Copenhagen Suborbitals - ready for launch

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Re: Copenhagen Suborbitals - ready for launch

Postby rocket_troy » Thu Sep 08, 2011 8:44 am

I believe from what I can gleen off their website the LOX is also self pressure feeding (Vapak style), which would limit tank pressure to below 200psi.


Jamie,
I don't keep a really close eye on their systems or activities, but I'm reasonably sure the HEAT 1X feed system was essentially a blowdown system with helium (upper 30% of oxidizer tank volume). However, for some reason they chose to intentionally cool the He with the aid of a cooling coil to -183deg C along with the LOX. I think this was to minimize the pressure drop as the tank emptied (ie more light weight pressurant within the system = less delta P with delta V) at least that's the theory. I vaguely recall their PC for a typical run started at ~12Bar and finished at ~6Bar - but don't take that as gospel.
I agree with your points about LOX with hybrids in general and have mentioned it to Peter Madsen directly. To their credit, they did, and are still, investigating other options. He's been pretty transparent with all their activities and philosophy and they're probably one of most objective and pragmatic groups out there.

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Re: Copenhagen Suborbitals - ready for launch

Postby spacelaunch » Thu Sep 08, 2011 8:58 am

I don't keep a really close eye on their systems or activities, but I'm reasonably sure the HEAT 1X feed system was essentially a blowdown system with helium (upper 30% of oxidizer tank volume)


Ahh that makes more sense then, I did write to them about pre-burning strategies some time ago. Never got a response though..

My thoughts where also that POGO may have been involved in the flight failure, the exhaust plume definitely seems to strobe quite heavily just prior to the vehicle pitching over. And the inside camera records the violent level of oscillations through the rocket body, which would have surely set up sloshing in the LOX tank.
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Re: Copenhagen Suborbitals - ready for launch

Postby rocket_troy » Thu Sep 08, 2011 9:36 am

My thoughts where also that POGO may have been involved in the flight failure, the exhaust plume definitely seems to strobe quite heavily just prior to the vehicle pitching over. And the inside camera records the violent level of oscillations through the rocket body, which would have surely set up sloshing in the LOX tank.


Those concerns were certainly relayed to them prior to the launch. I was skeptical as to how such oscillations could have such an impact on trajectory given what I've witnessed with experimental and HPR hybrids over the years, but my skepticism has waned a bit since then.

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Re: Copenhagen Suborbitals - ready for launch

Postby spacelaunch » Thu Sep 08, 2011 12:46 pm

rocket_troy wrote:
I was skeptical as to how such oscillations could have such an impact on trajectory given what I've witnessed with experimental and HPR hybrids over the years, but my scepticism has waned a bit since then.


Yes the matter moves from non-trival when many hundreds of liters LOX starts sloshing, and pockets a LOX vapour start forming in the feed lines & hammering.

I had a more detailed look over their site last night & watched the 18min speech the fella gave. I cant help but feel their key design rational are floored; for example the reasoning on the small diameter springs primarily from limiting themselves to a single cylindrical section, rolled from the largest alloy sheet they can source. Also that everything has to be shop weldable thus limiting them to metals, when many composites can be shop fabricated to a high standard these days. Also the same old concept that LOX is good because its cheap & available, without looking into the technical issues that complicate its successful operation. Or paying attention to the huge volume of historical failures at yeilding functional large propulsion systems based LOX by anyone other than multi-million dollar aero firms, is kinda silly in my books.

If I was going to take a crack at such a project I would be looking at storable propellant first off, most likely Peroxide. This would allow you to commercially source a very large & lightweight composite tank for low cost. As well as the use of COTS pluming and valve systems, so no more frozen ball valves. I wonder if these guys considered the difficulties of stopping ice build up while pumping LOX on an ocean based platform?. The Peroxide gives you excellent density, and pre-combustion with a cat pack; thus you avoid the combustion instability issues of LOX systems. Sure you have to clean everything and passivate metals, but you have to clean for LOX anyway and spills of either will kill you period. The arguments about the dangers of respective oxidisers become mute when you read the MSDS for any of them, as all can kill you in the quantities & application at hand.

I would then look at building a light weight external airframe skin (thin alloy sheet or composite) with an internal stringer structure (ie aircraft type structure), which could open your diameter up past 1.5m range. The vehicle would need active roll control and verticle stabilisation, but this could be achieved with a low grade vertical gyro & differential GPS.

A design with a central hybrid motor, surrounded by 4 vectoring mono-propellant chambers would give you viable steering.

Who wants make one ;-)
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Re: Copenhagen Suborbitals - ready for launch

