Mixed-Mode Rocket engine (tripropellant engines)

[Michel Van]

Mixed-Mode rocket Engines use two propellant with oxidiser
The idea to use dense propellant during Launch then switch to hydrogen for more performance
that why those engines are proposed for SSTO or air launch Shuttles

this document by Aerojet from may 1977
is in depth study of Mixed-Mode Engine under Various propellant with Hydrogene/Lox

Advanced high pressure engine study for mixed-mode vehicle applications

Advanced high pressure engine study for mixed-mode vehicle applications - NASA Technical Reports Server (NTRS)

High pressure liquid rocket engine design, performance, weight, envelope, and operational characteristics were evaluated for a variety of candidate engines for use in mixed-mode, single-stage-to-orbit applications. Propellant property and performance data were obtained for candidate Mode 1 fuels...

ntrs.nasa.gov

 

[OliverSedlacek]

Is it just me that's perplexed by this obsession with SSTO? I can see the sales pitch to venture capitalist who don't really understand the numbers and get seduced by the promise of obvious re-usability. Seeing that re-usable boosters are there for all to see, dragging the bulk of a whole rocket into orbit and then getting it through reentry is a millstone that cripples performance. Two stages let you optimise rocket motor design for two different regimes and you can use different fuels if you want. It looks like a development dead end to me.

 

[publiusr]

Breakthroughs in materials design may make all the difference.... there was a metal that got *stronger* when cold.

 

[Scott Kenny]

Is it just me that's perplexed by this obsession with SSTO? I can see the sales pitch to venture capitalist who don't really understand the numbers and get seduced by the promise of obvious re-usability. Seeing that re-usable boosters are there for all to see, dragging the bulk of a whole rocket into orbit and then getting it through reentry is a millstone that cripples performance. Two stages let you optimise rocket motor design for two different regimes and you can use different fuels if you want. It looks like a development dead end to me.

That was definitely the case before SpaceX and the Falcons.

It may prove more viable now.

Kerosene has some significant advantages over hydrogen or methane for first stage fuel, between small volume and large mass flows for high thrust.

 

[Archibald]

I have a bunch of Salkeld /Beichel/ Bulman papers (1978 / 2008 ) on my HD. Will try to post some of them.

 

[Byeman]

Breakthroughs in materials design may make all the difference.... there was a metal that got *stronger* when cold.

not enough to matter

 

[publiusr]

Article today entitled "Calculating the energy requirements for using moondust to create rocket fuel" at phys.org along with an article concerning "selective combustion."

The use of a catalyst allowed researchers to burn one molecule but not another via chemical looping, as per Matthew Jacob at the University of Minnesota.

This may have some utility in space.

 

[JetPropulsion]

Brief summary of content.
Chemical Automation Design Bureau named by Kosberg designed tripropellant (liquid oxigen/liquid hydrogene/kerosene) RD-0750 liquid propellant rocket engine. RD-0750 based on 11D122 LPRE consruction.
For testing RD-0750 was made RD-0750D demonstrator. RD-0750D have all 11D122 units, excluding gas generator. At RD-0750D gas generator - tripropellant, kerosene filling from fire test stand. Nominal level of thrust of RD-0750D was 50-60% of nominal thrust of RD-0750 (thrust limitation the limitation is caused by the limited kerosene supply pressure from the test stand; in the standard engine, kerosene is supplied by a turbopump).
8.04.1998 - first fite stand test, engine shut down by false alarm command/
16.04.1998 - second test, thrust level (26%) close close to design level of thrust is obtained from 3,9 to 4,05 seconds, from 4,38 second engine shut down by alarm command.

 

[Byeman]

Article today entitled "Calculating the energy requirements for using moondust to create rocket fuel" at phys.org along with an article concerning "selective combustion."

The use of a catalyst allowed researchers to burn one molecule but not another via chemical looping, as per Matthew Jacob at the University of Minnesota.

This may have some utility in space.

It is not going to matter much. it is still chemical propulsion, ISP is still limited.

 

[JetPropulsion]

Some photos of RD-0750D. Source: https://buranarchive.space/index?/category/139-rd_0750d

 

[Archibald]

As promised: a whole lot of Salkeld / Beichel documents. Mel Bulmann carried on their work, at Aerojet.

 

[Archibald]

Second wave !

 

[JetPropulsion]

Well, let's move on.
Cosmonautics News magazine, No. 22, 1994. It follows from this news article that RD-0750 was, in fact, created on NASA's order.

