HellFire, sponsored by the Utah Rocket Club (UROC) takes place this year August 3,4,5,6. Though HellFire is technically an amateur launch, we’re talking serious rocketry here. Participants from around the country launch rockets ranging from foot-tall wonders to towering monsters that weigh in at over one hundred pounds, feature high-tech electronics, use a propellant similar to that used on the space shuttle, and lift off with 750 pounds of pure thrust.
Now in its 22nd year, HellFire continues to grow. Many people attend not to launch, but simply for the thrill of watching. Between launches, visitors enjoy examining rockets and components close-up and speaking with the experts who build and launch them.
Spectator Admission to HellFire is free and the public is welcome. HellFire will be held on the Bonneville Salt Flats near Wendover, Utah. Take Exit 4 on Interstate 80 and follow easy-to-spot signs. The event takes place 9 a.m. to 5 p.m. Thursday, August 3 through Sunday, August 6.
Discounted registration for flyers is available for UROC members.
Many more details to come over the next weeks.
Tips for visitors:
UROC's planned NAR Sport Launch scheduled to take place on March 21st appears to be a go! UROC President Ken Park recieved notification from the BLM SLC Field office that the launch site has been cleaned up and our documentation is in place. Additionally, the FAA waiver is in place and will be activated if the launch commences. The weather appears to be cooperating for this launch and we will continue to update the UROC.org website with any further news or announcements regarding the launch.
It's time to get out there and fly!
UROC president Ken Park recieved a phone call today from the BLM agent responsible for taking care of the recent toxic waste spill at our Frank Hunt Field launch site.
The agent reported that the clean up is already in progress and they fully expect the launch site to be available for our February 21st Research Launch! This is much faster than any of us expected. Of course things change so please watch this site for further details and updates about the upcoming launch.
UROC would like to thank the BLM Salt Lake Field office for responding to this issue as quickly and professionally as they have. We really appreciate their support and assistance!
With this new, the new 2015 flying schedule will be posted to the website shortly. Stay tuned!
First, please read the fine print... There are many different solutions to the rocket design challenge. Rules of Thumb simply provide a solid starting point that many have found useful in the past, and that will, in many cases, provide a suitable solution for your design problem today. Rules of Thumb are guidelines. They're not laws. They are nominal solutions that usually, in many cases, most of the time, get the designer in the right ballpark. Once a rocket designer's judgement has been formed by lots of experience, some Rules of Thumb can be stretched, bent, stood on their head, or ignored completely.
Using Rules of Thumb certainly does not take the place of stability tests, or attention to safety. Proof of stability and a constant focus on safety are the most fundamental and unchangeable Rules of Thumb I know. If you know Rules of Thumb that are not mentioned here, e-mail them to Tom Savoie and they could appear in a future update with your name as the contributor. Comments are always welcome.
Motor Mount Size
Build your rocket for the largest motor you might want to fly in it. You can always adapt down, you can never adapt never up.
Whatever your choice, use a primer, finish and clear coats that are compatible. Many times this means sticking to the same brands-e.g., Krylon primer, Krylon finish coat, and Krylon clear coat.
Diameter And Length Of The Rocket
The ratio of rocket length to diameter, sometimes referred to the aspect ratio, should be from 10 - 20:1. For example, a six inch diameter rocket would mean a length of 60 -120 inches.
Reinforcing the Airframe
The larger the rocket, the more important reinforcement becomes. Two layers of a lighter fiberglass fabric work better than a single heavy layer. Two layers of 4oz fiberglass works well for 3-4 inch rockets, 2-3 layers of 6oz for 5-7.5 inch rockets. A final wrap of 2 oz glass provides a good sanding veil. Glass a rocket measuring 2.56" or greater that will reach equal or greater than 0.85 Mach.
A fin that is 2 diameters of the airframe in root length and span and a chord length of about 1 diameter will be effective.
Fin Shape or Planform
The shape you see more than any other is called the clipped delta, and is known for its effectiveness. The clipped delta resembles a parallelogram, with the fin swept somewhat to the rear. The root and chord lines are near parallel, and the leading and trailing edges are near parallel. There are many, many shapes that will get the job done. Some look cooler to me than others. One of the most efficient fin designs looks like a simple rectangle attached to the tube.
