Introduction: Supersonic Rocket - Mach My Day!
Want to break the sound barrier, but don't have a $100 million airplane to play with?
The Air Force didn't want you, or you don't want the Air Force?
Noooo Problem! You, too, can play Chuck Yeager on a much lower budget, even if you don't get to fly in the flying machine! This Instructable will detail the modification of a rocket kit to withstand the high stress of supersonic flight, how to log the flight so you know if your plan worked, and how to get your rocket back so you can fly it again. (If you think the rocket in the photos looks a bit beat up, that's because it's a veteran of several successful flights, and still airworthy even if the paint is scratched!)
Warning and Disclaimer:
This is a high-power rocket and not a project for rank amateurs. You need some sport rocketry experience under your belt before attempting something like this. Get involved with a rocketry club. You cannot legally buy the large rocket motors used in this project unless you are an adult and certified to fly high-power rockets. Join the National Association of Rocketry (NAR). They have all the information you need, and they will insure you against liability for your rocket launches as long as you follow the safety rules! Flying rockets is extremely safe if you understand what you're dealing with (Highly flammable materials, not explosives), and pay attention.
If your idea of fun with rockets is to put baggies full of gasoline in them, do not read any further; I refuse to be responsible for your idiocy.
Whew! Now that we've got the legalmumble out of the way, let's punch a hole in the sky!
As I was browsing an online hobby shop one day, I came across a rocket kit called the Nuke Pro Max. The price was only around 70 dollars. It didn't look like much at first, but then I looked at the flight predictions... Holy S***!! 830 miles per hour! Over 7,000 feet altitude!!! (on a J motor.)
That's Freakin'SUPERSONIC!Surely you don't mean to tell me I can build a Super-Sonic Real Flying Machine for under a hundred bucks?? And it's less than four feet tall? Where's my credit card??
Yes, you can (And Don't call me Shirley!), although by the time you're ready to fly, it might be more like five hundred bucks. Still, if you want to be a Rocket Scientist, here's your chance.
Step 1: The Road to Mach One
This is Real Rocket Science.
Supersonic flight puts many stresses on an airframe. The shock-wave coming off the nose can cause the airframe to crumple. The fins can succumb to flutter (Just what it sounds like; An uncontrolled flexing that, at best, will cause drag, and at worst, will tear the fins right off!). The drag goes way up as the speed approaches Mach one, further increasing stress on the vehicle and requiring even more thrust to overcome.
After buying the kit, I did a great deal of research on supersonic aerodynamics. I also researched on-board avionics (A recording altimeter, plus the capacity for firing parachute deployment charges) and tracking devices.
The stubby triangular fins of the Nuke Pro Max are the perfect shape for this sort of thing: Low drag and less susceptible to flutter than swept fins. The kit also comes with a payload bay that can be easily converted to an avionics compartment.
Just as the rocket scientists at NASA use computers to design and predict the flights of their rockets, you too can use software to design and simulate your rockets. The software I use is Rocksim, from Apogee Rockets. It's a little pricey, but considering the cost of one flight on a J motor (Over $50), it can be well worth it. It allows stability calculations, speed and altitude estimates with various motors, optimum ejection delay computation, plus parts lists, templates, and much more. There is a 30-day free trial version available. There's also a good free alternative, OpenRocket, which is not as capable, but may meet your needs. It works fine for simple designs such as this.
Light and Strong and Strong and Light
The rocket needs to meet five objectives for this project to be successful:
- Obviously, it needs to be strong enough to survive a supersonic flight.
- Not so obviously, it needs to be light enough to go that fast.
- It must be as aerodynamically "slick" as possible (low drag).
- Must have onboard instrumentation to record altitude and speed so I know if I've succeeded.
- And some kind of tracking transmitter is advisable, because a 4 foot rocket is really hard to see when it's more than a mile high, and I do want to find my rocket again.
