Controlled explosion


Controlled explosion

It takes more than just a match to detonate a space rocket.

Apparently the name is self-evident, at least according to Olav Grasvik, aerospace project manager with Kongsberg, when we ask him about the product with the strange name, Optopyro.

“All you have to do is break it down,” he continues. “Pyro is a prefix for objects which are explosive. Opto is the abbreviation for optic and tells us we are dealing with light. Put them together and you have Optopyro, a system whereby an explosion is triggered by a powerful pulse of light.”

“So this is a new development on the oldfashioned burning fuse which triggers the detonator which in turn sets off the dynamite?”

“I suppose, but for those of us working with product development for aerospace, the old pyro systems are not of interest. We are working on a project which will allow us to launch a pyro product made up of fibre optics, electronics and mechanical parts.”

“So, with optopyro, denotation is provided by a different type of energy?”

“You could say that, yes. The light energy is absorbed by the explosive which has been fitted inside the detonator and is converted to heat. The increase in temperature triggers a process which sets off the detonator and, in turn, the explosive.”

“Can you explain the entire process for us?”

“If we start with the pulse of light, this is generated under controlled conditions by a laser. The laser pulse is transmitted via fibre cables to what we call an initiator, which is set off when the laser pulse hits it. This results in the detonation of the explosive in the pyro function.”

“It sounds pretty advanced. Why is this type of detonation necessary?”

“The huge rockets used to launch satellites into space, including the European Ariane rocket which I’m sure you’ve heard of, require a whole number of pyro systems. These rockets are currently fitted with an extremely complex pyro system which has electronic detonators and detonating fuses. As the rockets are so huge, and because several parts of the rocket have to separate at different points in time – until only the satellite has to be separated – the entire system is packed full of wiring and detonating fuses.”

“Because there are so many different parts to detonate?”

“That’s right.”

“But why do you want to replace the electrical system with optopyro?”

“Firstly, the system we use now is extremely complicated. But the most important reason is that it is expensive and we are not able to test parts of the system prior to launch. There’s no way of testing that detonation works because then the detonator has been used.”

“That would be like testing out a firework before New Year’s Eve – you might find that it works, but you won’t have it any more.”

“Exactly. With the current system, all we can do is hope that the fuses work properly. We also have to comply with extremely stringent safety regulations which require a lot of manpower. When fitting the current system into a space rocket prior to launch, the entire launch area has to be shut down and cordoned off, and we have to maintain radio silence because of the electronic detonator. This operation is very costly and is required prior to each launch. What’s more, the detonating fuses are encapsulated in lead. This requires a lot of lead and represents two definite drawbacks: It makes the rocket heavier and is an environmental toxin. The advantages with optopyro are that it does not require environmentally damaging substances and you can run tests to check that the pyro system, up to the initiator, is intact prior to launch. Being able to run these tests makes the pyro system so much more reliable. Another advantage is that the pyro system has been designed to allow for scaling and adaptation to different rockets and satellites.”

“Can you envisage any other areas of application for optopyro?”

“I can’t think of any other examples right now, but optopyro is an extremely reliable system and I’m sure it will be of interest for a whole range of applications. A lot of the developments within the global aerospace industry tend to appear as spin-off products on the civil market after a few years.”

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In an optopyro system, intense laser pulses distributed via optical fibres are used for initiation of pyrotechnic functions.

Kongsberg’s optopyro system comprises a laser firing unit, an optical safety barriere and an optical harness.

Pyrotechnics is used in a multitude of applications, both on launchers and satellites.

On Ariane 5 the pyro system is used for:

  • Main engine ignition
  • Booster engine ignition
  • Separation rockets ignition
  • DAAV/DAAR cutting
  • Valve opening
  • Payload separation
  • Launcher destruction 

Main advantages of the opto-pyro system:

  • No primary explosives in the pyro-system (significantly reducing the integration cost)
  •  Low total mass
  • Built-in system for test/verification (fully testable on ground)
  •  Immunity to EMI/ESD
  • Green pyro, i.e. contains no lead


Ove Ronny Haraldsen

Corporate Communication Manager

+47 99 15 59 20

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