Postby rocket_troy » Thu Sep 08, 2011 2:04 pm

Yeah, it’s an interesting argument re: LOX vs storable monopropellants for hybrids. I’ve long advocated that storable monopropellant oxidizers are ideally suited to hybrid propulsion and that hybrid propulsion is ideally suited to storable monopropellant oxidizers. However, saying that, LOX hybrids have been successfully demonstrated and LOX (as an oxidizer) does have some compelling advantages over storable monopropellant oxidizers. The trick is: what complexity and nuisance value is required in order to provide a reliable, stable and performing system. For example, if you can achieve such requirements with clever injection or non consumable systems, then there is an argument to allocate the extra development budget to the LOX based system if the flight rate is high enough.
Re: the frozen valve- to be fair, the cause was probably more bad luck than incompetence there. IIRC their original tank and localized plumbing of that was stolen from a yard some time last year. Attached was a proper cryo rated ball valve (IIRC) that was used for the primary feed valve. They rushed to replace the tank and attached plumbing with an off-the-shelf stainless ball valve that was a standard industrial grade. These valves are made of exactly the same materials as the proper cryo equivalents and are pretty similar in construction, however there are some key differences that need to be appreciated and one is particularly is hidden – the cryo valves must come with cavity free seating ie, there’s a PTFE seat on each side of the ball, but there’s a cavity in between these PTFE seats that is susceptible to hold a volume of fluid that can be transferred from the bore of the ball when the valve is closed. Cyro valves and some industrial types also have 2 PTFE seats, but these extend all the way around the entire ball to fill in any cavity thereby providing no space for fluid to slip into when the valve is closed. What really hit the guys at CS is they performed a hydrostatic test of the tank before the 1st attempted test flight (remember the previous tank was stolen) of the rocket thereby allowing for the likely possibility of the cavity filling up with water when the valve is cycled and once fluid gets into that cavity, you need to be very careful to remove it. Alas, the guys at CS didn’t appreciate this – and I can totally understand how and why – which lead to water freezing during the LOX filling process. Because this wasn’t considered, their valve heating device (the hairdryer) just didn’t have the battery power to totally overcome this unexpected situation.

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Re: Copenhagen Suborbitals - ready for launch

Postby spacelaunch » Thu Sep 08, 2011 6:00 pm

While on this topic I thought I would knock up a quick CAD on my concept for a pancake style hybrid pre-burner, which should address the LOX combustion issues in their hybrid..I offered to design one of these for them but they didn’t take me up on my offer.. The unit could be run either oxygen or fuel rich, either way it should be easy to generate a sufficiently hot gas stream to help vaporise the LOX. The hot combustion by-product & the LOX further mix by turbulence in the hot GOX manifold, and gain further heat input from the splash plate. The hot GOX rich mix then leaves the unit through the slotted annulus into the hybrid motor for combustion with the fuel grain.

I hereby offer this concept here open source ...


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Re: Copenhagen Suborbitals - ready for launch

Postby spacelaunch » Thu Sep 08, 2011 7:38 pm

rocket_troy wrote:Alas, the guys at CS didn’t appreciate this – and I can totally understand how and why – which lead to water freezing during the LOX filling process. Because this wasn’t considered, their valve heating device (the hairdryer) just didn’t have the battery power to totally overcome this unexpected situation.


Did they run any form of cascade purging with dry nitrogen prior to LOX loading?.
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Re: Copenhagen Suborbitals - ready for launch

Postby rocket_troy » Fri Sep 09, 2011 9:02 am

While on this topic I thought I would knock up a quick CAD on my concept for a pancake style hybrid pre-burner...[snip]


Conceptually, I like it! Thanks for sharing.

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Re: Copenhagen Suborbitals - ready for launch

Postby rocket_troy » Fri Sep 09, 2011 9:12 am

Did they run any form of cascade purging with dry nitrogen prior to LOX loading?

Don't know for sure. I know they ran some GOX through the system some days before the launch. I know they ran high pressure air, followed by hot (90degC) air through the system after hydro testing it, but I'm not sure about last minute nitrogen purges.
What I didn't mention is they actually (or apparently) anticipated the cavity issue with the valve because they dried the system with the valve 50% open to help vaporize any residual trapped water from the hydro test, but just didn't appreciate the quantity of water that was capable of being trapped in quite confined places.

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Re: Copenhagen Suborbitals - ready for launch

Postby OverTheTop » Tue Jul 31, 2012 7:48 am

AIAA Daily Launch 30JUL2012
Copenhagen Suborbitals Launches Homemade Rocket.
Space (7/28, Malik) reported the amateur team of Copenhagen Suborbitals "launched a homemade rocket Friday (July 27) on a trial flight to test vital technologies for a private manned spacecraft." An unmanned SMARAGD-1 rocket launched form the Baltic Sea in a test which "marked the first mission for the non-profit Copenhagen Suborbitals since a 2011 test flight of its HEAT-1X rocket and a space capsule prototype. The group is now developing a small, one-person space capsule (called Tycho Deep Space) that resembles a miniature Apollo spacecraft." Despite the success, the organizers wrote a test of their launch escape system has been delayed after a pressure test failed.

http://www.space.com/16800-copenhagen-s ... aunch.html

This wasn't the same rocket as the previous attempted launches. More like a small sounding rocket.
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Re: Copenhagen Suborbitals - ready for launch

Postby jase » Tue Jul 31, 2012 8:51 am

Cool link OTT thanks for sharing :D

The rocket looks very similar to a Nike Cajun combo, albeit an extended Cajun...

Beautiful image 8)
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Re: Copenhagen Suborbitals - ready for launch

Postby OverTheTop » Tue Jun 25, 2013 8:25 am

Launch Success of Active Guided Rocket Sapphire
sapphire_launch_850_bt.jpg


Popular Science article on the launch:
http://www.popsci.com/technology/articl ... nch-sunday

Home page:
http://www.copenhagensuborbitals.com/
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Re: Copenhagen Suborbitals - ready for launch

Postby jase » Thu Sep 26, 2013 1:59 pm

The boys at Copenhagen Suborbitals have some more rocket eye candy:

http://www.wired.com/wiredscience/2013/ ... e-rockets/

HEAT2X booster and if you scroll down a bit, some full-scale fun!!!
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Re: Copenhagen Suborbitals - ready for launch

Postby OverTheTop » Tue Aug 22, 2017 7:29 am

Copenhagen Suborbitals in the News for the Wrong Reasons

http://www.9news.com.au/world/2017/08/2 ... ody-at-sea
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