Shaping the Fin
The leading edge of the fin should be rounded, the trailing edge shaped like a V. The chord edge should remain square.
Number of Fins
Three fins will almost always do the job. Four fins work too, but only marginally better as far as improving CP. Some have said that four fins reduce wind-induced spin.
Black Powder Ejection
Use enough BP to yield a 15 psi pressure within the airframe. See article on Ejection Charges for a detailed discussion.
Sizing The Parachute
You want your rocket to descend at about 15 feet per second under nominal conditions. Slow it up over playa and concrete. Use 3.5 square feet of chute per pound of recovered rocket weight. Determine chute size by doubling the square root of the weight of the rocket. For example, a 16 pound rocket would use a 2X4=8' chute. A 49 # rocket would use a 2X7=14' chute.
Streamers should be 10 times as long as they are wide.
Drogue recovery descent should be about 50 ft/sec.
A full-hemispherical canopy has very little performance gain over the more efficient and less bulky quarter-spherical--the top-half of a full-hemispherical chute.
Recovery Harness Strength
Tensile rating for recovery materials should be at least 50 times the static weight of the rocket.
Sizing Tubular Nylon
9/16" serves well in rockets up to 15 pounds. Go with 3/4 up to 30 pounds. 1" up to 50 pounds.
Length of model rocket shock cord
Make shock cords for model rockets a minimum of 2 to 3 times the overall length of the rocket. Middle or high power rockets should use tubular nylon at least 5 times the rocket length.
Use enough wadding to fill 2 x the diameter of your BT. Any more is probably overkill. Any less may allow hot particles through to hit your chute. Do not pack it tight.
Knots, Loops and Sharp Bends in Shock Cord or Bridle
Knots, sharp bends, including sewn loops, in the tubular nylon or flat webbing will weaken its load capacity by 50%.
How Tight is Tight?
Many people use masking tape to finesse the fit between an airframe and a coupler that must separate at deployment. A common question is: how tight do I want it to be? Use enough masking tape so that you can pick the rocket by the nose cone without the rocket coming apart. If you vigorously shake the rocket up and down, and don't see any movement off the coupler, you've probably got too much tape on, Jack.
Use 25% less Black Powder if your deployment system is piston driven.
Running a damp cloth through your airframe after flying will clean out powder residue and keep your piston moving freely.
Use shear pins on any rocket where you need a little extra piece of mind to know everything will stay in place until the proper time. Use 1/16" styrene rod or #2 nylon screws on almost any high performance rocket. For example two styrene shear pins each on a 2.6" phenolic airframe, 4 nylon screws on a 6" bird. See the article on Shear Pins in the CONSTRUCTION area for more detail.
Shortening Delay Elements
Note: Adjusting the delay as described below is considered a modification to the motor and is therefore against the rules in a TRA/NAR sanctioned launch. Delay grain burns at the rate of 1/32" per second. Shorten delay time by drilling a 1/16" bit to drill a hole into the ejection charge end of the delay. Drill to a depth of 1/32" for every second you want to shorten the delay. A piece of tape wrapped around the drill bit at the proper depth will help ensure an accurate depth. Don't drill more than 25% into the length of the delay.
Margin of Stability
The CG should be forward of the Center of Pressure by 1-2 calibers. A caliber is simply the diameter of the bird. One caliber of stability is also known as a margin of stability. In other words, in a four inch rocket, the CG must be ahead (closer to the nosecone) of the CP by 4 - 8 inches. More than .5 but less than 1 margin of stability (less than one caliber) and a rocket is "marginally stable'. More than two calibers of stability is known as "over stable". An over stable rocket will tend to dramatically turn into the wind. A marginally-powered, over stable rocket can end up almost horizontal.
Adjusting the Center of Gravity
To move the CG forward, add weight to the nose, lengthen the rocket, or lessen the weight in the aft end of the rocket. To move the CG aft, (for example, if your rocket is overstable), do the reverse.
Adjusting the Center of Pressure
To move the CP aft (more stable), increase the size of the fins. To move the CP forward, decrease fin size.
