[ PeterGage - 21 - 20:08:07
RE: [Greg] For space & weight why not use a powered
parachute platform ( reliable openings) to do the work along with a surface
based transmitter that can also parachute to the ground to transmit data
Modern parafoils have a good glide & powered they can fly for very long
periods of time. ( 6 th grade science class, Girard, Pa) Hi Greg. They
do use parachutes to slow the entry vehicle before the airplane comes
out. One of the design teams looked at using parafoils with the entry
vehicle so it wouldn't lose too much altitude while the airplane unfolded.
While parafoil Lift to Drag has certainly improved, it is still far less
efficient than an airplane with large span wings.
[ PeterGage - 22 - 20:11:41
RE: [Erin] What is the purpose for the Mars airplane,
and how did you think of the idea?
I'm afraid we didn't have the idea of a Mars
airplane. It is common for engineers to be asked whether some new idea
can be made to work. That's what happened with Mars airplane: scientists
wanted to fly close to interesting features on Mars (such as the huge
canyon called Valles Marineris) and they asked for a design that could
carry the instruments they wanted to use. See if you can figure out how
to carry the right instruments: try the design applet!
[ PeterGage - 23 - 20:14:29
RE: [Jenny] Would you have any idea whether the consumption of alcohol
in a microgravity would have a greater effect on motor skills than alcohol
consumed on Earth?
Well, Jenny, I don't know the answer to this one. I don't know why it
would have a different effect in microgravity. It's not an experiment
I expect to be tried soon: astronauts eat healthy food and try to stay
as alert as they can!
[ PeterGage - 24 - 20:18:37
RE: [Johnathan] I think they should stick a rover inside of the airplane.
This way, when it lands, or crashes, the rover can crawl out and explore
that area. Or maybe the airplane could fly over a good site and parachute
it down. This would be better for getting to more interesting places that
are hard to land at from space.
You have a good idea for how to get rovers to difficult spots on the surface,
Johnathan. It would be nice to build the combination that you suggest,
but it's hard enough to make an airplane work even by itself. After we
have more success with rovers alone and airplanes alone, NASA might try
missions that use both types of transport.
[ PeterGage - 25 - 20:22:53
RE: [Erika] In your opinion, are all astronauts pilots or scientists?
Hello, Erika. Lots of astronauts are pilots and scientists, because the
main jobs in space have been flying the spacecraft and doing science experiments.
Engineers also go to space as Mission Specialists. They have been doing
complicated assembly work on the Space Station. The Russians recently
took a tourist to the International Space Station: maybe you read about
Tito in the newspaper. In the early days of rockets, dogs and chimpanzees
were sent into space, too!
[ PeterGage - 63 - 19:53:39
RE: [monica] what is the tempiture on mars
It can get as warm as 70 degrees Fahrenheit
on Mars, which is like a nice day on Earth, or as cold as -225 degrees
Fahrenheit, which is VERY cold! Monica, you can find more information
about Mars at http://quest.arc.nasa.gov/aero/planetary/mars.html
[ PeterGage - 64 - 19:55:20
RE: [Ben] Do wings create lift in non atmospheric flight?
No, Ben. Wings only produce lift when there
is an atmosphere.
[ PeterGage - 65 - 19:58:07
RE: [Lisa] Why did the mars plane have
to be a fixed wing?
Interesting question, Lisa. The Mars airplane doesn't have to be a fixed
wing, but it is usually not as difficult to build a fixed wing as it is
to make a helicopter. Unless it's very important to hover (stay in one
spot over the ground), fixed wing aircraft work pretty well.
[ PeterGage - 66 - 20:00:01
RE: [Johnny] Would a helicopter work on Mars?
Johnny, it would be possible to make a helicopter
but a fixed wing is simpler and more efficient unless you really need
[ PeterGage - 67 - 20:02:04
RE: [Brian] Does it rain on Mars?
I don't think it rains on Mars, Brian. There is not liquid water to evaporate
and form clouds and then condense to make rain. Have you studied the water
cycle at school? Mars does have very big dust storms!
