# Making Liquid Hydrogen/Oxygen Rocket?

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#### thef-equals-ma-isstrong

##### Member
Question is as stated. Obviously a much more advance topic, will need much more rigorous safety protocols, and will need to get experience making regular solid ones before taking on a project this intricate.

However, would love to know if there are any great resources you guys know of for making a small prototype one. Interested in getting a feel for what's all entailed in building one, the level of difficulty, etc.

Thanks in advance for any input!

#### Chrisn

##### Well-Known Member
Taking experience and knowledge out of the question, your ambition will require you to take out a mortgage on your house, to even get started. This topic is definitely not suited for this forum, unless you are a tripoli member and a permanent resident or citizen of the United States to gain access to the restricted Propulsion sub forum

#### Larry Curcio

##### Well-Known Member
Well, the density of liquid H2 is only about 0.08 g/cc. You're going to need a very big rocket to have sufficient mass ratio to do much. Look at the tank on the Space shuttle, for example. It's blimp-like. Small rockets do better with denser, less powerful fuels.

OTOH, LOX is reasonably dense and readily available. In her later days, my mother had a tank of it in her house for her emphysema. A new tank was delivered every week or so. (Of course she had a prescription.)

#### Zeus-cat

##### Well-Known Member
One big problem you will have (other than cost) is finding a place to launch a rocket using liquid hydrogen and oxygen. Our club wouldn't even consider letting you on our field with such a rocket. And I doubt many clubs would.

#### cbrarick

##### Wildman CT
The other huge problem is how do you safely handle the LOX? Are you familiar with O2 safe cleaning processes? LOX acts very poorly around certain other common materials...

#### bill_s

##### Well-Known Member
Yeah don't do that, but just thinking about it: you might be able to make a motor that works for a couple seconds but fitting into a flyable rocket is another matter. Liquid is the better long burn tech, great for manned rocketry and extreme altitudes, but isn't so great for short burns anyway. The motor is small, the tank is large. Thus, Shuttle got solid boosters also. Liquid also almost always uses active control due to the low thrust ... IF someone could get all that to work, it would be very cool!

#### Nytrunner

##### Pop lugs, not drugs
TRF Supporter
Well, the density of liquid H2 is only about 0.08 g/cc. You're going to need a very big rocket to have sufficient mass ratio to do much. Look at the tank on the Space shuttle, for example. It's blimp-like. Small rockets do better with denser, less powerful fuels.

OTOH, LOX is reasonably dense and readily available. In her later days, my mother had a tank of it in her house for her emphysema. A new tank was delivered every week or so. (Of course she had a prescription.)
Are you sure it was liquid oxygen? I'd lean towards it being a bottle of GOx (gaseous).

Making a small static engine could be a cool project, but using propellants that aren't as reactive as H/O. The low specific impulse of liquid engines means you'd need either I huge launch rail/tower or some sort of active stabilization.

That and a good relationship with the FAA cuz (as stated above) this falls totally outside of the Sport's purview.

#### mikec

##### Well-Known Member
Are you sure it was liquid oxygen? I'd lean towards it being a bottle of GOx (gaseous).
It might have been LOx, there are home systems that use it: http://www.chartindustries.com/Respiratory-Healthcare/Liquid-Oxygen-Systems

Starting with a hydrolox engine is, in a word, nuts. If you have to build a liquid rocket, starting with one where both fuel and oxidizer are cryogenic liquids is inadvisable. One where the fuel isn't cryogenic (alcohol or kerosene) is a lot easier.

#### jderimig

Don't let the naysayers get you down. Go for it!

#### fyrwrxz

##### latest photo
Go for it! But you might want to start with hybrids first to understand and get familiar with all the machining that goes on with making injectors,,nozzles, etc. and dealing with pressurized propellants. All i can say is I worked on the real ones (Atlas, Centaur and the Shuttles) and I wouldn't even bother, but that's just me. It helps to have a captive machine shop with a deep supply line, too!

#### Reinhard

##### Well-Known Member
TRF Supporter
Question is as stated. Obviously a much more advance topic, will need much more rigorous safety protocols, and will need to get experience making regular solid ones before taking on a project this intricate.

However, would love to know if there are any great resources you guys know of for making a small prototype one. Interested in getting a feel for what's all entailed in building one, the level of difficulty, etc.

