Aim For The Moon - model rocket contest

Aim For The Moon - model rocket contest

Post by kevin.w.mcki » Thu, 28 Jun 1990 03:23:12



In the spirit of exploring this idea, I will pass on a few thoughts
which I have had about the Aim For The Moon contest.  Consider it
issues/reflections which may be relevant.

- This is a potentially very dangerous contest.  Even if none of the
  participants are injured, there is a significant chance for property
  damage.  The official launch could be effectively supervised, but
  the testing of launch vehicles cannot.  The political fallout from
  a major accident could have a result 180 degrees from the desired
  result.

- The most dangerous aspect is getting the launch out of the
  atmosphere.

- The most technically challenging aspect is orbital mechanics,
  guidance, reliability, and the payload (if of a scientific
  variety).

- A really solid reason for having such a contest is needed.

- It will not be possible to jump the political hurdles without
  the support of NAR and Tripoli and the buy-in of NASA and DoT.

- A full-time team of qualified engineers and scientists would need
  3-5 years to write requirements, design, build, and test a
  reliable flight vehicle and payload.

- If this contest is not on a solid scientific base, it will receive
  little support and much criticism (as will model rocketry).

I do think space exploration is going to see renewed levels of public
interest (and funding) and I think there is a potential to capitalize
in a positive way on that interest.  First there needs to be a good
reason for the contest.  How about

1. To generate interest in space travel/exploration as a practical
   and economic reality.

2. Generate interest in science and engineering.  The U.S. government
   is always concerned about levels of enrollment in engineering
   and research universities.

3. Demonstrate that space exploration is within the reach of
   "mortals".  This may not wash given the level of technical
   competence needed.  But it can show how model rocketeers can
   grow to reach that level of competence.

4. Advance the state-of-the-art of model rocketry.  This is one
   area that may interest manufacturers (aside from creating
   new customers).  Any innovations/inventions should become
   public-domain and all design entries published.

One of the key issues which must be resolved is leadership.  If
NAR and Tripoli are not interested...forget it.  Their buy-in
must come first.  Are there any officers of NAR and Tripoli
which have been monitoring this discussion?  How about some
input (off the record, of course :-)).  After they buy-in, it
sure would help to get NASA sponsorship.  And, DoT approval is
required.  Finally, on leadership, a highly visible spokesperson
would be very beneficial...any ideas?

Now, with the above said, what concept would produce a viable
contest?  Here's one idea (let's hear yours):

Goal: Fly a scientific payload to the moon in a model rocket (OK, high
      power).

Contest 1: Design, build, test, and demonstrate a flight vehicle
           capable of delivering a X Kg payload to the moon from
           a LEO (say 100 - 200 mi).  The contest could have a number
           of phases climaxing in a fly-off for the top contestants.

Contest 2: Design, build test, and demonstrate a scientific payload
           which can be delivered by the model rocket.  I should
           gather meaningful scientific data and transmit it back to
           an earth station.  Again, it could be done in a number of
           phases.

The winners of the two contests could then be teamed to develop the
actual flight vehicle and payload to be launched from the Space
Shuttle.

I would allow 2 years to lay the ground work, 2 years for the designs
to be completed, 2 years to hold the contests, and 1 year for the
final product to be built for launch from the Shuttle.

Comments?

Kevin

--------------------------------------------------------------------
Kevin McKiou                         UUCP:     att!ihlpy!kwm
NAR 51581

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Aim For The Moon - model rocket contest

Post by mccar.. » Sat, 30 Jun 1990 03:20:53


        I've read with some amu***t the stream on "model rockets
        in space", and I'm going to have a hard time not coming across
        as sarcastic in places. Please take this as constructive criticism.

        As a relatively long-standing Tripoli member (#142), who has
        specialized in turning paychecks into noxious fumes with great
        efficiency, I'd really like to address this contest in a
        pragmatic sense.

        Doubtless you think nobody else has ever considered this, but
        numerous people have. There are two classes of problems you
        must solve: The theoretical aspects of achieving flight, and
        the pragmatic problems of flying the rocket. Some of this will
        be rehash, but use it as a list of things to worry about. Lastly,
        I'll comment on legalities, definitions, and some organizations.

Theory:

        Hitting the moon is hard. You can't simply plot a course from
        point a to point b and shoot, because point b is moving, and so
        is point a. Your projectile starts with point a's kinetic
        characteristics. Typically moving from orbit about body a to orbit
        about body b involves creating an orbit about a which encompasses
        b, and then negating a's gravity effects. Bear in mind that the
        earth and the moon revolve around a common center of gravity, and
        so does your rocket. Let's use an exaggerated example of the sun
        and earth, since the CG of that system is most likely inside the
        sun.