[ Expert - 92 - 14:04:55
RE: [Dina] what is gravity on mars and how does it effect the four forces
Hi Dina, The amount of gravity on Mars is about 1/3 the gravity on Earth.
This is shown in a chart on the web site under Mars Facts. Since there
is less gravity, it takes less lift to make the lift equal the weight.
That's a good thing, because it is pretty hard to make lift since the
atmospheric density and pressure is so low.
[ Expert - 93 - 14:06:29
RE: [WHAKAZOOLU] HOW LONG IS A YEAR IN MARS
Hi Whakazoolu, The answer to the length of the year on Mars is given in
a chart on Mars Facts on the website. See if you can find the answer!.
[ Expert - 94 - 14:09:05
RE: [Rebecca] Why is subsonic better than supersonic in speed, if supersonic
makes it travel faster but not longer?
Hi Rebecca, that's a very good question. The drag caused by flying faster
than sound is very large. There is a good story about this in the web
pages called "new regime of flight" on the quest.arc.nasa.gov/aero site.
The high drag requires high thrust, so fuel is used very quickly. So it
generally is not worth it to go supersonic unless speed is really important.
[ Expert - 95 - 14:14:22
RE: [Dina] HOw well would a remnotecontrolled airplane fly on mars?
Hi Dina, yes, remote controlled airplanes fly
very well. A mars airplane would not be exactly remote-controlled, however.
The idea of remote control is that a pilot sitting on the ground can send
control commands to the airplane for it to respond. This can be done by
visually watching the airplane, or by looking at instrument readings and
video images that are sent back from the airplane. But the problem for
the Mars airplane is that it takes something like 8 minutes for the signal
to go to the airplane. By then, the control command would be kind of out-of-date.
So, instead of using remote control, we would use "autonomous flight"
for a Mars airplane. This means that it has preprogrammed control instructions
built into the flight control and guidance computer. Some of the instructions
can be based on what the airplane experiences, so the autonomous flight
computer might look at some instrument readings and make some control
inputs based on the readings. For example, we might have a radar scanner
on the airplane, and if it saw a big rock coming, the autonomous flight
control might turn or climb to miss the rock. But this would be all automatic,
not relayed from a remote pilot.
[ Expert - 96 - 14:18:05
RE: [esther] how well would a comercial jetliner fly on mars? why or why
Hi Esther, Well, the biggest problem of course
is that the engines would not work because there is no oxygen in the atmosphere
to use to burn fuel inside the engines. You can read about this in the
propulsion section of the web site. The other problem is the weight. Commercial
transports on Earth are built strong for earth atmosphere, and built to
carry a lot of weight. On Mars, it would not be possible to make enough
lift to fly with so much weight and with the wing size we use on Earth.
Mars airplanes will need much bigger wings for the same weight. OR, much
less weight for the same size wings.
[ Expert - 97 - 14:23:00
RE: [Sheniqua] how does the shape of an airp[lane affect the 4 forces?
Hi Sheniqua, The atmospheric flight web pages have some good examples
of how the shape of the airplane affects the four forces. First, the wing
airfoil shape effects how much lift and drag the wing can make. The wing
planform shape is important for drag too. The position of the engines,
fuel tanks, and cargo bay (or passenger seats) and the location and size
of the tail have a lot of influence on the "balance" of the airplane.
When we talk about the four forces, we also really should talk about the
three moments that tend to make the airplane change direction. It is important
to be trimmed and stable so the airplane will fly well, and this requires
shaping the components of the airplane so that everything balances right.
[ Expert - 98 - 14:25:07
RE: [Sam] Has anyone ever made a request
to be shot out into space after they died?
I don't know. It costs a lot of money to shoot things into orbit. Usually
there is a waiting list to shoot important stuff into space, so probably
it would be a waste of important launch opportunities to launch a dead
person into orbit. What if the body was like space junk and it hit something
important in orbit?
