News Archive
Toffee-fuelled rocket flies
Warlock takes to the sky fuelled by toffee -
yes, just the same stuff kids eat!
UH achieved its first flight of a toffee-fuelled hybrid rocket on Sunday 7th March 2010, at the first EARS launch event of the season, near Cambridge. The motor was a Pentamax hybrid, normally rated at 1500NS (K class), fitted with a modified injector designed by a UH student. The fuel grain was made up from toffee cooked up on a stove at home, lit by a piece of AP composite propellant. Recovery was by parachute, deployed at apogee using an RDAS altimeter.
The altitude reached on the flight was 1740 feet.
UH Rockets does Bang!
The engineering team prepare
the parachute on the rail trolley.
The spectacular finale of BBC1's new science series, Bang Goes the Theory, was broadcast on Monday 5th October, featuring a couple of hybrid rocket motors fuelled by toffee. Ray was approached to provide technical consultancy, working with Ben Jarvis, who has a lot of experience doing rockets and similar special effects for TV. Ray advised on the safety aspects of preparing and operating hybrid rockets, and also with the sizing of the injectors and nozzle. The presenter, Jem Stansfield, and two of the engineering team visited the University in July, and several test firings were carried out. One of these is featured on the Bang website (www.bbc.co.uk/bang). An amazing amount of smoke came from the first attempt, which was fuelled by wax, completely overwhelming the ventilation system of the rocket motor test cell, and setting off the fire alarms. It was generally agreed that wax probably wasn't the best choice to move forward with. Several more firings highlighted a weakness with the first design of nozzle. The toffee fuel burned so hot that it melted through the steel of the nozzle in just a second or two.
When the team came back a couple of weeks later they had a thicker nozzle, and this produced the best firing ever in the test cell - around 23 seconds long. This was possible because the nitrous oxide was supplied from a cylinder, so could be switched on and off as needed. Ray just left the motor firing until the nozzle eventually burned through.
On filming day near Aylesbury, there was the usual kicking around for hours as everything was set up. The early part of the day was spent filming the preparation, and Jem's explanation of how hybrid motors work. Part of this used our benchtop hybrid, using oxygen down a transparent fuel grain, and this can be seen on the show. Ray is out of shot cutting the oxygen while Jem explains how hybrids can be shut off, unlike solid motors. When the bike was being prepared, Ray and Ben discussed the best way to light the motor reliably. The bike would be moving, so a cable system was out - everything had to be on the bike itself, operated by Jem. A piece of composite (AP) propellant was epoxied into the forward end of the motor. Ignition was by an electrical igniter - a Davey match - and this was boosted by a piece of PIC to make sure the heat stayed around long enough to get the AP burning. This worked amazingly well, and there was enough heat left in the motor after the first 2- or 3-second burn for Jem to give it another burst. When he stopped, Jem desperately wanted to have another go, as he'd now got the measure of it, but there wasn't time. It turned out that it was just as well, as Chris Hill found that the toffee fuel was almost completely gone after the first firing.
The rocket trolley disappears in a cloud of leaves
and smoke as it powers towards the scene
of the crash.
Setting up the big trolley was a long job, and there were a few modifications advised by Ray and Ben on the day, as they hadn't seen the setup before. In particular, they were concerned that the parachute would break free, and might de-rail the trolley. Given the thrust-to-weight ratio, this might have resulted in an unintended first flight. The motor was again run from a cylinder of nitrous oxide with two valves - one to fire the motor and one to shut it off. This motor, of upwards of 1/4 tonne of thrust, was lit using oxygen from a cylinder next to the track, and an electrical igniter that was designed to flare to ensure it lit easily. In many ways this was going to be easier to light, as oxygen is very effective for lighting hybrids. The oxygen and igniter were controlled by Ray with his home-built launch controller, which has been extensively field-tested and has 100 metres of cable to ensure a safe distance.