It may seem counter-intuitive at first, but (up to a point) the lighter the rocket is, the faster it goes, and the heavier it is, the higher it goes, all else being equal. The reason for this is that weight, drag and total thrust are the main things that limit top speed, but inertia (or lack thereof), and coefficient of drag limit altitude. I determined, using Rocksim, that I needed to keep the empty weight down to 32 ounces in order to get at least 800 mph. The kit weighs in at 19.7 ounces, so I had about 12 ounces to work with. The avionics bay, tracking unit, fiberglass, epoxy, and everything else could not add more than that if I was to be successful.
In dry air at 68 °F, the speed of sound is 768 mph, but that figure goes up with increasing temperature, and I fly in Arizona. In the Summer. At 90 degrees, the speed is 783 mph, so it pays to fly in Winter. ("Speed of sound at sea level" is a common misconception; the speed is actually only dependent on temperature and humidity.)
The "Nuke Pro Max modified" file attached to this step can be opened with OpenRocket and used as a guide for planning both the construction and flight simulations.
Step 2: The Right Stuff
There's an old joke among kit builders (of all sorts) that you might spend $10 on the kit and $100 making it look like the picture on the box. There is truth to that, although in this case the extra money is about performance, not looks. Here's the list of major components. These will be discussed in more detail below.
- Nuke Pro Max kit: $69.25
- Entacore Altimeter with dual-deploy capability: $115
- 38mm Cesaroni 5-grain motor casing: $53.46
- Cesaroni J285 motor: $56.67
- Aero Pack motor retainer: $26.75
- Radio beacon: $85
- GPS GSM Tracker: About $25 on eBay.
- An extra parachute for use as the main. I made my own to be lighter weight than the kit part.
Most of this was purchased at Apogee Rockets, a fantastic company to do business with!
I'll save you the math. This adds up to $431.13, not counting finishing supplies, shipping, HazMat fees (required when shipping large motors), and miscellaneous hardware.
The kit: You get all the basic components in the kit: Body, fins, motor mount, parachute, and nose cone. You don't get any electronics, motor hardware, or motor retainer. This is a simple rocket to build; anyone that's built a few smaller rockets will have an easy time.
Altimeter: The altimeter I used is designed for rocketry and not only records altitude and speed (to download to a computer later), but is capable of firing two (dual deploy) parachute ejection charges. Why two? When your rocket goes way up, you want a small parachute (drogue) to eject at apogee so it's not a ballistic missile anymore, and a larger chute at a few hundred feet altitude for a soft landing. The faster descent rate of the drogue keeps the rocket from drifting nearly as far away, making recovery easier. If you don't need any deployment control, there are cheaper altimeters available, such as the Altimeter Two.
Motor Casing: Most high-power rocket motors are known as "reloadable" motors. This means you buy a metal casing one time and load it with a propellant package for each flight. The casing needs to be the proper size for the propellant you want to use.
J285 Motor: This is the propellant for the flight. The letter in the motor designation indicates the approximate total power (impulse) of the motor. Each letter is roughly twice the impulse of the letter below it, thus this motor has about 64 times the impulse of an Estes "D" motor (83 lbs. peak thrust). This is serious power, and needs to be taken seriously!
Motor Retainer: The motor must be prevented from parting company with the rocket, because of the expense of losing the casing. More importantly, the motor often provides the parachute ejection charge, and if you've got no chute, you just destroyed your rocket. This is a threaded positive retainer, and well worth the money.
Radio Beacon: This is optional, and sometimes rocket clubs have such equipment available for loan. Basically a miniature transmitter that can be tracked with a portable scanner and directional antenna. This particular transmitter requires an Amateur Radio license, which is also well worth the trouble.
GSM GPS Tracker: This is another (inexpensive) option for tracking that doesn't require a license. About half the size of a deck of cards and weighing around 2 ounces, this is a GPS married to a text-only cell phone. You'll need an AT&T or T-Mobile SIM card with an active number for this trick. Once the device has a GPS lock, you call it's phone number from another cell phone and it responds with a text message giving it's coordinates and speed. Very cool!