[ Susan/NASAChatHost - 99
- 15:11:17 ]
RE: [Alex] If NASA already knows the best design for an airplane to last
long on Mars (elliptical wing, oxidizer, propeller, subsonic) than why
did they start this project for students? HI Alex, well we thought
it would be interesting for students to work on some ideas that NASA engineers
work on. Mars is cool! Maybe with in your life time there will be a plane
on Mars. Some things that NASA works on are the property of aerospace
companies like Boeing and Lockheed and we can't tell you about them. But
Mars plane is just an idea so far so we can share that with you.
[ SteveSmith - 100 - 16:00:12
RE: [Will] Would the Mars airplane land with low gravity the same as on
Hi Will, you have asked a very good question because many people wonder
about landing, and what could be done with the airplane after it is through
flying. One problem of the very low pressure and density in the Mars atmosphere
is that flying speeds are very fast. For such a small, light plane to
be flying so fast, its very difficult to imagine it can make a safe landing.
Many people suggest using parachutes. A parachute does help, but again,
because of the low pressure atmosphere, it would take a very large parachute
to slow the airplane down before impact, and even then, it would probably
be damaged. The hope would be that the fuselage with the instruments and
data communication system would survive and be able to continue relaying
data. Many students have asked about rotary-winged Mars aircraft, and
they have many difficult challenges too, but one of the really great things
is that they would be able to make an actual landing, by hovering and
landing in the same way as a rotorcraft on Earth.
[ SteveSmith - 101 - 16:28:38
RE: [Sharona] Are the air molecules on Mars different from the ones on
Hi Sharona, I'll try to answer several of your questions in one message:
yes, the composition of the atmosphere is very different. On Earth, there
is mostly nitrogen and oxygen. There is some carbon dioxide. On Mars,
the atmosphere is almost all carbon dioxide. This is why regular fuel-burning
engines won't work - there is no oxygen to mix with the fuel to burn.
So, an engine on Mars would use special fuels that have oxygen with them,
or else take oxygen in a tank to mix with the fuel. That's why the fuel/oxidizer
motor works the best on the Mars airplane too. A real jet engine has a
whole stack of spinning fans that pull air in through the intake and compress
it. Then fuel is mixed and burned in the cumbuster. The hot exhaust is
expanded through the turbine which is another stack of fans that get turned
by the pressure of the expanding exhaust. The compressor and the turbine
are connected, so when the turbine turns, the compressor is turned with
it, so that keeps the engine running. You can find cutaway pictures of
jet engines in the atmospheric flight web pages under propulsion. (You
might have to look in the grades 9-12 section to see them.) Propellers
are very efficient ways to make thrust, especially at low speeds. The
only problem that limits propellers is when the speed of the propeller
tips gets to the speed of sound. At that point, the propeller can't go
any faster without wasting energy. So for slow airplanes, propellers are
great. For a Mars airplane, we think propellers are a good idea, but they
do put a limit on how fast the airplane can fly, and that in turn limits
how much payload weight the airplane can carry, because the lift has to
equal the weight, and if you slow down, you get less lift.
[ SteveSmith - 102 - 16:33:40
RE: [Vanessa] Will there be a Venus airplane?
Hi Vanessa, It would be fun to study what the special problems would be
for flying on Venus. They would be very different from the problems on
Mars. For example, there is plenty of atmospheric pressure, so generating
lots of lift would be easy. One problem is that the atmosphere of Venus
is VERY HOT. It is difficult to design the airplane materials, and all
the electronics for autonomous flight, and all the moving parts for the
controls, everything that goes into the airplane would have to be able
to tolerate the extreme heat. So far, the probes that we have sent to
Venus have only survived a few hours in the heat. There may be other challenges
too, like strong winds and turbulence.
[ SteveSmith - 103 - 16:38:31
RE: [Hillary] could you send a glider to Mars?
Hi Hillary, A glider is a great idea. The length of time that an airplane
can fly and send information back is pretty limited, maybe 20 minutes,
until sometime in the future when we have permanent data-relay satellites.