        Ever thought about those occasional suggestions to do things like
        launch all our nuclear waste into the sun? Know how much energy
        that would take? You don't just aim at the sun, you have to negate
        the amount of kinetic energy that holds the mass in orbit. The
        amount of energy required is the same (I believe) as would be
        required to lift off from the surface of the sun and achieve a
        93,000,000 mile orbit, but the effect of the booster weight is
        negated. You have similar problems actually hitting the moon.

        So first you must orbit the earth. This means several things:
        First, you should launch near the equator. An airborne launch from
        a plane traveling east would be best. If I were actually going
        to try this, I'd probably attempt to get permission to launch
        from Guyana. Second, you need active control, and not movable fins.
        You must have gimballed thrusters of some sort to keep control
        as the air density decreases an fin effect goes to zero. Third,
        as has been pointed out, most spacecraft assume a low, unstable
        orbit early in their flight and then add energy to achieve an
        orbit which is in space. This is done because if you launch
        straight up, you must make a turn and in the process eliminate
        all of the radial velocity achieved during ascent, which means
        wasting energy. This of course means spending more time in the
        atmosphere than you'd really like. You'll have a tough time
        getting a mutli-stage design to go supersonic in its lower
        stages, so plan on wasting mucho impulse heating up the air. To
        give an example, I've seen a single stage minimum diameter M
        rocket launched, and the paint on the nose cone melted and
        boiled off.

        If you want to try a straight uncontrolled shot there may be
        some trajectory that would get you near the moon, but it will
        take more impulse than orbit to orbit. In an earlier response
        it was suggested that you needn't reach escape velocity. This
        isn't totally accurate. It is true that as long as the rocket
        motor is firing with more thrust than the craft weight, it will
        accelerate away from the earth. However, unless you're going to
        burn until you get there at some point the motor will stop firing.
        At that point the rocket must be travelling at close to the
        proper escape velocity for that distance [I'm pretty sure that
        escape velocity is a function of distance from CG], at least so
        that it won't decelerate in less than 240,000 miles. And of course
        any weathercocking at launch may induce an error in trajectory
        which is literally in the "mega-mile" range.

Pragmatic:

        Somebody has to build this. How many of you have any experience
        with large composite engines? Let me tell you about some of the
        reliability issues you'll contend with.

        Let's assume a simple rocket with three K motors in the booster
        and a K motor for the upper stage. We wire the booster up with
        squibs for launch. Each squib has some thermalite attached to
        it so that the total igniter has more impulse. With this, a good
        relay system, and really well charged batteries, there's a good
        (>50%, probably as high as 90%) chance that all three engines will
        ignite. If they don't, or if one "air-starts" after leaving the pad,
        trajectory is shot, and probably so is safety. Now our rocket is
        moving. Not to make any claims of factuality, but from what I've
        seen the probility of one engine cato'ing at this point is probably
        10% anyway. The first stage burns out, and we ignite the second.
        We can do this by thermalite in the delay port of a lower stage,
        or electronically, with a timer or mercury deceleration sensor
        (don't try altitude sensing). The probability of failure here is
        the worst of the bunch. If the upper stage is multi-engine, it's
        much worse. Scale this up to a bunch of N-engines, and I'll give
        really good odds that you can't get it all to light.

        Then there's the problem of materials. It's tough to see what
        happens in mid-air, since you aren't there, but let me relate what
        I've seen and my interpretation: Two years ago, I launched a 20
        pound or so rocket at Fort A.P. hill in ***ia. It had plywood
        fins and 2 Aerotech J-285 engines (about 90lbs thrust, 4 sec. burn).
        I was looking at my camera a couple of seconds after launch and
        heard a shredding noise that I immediately recognized. Fins. They
        didn't just detach, they delaminated and disintegrated. I believe
        that the buffetting in the trans-sonic region causes harmonics in
        the fins, and that the vibration then disintegrated the glue. So
        now I use fiberglass fins. But they're still gonna vibrate, and
        that'll mean drag, and that means more impulse. Oh, and how are
        we gluing this together? N motors throw off a lot of heat (For
        example, using the Aerotech L1507, one leaves about 6 inches of
        the engine exposed at the tail, since that much of the casing
        ablates AFTER burnout). Internal temperatures of 400+ F. are
        easy to get. Most epoxies will fail after some exposure to this
        heat. Other materials are also problems. A suggestion was made
        to use a parachute for safety. Deploying a chute from a running
        N rocket will result in a cloud of fabric parts and some minor
        course deviation in the rocket. I've seen large rockets which
        simply deployed after a couple of seconds of free fall, and the
        chutes don't hold. You must deal with numerous materials problems.