Thanks in advance for any input!
See the aRocket list for these kinds of discussion. I'd suggest to lurk around a while or read the archives a bit to get a feel for the list before asking questions. Note that LH2 experience in particular is rare outside of government work, because it doesn't make sense performance wise in amateur rockets (and many professional ones) and it introduces significant additional hurdles due to its deep cryogenic nature.

Reinhard

#### GregGleason

##### Well-Known Member
LH2 as a fuel in a rocket only makes sense above the sensible atmosphere, which is precisely why all of the first stage Saturns, from SA-1 to the Saturn V, used RP-1 (aerospace-grade kerosene). It's related to Isp. Another thing is that LH2 needs to kept between &#8722;434.45 °F and &#8722;423.17 °F to stay liquid. RP-1 does not have these extreme temperature requirements.

As a bonus, the flame is more visible in daylight with RP-1 than with LH2.

Greg

#### mikec

##### Well-Known Member
LH2 as a fuel in a rocket only makes sense above the sensible atmosphere...
Depends on your definition of "makes sense". Both the Shuttle and the Delta 4 use LH2/LOx in their first stages, although many people think the costs outweigh the benefits.

If someone has a long history of successfully building and flying an easier liquid rocket, then it might be time to think about LH2/LOx. That's not being negative, just realistic.

#### GregGleason

##### Well-Known Member
Depends on your definition of "makes sense". Both the Shuttle and the Delta 4 use LH2/LOx in their first stages, although many people think the costs outweigh the benefits.

If someone has a long history of successfully building and flying an easier liquid rocket, then it might be time to think about LH2/LOx. That's not being negative, just realistic.
Fair enough, and the mission of the Delta IV allows the use of LH2.

But the reality is that RP-1 is far easier to handle than LH2, mainly because it is non-cryogenic. Because of the nature of the Saturn V with its classic staging, RP-1 and LOX were the path forward because of the technology of the day and its ability to meet schedule. The first stage sep occurred at about 38 miles, where the atmospheric density is 0.02% of sea level. The LH2/LOX propellants were for the stages that operated in near space and beyond when Isp matters most.

Rockets using LH2/LOX tend to be HUGE because of fuel density of LH2 and the requisite need for large tankage. For example, the S-II (Saturn V's second stage), had a huge LH2 tank compared to the LOX tank (and the very creative common bulkhead that separated them).

You see the same thing with the External Tank for the shuttle, the ET's length was due to accommodate the required LH2 to run the SSME's to orbit.

With the shuttle, the SRB's provided ~80% of the thrust at liftoff as compared to the 3 x LH2/LOX SSME engines (about 7% each).

The Delta IV variants use the LH2/LOX RS-68A engines which have less than half the thrust of the first generation RP-1/LOX F-1 engines of the Saturn V's first stage.

The use of LH2 at liftoff can be done (as does the Delta IV), but in the case of the Saturn V is was not the way to go.

That and the Saturn V has a very high coolness-factor at liftoff.

Greg

#### Peartree

##### Cyborg Rocketeer
Staff member
Global Mod
Okay folks. First, since this is clearly NOT a question for beginners, I am moving this thread from the Beginner Forum to the Watering Hole.

Second, I want to comment that liquid fueled rockets is something that someone ought not mess with until they have worked their way up through a long rocketry learning curve that includes HPR certification and a lot of experience.

Third, I want to warn everyone to be careful about what and how you answer this question so that the mods don't have to move it to the research forum.

#### thef-equals-ma-isstrong

##### Member
Okay folks. First, since this is clearly NOT a question for beginners, I am moving this thread from the Beginner Forum to the Watering Hole.

Second, I want to comment that liquid fueled rockets is something that someone ought not mess with until they have worked their way up through a long rocketry learning curve that includes HPR certification and a lot of experience.

Third, I want to warn everyone to be careful about what and how you answer this question so that the mods don't have to move it to the research forum.
My bad. Had a sense that since the big boys use these chemicals it probably wasn't something one should mess around with for a while. Definitely won't be planning on stepping near making these sorts of rockets until I at least get level 3 certified, seeing all the responses from the form.

That being said, thank you guys so much again for your two cents. Will definitely stick to solids for now, with liquids being a goal in the very, very long run.