By the time it was all set up, cameras positioned, camera positions and safety sorted out, the nitrous oxide filled and installed and all the back story filmed, it was well into evening. Then followed an interminable wait until a scheduled train came through - the crew could not afford to block the main line with an errant rocket trolley. When the train finally went out of sight, it was time to go for it. Ray switched on the oxygen and fired the igniter, then after a short count to give the oxygen time to get everything hot, Jem hit the button. The firing was amazing, and the trolley leapt down the track in a shower of leaves. Strange, but no-one had noticed the leaves when they walked the track. The chain that was intended to slow the trolley down was dragged for about a metre before the huge hook was just bent out of the way, and the parachute tore free. Ben, operating the kill switch, cut the thrust just before impact but the inertia re-opened the valve and the motor relit on impact. We must have guessed the nitrous oxide content pretty weel, because it only burned for another second or so. Well, they wanted a crash...
After the run, the trolley was bent in the middle by about 30 degrees, and cameras had been thrown everywhere. The footage is incredible, though, with no camera tricks required.
Here's the article on testing the hybrids, from the Bang website. There is another article from the Bang site, as well as this one, on our TV page.
1204 mph!
At Benington Lordship near Stevenage on Wednesday 18th March 2009, our team of engineering Masters students carried out two successful firings of their rocket sled. The first, a low-speed run of about 150m/s (around 300mph), was to simulate the effect of a bird strike on an aluminium composite panel. The panel was made up of a sandwich of aluminium alloy skins with alloy honeycomb between, an arrangement often used in aircraft. The impact energy was similar to the enrgy involved in a typical bird strike. The impact severely damaged the panel, almost breaking through completely. The second, and most spectacular, firing was the high-speed run, aiming at 1000mph over a distance of 87 metres. The final speed, as derived from a high-speed camera running at 600 frames per second, was a staggering 1204mph, and the shock wave ('sonic boom') could clearly be heard. We are grateful to the Lordship Estate who hosted us, and also to Paul Carter of Congreve Rockets for donating the motor cases for the impact runs.
5th December 2008: Rocket sled
A team of engineering Masters students are designing and building a rocket sled, planned to reach Mach 1 (760mph) in a distance of 60 metres! This requires an acceleration of around 100g. The sled will be used to research the behaviour of materials at very high strain rates during impacts. The first stage of the project has now been completed - a sub-scale sled, powered by a cluster of seven small motors, which reached over 140mph in only 6 metres and 1/6th of a second. The photo shows the sled about one metre down the track - most of the sparks seen are from the 'Quickmatch' used to make sure all seven motors ignited simultaneously. With most of the thrust from these motors delivered in the first 0.15 seconds, there wasn't much point in igniting a motor late. The sled, weighing about 80 grammmes before launch, impacted on a large piece of honeycomb material at the end of the track, to absorb the energy and stop it breaking free. Two runs were carried out, and both were successful, although the timing gates didn't work. We will confirm the final speed once the video has been analysed.
18 Dec: we've now done a third run, and the timing system worked fine. We also had a high-speed camera running at 300 frames per second. The speed was measured at 62m/s or 142mph, covering the 6-metre track in about 1/6 second. There's a video taken from the high-speed camera, slowed down to 1/10th actual speed, on Facebook.
16th June 2008: Scrapheap Challenge
In the summer of 2007 Ray assisted Paul Lavin of Deepsky Rocket Shop on an episode of Scrapheap Challenge for series 10. The sequence involved Rob Llewellyn 'riding' in a rocket-powered railway car, although a tailor's dummy was substituted for the final shots. Filmed at the Scrapheap Challenge film set, on an MOD site near Basingstoke, the sequence took several hours to shoot. Safety was a key issue with such a large motor - a Cesaroni Pro75 M - and we could only do one take. Eventually, the whole thing came together and a spectacular firing was the result. The photos in the slide sequence were all taken by Ray.
3 March 2008: UH-Built Hybrid Motor First Flight
A hybrid motor built by a final-year project student made a successful flight at Benington on 2nd March. Using the fuel grain and nozzle from a RATT Works I-80 motor, Mike designed and built an entire motor himself, and it's much shorter than a conventional one. Mike Reynolds' rocket, a LOC Caliber ISP, defeated difficult wind conditions to make a perfect flight to an estimated 2000 feet.