Legalities:

        Please stop calling these things "model" rockets. A model rocket
        is carefully defined in NFPA-1122, from which most state law is
        derived. Model rockets weigh less than 1.5kg. and are restricted
        (I believe that this is still the new regulation) to 4 oz. of
        propellant, regardless of propellant ISP. This is about two G
        engines.

        The rocket community has taken to using two other terms for
        rockets above these restricitons:

        Advanced rocket: A rocket >1.5KG or 4oz. propellant, but made
        of non-metallic materials and using professionally manufactured
        engines.

        Amateur rocket: All other non-professional rockets.

        I believe that you want to refer to Advanced rockets.

        Just as a point of information, purchase and use of rocket motors
        which are not "class C toy propellant devices" is restricted to
        4 classes of consumers:

                1) The military
                2) Professionals involved in rocketry
                3) Educational institutions
                4) Research institutions.

        Tripoli rocketry association is incorporated as a research institution.
        This entitles its members to purchase motors as agents of the
        corporation. Tripoli polices this with its confirmation program. A
        member must demonstrate proficiency and safety at a sanctioned launch,
        at which point someone from the "authorized persons" list may sign
        that members confirmation card. The motor manfuactureres are
        periodically provided with a list of those members who can purchase
        motors.

        This covers us in states whose rocketry law is derived from NFPA-1122.
        Bear in mind that flying non-NAR legal rockets is against state law
        in some places, notably the State of California and the Commonwealth
        of Massachusetts. California is working on a new pyrotechnics license
        class for advanced rocketry. I think this is a great idea.

        As for clearances, although you may need whatever orbital
        certification   is required, the FAA most certainly does have
        a say. This is specifically called out in the FARs (101.5 I believe)
        and you must have a waiver from the FAA to fly anything above
        F engines. (Note that this includes some model rockets). Bear in
        mind that the FAA must trade off use of air routes by commercial
        jetliners versus your rocket to the moon. Expect hassles.

        We do not, as a rule, use range safety charges, since they are
        viewed as an addtional danger. What we do is to use large desolate
        areas where only people who understand the process are present.
        We also carry insurance for those launches.

        With respect to support from the NAR and Tripoli, I'm pretty sure
        the NAR won't want to know from any of you, unless you can get
        two G engines to hit the moon. Tripoli (I'm speaking as a member.
        I am not an officer.) will no doubt support you to the extent that
        it supports any of its member (assuming you become a member). That
        is, will try to grease the skids legally.

        I suspect that both organizations will advise you to learn to
        crawl before trying to walk. Get some experience with smaller
        advanced rockets and learn what the problems are. Judging by the
        discussion so far, if you came to me for corporate sponsorship
        (you'll find out you need that), I'd ask a few basic questions
        and then send you packing. By the way, I wouldn't fund it anyway
        because
...

read more »

 
 
 

Aim For The Moon - model rocket contest

Post by Vincent Ca » Sat, 30 Jun 1990 12:33:13



Quote:
>Hitting the moon is hard. You can't simply plot a course from
>point a to point b and shoot, because point b is moving, and so
>is point a.  [...]

The idea is to aim for the moon, not to hit it.   I appreciate the
difficulty in hitting a target that is about 240,000 miles away
and only 2,000 miles in diameter.  The plan is just to get within
100,000 miles of it (a ball target with 10,000 times the surface
area!).

Quote:
>Ever thought about those occasional suggestions to do things like
>launch all our nuclear waste into the sun?     [...]
>The amount of energy required is the same (I believe) as would be
>required to lift off from the surface of the sun and achieve a
>93,000,000 mile orbit, but the effect of the booster weight is
>negated. You have similar problems actually hitting the moon.

The energy to send something from the surface of the Sun straight
up to hit the Earth (aiming for where the Earth would be at some
time later) is less than the energy to get that high and be in
orbit (in the first case you only have potential energy in the
second you have potential and kinetic).  

Quote:
>So first you must orbit the earth.

No.  This is just not true.  Not only is it not needed, it a
bad idea if all you want to do is go up.  To get into orbit you
need to first go up to get above the atmosphere and then turn
and go around the Earth.  This wastes lots of energy and takes
a rocket with control mechanisms which means a heavier rocket.
There are good reasons to get into orbit first if there are people
onboard but this is not the case here.