So, a glider that can fly for 20 minutes would be almost as useful as
a powered airplane. Taking the weight of the motor and fuel out of the
airplane, it could carry more instruments instead. Or, maybe since they
are lighter without the engine and fuel, we could make two small gliders
to launch and fly to two different places instead of just one. So that
is a good possibility!
[ SteveSmith - 104 - 16:41:09
RE: [Andrea] what material is best for a flight to mars(considering the
temperatures and atmospheric conditions)?
Materials for a Mars airplane need to be strong, but very light weight.
This is even more important for Mars airplanes than Earth airplanes. So
very likely, they would use carbon-fiber composites for important parts
of the structure. Some parts could still be aluminum.
[ SteveSmith - 105 - 16:49:46
RE: [esther] How does airspeed affect how air flows around a wing to generate
Hi Esther, there is a lot of good information about airflow and lift in
the atmospheric flight pages. If the angle of attack is low, the basic
airflow pattern won't change with airspeed very much. But the amount of
lift will vary in proportion to the square of the airspeed. You might
have to have your teacher explain what that means. Since the lift equals
the weight in flight, there are two factors that change when you change
airspeed. One is the airspeed, but the other is the angle of attack. Lift
increases in proportion to angle of attack, up to a certain limit. And
as I said above, lift increases in proportion to the airspeed squared.
So when an airplane speeds up, it reduces angle of attack to compensate
to maintain the same lift. When angle of attack gets too high, the airflow
can't follow the airfoil shape, and separation, or stall, happens. There
is information on that in the web pages too. Now, there are some subtle
changes in the actual airflow pattern that happen as the airspeed is changed.
These changes happen in the boundary layer where the flow is rubbing on
the wing surface. These changes can be difficult to understand, but they
are less important than understanding the basics.
- 106 - 16:54:41 ]
What are reasons we want to explore mars
Hi Jordan, many people ask that question, especially
when it costs a lot of money to try to explore Mars. Maybe the best way
to answer is to ask more questions: 1) why did Christopher Columbus sail
across the Atlantic ocean? 2) why did Lewis and Clark explore to the origin
of the Missouri river and across the mountains to the Pacific ocean? Why
did men walk to the north pole and the south pole? We are explorers. That
is in our basic nature to want to know what is out there. How it got there.
How did we get here? Is it possible that there is life somewhere else?
We think it surely is. Mars is just the next step. We will never stop
[ SteveSmith - 107 - 17:00:01
RE: [Sam] Why is an elliptical wing the best for the mars plane?
Hi Sam, In theory, the "induced drag", one part of the drag on a wing,
is minimum when the lift on the wing is spread out in the shape of an
ellipse. One way to do that is to make the wing planform shape an ellipse.
There are practical limitations that make tapered wings easier to build,
so most modern airplanes use a tapered wing with some twist to approximate
the benefits of the elliptical wing. There are also sometimes other considerations
that require the lift distribution to be different from an ellipse. But
when there are no limitations, it might as well be elliptical so it is
the best for induced drag.
[ Susan/NASAChatHost - 108
- 23:07:37 ]
RE: [Hillelcommunitydayschool] hi. everyone from hillel community day
school thank you for taking the time and answering owr questions. thank
you. have a nice day.
Thank you Hillel for some great questions! Come back soon!
[ AndyHahn - 113 - 08:53:51
RE: [Andrea] how long can a fusoin engined airplane last on mars?
Hi Andrea, Well, I will assume that when you say, "fusoin", that you really
mean nuclear. Nuclear power can come from fusion, fission, or the heat
from natural decay. A nuclear power source could last for years, but there
are problems. Right now, no one can get a sustained fusion reaction, so
that's out. A fission reactor is huge and heavy, so that's out. We have
flown Radio Thermal Generators (RTGs) on spacecraft, which harness the
heat of natural radioactive decay to produce electricity. This is potentially
an option, but while the total energy contained per kilogram of mass is
very very high, the rate at which we can extract it (the power) is very
low per kilo. Even if we could make a flight weight nuclear power source,
the rest of the airplane would have to be very reliable, which is hard
[ AndyHahn - 114 - 09:01:40
RE: [Isaac] what is the best propulsion system to glide over mars?