Traditionally, one of the problems with converting an existing rocket to fly on hybrid motors is the length of the motor - a RATT Works I-80, for instance, is around 30 inches or 760mm long - and rockets not designed with long motor sections with hybrid motors in mind are often just too short to accept the motor. The configuration of Mike's hybrid, built into a Dr Rocket 54mm solid-motor case, makes it much more convenient to convert a rocket for a hybrid motor. Mike's motor is designed to offer the same perfromance as the RATT, but in a case only 250mm long. It achieves this by increasing the diameter to 54mm - the I-80 is only 29mm diameter. The increased diameter is exploited by wrapping the nitrous oxide tank around the combustion chamber rather than placing it in line. This requires a complete re-design of the motor internals.
Because we are in the process of rebuilding our test facilities, it was not possible to fire the motor on the ground, so Mike decided to go the whole hog and fly it. The motor behaved perfectly, igniting normally and lifting the rocket smoothly into the sky. Burn time was exactly as predicted - a little under 5 seconds - and the recovery system deployed at apogee giving a safe landing. Not only was this the first flight of this experimental motor, it was Mike's first ever hybrid flight.
9 Feb 2008: Demo hybrid
See the details of our new see-through demo hybrid motor.
9 Feb 2008: Great news about AP motors
After several years of effort by people from UKRA, the Health and Safety Executive have introduced an exemption to the explosives legislation, to allow rocketeers to buy and keep some composite (AP) motors without needing an explsoives certificate. This applies to motors containing not more than 1kg of propellant, and allows storage of up to 5kg. This means that rocketeers can now take their Level 1 and Level 2 certifications without the time-consuming process of obtaining an explosives certificate. Great news, and full credit to those who have worked so hard to achieve this. The UK now enjoys the most rocketeer-friendly legislation around. For moe information, check the details on the UKRA website.
9 Feb 2008: Virgin Galactic to fly in July 2008?
Virgin Galactic, who plan to take tourists into space using a hybrid rocket motor, have announced they plan to make their first test flight of SpaceShipTwo in July 2008, and hope to begin full commercial operation in early 2009. If you have a hundred thousand pounds or so to spare, there's stil time to buy a ticket, but the waiting list is growing... website
6 August 2007: Scouts take rocketry world record
Around 40,000 scouts from all over the world attended the World Scout Jamboree at Hylands Park, near Chelmsford, Essex for the World Scout Jamboree, in this centenary year of the Scout movement. Over 1000 scouts each built a model rocket during the week, and many of them flew. On Monday 6th August, at around 5.30pm, a simultaneous launch of over 1000 rockets took place, setting a new World record. The official count was 1032 rockets.
Guinness World Records require the attempt to be witnessed and ratified by someone with expertise in the area and of professional standing, and Ray Wilkinson was asked by the organisers to do this.
The record attempt was sponsored by modelrockets.co.uk and Ripmax, and the record, subject to acceptance by GWR, is held by 'Scouts of the World', beating the previous record of 965, set by Scouts in the USA.
1 June 2007: Rocket-powered rail car for Scrapheap Challenge
Ray worked with Paul Lavin of Deepsky Rocket Shop on a film set recently, with a rocket-powered vehicle for a gag involving railway locomotives with unusual power sources. It was filmed at a military base near Basingstoke, where all of the Scrapheap Challenge episodes are filmed. The vehicle we worked on used a Cesaroni Pro75 M1400 motor producing an average of 1400N of thrust for about 4.5 seconds. The vehicle was predicted to reach almost 60mph, although it wasn't measured. Unfortunately we can't show any pictures ahead of the programme going to air, but there will be plenty to see once it goes out.
15 May 2007: Rockets on the NHS
Ray worked on behalf of Deepsky Rocket Shop on a film set recently, flying some rockets for a new advertisement as part of the NHS's anti-smoking campaign. The ad involves taping packets of cigarettes to a rocket and launching it. With the expert help of Gaby Lavin, eight flights were made, using rockets built by Paul Lavin from Deepsky, on Pro38 smoky G motors. The 40-second advert is due to air in June, in advance of the change of the law on smoking in public places. It was filmed at a private airstrip near Stevenage.
Update 5th June - the advertisement is now showing on various Sky channels, and can be downloaded from http://www.gosmokefree.co.uk/onlinematerials/campaigns.
3 April 2007: Pentamax flown
The Pentamax hybrid was flown at EARS in its J configuration on Sunday April 1. In the first-ever flight of a Pentamax motor in the UK, in our extended Warlock, the motor ignited quickly and heaved the rocket into the skies of Cambridgeshire. For full details, see the launch report.