Quote:
>If you want to try a straight uncontrolled shot there may be
>some trajectory that would get you near the moon, but it will
>take more impulse than orbit to orbit.

I don't think so.  If you were on the surface of a planet without
an atmosphere the lowest delta-V to escape is "Escape velocity"
and you escape by just going straight up at this velocity.  This
is the speed you would be going at when you hit the surface if
you fell starting at infinity.

Quote:
>In an earlier response it was suggested that you needn't reach
>escape velocity. This isn't totally accurate.
>[...]
>At that point the rocket must be traveling at close to the
>proper escape velocity for that distance [I'm pretty sure that
>escape velocity is a function of distance from CG],  [...]

The escape velocity at each point is exactly what an object
that started the surface with escape velocity would have slowed
to by the time it had gotten that far from the planet.  It clearly
takes less velocity than this to only get up to the moon.  This
is the speed you would have if you fell from the moons altitude
which is less than if you fell from infinity (think force times
distance).

Quote:
>And of course any weathercocking at launch may induce an error in
>trajectory which is literally in the "mega-mile" range.

True.  Again, the odds of hitting the moon are very small.  One
interesting point is that if you launch from a balloon you are
moving with the wind and do not have to worry about weathercocking.

Quote:
>Let's assume a simple rocket with three K motors in the booster
>and a K motor for the upper stage.  [...]

Since we can always get larger engines (even above N) and it is
possible to get custom engines, I can't see why anyone would want
to use multiple engines at a given stage.  As you point out,
multiple engines will decrease the reliability.

Quote:
>Then there's the problem of materials.

Yes.  The problems must be dealt with.  Yes, wood (plywood or balsa)
and cardboard are not going to be good enough for such a rocket.

Quote:
>Please stop calling these things "model" rockets. A model rocket
>is carefully defined in NFPA-1122, from which most state law is
>derived. Model rockets weigh less than 1.5kg [...]

Note that the subject line has been edited.  I would not want to
do anything against the law.

Quote:
>The rocket community has taken to using two other terms for
>rockets above these restricitons:

>Advanced rocket: A rocket >1.5KG or 4oz. propellant, but made
>of non-metallic materials and using professionally manufactured
>engines.

>Amateur rocket: All other non-professional rockets.

>I believe that you want to refer to Advanced rockets.

However, people might use metal and then we would still be in trouble.  

I think we can avoid this whole mess by just calling them "rockets".  
As far as I know, there are no legal restrictions on the use of this word.

Quote:
>We do not, as a rule, use range safety charges, since they are
>viewed as an addtional danger. What we do is to use large desolate
>areas where only people who understand the process are present.
>We also carry insurance for those launches.

One very nice thing about a balloon launch is that it gets the rocket
20+ miles up before it fires.  Also, you could launch the balloon
from a boat out in the middle of the ocean.  We most certainly need
to get insurance for this event.

   -- Vince

 
 
 

Aim For The Moon - model rocket contest

Post by Norman Yarv » Sat, 30 Jun 1990 12:44:16


Quote:

>Other materials are also problems. A suggestion was made
>to use a parachute for safety. Deploying a chute from a running
>N rocket will result in a cloud of fabric parts and some minor
>course deviation in the rocket. I've seen large rockets which
>simply deployed after a couple of seconds of free fall, and the
>chutes don't hold.

There was a article in Scientific American a couple of months ago about high
performance parachutes.  Building or even designing these things is a bit
out of our range, but they do exist.

How high performance?  Well, the ones mentioned were slowing down 500-pound
objects dropped from a fighter at Mach 1.1.  The article has diagrams of
airflow... including shock waves!

Yes, they _are_ made out of Kevlar.

--

 
 
 

Aim For The Moon - model rocket contest

Post by Phillip Harbis » Sun, 01 Jul 1990 07:51:22


Quote:


> > Hitting the moon is hard. You can't simply plot a course from
> > point a to point b and shoot, because point b is moving, and so
> > is point a.  [...]

> The idea is to aim for the moon, not to hit it.   I appreciate the
> difficulty in hitting a target that is about 240,000 miles away
> and only 2,000 miles in diameter.

