Peroxide biprop ignition

Some methods I've seen mentioned for peroxide biprop ignition a

Decompose the peroxide with catalyst pack.
Pyrotechnic igniter in the chamber.
Dissolve catalyst in fuel.
Hypergolic starting slug in fuel feed line.

How about mixing some liquid catalyst into the peroxide feed for a few
seconds until there is stable self-sustaining combustion in the
chamber? Liquid catalysts for monoprops have been abandoned in favor
of catalyst packs for good reasons but they seem to have some
desirable properties for biprop ignition:

Usable with high concentration peroxide.
Can be used with strongly stabilized peroxide.
No hazardous materials.
Restartable and reusable.

The catalyst is mixed into the peroxide just before injection into the
chamber. This cannot be done safely with a fuel but catalytic
decomposition is slow enought to give some time for mixing. The
injector is optimized for operation with uncatalysed peroxide. It may
not perform optimally with the mixed-phase decomposing peroxide; it
just needs to be good enough for the ignition phase. The injector and
mixing chamber are flushed of any residues by ample amounts of
peroxide (except on some emergency shutdowns) so the catalyst should
not contaminate the upstream oxidizer lines .

Oren

In article ,
Oren Tirosh wrote:
How about mixing some liquid catalyst into the peroxide feed for a few
seconds until there is stable self-sustaining combustion in the
chamber?

This is a minor variant of the "hypergolic starting slug" approach.

No hazardous materials.

Depends on what catalyst you're using. Even permanganates are not exactly
mother's milk, and things like TEA are definitely hazardous.

Restartable and reusable.

Subject to the need for yet another fluid system, with the added
complexity that entails.

The catalyst is mixed into the peroxide just before injection into the
chamber. This cannot be done safely with a fuel but catalytic
decomposition is slow enought to give some time for mixing.

I have real doubts about that part of the idea. Catalystic decomposition
will not be slow with high-concentration peroxide and an effective liquid
catalyst mixed well together. Mixing *in* the chamber sounds both better
and safer.
--
MOST launched 30 June; first light, 29 July; 5arcsec | Henry Spencer
pointing, 10 Sept; first science, early Oct; all well. |

Henry Spencer wrote:


Restartable and reusable.

Subject to the need for yet another fluid system, with the added
complexity that entails.

The catalyst is mixed into the peroxide just before injection into the
chamber. This cannot be done safely with a fuel but catalytic
decomposition is slow enought to give some time for mixing.

I have real doubts about that part of the idea. Catalystic decomposition
will not be slow with high-concentration peroxide and an effective liquid
catalyst mixed well together. Mixing *in* the chamber sounds both better
and safer.

Once the rocket is firing, is it possible to use non catalysed HTP?

In article ,
Julian Bordas wrote:
I have real doubts about that part of the idea. Catalystic decomposition
will not be slow with high-concentration peroxide and an effective liquid
catalyst mixed well together. Mixing *in* the chamber sounds both better
and safer.

Once the rocket is firing, is it possible to use non catalysed HTP?

Yes, definitely. As with any propellant combination, once it's lit it
will generally stay lit, modulo combustion-stability issues. People have
built rocket engines using peroxide as oxidizer with no catalyst at all,
just a conventional ignition system.
--
MOST launched 30 June; first light, 29 July; 5arcsec | Henry Spencer
pointing, 10 Sept; first science, early Oct; all well. |

Henry Spencer wrote:
In article ,
Julian Bordas wrote:

I have real doubts about that part of the idea. Catalystic decomposition
will not be slow with high-concentration peroxide and an effective liquid
catalyst mixed well together. Mixing *in* the chamber sounds both better
and safer.

Once the rocket is firing, is it possible to use non catalysed HTP?


Yes, definitely. As with any propellant combination, once it's lit it
will generally stay lit, modulo combustion-stability issues. People have
built rocket engines using peroxide as oxidizer with no catalyst at all,
just a conventional ignition system.

Thanks Henry. I'm one step closer :-)

Julian

Henry Spencer wrote:
In article ,
Julian Bordas wrote:

I have real doubts about that part of the idea. Catalystic decomposition
will not be slow with high-concentration peroxide and an effective liquid
catalyst mixed well together. Mixing *in* the chamber sounds both better
and safer.

Once the rocket is firing, is it possible to use non catalysed HTP?


Yes, definitely. As with any propellant combination, once it's lit it
will generally stay lit, modulo combustion-stability issues. People have
built rocket engines using peroxide as oxidizer with no catalyst at all,
just a conventional ignition system.

Thanks Henry. I'm one step closer :-)

Julian

In article ,
Julian Bordas wrote:
I have real doubts about that part of the idea. Catalystic decomposition
will not be slow with high-concentration peroxide and an effective liquid
catalyst mixed well together. Mixing *in* the chamber sounds both better
and safer.

Once the rocket is firing, is it possible to use non catalysed HTP?

Yes, definitely. As with any propellant combination, once it's lit it
will generally stay lit, modulo combustion-stability issues. People have
built rocket engines using peroxide as oxidizer with no catalyst at all,
just a conventional ignition system.
--
MOST launched 30 June; first light, 29 July; 5arcsec | Henry Spencer
pointing, 10 Sept; first science, early Oct; all well. |

Catalystic decomposition
will not be slow with high-concentration peroxide and an effective liquid
catalyst mixed well together.
I've only heard of solid catalyst beds. What's a [non-exotic] liquid catalyst
for HTP, [High Test Peroxide over 85% pure]?
^
//^\\
~~~ near space elevator ~~~~
~~~members.aol.com/beanstalkr/~~~

Catalystic decomposition
will not be slow with high-concentration peroxide and an effective liquid
catalyst mixed well together.
I've only heard of solid catalyst beds. What's a [non-exotic] liquid catalyst
for HTP, [High Test Peroxide over 85% pure]?
^
//^\\
~~~ near space elevator ~~~~
~~~members.aol.com/beanstalkr/~~~

Henry Spencer wrote:


Restartable and reusable.

Subject to the need for yet another fluid system, with the added
complexity that entails.

The catalyst is mixed into the peroxide just before injection into the
chamber. This cannot be done safely with a fuel but catalytic
decomposition is slow enought to give some time for mixing.

I have real doubts about that part of the idea. Catalystic decomposition
will not be slow with high-concentration peroxide and an effective liquid
catalyst mixed well together. Mixing *in* the chamber sounds both better
and safer.

Once the rocket is firing, is it possible to use non catalysed HTP?