Amateur rocketry can be fun and exciting.  As a parent, it is a fun way to interest your children in science and space.  It is also a way to show them that even rocket science need not be difficult.  One of the problems that deter people from this entertaining hobby is the expense.  You buy a launch pad kit for forty dollars and you spend another four to ten dollars on engines and another fifty dollars on a nifty rocket that you spend four hours assembling and the first launch goes great, but you never see the rocket again.  It arches up, up and away, and way up in the sky you see the rocket pop apart and the parachute deploy.  Then the wind catches it and blows it beyond the trees to Oz or someplace and you get frustrated and you and the kids don't want to invest so much effort and money into something you will never see again.  Well, I recommend buying the launch pad kit and the engines, but save your money on the rockets except for a birthday maybe.  All you need is a plastic drinking straw (used and clean will do), some glue and some cardboard to make high-flying fun rockets.

 Here is an easy way to build a cheap rocket.  (Note: I am assuming you already own a launch kit here.  I may cover how to build your own later, but for what you get the kits are a good buy.)

 The Tree Hopper El-Cheapo:
 Parts/supplies:
  1) A small engine in the A scale.
  2) A sheet of paper, either typing or loose leaf.
  3) Transparent tape
  4) Two squares of card board (not corrugated, flat like a cereal box), a few inches across
  5) A plastic straw
  6) Glue, either white glue or a hot glue gun. (Personally, I recommend the glue gun)

 Step one:  Roll the paper around the engine, leaving just a bit of the engine sticking out, a eighth of an inch or so.  Make sure you get the edges even and the roll tight.  Now, unroll it and apply a bit of glue to the paper that will be the first layer around the engine.  If you are using white glue, you will need a bit of the tape for the next part.  Roll the engine back up in the paper; again, making sure it is tight and even.  Apply glue along the edge of the paper and finish the roll.  If you are using white glue you will need to use some tape to hold it closed while the glue dries.  Get the tape even and flat and do not over do it, as the tape will be staying on the rocket.  Set tube with engine aside to dry, or cool as the case may be.
 Step two: Take one of the squares and cut it into 4 right triangles.  This is fairly easy and accuracy is not as important as you might think.  Once the tube with the engine is dry, glue the triangles to the base of the tube, being sure not to allow them to go off the paper.  We want these fins a little above the engine.  With a hot glue gun, this is easy, apply the glue to the edge of the triangle, align on the tube, press against the tube and hold for a minute to allow it to cool.  Then repeat the process, trying to get them evenly spaced and straight along the tube.  With white glue, this will be a slow process.
 Step three: Using a cup or glass, draw a circle in the center of the other square of cardboard.  Draw a radial line from the center of the circle to the edge of the circle.  Now, cut out the circle and cut along the radial line to the center of the square.  You can now fold the circle into a cone that will fit over the top of the tube.  You do not want much overlap on the rocket.  The lip will interfere with the launch rod, so wrap the cone tightly to make it only slightly larger than the tube.  A hot glue gun is a real handy gadget here.  Glue the cone and then glue the nose cone to the rocket. 
 Step four: Cut a one to two inch piece of the plastic straw.  Glue it slightly above the fins, but evenly between one pair, vertically along the tube.

 Now you have a rocket.  You can turn three of these out in about an hour (provided you used the hot glue gun) without straining and all you probably spent was the cost of the rocket engine.  Most of us have the rest of the stuff around the house.  After you build and fly one or two of them, you can help the kids build them.
 
 You may have noticed that I did not include a parachute…  These do not fall very fast, so injury is very unlikely.  They are not reusable as the engine is glued in place.  They are very cheap and biodegradable.  Why hassle with a parachute?  That is for the advanced class.
 
 With an A3 engine, this rocket ought to go between 50 and a hundred and fifty feet in the air, depending on weight and wind speed and the aerodynamics. 
 

The Hubble telescope has spied a giant celestial "eye," known as planetary nebula NGC 6751. The Hubble Heritage Project is releasing this picture to commemorate the Hubble telescope's tenth anniversary. Glowing in the constellation Aquila, the nebula is a cloud of gas ejected several thousand years ago from the hot star visible in its center. Planetary nebulae have nothing to do with planets. They are shells of gas thrown off by Sun-like stars nearing the ends of their lives. The star's loss of its outer, gaseous layers exposes the hot stellar core, whose strong ultraviolet radiation then causes the ejected gas to fluoresce as the planetary nebula. 

Credit: NASA, The Hubble Heritage