Comments on: Pumped Monoprop http://selenianboondocks.com/2008/10/pumped-monoprop/ Random Musings from the Warped Minds of Jonathan Goff, Ken Murphy, John Hare, and Kirk Sorensen Sat, 05 May 2012 20:53:30 +0000 hourly 1 http://wordpress.org/?v=3.3.1 By: john hare http://selenianboondocks.com/2008/10/pumped-monoprop/comment-page-1/#comment-3328 john hare Wed, 15 Oct 2008 08:59:43 +0000 http://selenianboondocks.com/?p=644#comment-3328 Tony, The tank pressure must be high enough to move the liquid to the pump and not cavitate in the impeller due to low pressure vaporization. The 15 psi or so forces some peroxide into the impeller and through the cat pack. The perhaps 10 psi pressure differential across the turbine at start begins the spin up. Gradually the spin increases the pressure through the impeller and cat pack, which increases the power through the turbine, which increases the rpm, which increases the pressure developed by the impeller, and so on. It could take 1 to 5 seconds to reach full pressure depending on assumptions. Tony,
The tank pressure must be high enough to move the liquid to the pump and not cavitate in the impeller due to low pressure vaporization. The 15 psi or so forces some peroxide into the impeller and through the cat pack. The perhaps 10 psi pressure differential across the turbine at start begins the spin up. Gradually the spin increases the pressure through the impeller and cat pack, which increases the power through the turbine, which increases the rpm, which increases the pressure developed by the impeller, and so on. It could take 1 to 5 seconds to reach full pressure depending on assumptions.

]]> By: Tony B http://selenianboondocks.com/2008/10/pumped-monoprop/comment-page-1/#comment-3326 Tony B Wed, 15 Oct 2008 04:02:54 +0000 http://selenianboondocks.com/?p=644#comment-3326 Hi, This may be a stupid question as I don't know much about pumps, I've been pretty much a structures guy my entire adult life. How does the pump start? I understand how once the peroxide hits the catalyst the pump keeps moving, I just don't see how it starts. Is there a solenoid valve or something with the peroxide under some pressure to push it into the pump housing? Just curious, Thanks. TB Hi,
This may be a stupid question as I don’t know much about pumps, I’ve been pretty much a structures guy my entire adult life.
How does the pump start? I understand how once the peroxide hits the catalyst the pump keeps moving, I just don’t see how it starts. Is there a solenoid valve or something with the peroxide under some pressure to push it into the pump housing?
Just curious,
Thanks.
TB

]]> By: john hare http://selenianboondocks.com/2008/10/pumped-monoprop/comment-page-1/#comment-3324 john hare Tue, 14 Oct 2008 21:34:54 +0000 http://selenianboondocks.com/?p=644#comment-3324 Iain, Fuel through the turbine blades is exactly what I have in mind though it will be an extensive post. I believe I can address the issues you raise. Part of it is sacrificing efficiency for simplicity and ease of handling. Tim, I am thinking in terms of using the section out of the jet that seals the turbine tips and using it to mask the connection. An inch section or so would be a small price to pay if the concept works. Pete, I couldn't figure out how to translate the page. It sounds like the sort of thing that interests me. Old and obsolete are often two very different things. My primary reference on air-turborockets was written in 1956 and is still valid for most of the basic points. Charles, I see your point. For your purposes, my salvaged parts method doesn't work at all. For some other people, it might be worth looking into. That is the point I kept missing, that one concept doesn't fit all, or even most, even if it works. Iain,
Fuel through the turbine blades is exactly what I have in mind though it will be an extensive post. I believe I can address the issues you raise. Part of it is sacrificing efficiency for simplicity and ease of handling.
Tim,
I am thinking in terms of using the section out of the jet that seals the turbine tips and using it to mask the connection. An inch section or so would be a small price to pay if the concept works.
Pete,
I couldn’t figure out how to translate the page. It sounds like the sort of thing that interests me. Old and obsolete are often two very different things. My primary reference on air-turborockets was written in 1956 and is still valid for most of the basic points.
Charles,
I see your point. For your purposes, my salvaged parts method doesn’t work at all. For some other people, it might be worth looking into. That is the point I kept missing, that one concept doesn’t fit all, or even most, even if it works.

