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Copenhagen_Suborbitals

Copenhagen_Suborbitals

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New blog

Under pressure

by Peter Madsen, 16. okt 2013 kl. 14:28'

My task in CS is both incredibly exciting and very difficult. Basically, I have to get the best out of a certain limited set of resources. If I am too cautious, we fail by not getting anywhere. If I am too bold, we fail by never getting anything to work. It's like driving a Formula 1 racecar through a very demanding track where all your dreams are what's at stake.

The Formula 1 driver approaching a turn, make an intuitive guess about how much friction he can expect from the wheels and the suspension. He must calculate the trajectory through the turn, so he carefully optimise the path to use the least possible friction and thus find the path through the curve which gives maximum radius and thus require the minimum lateral forces on the wheels and suspension. If he followed the advice of my old driving instructor, he would get through the curve by first stopping up completely and then rolling slowly through while looking over the right shoulder. It is safe, but it is also a losers strategy. If he does it the right way, he drives all the way just a fraction below loss of friction and come through with almost no tolerance. It is dangerous, but it's a winning strategy. If he forces it just a little bit further, he ends up in the barrier as a loser and perhaps dead or injured. Driving Formula 1 is about being best to guess or calculate how far the equipment can be stressed without failing.

The same applies to CS.

If I had unlimited resources, we would test run our Tordenskjold engine to pieces in a test rig before it was built into our HEAT-2X airframe. We would run tests every other weekend and we would test both below rated load, at rated load and to destruction. The engines would be built on an assembly line, and their tolerances would be small. We could measure their internal tolerances with ultrasound, x-rays or whatever. But we are far from having the resources - primarily in available man-hours - as this comprehensive step-by-step testing requires. Therefore we are forced to follow an "all-up" strategy, where we take some chances - like a Formula 1 driver - to optimise the few scattered hours we have access to.

If you just are sufficiently skilled you can also succeed anyway.

HEAT 2X full duration test is a true thoroughbred, nerve wrecking, 90 seconds long trip in purgatory for CS.

If it goes well we are on track for a potential spaceflight in 2014. That is, after more nail-biting, nerve-disintegrating concerns about guidance, recovery, organisation, refuelling at sea and 1.23 x10^17 other challenges. But we'll at least be in the final.

If Tordenskjold doesn't succeed and e.g. explodes in a classic hard start, it will break the air frame and the whole stack ends up as scrap. Similarly, if we get a thermal fault and burn a hole in the engine. It's built into the rocket, so if the hundreds of thousands of kilowatts escape the engine the wrong way it will be extremely destructive. The 160 tons of steel and concrete in VTC 3 ensures that the fault has no effect on anything except the 2X itself, but it will be costly for CS. It represents many months of work that can be destroyed. A situation like when the Formula 1 driver reaches the curve and have to assess exactly how hard he can push the equipment.

Well, what is the alternative? Sure, we have the good, proven HATV hybrids. We could fly some more of them and then postpone the large HEAT rockets few years. We could, after we think we've flown enough Sapphires, look at a flying the 2X again in 2020. Then a couple of years with them until we master it in 2025. Then some years of turbine testing on the ground - and perhaps a first flight with a HEAT 1600 in 2030. We don't have to force anything through, - or what?

It just cannot work out economically. The rent in HAB is the same whether we are very much or somewhat active, and there are limits to how far we can stretch this before there is too little activity compared to the cost. I would personally get bugged down and get stuck in cobwebs in the office chair. CS will dry out and mummify as a coffee and pizza club.

That is why we invest. That is why we take the "all-up" model and test the complete rocket stage. If it goes well, it is possible for us to succeed with our project. If it goes bad the alternative is not the slow strategy because we cannot win the Formula 1 race by following my driving instructor's advice and stop. Whether we realise it or not, we do not have thirty years to do this.

The racing driver must guess his coefficient of friction, but it's worse than that. He's probably not aware of the force diagrams and theoretical conditions for his suspension that will determine if he survives curve. We can as a "rocket engineers" do a lot of measurements on the ground before we drive into the curve ( before we fly ). With measurements and theory in hand we can calculate what will happen. We can test unmanned race cars before we ride them. We can be deliberate and targeted in our ride through the curves. We do not rely on common sense, omens or black crows on our shoulder. We can do a lot of testing and measuring on a small scale before we push our speed machine into the curve and take a bet with the devil about who is the fastest and smartest.