Thus, KB Khimavtomatika (Voronezh) and Aerojet are working on modification of the Russian RD-0120 engine used in the second stage of the Energia launch vehicle into a three-propellant engine in accordance with a contract issued in August 1994 by NASA's Marshall Space Flight Center. The three-propellant version is intended for NASA's single-stage, reusable launch vehicle, which could replace the existing Space Shuttle transportation system in 2010-2012. The contract funds allocated ($17.2 million) are sufficient to fund work in the U.S. and Russia through February 1998. On November 3 (1994), a team of Marshall Center engineers traveled to Russia to visit the Khimavtomatika Design Bureau.

 

[Archibald]

Now that's extremely interesting !
Trying to wrap my brain around this.
- I thought the RD-701 had been the only triprop rocket to go west. Ok, so they wanted to tweak the Soviet equivalent of the SSME, hydrolox:
-which mean they would add kerosene combustion to it. Would have been a very impressive triprop engine !
-Next, from your posts:
https://www.secretprojects.co.uk/th...gine-tripropellant-engines.45252/#post-768951

https://www.secretprojects.co.uk/threads/mixed-mode-rocket-engine-tripropellant-engines.45252/#post-769622

They tested it on the ground ? a triprop Soviet SSME-like ?

Did NASA paid for those tests ?

 

[JetPropulsion]

I thought the RD-701 had been the only triprop rocket to go west.

RD-701 was a project pf NPO "Energomash" (Khimki town, near Moscow). RD-701 was develop for MAKS launch vehicle (system with air launch). From Cosmonautics News magazine, No. 22, 1994:

The second joint work is being done by NPO "Energomash" and the propulsion department of "Pratt and Whitney", which is building a three-propellant RD-701 RD-701 on the basis of RD-170 (used for the first stage of the "Energia" booster) (earlier this engine was planned to be used in the orbital aircraft of the reusable MAKS aerospace system developed by NPO "Molniya"). This work is also paid for by NASA, which in August allocated 5,4 million $ for it. Representatives of the U.S. firm believe that this development is further advanced than others, citing as evidence the fact that they had asked NASA for a substantially smaller sum. In November 1995, the Marshall Center is scheduled to begin tests of RD-701.

As we know, development of RD-701 was died and there were no tests of full-scale engine.
At the book "Path at rocket technique", Moscow: "Mashinostroenie", 2004, edited by academician B. I. Katorgin (official book about history of NPO "Energomash") we can read next information about tests of small RD-701 prototype:

Development of an experimental three-propellant engine was carried out at NPO "Energomash". The first firing test (the world's first) was conducted on the stand at NIIHIMMASH on August 9, 1994. The experimental three-propellant two-mode engine had a thrust of 6,5 tonns-force (in the first mode) and 3 tonns-force (in the second mode). The engine chamber had a mixing head with 19 mixing elements (injector elements), the geometric dimensions of which corresponded to the dimensions of similar elements in the mixing heads of the RD-704 engine chamber. The design of the chamber provided for the possibility of changing its configuration by replacing the constituent elements.
The main objectives of the tests of such an engine were experimental confirmation of the performance of the developed variants of the mixing head of the chamber, which provided mixing and combustion of three propellant components, determination of the efficiency of the combustion process of three-component propellant (oxygen - kerosene RG-1 - hydrogen), realization of the transition from the first to the second mode with subsequent operation in the second mode. 44 firing tests of experimental three-propellant engines on the NIIHIMMASH stand were carried out.
The tests were carried out in the following range of parameters: pressure in the chamber 114...220 kilogram-force per centimeter square; change of hydrogen percentage in the propellant in the first mode from 2 to 6,7%; temperature of oxidizing gas 249...737 degrees Celsius; duration of operation in the mode 5...100 seconds.
In the process of testing the experimental three-propellant two-mode engine, the following results were obtained: the working mixing elements for the full-size chamber were selected; the combustion efficiency coefficient in the three-component mode (first mode) and two-component mode (second mode) was determined; the peculiarities of the chamber operation in the transient modes of starting, cut-off, as well as in the transitions from the first mode to the second mode were revealed.
The test results confirmed the possibility of realization of a highly efficient combustion process of three-component fuel with achievement of the propellant combustion efficiency coefficient values close to the values of oxygen-hydrogen propellant. In the range of values of hydrogen mass fraction in propellant from 4,5 to 6,7%, according to the data of the conducted fire tests, the value of this coefficient was 0.999.

It is interesting for me: is this prototype was only a three-component chamber (I think, it was), or it was engine with gas generator, turbopupms and other elements. I will looking for about this.
So, I have AIAA article about RD-701, but I don't know politic of this site to post articles like this.

 

[Archibald]

A whole lot of the pdf papers I posted are from the AIAA.

 

[JetPropulsion]

They tested it on the ground ? a triprop Soviet SSME-like ?

