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kbd512

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Registered: 2015-01-02

Posts: 7,850

SSTO Engine Technology

For SSTO to work, we do require very high performance LOX/LCH4 or LOX/RP1 engines, so to kick off this topic I present the following:

Launcher's E-2 LOX/RP1 Oxidizer-Rich LOX-Cooled Staged Combustion Engine

Rather than just watching a video of the engine, beautiful as that is, you get to see the performance data onscreen:
E-2 Test - Highest-performance kerosene rocket engine turbopump ever manufactured in the U.S.

My favorite video of the E-2 engine (brilliant blue flame, just like Methane and Hydrogen):
Who has ever seen a LOX/Kerosene liquid engine with a blue plume?

The characteristic sooty exhaust from most LOX/RP1 engines is replaced by a brilliant blue and orange flame, without a trace of soot, except for a very brief puff at startup and shutdown.

Thrust: 22,000lbf / 97,861N
O/F Ratio: 2.62:1
Isp: 365s (vac)
C* Efficiency: 98%+
Chamber Pressure: 100 bar

Turbopump Characteristics (you can see some of this data live during an engine test if you watch the first YouTube video link)
Pressure: 310 to 330 bar
Efficiency: 72%+
Power: 1.4MW
Pre-Burner Temperature 200°C
Inducer / Impeller rpm: 30,000
Impeller Material: 3D printed from Inconel 718
Combustion Chamber: 3D printed CuCrZr alloy using AMCM M 4K 3D metal printer
Co-Axial Injector: 3D printed using a Velo3D Sapphire 3D metal printer
Nozzle Diameter: 16 inches

Edit:
I forgot one other little tidbit about this engine- 99%+ combustion efficiency was ultimately achieved.  It's a fine-tuned hypersonic speed machine.  The exhaust plume makes it look just like a miniature Raptor.

Last edited by kbd512 (2024-05-25 20:52:53)

SpaceNut

Administrator

From: New Hampshire

Registered: 2004-07-22

Posts: 29,431

Re: SSTO Engine Technology

With a heavy ship in the near approximate launch mass of a falcon Heavy 9 and this fuel type.

PROPELLANT    LOX / RP-1

ENGINES MERLIN SEA LEVEL

Merlin is a family of rocket engines developed by SpaceX for use on its Falcon 1, Falcon 9 and Falcon Heavy launch vehicles. Merlin engines use RP-1 and liquid oxygen as rocket propellants in a gas-generator power cycle. The Merlin engine was originally designed for recovery and reuse.

THRUST    845 kN / 190,000 lbf

ENGINES MERLIN VACUUM

Merlin Vacuum features a larger exhaust section and a significantly larger expansion nozzle to maximize the engine’s efficiency in the vacuum of space. Its combustion chamber is regeneratively cooled, while the expansion nozzle is radiatively cooled. At full power, the Merlin Vacuum engine operates with the greatest efficiency ever for an American-made hydrocarbon rocket engine.

THRUST    981 kN / 220,500 lbf

SpaceNut

Administrator

From: New Hampshire

Registered: 2004-07-22

Posts: 29,431

Re: SSTO Engine Technology

GW post on engines and equations

GW Johnson just posted a couple of studies on Single Stage to Orbit and Two Stage to Orbit ....

The spreadsheets can be provided if anyone is interested in seeing them.

Attached are copies in pdf format of two articles I wrote and just recently published on "exrocketman".   They are bounding calculations on what can be done toward expendable and reusable vehicles to reach Earth orbit from the surface.  One investigates and bounds what can be done SSTO.  The other investigates and bounds TSTO.  If you want to post these in the drop box thingie,  go ahead. 

<snip>

This is very simple rocket equation stuff,  done in a couple of spreadsheets.  The ascent-averaged Isp data come from other stuff I have recently published on "exrocketman",  about estimating rocket engine performance.  Some of that was done with a version of the bell nozzle rocket spreadsheet used in the orbits+ course.  The free-expansion stuff came from a post on "exrocketman" dealing with aerospike nozzles.  If anyone wants the spreadsheets,  they can have them.

GW

The first file is to be linked from here (SSTO):
https://www.dropbox.com/scl/fi/hu5zc3qc … 3lptv&dl=0

The second file is to be linked from here (TSTO):
https://www.dropbox.com/scl/fi/4dnyyqjn … gsvmd&dl=0

Here is an update:

This is the one that supports the other two you just posted for me.  I meant to post this on "exrocketman" some time ago,  but never got around to it until today. 

It shows vividly just how easy it is to use the "r noz alt" worksheet in the "liquid rockets.xls" spreadsheet file,  plus the Paintbrush-made "engine sizing report.png" file to very rapidly size multiple engines and run trade studies.  This is where I got my recommendations for how to size a fixed "compromise" bell nozzle to get really good ascent performance out of it. 

That spreadsheet file is an update of the one that is part of the orbits+ course materials.  I took that one,  deleted the extraneous worksheets,  added an altitude performance calculation block with automatic plots,  and added a output data block that works perfectly with a "Paintbrush"-made engine sizing report. It becomes cut-and-paste with some minor edits to report a design.

The multiple engine designs I sized for the trade study also make a good data library.  Pdf document file attached.  It should go with the other two,  which were "Bounding Calculations for SSTO Concepts" and "Bounding Calculations for TSTO" that you just posted for me.