Thus also last night at the HAB.

Part of my life is about building a rocket engine that will not melt. I do this by jamming propellant - that seconds after will be burned - through Tordenskjolds quite advanced cooling system. The problem is that the heat input in the engines most critically affected parts are quite enormous. Without cooling it would burn a hole in the 3 mm thick steel wall within approx. 5 seconds. This is not a guess but based on practical experience. When we need to run for an eternity - 90 seconds for a rocket engine equates 90 years for a human - we must remove all of the heat. The engine must achieve thermal equilibrium within the first 15-20 seconds, such that all the heat input to the engine wall is removed by the cooling system. If the engine just stood submerged under water it could not prevent burning a hole anyway. In order to remove enough heat should I force coolant past the wall at high speed in order to create the required contact between refrigerant and metal. This is the core problem with all heat exchangers. Only a high flow rate can remove enough kilowatts. The temperature just a few millimetres inside of the combustion chamber exceed the boiling point of steel.

High flow rates cost give pressure drop and then we just do not have enough unlimited pressure. The tanks on HEAT 2X - especially the fuel tank - will be pushed to the limit in order to deliver sufficient feed pressure to both squeeze the refrigerant (fuel) through the cooling system, to then atomise it in the hundreds of nozzles in the injector and finally to have some pressure left to produce internal tank pressure. Our Ø650 x 6 mm light metal tank burst at about 34 to 38 bar. We have a reasonable confidence that it will sustain the pressure test at 30 bar. If it was an industrial system, we would then be able to use an operational pressure of up to 20 bar. Compared with an air tank for diving being pressure tested to 300 bar and which is used at 200 bar. When we pressure tests very often and take care not to throw the rocket about as you can do with an air tank, we may increase the limit a little above 20 bar. Perhaps 22 to 24 bar. We pressurise the tank without people around, so it's not a disaster if something happens. But we will lose one airframe.

Yesterday we measured the pressure drop across the cooling system: During the 42 seconds we pumped 400 litre of water through the system with a pressure drop of 0.8 bar. This corresponds to a pressure drop of more than 1.5 bar when using the alcohol/water mixture targeting nominal flow (no more than 10 kg/s). The test shows that the tolerances in the cooling system are as they should be and that the flow rate at the most critical parts is near the expected 10 to 12 m/s.

This mean that our race car driver now know much more about the coefficient of friction in the curve. The Tordenskjold can still melt and smash everything when we run the test, but now we have at least measured that we are where we should be - and actually at the high end of what other engines with similar pressure, propellant and material has been running successfully with.

But we may still have a hot spot - or a hard start - and now soon I will soon no more nails left to bite!

It's nerve-wracking. I have an ability to pad myself into a kind of "reality screen" when we have tests. It just will not work out for me to run around on the VTC 3 and say, "Argh - I can not take it. I want my mother - arghh!" We must meet the challenge and take it like a man. Whether it works out well or not, you still learn something new.

Sometimes it can be hard to convey the message that it is ok when things goes different than planned.

Watch this CATO video:

<video link>

Galcit testing engine goes CATO.

After this CATO I would have liked to wait to tell about it until the error had been found and fixed. For that reason the video department agreed to send the video out to the CS only at first. Now it's like any other video freely on display. The problem has long since been solved. We had a little debate about "how open - open source is it" because you always end up editing whatever reality is shown. I now think we get the best result by preparing people that tests are most likely to go wrong, and then rejoice when things are going well.

Note that even if you truly are under pressure, you can still be quite cool when problems happen. There's no point in panicking or freaking out. So we don't. Immediately after a "situation" there is always a lot of theories thrown about. I always ask people to stop it guessing, save their data and information and not to speculate too much. The best part is - literally - to pick up the pieces and analyse fractures, photos, video, high speed and measurement data and then draw the right conclusions few days later.

In the case of the Galcit CATO the fractures revealed that it was cast at too low temperature, which had resulted in a "de-bonding" between the motor case liner/coating and the propellant. This typically results in CATO in a solid engine. So we changed the casting procedure, and it was resolved. This is how you have to work. I'm happy about the blast because it showed us some limits. This is what bugs me a little about the H202 plant - it has never had any problems. So I do not know the margins for sure.