#### Larry Curcio

##### Well-Known Member
Yup. It was LOX. That's what they use now. It came in a nice cryogenic tank.

#### dave carver

##### ....what hump?
Simplest way to get into liquid propellants, if you can find it pure enough, is Hydrogen Peroxide. It's a very simple blow-down system requiring one valve and a burst disk. The valve goes between a small tank of Helium and larger tank of H2O2. The burst disk goes between the H2O2 and a catalyst, like the Paladium core from a Automobile exhaust. Helium in the pressure tank because it needs the smallest orifice to flow, all the other gaseous Elements the molecule is bigger. The Burst disk lets go and the H2O2 flashes to steam across the catalyst.

You can find lots on this sort of set-up online. In the late '50's two High Schoolers built and flew a rocket of such a configuration...and this doesn't violate any security laws...good luck finding pure enough H2O2. It's out there but it ain't cheap but what is in rocketry?

#### dave carver

##### ....what hump?
Yup. It was LOX. That's what they use now. It came in a nice cryogenic tank.
Dewar's (a giant Thermos bottle) of LOX are easily available from Norco for one. The use it in Hospitals for instance because storage takes up less space. It has the huge advantage of being stored at atmospheric pressure. I have a friend that blows glass, his torchs run on LOX and Propane. They run on the oxygen that evaporates naturally from the Dewar.

#### XolveJohn

Not practical for amateurs. Need to take some college classes first. Then have about $50K in eqpt to get started. And a good insurance policy. Probably better off with hydrazine. Just don't breath it! #### Nytrunner ##### Pop lugs, not drugs TRF Supporter And a good insurance policy. Probably better off with hydrazine. Just don't breath it! Just add a few thousand$ more for protective equipment, hazards storage, and containment.

For consideration: the Hydrazine Song

#### dave carver

##### ....what hump?
The really dangerous stuff is Furfuryl Alcohol and Red Fuming Nitric Acid. They are Hypergolic. This is a road best not traveled by amateurs, RFNA touches anything organic and it will burst into flames.... :eyepop:

#### dhbarr

##### Amateur Professional
So, the challenge is clearly to select a liquid, cryogenic, hypergolic, carcino/terato-genic combo.

( notelease do not actually do this! )

#### Larry Curcio

##### Well-Known Member
Just add a few thousand \$ more for protective equipment, hazards storage, and containment.

For consideration: the Hydrazine Song
If only he had penguin feet!

#### tmacklin

##### Well-Known Member
Bits of aluminum foil dropped into a solution of sodium hydroxide in water will react and produce copious amounts of hydrogen gas. (David G. Sleeter/Teleflite Corporation, Homemade Hydrogen Report) Getting it cold enough to liquify is beyond my pay grade.

TRF Supporter

#### boatgeek

##### Well-Known Member
Bits of aluminum foil dropped into a solution of sodium hydroxide in water will react and produce copious amounts of hydrogen gas. (David G. Sleeter/Teleflite Corporation, Homemade Hydrogen Report) Getting it cold enough to liquify is beyond my pay grade.
Heck, you can just go down the street and buy a Dewar flask of hydrogen from a technical gas supplier. I wouldn't mention rockets to them, though. They might get sketched out and refuse to sell to you. http://www.praxair.com/gases/buy-compressed-hydrogen-gas-or-liquid-hydrogen

If you're determined to end up dead, trying to build an LH/LOX rocket with no other training would be a spectacular way to do it if you can jump the hurdles before the massive fireball. Just losing an arm to cryogenic liquids would be kinda boring.

#### cerving

##### Owner, Eggtimer Rocketry
TRF Supporter
Bits of aluminum foil dropped into a solution of sodium hydroxide in water will react and produce copious amounts of hydrogen gas. (David G. Sleeter/Teleflite Corporation, Homemade Hydrogen Report) Getting it cold enough to liquify is beyond my pay grade.
When I was in college we used to amuse ourselves by doing just that, you'd have to use a glass 1/2 liter bottle in a bucket of ice water though because the reaction is highly exothermic. We'd put a balloon over the mouth of the bottle and wait for it to fill up, tie it off, put a piece of string around it soaked in lighter fluid, light it and let it go. Nice airburst.

It's a wonder we didn't all kill ourselves... you just don't think of those things when you're young.

TRF Supporter