Whether you use either or both tracking options depends entirely on how confident you are of locating your rocket once it's down, which in turn depends greatly on your flying field, skill, and weather conditions. I chose to include both, and as you'll see later, I'm glad I did!
Step 3: Enough Theory, Let's Build!
Except for the modifications I detail here, the rocket is built according to the kit instructions. 30-minute epoxy is used throughout as the adhesive for joining parts, because it's stronger than 5-minute epoxy, and I want the extra working time anyway. I'm going to begin at the nose and work my way back.
Radio energy can play all kinds of tricks on other electronics, causing them to do weird things, or completely cease to function. For this reason, the nose cone interior is a very useful place for the radio transmitter. That gets it as far away from the altimeter (which is in the mid-body), as reasonably possible.
Since the nose cone is hollow plastic, it's fairly easy to cut a hatch in the shoulder (The part that slides into the body tube) for a tracking payload. Lay out a square or rectangular area on the shoulder, and outline it with tape. Using a new X-acto knife blade and a strong stroke, cut a beveled incision. If you bevel your cut toward the inside of your square hatch, the cut out lid will be bigger than the hole, and won't fall into the nose cone. Don't make the hatch any bigger than about 1/3 the total circumference; you need the nose cone to keep it's strength. You can use a piece of tape as a hinge and hold the hatch closed with another piece of tape once you've installed the payload. A few pieces of soft foam padding prevent the payload from shifting.
This is also where I started to think about the recovery system. The various parts are held together with Kevlar rope so the rocket comes down all together. Why Kevlar? It's heat resistant and will not melt if it gets flamed by the black-powder ejection charge.
I attached a 10 foot length of 1500 lb. Kevlar to the eyelet in the nose cone for the upper parachute in my dual-deploy setup. This is called a shock cord. It's long because the ejection of the recovery system is violent, and you need some length to absorb the shock of that event. The recovery system should be able to withstand at least 50 Gs, meaning in this case you should be able to put a 100 pound load on it without anything breaking. I tied the shock cord to a tree and put my full weight on it, and nothing failed.
The nose cone is prevented from separating in flight by a pair of removable plastic rivets, because this design separates mid-body, at the avionics bay.
Sorry I don't have any "In progress" photos... I was too busy building!
Step 4: Fiberglass-Worth the Weight?
The Nuke Pro Max kit has a very sturdy paper tube and plywood fins. It might have been fine as-is for supersonic flight, but I wanted to be sure, so I beefed it up with fiberglass.
This was my first fiberglass project, so I did some reading up on the subject.
Some basic fiberglassing information can be found here.
The key is to make sure there is just enough epoxy to completely wet the fabric, because epoxy is heavy, and more doesn't add any strength. Draw a line straight down the body tube to use as a guide when starting to lay on the cloth. Cut one layer of cloth to go all the way around the tube with a small overlap. I brushed the epoxy on, then used an old gift card as a squeegee. 1/2 fluid ounce of epoxy goes a lot further than you'd think! I used less than 3 ounces on the whole thing. Once the cloth is saturated, squeegee off the excess, watching for bubbles, wrinkles, and dry spots. Just keep working your way around with a slightly stiff paintbrush, squeegee, and sometimes gloved hands until it's as smooth as you can get it. You can also try smoothing a layer of plastic wrap onto the epoxy while it sets to cut down on sanding. I tried this, but wasn't happy with the result.
I did not use the West System epoxy most folks recommend because I didn't need much. Instead I used "Finish-Cure," available at most RC hobby shops, otherwise known as finishing resin. It has about a 20 minute working time, which is enough if you mix up small batches of 1/2 ounce at a time.
Before any major assembly, I covered the front and rear body tubes with 2 layers of .5 oz. (the lightest you can get, it looks like a wedding veil) fiberglass and the epoxy resin (which doesn't smell nearly as bad as polyester resin, so you can use it indoors if you don't mind the mess). This added about 1.7 ounces. Since I didn't want to make this my life's work, I threw together a very simple "rotisserie" from some scrap 2 X 4 and PVC pipe, allowing me to rotate the tube as I laid on the glass. Two Saran Wrapped couplers inserted halfway into the ends of the body tubes kept the resin out and let me remove them easily.