Watch this video :

twice testing galcit after change in casting procedure

The press will always look out for where the excitement is or where to find conflicts. They don't understand that this it's not at about the feelings of my family regarding my role in the project, or if it will be von B or me or someone else that end up be launched. That is not what this is about.

The conflict is between the cooling system and heat input. Between guidance and deviation. Between the turbine blades, scalding hot steam at high pressure and violent centrifugal forces. Between parachutes and crash. These are the things that matter and not some of the romantic hogwash, unimportant side stories about feelings and whether you dare this or that or the other. I say screw all that.

In reality it is quite interesting to see if we succeed with the test of 2X, so we can get into the finals for the big race for the stars.

Peter Madsen

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tom1499

tom1499

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Posted

Wait do you use arduinos as control systems? Oh god I love you guys. I wish I could come up for a tour.

If so, how are you handling multiple sketches running at once?

Would you be better off using something like a BeagleBone for the RealtimeOS?

Or do you have multiple arduinos? Homemade or purchased?

So many questions! I recently got into electronics and have been quite interested in a small rocket, with an Arduino control system. Unfortunately I don't have the facilities to get propellants where I live, or the facilities to make this stuff.

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Copenhagen_Suborbitals

Copenhagen_Suborbitals

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Calling Huntsville, Alabama.

By Peter Madsen, October 30, 2013

Dear readers,

Tonight the subject is not technology but rather real live people as part of history.

In my dorm in Albertslund I once set fire to a piece of gun powder. The piece was recovered by divers from the sea bed close to the Norweigan port of Horten. It had been part of the ammunition of the very large 38 cm Bismarck canon position from 1944. Together with a similar position at Hanstholm, Denmark, they controlled the access to Skagerrak.

In such heavy artillery the propellant charge is of the shape and size of the panels of the striking surface on a household matchbox.

When the cordite smoke rose to the ceiling of room 241 I realized that the smell burning in my nostrils was the smell of World War II. That was the smell of the terrible battle between Bismarch and the battlecruiser Hood in Denmark Strait.

Picture text: The battle cruiser Bismarch discharges it’s 38 cm canon against the weakly shielded HMS Hood and sinks the ship. A few days later Bismarch meets similar fate.

This made me stop and think. The history suddenly became very present right there in my room. Ouch.

The same thing happened tonight, though due to a friendly voice rather than cordite smoke from a fateful sea battle.

I’m really touched and literally moved to tears. Let me share with you what just happened.

I had located one of my favorite documentaries, the magnificent first part of the Moon Machines series. You can find it on YouTube. The first part is about the moon rocket launcher Saturn V.

http://youtu.be/DqQmoJafQlg

The documentary relates in a very sober and beautiful way the story about the Apollo project and all the engineers and technicians who helped create it.

Those people have always been special to me, maybe even more so than the astronauts who are much better known to the wider public.

One of the more colorful figures of the Saturn project is Mr. Robert Schwinghamer. In the documentary he tells about his work on the Saturn booster stage S1-C and about the huge test stands in Huntsville, Alabama. He tells about the relationship with von Braun – “He was very charismatic. You know, he could sell a refrigerator to an Eskimoâ€Â. The old rocket engineer has plenty of charisma himself as he sits there on the lip of the flame deflector of the world’s largest rocket engine test stand.

Picture text: The model for VTC3 – MSFC’s Saturn V test stand fronted by Mr. Schwinghamer.

If anything, Huntsville is the birth place of the moon rocket. This is where the incredible machines were built which made the hitherto most ambitious expedition possible. It was in Huntsville at the Marshall Space Flight Center that von Braun and his German engineers designed and built the constructions that the American airplane industry later would extract from the earth. Though the majority of the work constructing and testing the very large rocket engines were carried out by American technicians and civil engineers.

One of these was Mr. Schwinghamer. He’s 85 years today and his health is deteriorating. During the space race he was one of the engineers responsible for the construction of and testing in the giant test stands.

While I was watching the documentary I had a crazy idea. Would it be possible to call up the Apollo program? Could you actually discuss with Mr. Robert Schwinghamer how to build rocket tanks and construct test stands?

Google Google … Bingo! Mr. Schwinghamer still lives in Huntsville, Alabama with his daughter Elizabeth.

I punch in the number …

A friendly female voice answers in a very southern accent.

“Schwinghamers speaking…â€Â

For a moment I’m paralyzed… hey… What have I done? I’ve called Huntsville… and they pick up the phone!