The task is more complicated than just hitting a (relatively) small
object at a large distance.  Both the earth and moon are moving, and
at fairly fast speeds.  It may not seem like it from our frame of
reference, but the earth is moving through the cosmos at a fairly
fast speed.  My rough calculations (assuming an orbital radius of
240,000 miles) show that the moon must be moving at a speed of
60,000 miles per hour relative to the earth.  Hitting such a fast
moving object from such a long distance will be difficult (the
understatement of the decade :-).  Just getting a model rocket
into LEO will be difficult enough considering the unreliability
of upper stage ignition in model rockets.  A more worthwhile goal
would be to first develop a reliable staging mechanism, then try
for a LEO that would decay after a few days (to avoid leaving
more space junk in orbit).

--
Live: Phil Harbison, Xavax, P.O. Box 7413, Huntsville, AL 35807

Bell: 205-883-4233, 205-880-8951

 
 
 

Aim For The Moon - model rocket contest

Post by Henry Spenc » Sun, 01 Jul 1990 00:33:51


Quote:

>How high performance?  Well, the ones mentioned were slowing down 500-pound
>objects dropped from a fighter at Mach 1.1...

The most amusing part of the whole article was how they carefully skated
around telling you *what* those objects are meant to be.  Nuclear bombs.
(This is not just speculation; in one or two obscure spots in the article
they refer to one of the objects as a "Bnn", where nn is two digits, and
that's a nuclear-bomb designation.)
--
"Either NFS must be scrapped or NFS    | Henry Spencer at U of Toronto Zoology

 
 
 

Aim For The Moon - model rocket contest

Post by Donald Heske » Sun, 01 Jul 1990 02:33:31


Excellent response to the basic modroc-to-the-moon suggestion.  It was
all well thought out and accurate.  It's nice to see some logic and
common sense emerge out of the maelstrom or overoptimism, rumor,
misinformation, etc.

Any chance you could be talked into explaining Tripoli's aims,
purposes and accomplishments?

 
 
 

Aim For The Moon - model rocket contest

Post by Donald Heske » Tue, 03 Jul 1990 05:08:06


I suggest you redo those calculations!  60,000 mph is about 2.4 times
escape velocity at earth's surface!  If the moon were going that fast,
it would be GONE!  The moon's orbital speed is roughly 2300 mph.  That
corresponds roughly to 60000 miles/day...any chance you forgot to
divide that number by 24, for the number of hours in a day?

The earth's (and moon's) speed through the cosmos has nothing to do
with the problem.  All we're worried about is motion relative to the
common center of gravity of the earth-moon system.

 
 
 

Aim For The Moon - model rocket contest

Post by Phillip Harbis » Wed, 04 Jul 1990 07:28:01



Quote:

> I suggest you redo those calculations!  60,000 mph is about 2.4 times
> escape velocity at earth's surface!  If the moon were going that fast,
> it would be GONE!  The moon's orbital speed is roughly 2300 mph.

Yes, you got me on that one.  Please accept my apologies.  Can you
see me blushing from Texas?

Quote:
> That corresponds roughly to 60000 miles/day...any chance you forgot
> to divide that number by 24, for the number of hours in a day?

No, but I did forget to devide by the period of revolution, which I
believe is about 28 days.

Quote:
> The earth's (and moon's) speed through the cosmos has nothing to do
> with the problem.  All we're worried about is motion relative to the
> common center of gravity of the earth-moon system.

I still suggest that hitting a moving target at a distance of 240,000
miles, whether moving at 2400 mph or 60,000 mph, is a difficult task.

--
Live: Phil Harbison, Xavax, P.O. Box 7413, Huntsville, AL 35807

Bell: 205-883-4233, 205-880-8951

 
 
 

Aim For The Moon - model rocket contest

Post by Joe Pfeiff » Fri, 06 Jul 1990 23:56:33


Anybody who wants to try to actually hit the moon should take up trap
shooting (this is a shotgun game which emulates bird hunting.  You
launch a small clay disk called a ``pigeon'' from a mechanical device,
and try to hit it in the air with a shotgun).  The *** of
pointing straight at 25 pigeons in a row and missing every single one
before finally figuring out how to lead it a smidgeon should disabuse
everyone of the notion that hitting the moon is even vaguely
reasonable; particularly those people who posted ideas for launching
light-seeking rockets at a full moon.

-Joe.

 
 
 

Aim For The Moon - model rocket contest

Post by Donald Heske » Mon, 16 Jul 1990 03:05:22


Actually, if you read the original posting, you'll see that the author
was well aware that the chance of any of the payloads hitting the moon
was remote.  I believe he suggested that coming within 100,000 miles
be considered "success", with a special award for whichever group came
closest.