Design bureau Chemical Automation named by Kosberg (KB Khimavtomatiki) was tested RD-0750D demonstrator. What the difference between baseline design RD-0750 and they RD-0750D demonstrator?..
RD-0750D demonstrator has no they own kerosene turbopump, kerosene was coming from test stand feeding system. Test stand feeding system can't feed kerosene at the required pressure, as RD-0750 turbopump. So, chamber pressure and thrust of RD-0750D was smaller, then RD-0750. We can see difference between RD-0750D and RD-0750 at they pneumohydraulic scheme (see pictures). At the colored pneumohydraulic scheme of RD-0750D colors means: blue - oxygen, yellow - hydrogen, dark green - kerosene from test stand feeding line.
So, in conclusion: we know about two tests of RD-0750D. There were no tests of RD-0750.

Did NASA paid for those tests ?

I don't know...

 

[JetPropulsion]

It is interesting for me: is this prototype was only a three-component chamber (I think, it was), or it was engine with gas generator, turbopupms and other elements. I will looking for about this.

There is proverb in russian laguage: a beast runs at the hunter (the ball comes to the player).
From article (look attachment):

An important stage in the development of such an engine is the experimental study and confirmation of high power characteristics of these engines. For this purpose, NPO Energomash developed an experimental three-component engine with thrust at the Earth of 6 - 8 tons, consisting of a combustion chamber operating on three-component fuel with subsequent transition to a two-component (oxygen - hydrogen) mode, an oxidation gas generator, automation units providing start-up, change of operating modes, engine shutdown, and other inherent to the engine units. Supply of propellant components with the required pressure in the engine chamber is provided by the bench system.

So, there are no turbopumps. Picture of this model engine at the attachment.

A whole lot of the pdf papers I posted are from the AIAA.

Ok, look attacment.

 

[JetPropulsion]

Some more information about RD-701.
RD-701 page on Buran.ru site (in English!): http://www.buran.ru/htm/rd-701.htm.
Excerpt from Gubanov's book (in Russian, but the modern translator built into Chrome works wonders): http://www.buran.ru/htm/40-3.htm.
I hope nobody will get confused with designations and will not confuse RD-0750 and RD-701.
So.
RD-0750 was developed by KB Khimavtomatika (Voronezh) on the basis of 11D122/RD-0120 (11D122 - oxygen-hydrogen engine of the second stage of 11K25/Energia; Russian SSME).
RD-701 was developed by KB Energomash (Khimki) on the basis of 11D520/RD-170 (11D520 - oxygen-kerosene engine of the first stage of 11K25/Energia).
By the way. The designations of the two companies are close. At Energomash the first digit in the index meant the type of propellant:
1 - liquid oxygen oxidizer;
2 - oxidizer based on nitric acid or nitrogen tetraoxide;
3 - oxidizer fluorine;
4, 6 - nuclear engines;
5 - oxidizer hydrogen peroxide;
7 - three-component engines.
KB Khimavtomatika has the same, only zero is added to distinguish it from KB Energomash.

 

[Archibald]

Thanks a lot for all this !

 

[publiusr]

That just makes me want to cry…how many revolutionary developments either on the vine due to lack of support?

 

[Scott Kenny]

That just makes me want to cry…how many revolutionary developments either on the vine due to lack of support?

Many/all of them.

 

[Byeman]

That just makes me want to cry…how many revolutionary developments either on the vine due to lack of support?

What makes you think this one is worth it? Or any of them? there are good reasons they die on the vine.
ISP or thrust is no longer the holy grail of chemical propulsion. It is cost. The 80/20 rule applies here. No need to spend tons of money to eke out a few more seconds of ISP or add complexity. Trimode, SSTO and air launch are perfect examples. Do they lower the cost per lb to orbit? Show how these can make a vehicle cheaper than the Falcon 9 concept (common tank components, common engines, no ordnance, no hypergols, etc)

 

[JetPropulsion]

What makes you think this one is worth it? Or any of them? there are good reasons they die on the vine.

Great explanation! You are right, this is the reason why three-component engines have not found application. Many engineers (and engine builders in particular) are guided by John F. Kennedy's testament: We don't do it because it's easy, we do it because it's hard.

 

[publiusr]

Boostback was only ready, when it was ready.
The Wright brothers used wing warping--something that may return as materials advance.
For now, we use Bleriot's approach.

 

[JetPropulsion]

Some details about construction and parameters of tripropellant gas generator of RD-0750.

 

[Zoo Tycoon]

Here you go, the mixed mode Tri prop engine from Alexander the Ok

View: https://youtu.be/5MHDLHgsRi4?si=cVaJyp1cApcIjXT5


Our site even gets a mention.