How Long is Too Long
A rocket must maintain its rigidity in flight. Any tendency to bend will be magnified in flight resulting in a kinked tube and likely a failed flight. If you hold a rocket horizontal by its tail section and notice any curvature in the rocket, your bird probably isn't stiff enough. Sorry, rocketeers, Viagra will not cure this problem.
Sizing the Motor
In selecting a motor to power your rocket, you need to have at least a 5:1 thrust to weight ratio. See a detailed discussion of this guideline Motor Selection in the PROPULSION area.
Launch Rod Diameter
Determine by motor size:
A,B,C - 1/8"
D,E - 3/16"
F,G,H and a body tube less than 2.6" - 1/4"
F,G,H,I w/ 2.6" to 4.0" body - 7/16"
I,J - 1/2"
Over J and body tube over should use rail buttons
Minimum Speed for Stable Flight
44 fps (30mph) is generally accepted as a minimum safe speed for stable flight. Faster speeds are necessary to achieve stability in windy conditions.
Mounting launch lug(s)/button/s
When mounting a single lug, cover the center of gravity with the lug. Always mount at least two rail buttons. When mounting two lugs or buttons, mount the lower piece at the rear of the airframe. The second should be on or just behind the center of gravity.
Submitted by Tom Savoie
Originally printed in Extreme Rocketry Magazine
Rocketry is one of those things you do in life that has no in-between. You have either a complete success, or an unmitigated disaster. Every flight, including failures, is a new andunforgettable learning experience. While some of the disasters can be attributed to bad or defective equipment or materials, a lot of failures can be attributed to incorrect preparation.
You certainly feel bad when you forget wadding in your Big Bertha, but it pales in comparison to forgetting something when flying your Big Kahuna. And the more we pay attention to the successes and failures of others and ourselves, the more we learn and the better our chances are for successful flights in the future.
Flights with a regular model rocket are basic. Wadding-parachute-motor-igniter-plug and you're off to get a launch pad. Mid- and high-power rockets are more complex, so more things can go wrong. The lack of proper preparation reminds me of one flight I saw. The rocket represented a considerable investment of time, effort and money for this person. The lift-off, boost and coast were perfect, and separation charge fired at apogee. However, during separation, everybody saw the one little "oops" this rocketeer forgot: to fasten the shock cord to both sections of the rocket. The upper part of the rocket came in under parachute, but the booster came in ballistic. Ouch.
Trying to document all of the possible ways to go wrong would fill a James Michner novel. Here is a small list of failures what I have either witnessed or been guilty of myself: All it takes is something like a forgotten O-ring in the motor and you get a CATO. Or there's not fastening the shock cord correctly and you get more pieces coming down than went up. Forgetting to arm the recovery electronics gets you a ballistic rather than parachute recovery. Using the wrong size launch rod will send your rocket off in unwanted directions, if it cleared the rod at all. Forgetting wadding turns your parachute into either a melted wad or the equivalent of a screen door, both bad for future flights. Not verifying your CG on assembly can turn your vertical flight into a horizontal one. That's not a good way to get the crowd to do the Wave.
Since we are all rocket scientists, I decided to take a "page" from the professional rocket scientists and write check-off lists, or "procedures" as they call them, for rocket preparation and launch evolutions. Even in the middle of the Apollo 13 disaster, everybody had a procedure for everything. If there wasn't one, you wrote it to make sure everybody was clear on what they needed to have and what they were supposed to do. This made sure everybody was "on the same page."
Procedures are essential to a person like me. I would forget my head, as the saying goes, if it wasn't permanently attached. I run down a procedure to make sure I don't forget something every time I leave the house. If I didn't, I would leave at least one essential thing behind, every time. I started using procedures years ago when I was SCUBA diving. It is embarrassing to get to the dive site and discover you forgot your weight belt, regulator or fins (or all of them) as I did on several occasions.
The source of my organization comes from my Palm Pilot. Not only do I use it to help keep me organized, I can also recover flight data from my onboard computer into it while on the flight line as well. I mention Palm specifically because there is a shareware program called HandyShopper that I use for these lists. I use the Aisle #'s as step #'s so that I can easily adjust the order of things in a procedure if I have to. In practice, after completing a step, I merely check it off, just like if I had just grabbed the bread or eggs. If you don't have a handheld computer, clipboards and paper served the professionals for years.