Hi Isaak, The problem with designing for these kinds of missions is that
the answer depends on many considerations, some not so obvious. Frequently,
we have to make decisions based on incomplete or even wrong information,
we are hemmed in by very stringent requirements and constraints, and some
technologies are simply less risky to choose than others at the time we
have to make decisions. Right now, we favor a rocket motor because it
is a safe choice, but some testing could prove our belief that an electrically
driven propeller will be better. My personal favorite combines these two
into a rocket driven turboprop. However, this is the least mature of the
[ AndyHahn - 115 - 09:02:32
RE: [Michael] what sorce of thrust is best for the mars airplane and why
Hi Michael, see #37 for Isaac.
[ AndyHahn - 116 - 09:07:51
RE: [Larry] What is the best kind of engineering to study?
Hi Larry, The best kind of engineering to study is what's best for you.
You have to weigh your talents, interests, and desires for compensation.
You know, engineering itself isn't for everyone. I once had a high school
student for an intern and I asked her how she felt about the job at the
end of her term. She replied, "I think I want to be a Doctor." That's
OK. We all need to find our niche in life.
[ AndyHahn - 117 - 09:13:32
RE: [Rebecca] Why is it that a propeller works best on a plane that will
fly to Mars?
Hi Rebecca, Actually, if you remember from my webchat, we finally decided
on a rocket, so we felt the propeller wasn't best. The reason was that
we couldn't be sure the propeller would work as predicted, but that the
rocket probably would. Ideally, we would build and test propellers under
conditions similar to Mars, proving our predictions. If the propeller
would work as predicted, it would be far more efficient.
[ AndyHahn - 118 - 09:16:56
RE: [Samantha] What is the difference in the air/atmosphere of Mars' upper
atmosphere and lower atmosphere?
Hi Samantha, the glib answer is, "Not much." But seriously, there is vacuum
all the way out in space and the atmosphere at the surface is very low
density, compared to here on Earth. It's like the difference between zero
and not much more.
[ AndyHahn - 119 - 09:23:29
RE: [stacy] is it possible for there to be life on Mars
Hi Stacy, Is it possible for life to be on Mars?
I don't know. I guess anything is possible. If the Mars missions find
life, then we will have proven that it is possible. If we continue to
not find life, we haven't proven anything. There's always another rock
to turn over, potentially exposing life. Still, consistently not finding
life certainly reduces the odds of life being present.
[ AndyHahn - 120 - 09:57:20
RE: [Jennifer] how does the gravity on mars affect the four forces?
Hi Jennifer, As you know, the four forces
are Lift, Drag, Thrust, and Weight. It is pretty obvious that the lower
gravitational attraction makes Weight smaller. It is less obvious that
the density if the air is directly dependent on gravitational attraction,
and that the aerodynamic forces are proportional to density. So, believe
it or not, all of the forces are lowered. In the particular case of Mars,
the atmospheric density is 1% of that on Earth (at Sea Level), while the
gravity is about 33% (roughly). So, the aerodynamic forces are way smaller
while the weight force is small, but relatively larger. That's why flying
on Mars is so hard.
[ AndyHahn - 121 - 10:00:33
RE: [Jennifer] dOES THE DENSITY OF THE AIR AFFECT HOW THE Air flows around
an airplane? Hi again Jennifer, The density does affect the size of
the forces that can be generated, and the details of the boundary layer
do depend partly on density, so yes, density does affect how the air flows
around the airplane.
[ AndyHahn - 122 - 10:08:54
RE: [Samantha] How does airspeed affect how air flows around a wwing to
Hi again Samantha, In a very similar way that density affects the flow
around the plane(see Jennifer #121), velocity affects both the magnitude
of the forces and the details of the boundary layer. Velocity is actually
more important because it changes the magnitude of the forces much more
than a similar change in density, it changes the boundary layer about
the same as a similar change in density, and if velocity approaches or
even exceeds the speed of sound, the airflow changes dramatically.