The lower body tube is pre-slotted for fin attachment, and I had to keep those slots open. A good way to do this is lay up the glass, wait an hour or two until it has set but not completely hardened, then trim out the slots with a sharp hobby knife. The overlap on the ends can be trimmed the same way and finished up with sandpaper.
We'll also fiberglass the fins later.
Step 5: Motor Mount and Fins
Even though light weight was a near obsession in this build, (my digital scale became my constant companion!) I replaced the kit 10 inch motor mount tube with a new one 14 inches long (the length of my proposed motor), and added a third centering ring (.4 oz.), since I was going to be hitting it with more than 25 Gs at launch ( rocket weighs 3.3 lbs loaded, engine thrust is 83 lbs!). A ten foot length of 1500 lb. Kevlar rope was epoxied to the motor mount tube and through the forward centering ring. I used just enough epoxy to produce good fillets on each ring. Again, I used 30 minute epoxy, both for strength and working time. This allowed me to epoxy each of the 2 top centering rings individually as I slid the motor mount into place. The bottom centering ring was installed later.
Note: If you're planning a tailcone, make sure you have enough motor mount tube protruding from the body to accommodate the tailcone. This is a deviation from the kit instructions. Test fitting is a must!
Here's where fussy construction practices really pay off; precision is essential here. I sanded the fin edges to as accurate a 15 degree knife-edge bevel as I could manage to reduce drag, before installing them. Many supersonic rocket designs use a sharp edge on both leading and trailing edges, rather than the traditional rounded airfoil shape. The air piles up and compresses on rounded shapes (nosecones and fin leading edges) and it takes energy to compress air, which creates drag. I also visited http://www.payloadbay.com/page-Tools.html and made a fin positioning jig from corrugated cardboard to ensure the fins were at exactly 90 degrees to the fuselage. Any variation from symmetry will probably cause the rocket to spin, which creates drag.
After filleting (reinforcing the fin/body joint) with epoxy putty, I covered the fins tip-to-tip (from the tip of one fin, across the body, to the tip of the adjacent fin) with 3 oz. Fiberglass (.5 oz added). I filled the spaces between the fin tabs inside the body tube with 2 part expanding foam (weight: negligible) to add some extra rigidity. I installed the bottom centering ring once the foam had set.
Step 6: Tailcone and Motor Retainer
Simulations said I could get a little more speed with a tailcone, because the blunt rear end of something moving through the air creates lots of drag. I made one from paper covered with fiberglass, using Payloadbay's transition template (.25 oz.). This was done by printing out 2 tailcone templates on card stock, gluing them into shape, then slipping them one inside the other and saturating with low-viscosity epoxy, (the same stuff I used for the fiberglass). After the epoxy set, two pieces of lightweight fiberglass were cut to the same template and laid onto the cone, one layer at a time. The tailcone was slipped over a Saran-Wrapped tube and centering ring so it would be perfectly round when it set. This gave me a very light, very strong part that fit perfectly after trimming and sanding.
I also installed an Aeropac motor retainer (.8 oz.), reasoning it was worth the weight for foolproof motor retention that would work with the tailcone. The part with the male threads epoxies onto the end of the motor mount tube. The retaining ring simply screws on after the motor is installed.
Step 7: Avionics Compartment
Here's where things get really interesting!
The Nuke Pro Max was designed as a payload carrier, with the payload bay being in the upper part and about half the total length. I re-purposed the mid-body coupler from the kit as an avionics bay, converting the upper fuselage into a secondary parachute compartment. Commercial avionics bays of this size weigh about 8 ounces. I needed mine to weigh 3 ounces, so I challenged some assumptions: Does it really need 1/4" plywood bulkheads? Do we really need 2 or more lengths of #10 all-thread? What about all those super-strong space age materials...?