The best way to develop your own procedures is to sit in a quiet area and go through everything in your mind, start to finish. After you have imagined them, write them down and go through the list again. Then go and perform the procedure, adding notes and adding/changing steps as you go. As with all endeavors in our lives, your mileage may vary. The standard that you should aim for is that anybody can understand and complete your procedures. Imagine yourself in a full body cast with your jaw wired shut. A fellow rocketeer of approximate experience should be able to get you to the range, prep and fly your rocket without any "input" from you.
The first list is the material preparation procedure. You make sure your rockets are ready, double check you have everything, test electronics, dip a few igniters, whatever you need to do to make yourself ready. This will prevent the proverbial running around like a headless chicken the morning of the launch, which cuts into flying time. Doing this over an evening or two during the week gets you 90% ready. All you have to do the night before is quickly check everything before packing it into the car to make sure no one has "borrowed" something. I verify my range box, motor box, etc. are properly stocked by writing in the bottom or on the cover of every compartment what is supposed to be there, so anything missing jumps out you.
Next you can concentrate on the family. Lay out clothes for everybody, make sure your club ID's, cash for range fees and so on are on hand (preferably packed in your range box).
The next procedure is car-packing. The order that I use to pack the vehicle is the opposite of what I will need on the range. Things that have to come out first (tables, chairs, etc.) go in last. If you pack everything but food and drink the night before, you can do it calmly and you have the time and leisure to double-check and properly secure the items. You also make sure the vehicle is up to the job. Check the fluids, tires, gas and so on. If your alarm doesn't go off and you wake up late on launch day, you can jump into your clothes, dash out to the car and drive off, with the worst consequences being you have forgotten food, drinks and family members.
Once you are on the range and set up, you can relax a bit and take a break. Fly some model rockets, catch up with club members, volunteer as RSO/LCO for a shift, whatever. Your prior planning has given you this break.
Once you are ready to launch a big rocket, pull out its' pre-flight procedure. You will probably need an individual procedure for each of your HPR rockets. This procedure should take your rocket from cold (unprepared) to warm (ready for RSO and the launch pad). The number of individual steps is not important. Clarity of the steps is important. Thirty-seven steps to load and secure the motor into the rocket might be a bit of overkill, but you don't want to have just "stick it in and tape it down" either. Make sure your flight card is filled out, electronics are installed and ready, your CP/CG ratio is good and everything is connected and ready to go.
Now comes the final countdown. Get your rocket approved by the RSO, draw a pad from the LCO, and head out with the rocket and your final preparation procedure. Verify the launch pad can handle your rocket, put the rocket on the pad, insert the igniter, arm the electronics, take the rocket from warm to hot (ready) and head back to the range head to ready your cameras.
If you have invested the time in developing your procedures, you have eliminated 98% of human error on your part. You have done everything you could to ensure a safe flight that ends in a recovered rocket.
The investment of time you spend at home developing these procedures will save countless hours and rockets on the range. As the military puts it, "The more you sweat in peacetime, the less you will bleed in wartime."
Safe and successful flying!
Remember, the things you need FIRST go in LAST.
Throughout the year, the Utah Rocket Club welcomes Educational, scouting, Civil Air Patrol, 4H and other youth groups to attend our launches. Utah Rocket Club members are also available for presentations to schools, scout troops, and other educational and youth groups.
If you are interested in having a presentation or a launch for your organization, please contact one of the club officers.
UROC does not charge for youth or educational groups to participate in our launches. However, because of the heavy demand throughout the year, we ask that you contact us as far in advance as possible. If your group would like to attend one of our launches please contact us at least 4 weeks prior to the date of the launch.
Because of the nature of some of the launch events we hold throughout the year, NOT ALL LAUNCHES ARE OPEN TO YOUTH OR OTHER GROUPS. If you show up without checking first and the launch is not one open to public you will not be allowed to fly.
We also expect that there is an appropriate number of senior group members to assist in making sure that the kids are safe and under control at all times.