The conversation that ensues is wonderful. This evening – tonight – the health of Mr. Schwinghamer is not too good, but his daughter would very much like to hear what I have to say.

I told her about the time at the age of 7 when I showed my mom a drawing of a Saturn V and told her that this was a moon rocket.

"So you see, it strikes me... that when I was a little boy I made a drawing of your dad's rocket for my mother..."

I told her that in Copenhagen in the year 2013 deeply influenced and inspired by the space race and the rocket from Huntsville we once again weld large tanks from thin sheets of light metal. I mentioned the dimensions of VTC3 and HEAT 1600.

Actually, the nice lady from the southern states of America wasn’t all that young… but did she know of propellant tanks, turbo pump fed rocket engines and rocket engine test stands? Indeed she did!

She was incredibly knowledgeable. She said that this was their whole life in their family. She told about the violent static tests that cracked the window panes in their house in downtown Huntsville. She told about Mr. Schwinghamer and a family that though they missed their busy dad, they were very proud too to be a small part of one of the proudest chapters in the history of USA.

"We loved it. We were all engulfed in the space program. We all felt so lucky to live in a time of exploration and shaken windows were not a problem. We were proud of every crack."

Elizabeth asked me to tell her about our rocket in details. She noted everything down and asked about height and weight of VTC3, the dimensions of HEAT 1600 and everything.

"I wanna tell Bob all the details. He will be so excited that you do this today - that you carry on and that you are inspired by the Saturn rocket."

"How tall is the test stand?"

"Did you say one hundred sixty tons of steel and concrete?"

"Sir, are you really calling from Denmark...? I didn't even know that you develop space boosters in Scandinavia."

"What kind of program is it? It sounds so unbelievable."

"Bob will be so excited when I tell him this."

"And it will be manned... and you use an American designed spacesuit...oh my..."

I felt that I could discuss very intrinsic technical details of rocket science with Elizabeth. It was a very special feeling to me.

She asked me to send her a mail containing photos… and call back soon. Bob is struggling with his health and some days are better than others.

We said heartfelt goodbyes and talk to you soon.

I’m left with a very, very special warm feeling in the stomach; Moon Machines is not only about machines, but also about real passionate people who many years after the last Saturn V F1 engine reached its MECO still feel the rush and the roar from the exceptional part of history.

I really want to meet just one of these people before it’s too late. I actually think I will. After this conversation I will never again be able to watch the Moon Machine documentary without experiencing that warm and friendly feeling in my stomach.

Only people really matters; the machines we create are secondary. It’s the driving force, the passion and the pride that are the true values and sources of happiness for the people creating things in the world.

Peter Madsen

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Krevsin

Krevsin

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Oooh, I wonder why I hadn't stumbled upon this thread before. I really liked the look of the Tycho Brahe spacecraft, it reminded me of those cheesy 1950s sci-fi drawings.

Good to hear you're doing (reasonably) well and I wish you luck on your further endeavours, Copenhagen Suborbitals!

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Copenhagen_Suborbitals

Copenhagen_Suborbitals

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Posted (edited)

The preliminary report for the HEAT-2

And a couple of update pictures.

Btw, we have finally expanded our shop, we have gotten hold of more space since we where running out fast, so if you have a couple of spare dollars, to help with the rent - feel free to use our Donate page.

Wired blog about our new facilities

The 1600 is coming along...

_MG_0053.jpg

_MG_0046.jpg

If anyone is in Oregon, Hillsboro. Stop by and hear Cameron Smith talk about the spacesuit he is building for us.

http://www.omsi.edu/sciencepubhillsboro/111813

You can read an article here:

http://www.explorersweb.com/polar/news.php?url=emigrating-beyond-earth-cameron-is-suiti_138187866

Edited by Copenhagen_Suborbitals
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Camacha

Camacha

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Should sell ad space on the side of your rocket. I'm sure Squad would pay you €20 to have a giant picture of Jeb on the side of the rocket. :D

You know even putting a giant Jeb on there costs considerably more than €20, right?

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Camacha

Camacha

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That is one manly lathe.

That was exactly what I was thinking to myself. I am used to some serious non-hobby grade equipment, but I had to do a retake to make sure I was not mistaking what I saw. I would not mind having that at home, even though I think my home would become inhabitable by its mere presence :D

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