A traditional avionics bay needs to absorb all the tension and punishment of the shock cord during ejection (50+ Gs!). That means thick bulkheads, big screw eyes, and heavy duty all-thread. But what if the bay didn't need to stand up to all that shock cord tension? The shock cord is already strong enough to absorb the tension... Aha! If we run the shock cord through the bay, then the bay just needs to be strong enough to hold itself together.
The answer was to run a short piece of heavy Kevlar rope with looped ends all the way through the bay, slightly off-center. The upper and lower shock cords were connected to the center rope with aluminum quick links (weight saved over steel: .25 oz.) One piece of 6-32 all-thread, through the center, with wing nuts on the ends, holds the bay together. The end caps were made of 1/8 inch plywood cut to the outside diameter of the coupler, and laminated with rings cut to the inside diameter. The Kevlar was sleeved where it went through the bay with heat-shrink tubing, because Kevlar, while very strong, has little abrasion resistance, the holes it goes through need to be snug to seal against ejection gases, and the bulkheads need to slide on the Kevlar in order to open the bay. A couple of knots in the Kevlar just inside the bulkheads, to prevent it from sliding out of place, completes the bay.
An alternative to the Kevlar approach is to replace the Kevlar rope with 10-24 all-thread, coupling nuts, and 10-24 screw eyes. This makes opening the bay a bit more convenient but adds about 3/4 ounce of weight. I changed to this approach after the supersonic flight because the Kevlar is more difficult to work with.
In constructing the interior, I started by mounting the altimeter on a piece of plywood known as the "sled." The aluminum tubing on the back is for the 6-32 all-thread that holds the bay together. I made the sled long enough to accommodate a 9 volt battery as the power source. The battery must be very firmly attached so it does not shift during boost. Remember, everything here is going to weigh 25 times more than normal for a couple of seconds!
The altimeter has terminal blocks on each end for power and to control the ejection charges. I extended the ejection charge wiring to terminals on the end caps of the bay. I installed the ejection charge canisters on the end caps with copious quantities of epoxy. The canisters, in case they look familiar, are made from .38 caliber cartridge cases, which are just the right size to hold a half-gram of black powder. It is very important to wire this correctly. There are two sets of terminals on the altimeter; One for apogee (drogue) deployment, and the other for main parachute deployment. Don't mix them up. On my rocket, I put the drogue in the lower body, because I'm using the ejection charge in the motor as a backup to the altimeter. That way, if my altimeter fails, I still at least get a drogue out. This can be done other ways as you gain experience, but backups are always a good idea.
I made a couple of washers with two holes to reinforce the end caps where the Kevlar and all-thread comes through, and coated the end caps with epoxy to cut down on damage from ejection charges.
The switch is made from a 1/8" headphone jack, available at Radio Shack. This is of the "closed circuit" variety. This means it has a set of contacts that are normally closed, but open when something is plugged into it. These are very common in portable radios and such, where the jack cuts off the speaker when headphones are plugged in. In this case, the switch is attached to the sled and only requires a 1/8" hole in the bay for a pin to be inserted. I made a pin out of 1/8" brass rod and attached a "Remove Before Flight" flag to it. Plugging the pin in turns off the power.
The short, 1" piece of body tube (the red part) is glued to the midpoint of the coupler that forms the body of the avionics bay. There are two holes in this: A small (1/16") hole that lets outside air in so the barometric altimeter can function properly, and a larger (1/8") hole that will line up with the headphone jack on the sled so a pin can be inserted from the outside. The upper and lower caps are labeled, and there is a "this end up" arrow on the bay so I won't accidentally install it in the rocket backwards.
Before I flew the rocket, I wrote my name and phone number on the bay so someone finding the rocket could return it to me.
Step 8: Finishing
I completed construction with a pair of streamlined rail guides instead of the 1/4" launch lug in the kit, rounding them off and polishing the burrs they had from the factory. I'm not sure if this reduced drag or not, but I've seen launch lugs torn off by rod whip and that would definitely slow the rocket down. This is another good reason to find a rocket club. They often have heavy-duty launch equipment you can use.
