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I love scientific competitions

  1. May 29, 2009 #1
    Hi
    I’m a 14 year old student and my school is having a science competition for the students in the grades above me, but i thought I would enter because I love scientific competitions.
    Basically the competition is a hypothetical scenario where you have a group of scientists/engineers and $200,000 in cash and you can do whatever you want (as long as it's realistic) and the winner is the one who comes up with the most interesting idea

    What I came up with is sky diving from space and I thought I would run a couple of ideas past you to see if they are realistic or not.

    To get up to the correct height of 100km, I initially thought of using a modified sounding rocket but would a human payload experience too much g-force during the boost phase?

    As for the suit I thought of using a mechanical counter pressure suit, which would be lighter than the usual gas pressure suits that are normally used but would the suit hold up in a vacuum?

    Also to protect against high temperatures when freefalling I thought of using heat resistant materials like nomex that f1 drivers use
    Isn't aerogel a very good insulator as well? but I don't know how you could fill a suit with the stuff
    What about a ceramic paint or thermal suit like what scientists use when collecting lava samples?

    The person would obviously need to breathe, so how about a rebreather system like what divers use but modified for high altitude and with enough air to last 45 minutes.
    What about temperature inside the suit, is it true that a counter pressure suit doesn’t need a heat management system because you are so tightly wrapped in?

    I read somewhere that when you jump from very high altitudes you can go into an uncontrollable spin, why is this? and how could this be solved?

    When they jump out from 100km they will reach very large speeds during freefall but as they hit air will their velocity come down to acceptable skydiving speeds by 5,000 feet?

    Any advice will be great

    If any of you guys have any other interesting ideas that I could do for my competition entry, I’ll be glad to hear it




    Another idea I had was to have a small dimension nuclear reactor producing about half a Megawatt Electric, would it be possible to make and fit something like this (including the reactor and the generator) into a container?
    I ask because I’ve just read about a proposed reactor design called the Liquid Fluoride Thorium Reactor and it seems really interesting.
     
  2. jcsd
  3. May 29, 2009 #2

    mgb_phys

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    Re: SpaceDiving

    Presumably the aim of the competition is to show if it's feasible or not using physics. So even if it's not it could still be a good project.

    Well humans can obviously survive some large rocket launches. Lookup what the g force for an apollo launch was and then the speed of a sounding rocket.

    A USAF pilot called Joseph Kittinger made a famous parachute jump from about 30km, do some searches on this.

    To hold up in vacuum it has to survive one atmosphere of internal pressure. That's not very much.

    if you assume that all their potential energy becomes kinetic energy and then becomes heat energy. Then you can use their falling speed to work out how much heat is being generated and then you can use thermal resistance to estimate how much insualtion you would need.

    You don;t need a rebreather - there is a specific reason why these are important at high pressures but they are nothing to do with this low pressure. Find out how much air you breathe in 45min and work out how much oxygen you would have to carry.

    Time to hit wikipedia!

    Good luck -
     
  4. May 29, 2009 #3
    Re: SpaceDiving

    I actually had a dream about this once. I ended up in australia. I made my way to a stadium and landed perfectly in a seat. I say go with a balloon. Much cheaper.
     
  5. Jun 3, 2009 #4
    Re: SpaceDiving

    thanks for the post mgb_phys and i apologise for my own late reply

    well the apollo astronauts experienced nearly 8g during lift-off of the saturn rocket, the sounding rocket that i could find proper figures for has a maximum velocity of 3500m/s and an acceleration force of 15g but i worked out that after the boost phase the rocket will travel another 625km before it's velocity reads 0
    also the rocket has a payload capacity of 800kg which is too much to send a person

    i think a potential rocket would need to carry a payload with a mass of 300kg (120kg for a person plus his suit and the rest for the shroud to protect the person until he reaches apogee)

    so what i worked out from the figures of the sounding rocket was that if you had a rocket travelling at 1500 m/s (about 3350 mph) after boost it would coast up 115km before it's velocity became zero and if you had the same boost time (with a less powerful motor) as the larger rocket mentioned above would the G be 2.3 times less on the smaller rocket? (i got 2.3 because the velocity during a given time of the larger rocket is 2.3 times more than the velocity of the smaller rocket)

    so you're saying that the use of a counter pressure suit is entirely possible?

    i can't seem to find an equation that would allow me to find out how hot a suit will get on re-entry and another thing is i can't work out the max velocity that a person will reach when falling from 100km because i don't know at what altitude the atmosphere starts to slow you down
    can you help me with that?

    well, a person at rest need 23 litres of oxygen per hour and because they are going to be jumping from space lets say that their breathing is double the normal amount and say that they will need 46 litres per hour and the 'ride' will be way less than an hour.

    i've read about kittinger and that's why i was curious as to why a person can go into an uncontrollable spin at high altitudes
    what would be a good thing to have as to not let a person start spinning?
    a drogue shoot or something similar to the RCS system on the shuttle?
     
  6. Jun 3, 2009 #5

    mgb_phys

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    Re: SpaceDiving

    It also depends on the position of the person and how long for.
    Laying on your back I suspect you could survive 15g for a short time.

    You probably only have to consider air resistance for the first 30-50km, then the air gets pretty thin so after that it's just a balistic trajectory.

    Not sure what a counter pressure suit is but.
    You need to supply 0.2atm of oxygen to keep your payload happy. You can do this with a full pressure space suit and regular air (containing 205 O2) or with a suit holding 0.2atm of pure oxygen.
    Pure oxygen means you are carrying less mass (not really relevant for such a short trip) and you have less pressure difference across the suit. But you need some way of balancing the pressure when they are on the ground at the start and end of the flight - think what happens to a balloon with only 0.2 atm of pressure inside on the grounf and in vacuum.

    The point is to make estimates. You aren't going to break the speed of sound in freefall, so if you look up the speed of sound at different altitudes you can use this as an upper limit.

    A regular scuba cylinder can hold 80litres so not too difficult.

    Reaction control doesn't really give you very much torque. It's fine for very slow precise moves in space but you need rather a lot of propellant to steer someone in the air - that's why aircraft use flaps rather than rocket thrusters!
    A drogue chute probably makes sense but it's really a detail compared to working out the real physics.
     
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