All flyers should be on their best behavior during a launch event. Building and launching rockets is fun but safety is paramount. If a group is too unruly or creating an environment that is unsafe for themselves or others they will be asked to leave. Group leaders and participants should read and understand the NAR safety rules before the day of the event. For Boy Scout groups we suggest that you get a current copy of the Space Exploration merit badge book available in local stores and online.
Participants may bring other model rockets for the launch if there is sufficient time, and the rocket passes safety review. Weather permitting, we will setup and run a model rocket range running under the NAR safety rules. If the weather does not permit launching UROC will schedule an alternate weekend for the event.
The Bonneville Salt Flats are used with the permission of the US. Bureau of Land Management (BLM). We have a waiver in place at the HellFire Launch from the Federal Aviation Administration (FAA) that allows our members to fly high-powered rockets to altitudes as high as 25,000ft. HellFire is insured by the National Association of Rocketry and/or the Tripoli Rocketry Association.
Whatever you've heard about the Bonneville Salt Flats, it is probably true. The vastness will humble you. The Bonneville Salt Flats are one of the most unique natural features in the United States, the flats stretch over 30,000 acres at an altitude of approximately 4320 feet above sea level. Bonneville's heat will cook you alive (hence the name HellFire). We've all experienced bright sunlight, but at Bonneville its intensity is reinforced by being prismatically reflected off the ocean of salt that surrounds you.
You're going to need to block the sun from your face and arms. Bring some good lip balm and sun block, and use them both throughout the day. Protect your eyes and head. It's easy to spot the people who are there for the first time - they' re the ones without sunglasses and hats. If they've been on the salt flats for more than two days, avoid standing downwind from them, since the wind often blows chunks of crispy, toasted skin off their faces and lips, which eventually settles into a fine crust on the flats.
One of the great things about holding a launch on the Bonneville Salt Flats is the launch site’s proximity to the town of Wendover (about 15 minutes away from the launch site!) The town is perched on the border of Utah and Nevada. Because of this, it has become an oasis for Utahns wanting to experience some “night-life”.
The Nevada side of Wendover is teeming with casino/resort complexes that include all of the amenities such as pools, spas, exercise equipment, great food and the ever important air-conditioning. It’s a real bonus being able to come in from the heat after a good day of flying. Hotel and accommodation information is available through the Wendover Tourism and Convention Bureau, 1-775-664-3138 or Toll Free 1-866-299-2489.
If you intend to set up a 'semi-permanent' spectator area, you must secure a tarp as a floor covering on the salt. Don’t forget your camera and bring lots of film, because you will want to remember everything you see. Binoculars are also a great idea since the rockets can be as far as a 1/4 mile away as they lift off.
Please pick up ALL of your trash and take it with you everyday. There will not be dumpsters provided. HellFire is a "Pack it in, Pack it out event."
Enter your address in the "From Address" box below for turn by turn instructions for your trip to the Bonneville Salt Flats
Help Protect the Flats
Managed by the BLM as an Area of Critical Environmental Concern and Special Recreation Management Area, the Bonneville Salt Flats are a 30,000 acre expanse of hard, white salt crust on the western edge of the Great Salt Lake basin in Utah. "Bonneville" is also on the National Register of Historic Landmarks because of its contribution to land speed racing. The salt flats are about 12 miles long and 5 miles wide with total area coverage of just over 46 square miles. Near the center of the salt, the crust is almost 5 feet thick in places, with the depth tapering off to less than 1 inch as you get to the edges. Total salt crust volume has been estimated at 147 million tons or 99 million cubic yards of salt! The Bonneville Salt Flats are comprised of approximately 90% common table salt.
To aid in the management of the public lands, we ask that you follow proper land use etiquette such as Tread Lightly! and Leave No Trace. A few examples of these principles are the proper disposal of human waste, packing out litter, and ensuring any livestock feed used or transported across public lands is certified weed-free.
Stay on Existing Roads or Trails Stay on existing roads or areas designated for vehicles. Despite the appearance of a hard surface, much of the area is a thin salt crust over soft mud. It easily breaks under the weight of a vehicle.
Stay off the Wet Salt - Stay off the salt surface when it is covered by water. When wet, the salt surface is soft and easily damaged by vehicles. Furthermore, the salt water is highly corrosive and can short-out the electrical system in your vehicle.