I'm doing the finishing prior to final assembly because it's easier to paint parts individually, especially when several colors are involved.
An aerodynamic finish also helps with speed, so I put considerable effort into making the paint as smooth as possible. The fiberglass needed a lot of smoothing, so after the rough sanding, (don't do this in the house, and a dust mask is advisable!) which included reshaping the fin bevels, I applied several coats of Kilz spray primer (available at WalMart) , which goes on quite thick and can be either dry or wet sanded. The last primer coat was wet-sanded with 400 grit paper, and the finish coat was worth the effort. The final product weighs 32 ounces (including the parachutes), exactly my target weight.
Just because it's aerodynamic doesn't mean it can't look cool, too! I painted the forward section orange, then painted on some red without masking so the colors would blend together. Then I purchased some flame masking from an RC hobby shop, and masked the flame-shaped areas that I wanted. A coat of black finished this part.
I painted the aft part white with a couple of black "roll stripes," and the nose and fins are fluorescent orange for high visibility.
Side Note: Many folks have found it difficult to get a finish to stick to the (Polyethylene?) nose cones that LOC Precision (This kit's manufacturer) uses. Here's one way: sand the entire cone thoroughly with 150 sandpaper, using a power (orbital) sander if possible. This is the key step. Sand off all the mold marks at this point. Use a heavy coat of "plastic primer" (Krylon and RustOleum both make this), and wet sand with 320 till most of the primer is sanded off. Fill any holes at this point. Prime again with the plastic primer as necessary, sanding between coats. Wet sand the final coat of primer with 400 grit. Now the finish coat will actually stick!
Step 9: Parachutes and Final Assembly
The only problem with this kit designer is they over-engineer things to the point of being bulletproof. The kit parachute is over-built, so I substituted my own, made from lightweight nylon. The drogue is 16' and the main chute is 24", which is slightly small for a rocket of this weight, but it is a very strong rocket, so it should land okay.
That ten feet of Kevlar rope coming from the nose cone, through the upper body tube, is attached to the top end of the avionics bay with a speed link. I tied a loop in the rope about 8 inches away from the bay, and attached the main chute there. I also attached a Kevlar "Chute Shield," a flameproof cloth to protect the chute from the ejection charge.
The Kevlar shock cord coming from the lower body is attached to the bottom end of the avionics bay. The drogue chute and it's chute shield are attached the same as for the main. Now the entire rocket is one unit, and will come down together.
Step 10: Shakedown Cruises
Plan your flight, fly your plan
That first picture is a simulation from OpenRocket, not a picture of a real launch. The other shows my rocket on the pad.
Now it's time for the shakedown flights, starting with F motors and working up. (That's the great thing about this rocket - You can fly it on small motors that don't require certification, and it will grow with you!)
Preflight Checklist, starting at the nose:
- Turn on and install Radio beacon in nose cone. Verify You can hear radio signal on scanner.
- Attach GPS tracking unit to shock cord just below nose cone. Verify GPS function. Stuff a piece of foam rubber into the top of the body tube to pad the GPS.
- Slide GPS into top of body, install nose cone and secure with plastic rivets.
- Inspect entire recovery system for damage.
- Check or install battery in avionics bay. Close up avionics bay.
- Check all avionics bay hardware for tightness, including speed links.
- Pack main parachute, wrap in chute shield "burrito fashion," insert excess shock cord and chute in forward body.
- Attach an igniter to terminals on forward avionics bay bulkhead. Place tip of igniter in bottom of ejection charge canister and tape leads down to bulkhead.
- Measure 1/2 gram of black powder into canister. Tamp in a small piece of crumpled paper and secure with plenty of masking tape.
- Insert forward end of avionics bay into forward body.
- Repeat steps 7-10 with drogue parachute and aft bulkhead.