[ AndyHahn - 123 - 10:17:27
RE: [Sharona] what exactly is a jet engine?
Hi Sharona, Technically, a "jet" engine is any engine that produces thrust
from accelerating a small mass to a high velocity. This can include a
rocket (the military had rockets that they called Jet Assisted Takeoff
(JATO) units), turbojets, turbofans, and even skiboat drives (using a
"jet" of water). Usually what people mean when they say "jet" is the air
breathing turbojets and turbofans on airplanes. You can make your own
jet engine by blowing up a balloon. You can just let it go, or even attach
it to a toy to make it "jet" powered.
[ AndyHahn - 124 - 10:22:40
RE: [esther] how important is the tail section of the airplane?
Hi Esther, If the airplane was designed to have a tail, then it is very
important. The tail is the most common device used for giving an airplane
both stability and control. If a plane were to loose its tail, it would
crash. There are some planes designed without tails, but in those cases,
the designer is using other devices to provide stability and control.
[ AndyHahn - 125 - 10:26:46
RE: [Sam] If I lived in space, would the insides of my body be floating
around inside me?
Hi Sam, that is really an interesting question.
I never really thought about it that way, but yes, I suppose that to the
extent that your insides can move around, that they would "float " around
inside you. I don't know, but maybe that's why so many astronauts get
sick in orbit. It must be a lot like going down on a steep roller coaster,
all the time!
[ AndyHahn - 126 - 10:34:53
RE: [Marie] Will the other questions posted be answered?
Has any new technology been developed for this project that will be useful
for us here on Earth? Hi Marie, We are still here! Mostly, we are making
use of technologies developed on Earth for the MarsPlane project, but
reapplied to a very different problem. It is conceivable that experience
gained on the MarsPlane will allow us to apply technology in new ways
here on Earth, like for Very High Altitude Uninhabited Aerial Vehicles.
If we develop something like the rocket driven turboprop, then that would
be an example of MarsPlane tech being available for use on Earth, but
there is no plan to do it right now.
[ AndyHahn - 127 - 10:58:48
RE: [Sharona] what exactly is a jet engine?
What is a normal day at work like for you? How does the atmosphere of
mars affect the performance of a propulsion system? Hi again Sharona,
My typical day involves mostly office type work (answering the phone,
e-mails, mail, talking to co-workers), some use and programming of computer
codes, some school/training/self teaching, and a little time for answering
questions from folks just like you. The Martian atmosphere certainly does
affect the propulsion system. The biggest effect is that it doesn't allow
air-breathing engines (like turbojets or turbofans) because there isn't
free oxygen available. That makes life very hard for us. Also, the low
atmospheric density forces us to fly fast, which propellers don't like,
and the propellers have to be very large to capture a usable mass flow
[ AndyHahn - 128 - 11:03:35
RE: [RipvanWinkle] What kind of propulsion systems and fuels can be used
to power airplanes?
Hi RipvanWinkle, There are many non-air-breathing
candidate propulsion systems, but we finally settled on a rocket as the
most likely to work, an electric driven prop as the next best if it worked
as expected, and a rocket fueled turboprop as the most attractive but
also by far the most risky.
[ AndyHahn - 129 - 11:06:53
RE: [esther] how would a small propeller airplane fly on mars? Hi again
Esther, Our MarsPlane was a small propeller plane and while it would meet
the mission requirements, it was short duration, small payload, and difficult
to fly. Size matters on Mars, and bigger is better (easier to design a
more capable plane).