]]> By: Charles Pooley http://selenianboondocks.com/2008/10/pumped-monoprop/comment-page-1/#comment-3323 Charles Pooley Tue, 14 Oct 2008 18:58:59 +0000 http://selenianboondocks.com/?p=644#comment-3323 John Hare's 2:28 am--Yes, easier to fabricate a turbine to own design than try to adapt something meant for something else. But cooling passages in turbine blades? Not needed for low (<500 K) gas. High T/W? I think, for 1 ton thrust or so, T/W could be over 200. John Goff, 8:15 am--Of course aluminum would be out for a delivery truck pump. But for a very small engine, maybe not to be ruled out. For quick prototypes, though, brass might be good. Machines and solders well. John Hare’s 2:28 am–Yes, easier to fabricate a turbine to own design than try to adapt something meant for something else. But cooling passages in turbine blades? Not needed for low (<500 K) gas. High T/W? I think, for 1 ton thrust or so, T/W could be over 200.

John Goff, 8:15 am–Of course aluminum would be out for a delivery truck pump. But for a very small engine, maybe not to be ruled out.
For quick prototypes, though, brass might be good. Machines and solders well.

]]> By: Pete Zaitcev http://selenianboondocks.com/2008/10/pumped-monoprop/comment-page-1/#comment-3322 Pete Zaitcev Tue, 14 Oct 2008 17:54:40 +0000 http://selenianboondocks.com/?p=644#comment-3322 Tangentially, check this link (I hope translate.google.com can handle it): http://www.novosti-kosmonavtiki.ru/content/numbers/233/19.shtml Initially it talks about the NK-33-1 with the extendible nozzle (and adding roll control), the costs of NK-33 derivatives vs. RD-191. Generally, the article is obsolete. However, the journalist also asked about the cross-over between aircraft engines and rocket engines at Klimov (re. John Hare's point above). Notice the discussion of enamel covering (plaque) vs. nickel-based alloys. That damn oxigen! Tangentially, check this link (I hope translate.google.com can handle it):
http://www.novosti-kosmonavtiki.ru/content/numbers/233/19.shtml
Initially it talks about the NK-33-1 with the extendible nozzle (and adding roll control), the costs of NK-33 derivatives vs. RD-191. Generally, the article is obsolete. However, the journalist also asked about the cross-over between aircraft engines and rocket engines at Klimov (re. John Hare’s point above). Notice the discussion of enamel covering (plaque) vs. nickel-based alloys. That damn oxigen!

]]> By: Jonathan Goff http://selenianboondocks.com/2008/10/pumped-monoprop/comment-page-1/#comment-3321 Jonathan Goff Tue, 14 Oct 2008 15:15:11 +0000 http://selenianboondocks.com/?p=644#comment-3321 Charles, I have no problem with using aluminum in rocket engines. I just get leary with using it in areas where you have parts moving very rapidly with tight clearances. I could be wrong, but all the literature I've seen (and all the cryo pump guys I've spoken with) have said that aluminum--even anodized aluminum--is a big no-no with things like LOX pumps. They could be wrong, but I would want to verify that before risking too much expensive hardware. ~Jon Charles,
I have no problem with using aluminum in rocket engines. I just get leary with using it in areas where you have parts moving very rapidly with tight clearances. I could be wrong, but all the literature I’ve seen (and all the cryo pump guys I’ve spoken with) have said that aluminum–even anodized aluminum–is a big no-no with things like LOX pumps. They could be wrong, but I would want to verify that before risking too much expensive hardware.

~Jon

]]> By: Tim http://selenianboondocks.com/2008/10/pumped-monoprop/comment-page-1/#comment-3320 Tim Tue, 14 Oct 2008 12:13:24 +0000 http://selenianboondocks.com/?p=644#comment-3320 Won't spearating at the equator for maintenance put the seam/seals in the same place as the turbine rotor? I figure trying to get a decent seal in the same place you're trying to get a small gap between the turbine blades and the chamber wall (the technical way to say that eludes me) will make things a little crowded. Maybe have a short cylindrical section (maybe an inch), so you've got room to put the seam and the turbine rotor in different places?? Won’t spearating at the equator for maintenance put the seam/seals in the same place as the turbine rotor? I figure trying to get a decent seal in the same place you’re trying to get a small gap between the turbine blades and the chamber wall (the technical way to say that eludes me) will make things a little crowded. Maybe have a short cylindrical section (maybe an inch), so you’ve got room to put the seam and the turbine rotor in different places??