- Pull pin from altimeter long enough to test (Read owner's manual, and keep away from face!), re-insert pin.
- Assemble motor according to reload instructions, insert into motor mount, and secure.
- Place rocket on pad, insert and hook up igniter, pull pin on altimeter and verify altimeter function one more time.
- Move to minimum safe distance, and launch when ready.
Do you feel like a rocket scientist yet? Well, do ya, punk??
The rocket flew flawlessly; the only surprise was the vehicle was going a lot higher than predicted. I worked the problem backwards and determined the drag coefficient to be .47, way lower than the .75 that the software assumed. I patted myself on the back: That meant I'd done a very good job on the construction and finish. An H motor took it to 3500 feet, and with an I motor, it went to 5600 feet! Wow!
Time for the main event!
Step 11: Punch a Hole in the Sky!
Wait a minute - There's a snag. To fly high-power rockets, you need a waiver from the FAA. The clubs usually handle that sort of thing. Problem is, my local club's waiver tops out at 6500 feet, and it's going to go much higher than that on a J motor! (That sound you just heard was my plan coming to a screeching halt.) Well, here is a club that has an 8500 foot waiver, but it's 150 miles away! But I want that sound barrier Bad, so I'm going!
Most clubs only launch once a month, so I plotted and planned. Come launch day, the wind was picking up, and I hemmed, hawed, and finally decided the wind wasn't that bad and went. When I arrived, the ground wind was over 12 mph, and I started to worry. Yes, but I do have two, count 'em, two tracking devices, so how hard could it be?? I don't want to have to make this trip again!
Rocket on pad. Radio signal strong. Check.
3, 2, 1, Launch. GONE!
That sucker took off so fast it'd make your head spin. As soon as the 2.2 seconds of motor burn were over, I lost sight of it in the clouds. I started counting seconds. It should hit apogee at about 18 seconds, and I was still getting a signal, so it hadn't blown up (yet). I kept counting seconds and listening to the beeps from the transmitter. After about a minute, I knew there was a parachute out because otherwise it would have been a crater by now. After about 4 or 5 minutes, the signal stopped, indicating it was down (Radio signals don't travel nearly as far on the ground as when the transmitter is in the air). The amount of time in the air meant it had a good chute. Meanwhile I kept querying the GPS for a position report.
The last report I received from the GPS said it was 1.8 miles away, and moving 16 miles per hour. Uh-oh. That means it was still in the air when it sent the last report. Must've landed with the antenna facing down, and now it can't get a fix. Sigh. Nothing to do now but pick up my antenna and go fetch it. I took a bearing on the last known position and started walking. And walking. Did I mention this was the Arizona desert? In June? Did I also mention that I remembered to take everything with me, except a canteen? Don't bother me, I'm too busy imagining myself looking like all those cow skulls I keep walking past. And walking!
Finally! After following the bearing past the last position, over two miles out, I picked up a faint beep. Yesss! Come to Mama! The radio signal has a range of about 1000 feet on the ground (I'd tested that beforehand), so I followed it right to the rocket, which was sitting there completely undamaged, with both parachutes out, waiting for me. I am so glad I used both trackers!
Now, I just had to walk the 2.3 miles back... Without water... In the summer. Don't bother me, I'm too busy dying of thirst...
I lived. Fortunately, I had water back at the launch site (I'm not a complete dummy). My friends there signed me off for Level Two high-power certification, but I had to get back to my computer before I could find out if I really had "gone mach."
The Final Score:
- 8178 feet altitude
- Mach 1.07 (801 mph!)
- A nice (?) 4.6 mile hike (both ways)
- The satisfaction of having built a "Great Rocket" by Homer Hickam's definition: One that does exactly what you engineered it to do!
The last picture is a graph of the supersonic flight taken from the on-board altimeter.
Before this flight, I had named this rocket the Belchfire 3000. It has earned it's new name, Mach My Day!
Now go out there and be inspired! First person to go mach with a rocket of their own construction wins a one year pro membership. Must supply tracking data as proof!