- 130 - 11:14:43 ]
RE: [Andrea] how long does the mars airplane have to deploy its wings
before it would not have enough time to get enough lift to fly
Hi again Andrea, The time a MarsPlane has
to deploy its wings depends on how high the aeroshell can open up and
on the height that the plane was designed to fly. If the aeroshell slows
down quickly, it can open up high. That's why I mentioned the Ballistic
Coefficient of the different shapes. Some shapes just decelerate better
than others. As far as the altitude that the plane can fly at, we found
that it is very hard to fly even at zero altitude, while going higher
was just harder. So, we probably would release as low to the ground as
we could without actually hitting it. The good news is that the actual
time required to deploy the wings is short (maybe 30 seconds) so there
was plenty of margin between what we could get and what we actually needed.
AndyHahn - 131 - 11:44:24 ]
RE: [esther] what is the best(most efficient) airspeed at which reconnaissance
flights are made?
Hi again again Esther, The best speed to fly for reconnaissance is dependent
on the mission requirements and constraints. The Air Force has had spyplanes
that fly from about 0.6 to 3 times the speed of sound.
- 132 - 11:46:02 ]
RE: [sharona] Is the plane to mars allowed to have a propellar?
Hi again again Sharona, There are no rules against having propellers,
so yes, they are allowed.
AndyHahn - 133 - 11:50:04 ]
RE: [Sam] Is it possible to make artificial gravity?
Hi Sam, I don't know if creating a gravity field is possible, but we can
simulate gravity. Gravity is a body force that appears as an acceleration
and we can put a mass in continual acceleration by spinning it. That is
usually the idea behind rotating space stations and ship sections that
you see in the movies.
[ AndyHahn - 134 - 12:19:15
Hi Dina, I will try to answer all your questions at one time. Best type
of propulsion? - Please see my responses to Isaac, Rebecca & Sharona.
How does pressure affect flight? - Pressure and density are inversely
linked in a fluid, so if pressure changes, density changes. Please see
my response to Jennifer about density. Can a balloon carry info back from
Mars? - Nope. A balloon works by displacing a gas that, while light, does
weigh something. In space, there is no gas to displace, so it can't float
into space or travel back to Earth. Is it a good idea to send a balloon
to Mars? - If by that you mean fly a balloon to Mars, that won't work
(see above). If you mean to fly a balloon on Mars, then it may be a good
idea. Flying on Mars is a lot like flying at 100,000 feet here on Earth.
The only vehicles that routinely fly under these conditions are balloons.
Balloons also have a neat feature in that the envelope can be packed in
a very small space and the gas to fill it can be compressed to a very
small space, while both are pretty light. This makes it relatively easy
to transport a large vehicle, which is helpful because it would have to
be huge. The website has a balloon sizing function that shows how big
it would have to be (at a minimum). What are the factors that aerodynamic
forces depend on? - Lift and Drag are aerodynamic forces. They depend
on atmospheric density, velocity, the size of the vehicle, and the non-dimensional
force coefficient that is characteristic of the shape of the vehicle.
Whew! I'm tuckered out. You really gave me a workout.
[ Chase - 135 - 12:25:34 ] i love this website.
[ AndyHahn - 136 - 12:30:53
RE: [Rebecca] Why is it that a fuel-oxidizer would work the best on a
fixed wing plane to fly to Mars?
Hi Rebecca, There are basically three reasons
why a rocket (fuel & oxidizer) is preferred. First, there is no usable
(free) oxygen in the Martian atmosphere. This means that the engine can't
breath any better than we can. Just like we have to carry our own oxygen,
so does the engine. Second, Fuel & oxidizer has such a high energy content
per kilogram, that it is attractive even if not particularly efficient.
In other words, there is so much energy that we can afford to be somewhat
wasteful. Third, a rocket pretty much works in most environments. It is
a robust, predictable propulsion, whereas some might be more efficient,
but the risk of failure is higher.
- 137 - 12:37:33 ]
RE: [MikeRoch] Can a regular jet engine be used to power an airplane on
Mars? Why or Why not?
Hi MikeRoch, No, a regular jet can't be used on Mars. I wish it could
because my life would be much easier. Jet engines (I assume you are referring
to turbojets or turbofans) are air-breathing devices. If there is no free
oxygen in the Martian atmosphere, then they won't run.
Fri May 25 14:03:01 2001