]]> By: john hare http://selenianboondocks.com/2008/10/pumped-monoprop/comment-page-1/#comment-3318 john hare Tue, 14 Oct 2008 10:16:49 +0000 http://selenianboondocks.com/?p=644#comment-3318 Paul, The low pressure 250 psi or so might not be worth it to most people. It probably depends on how the helium bill affects their budget. There is also the issue that the pump adds to whatever tank pressure you are running. If you have 250 psi tank pressure and a 250 psi pump, then chamber pressure of 500 psi is attainable. Whether or not this is worthwhile is going to be a different decision to different groups. That I wish Armadillo good luck at the NGLLC does not mean I wish you ill. I want good luck for both of you, though only one can take the large purse. Paul,

The low pressure 250 psi or so might not be worth it to most people. It probably depends on how the helium bill affects their budget. There is also the issue that the pump adds to whatever tank pressure you are running. If you have 250 psi tank pressure and a 250 psi pump, then chamber pressure of 500 psi is attainable. Whether or not this is worthwhile is going to be a different decision to different groups.

That I wish Armadillo good luck at the NGLLC does not mean I wish you ill. I want good luck for both of you, though only one can take the large purse.

]]> By: john hare http://selenianboondocks.com/2008/10/pumped-monoprop/comment-page-1/#comment-3317 john hare Tue, 14 Oct 2008 09:28:46 +0000 http://selenianboondocks.com/?p=644#comment-3317 Charles, Some of the turboshaft engines operate at 30 atm and have turbine disk sizes that are in the range we are discussing. 450 psi turbine entry and 250 psi combustion chamber would be about the limit if they cannot be persuaded to work with denser cooler flows. If it would be easier to fabricate your own, there are some totally wicked possibilities for high Isp and T/W engines in small envelopes. Several of them involve cooling passages in the turbine blades for liquid regenerative cooling though. Designing and building it all from scratch could be a time and cash eater though. Charles,

Some of the turboshaft engines operate at 30 atm and have turbine disk sizes that are in the range we are discussing. 450 psi turbine entry and 250 psi combustion chamber would be about the limit if they cannot be persuaded to work with denser cooler flows.

If it would be easier to fabricate your own, there are some totally wicked possibilities for high Isp and T/W engines in small envelopes. Several of them involve cooling passages in the turbine blades for liquid regenerative cooling though. Designing and building it all from scratch could be a time and cash eater though.

]]> By: Charles Pooley http://selenianboondocks.com/2008/10/pumped-monoprop/comment-page-1/#comment-3316 Charles Pooley Tue, 14 Oct 2008 07:15:58 +0000 http://selenianboondocks.com/?p=644#comment-3316 Paul mentions minimum O2 pressure for aluminum burning. Actually, if not ignited it doesn't burn at all. It is easy to anodize it with a strong oxide coating. Aluminum is worthy of consideration. Wasn't the Agena engine made of aluminum? Minimum gage for low pressure tanks: the mass of the pressurizing means has no real minimum as the tank pressure is lowered. A heavier than minimum tank could be justified in terms of cost, durability. I'm thinking irrigation tubing... Also, a chamber pressure only a few times tank pressure will still be taking advantage of the several times chamber pressure for regenerative cooling, atomizing pressure etc. These things take substantial pressure drops and it's better that be accomplished in some tiny whirling thing than heavier tank walls. Paul mentions minimum O2 pressure for aluminum burning. Actually, if not ignited it doesn’t burn at all. It is easy to anodize it with a strong oxide coating. Aluminum is worthy of consideration. Wasn’t the Agena engine made of aluminum?

Minimum gage for low pressure tanks: the mass of the pressurizing means has no real minimum as the tank pressure is lowered. A heavier than minimum tank could be justified in terms of cost, durability. I’m thinking irrigation tubing…

Also, a chamber pressure only a few times tank pressure will still be taking advantage of the several times chamber pressure for regenerative cooling, atomizing pressure etc. These things take substantial pressure drops and it’s better that be accomplished in some tiny whirling thing than heavier tank walls.

]]>