Remember it is a Desert!- Be prepared for desert conditions. Temperatures can exceed 100 degrees in the summer and drop well below 0 in the winter. There are no facilities or services on the salt flats. Temporary facilities are available during racing events and HellFire.
No Camping on the Flats - Overnight stays are prohibited on the salt flats. Camping is encouraged on surrounding public lands. Private campgrounds and hookups are available in nearby Wendover City ten miles west of the Bonneville Salt Flats. Other accommodations and services are also available in Wendover.
Call 1-800-426-6862 for more information about the Bonneville Salt Flats
Links to further information about the Salt Flats
KUTV - Salt Lake City Channel 2 News Report on Bonneville - Chris Miller | June 1, 2016
Racers plan to look to Congress for action on Bonneville Salt Flats in Utah - Ogden Standard Examiner | May 27, 2016
Bonneville Racers Accuse BLM of Dragging its Feet - Hemmings Daily | May 24, 2016
Bonneville Salt Flats Vandalism - Fox 13 Salt Lake | May 23, 2016
Position Paper presented at Historic Bonneville Summit in Salt Lake City - Save the Salt & Utah Alliance | May 17, 2016
Department of Interior Bonneville Salt Flats Fairy Tale - Update | May 9, 2016
"The Rape of Bonneville" by David Tremayne - Grand Prix Magazine | Apr. 17, 2016
KUER Public Radio "Salt Report" - KUER 90.1 NPR Utah | Mar. 19, 2016
Bonneville Salt Flats Restoration Approved by Utah Legislature - TheShopMag.com | Mar. 4, 2016
Ab Jenkins Family Appeals to BLM - Grandchildren Offer 80 year Perspective | Mar.2, 2016
Utah lawmakers urge BLM: Restore Bonneville Salt Flats, ASAP - By Phillip Thomas | Hot Rod | Feb. 25, 2016
Utah lawmakers urge BLM to restore Bonneville Salt Flats for high-speed racing - By Emma Penrod | The Salt Lake Tribune | Feb. 19, 2016
Utah Legislature Supports Land Speed Racers (.pdf) - Save the Salt Press Release | Feb. 19, 2016
2015/2016 Salt Laydown Report - By The Utah Alliance | Sept. 9, 2015
Utah officials join racers' push to protect salt flats - By Michelle L. Price | The Associated Press | Dec. 1, 2015
Wendover mayor wary as politicians join campaign for Utah's iconic Bonneville Salt Flats - By Emma Penrod | The Salt Lake Tribune | Nov. 30, 2015
Unified effort underway to fix Bonneville Salt Flats - By Chris Bruce | auto blog | Nov. 28, 2015
A new day may be dawning for the Bonneville Salt Flats - By Daniel Beaudry | Hemmings Daily | November 23, 2015
Save the Salt Foundation Offers Plan for Imperiled Bonneville Salt Flats - By Save the Salt | November 5, 2015
Land-speed racers show off cars, talk about plight of Utah's salt flats - By Rick Egan | The Salt Lake Tribune | Sept. 9, 2015
The Race to Save the Bonneville Salt Flats from a Slushy Demise - By Kat Long | Scientific America | Aug. 27, 2015
The Bonneville Salt Flats are disappearing, as are the races staged on them - By Scott Sandsberry | Yakama Herald | Aug. 25, 2015
Bonneville Speed Week cancellation spurs proposals for salt flats replenishmen - By Daniel Strohl | Hemmings Daily | Aug. 20, 2015
The Shrinking Salt Flats - By Matt Canham | Radio West | Aug. 6, 2015
“Speed Week” at Bonneville Salt Flats Cancelled Due to Deteriorating Conditions, Lack of Salt - By Save the Salt | July 20, 2015
Utah’s famous Bonneville Salt Flats are disappearing - By Emma Penrod | The Salt Lake Tribune | July 12, 2015
Trib Talk: Bonneville Salt Flats minus salt? - By Jennifer Napier-Pearce | The Salt Lake Tribune | July 13, 2015
Portion of Bonneville Salt Flats Resurfaced: Dry Salt Laydown Program May Be Key to Restoring Land Speed Racing Venue - By Save the Salt | June 24, 2014