Link to pdf goes here:
https://www.dropbox.com/scl/fi/s8v6c0zc … upmdo&dl=0

(th)

SpaceNut

Administrator

From: New Hampshire

Registered: 2004-07-22

Posts: 29,431

Re: SSTO Engine Technology

I began to wonder if the Falcon first stage with modifications would be capable of a single stage to orbit.

https://en.wikipedia.org/wiki/Falcon_9_Full_Thrust

Mass (without propellant)[39]    22,200 kg (48,900 lb)
Mass (with propellant)    433,100 kg (954,800 lb)
Liquid oxygen tank capacity 287,400 kg (633,600 lb)
Kerosene tank capacity 123,500 kg (272,300 lb)
Payload fairing      1,700 kg (3,700 lb)

Thrust (stage total)[4]    7,607 kN (1,710,000 lbf) (sea level)
Specific impulse    Sea level: 282 seconds[

RGClark

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From: Philadelphia, PA

Registered: 2006-07-05

Posts: 765

Website

Re: SSTO Engine Technology

I began to wonder if the Falcon first stage with modifications would be capable of a single stage to orbit.

https://en.wikipedia.org/wiki/Falcon_9_Full_Thrust

Mass (without propellant)[39]    22,200 kg (48,900 lb)
Mass (with propellant)    433,100 kg (954,800 lb)
Liquid oxygen tank capacity 287,400 kg (633,600 lb)
Kerosene tank capacity 123,500 kg (272,300 lb)
Payload fairing      1,700 kg (3,700 lb)

Thrust (stage total)[4]    7,607 kN (1,710,000 lbf) (sea level)
Specific impulse    Sea level: 282 seconds[

We can estimate using the Silverbirdastronautics.com payload estimator. Some quirks of the program have to be noted though. First, always use the vacuum thrust and vacuum Isp, even for first stages. This is because the program already takes into account the diminution at sea level. Note in the images below the engine thrust and Isp fields have the vacuum values even though this is for the Falcon 9 first stage.
Secondly, input the “Inclination” for the launch as the latitude of the launch site. This is just a fact of orbital mechanics that the launch angle should match the sites latitude to maximize payload. So for a launch from Cape Canaveral I input 28.5 degrees.
Third, for the “Restartable upper stage?” Option, select “No”. Selecting “Yes” often reduces payload, perhaps because it keeps some propellant on reserve for a restart.

Then this is what the input and results screens look like:

About 3,400 kg to LEO for the Falcon 9 first stage as an expendable SSTO. About the expendable scenario, note I subtracted 2,000 kg from the dry mass input field taking the dry mass down from 22,000 kg to 20,000 kg since reportedly the landing legs add about 2,000 kg to the dry mass of the first stage.

The question arises then why subtract that off if you’re aiming for a reusable system? A few reasons. It is my opinion that the opposition to SSTO’s is so engrained that just doing a launch carrying a payload would be an important thing to do. So first accomplish the expendable case then proceed to the reusable case.

[Sidebar: this is one of the reasons why I disagree with the approach SpaceX is taking with the Starship. SpaceX was spectacularly successful by first getting the expendable Falcon 9 then proceeding to reusability. If they had taken that approach to the Starship, they would already be flying expendable rockets to orbit at a profit. Moreover, they would already have rockets capable of single flight missions now to the Moon or Mars. No refueling flights nor SLS required. I mean they could do that literally like tomorrow.]

Secondly, the margins for a SSTO are slim, so you want to maximize the payload. So for the operational SSTO you want to use the known technology of altitude compensation. Using this instead of the vacuum Isp for the Merlin being 311s you could get the highest known possible vacuum for a kerolox engine, ca. 360s, while still having an engine able to fire at sea level.

This will greatly increase the payload possible, at least to 10,000 kg possibly higher, simply by having a variable nozzle. Now, when you have that higher payload then you can add on reusability systems.

  Bob Clark

Last edited by RGClark (2024-07-03 09:00:22)

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Old Space rule of acquisition (with a nod to Star Trek - the Next Generation):

      “Anything worth doing is worth doing for a billion dollars.”

RGClark

Member

From: Philadelphia, PA

Registered: 2006-07-05

Posts: 765

Website

Re: SSTO Engine Technology

In addition to using a Falcon 9 first stage, I would like to see smaller versions tried, specifically using the F9 2nd stage. The Merlin Vacuum on the 2nd stage can’t operate at sea level because of its high expansion. And the sea level Merlin would not have enough thrust to loft the stage from the ground.
So I’ll reduce the propellant load by 1/2. A single sea level Merlin could then launch it. I’ll estimate this half-size 2nd stage’s dry mass by first subtracting off the engine mass from the dry mass, taking half the remaining mass, then adding back on the mass of the engine. The reason is you still need the full engine size and mass to lift off, not a half-size engine.

The results are as below:

So about 670 kg to orbit as an expendable. Again for an operational SSTO you really want to use altitude compensation. I estimate using it you could raise it the payload to ca. 1,600 kg or possibly higher.

Another nice thing about this is you could get 10 of the these small SSTO’s from one Falcon 9, since there are 10 Merlins on the Falcon 9, and the total propellant size on the Falcon 9 of 500 tons amounts to 10 of the small size SSTO’s.

So you could buy a single reused Falcon 9 at $40 million, and break it down to 10 of the small SSTO’s at $4 million each.

  Bob Clark

Last edited by RGClark (2024-07-03 08:57:45)

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Old Space rule of acquisition (with a nod to Star Trek - the Next Generation):

      “Anything worth doing is worth doing for a billion dollars.”

SpaceNut

Administrator

From: New Hampshire

Registered: 2004-07-22

Posts: 29,431

Re: SSTO Engine Technology

Thanks for the working of the reuse with https://silverbirdastronautics.com/