ARCA

[Steven Pietrobon]

ARCA did their third test of their LAS 25DI engine on 26 October.

https://www.facebook.com/arcaspace/videos/816126618801890/

[Steven Pietrobon]

Two more videos from Arcaspace. The second (18 October) and third tests (26 October) of the LAS-25D motor.
These were done at higher temperature and pressures.

[TrevorMonty]

Two more videos from Arcaspace. The second (18 October) and third tests (26 October) of the LAS-25D motor.
These were done at higher temperature and pressures.
...

This looks like steam rocket not Aerospike engine. Be luck if it ISP hits 100.

https://en.m.wikipedia.org/wiki/Steam_rocket

[Steven Pietrobon]

This looks like steam rocket not Aerospike engine. Be luck if it ISP hits 100.

https://en.m.wikipedia.org/wiki/Steam_rocket

That's exactly what this engine is. Later versions will use an aerospike. There are heater elements within the tank that heat the water to about 250 C. Isp is 50 s for LAS-25D with the later versions going up to 67 s. They are looking to use this technology for the first stage of their launch vehicle. See their white paper for more information.

http://www.arcaspace.com/docs/ARCA_LAS_White_Paper_May_1_2019_Issue_1.pdf

[Steven Pietrobon]

ARCA have been busy! Their aerospike engine has a mass of 184 kg and thrust of 25 t (245 kN).

[Steven Pietrobon]

The ARCA aerospike engine has 15% greater Isp compared to their bell nozzle engine. Launch Assist System (LAS) vehicle test flight in April 2020.

[Lars-J]

“In April 2020 ARCA will launch the fully reusable launch assist system test vehicle”

No, they will not. They will not launch anything this year. Or next. And then they will switch to a brand new engine technology and the cycle repeats.

[Steven Pietrobon]

This video shows ARCA building the propellant distribution system inside the engine.

[Steven Pietrobon]

The ARCA aerospike test was performed on 20 December 2019.

[Comga]

ARCA have been busy! Their aerospike engine has a mass of 184 kg and thrust of 25 t (245 kN).

While not as adamant as Lars-J I am confounded as to how Arca expects to fly.
From where does the power come?
Those plans all have single tanks but they’re not using a classical monopropellant.
An aerospike is 15% more efficient but 1.15*0=0.
OK. Maybe it’s 1.15 times some small fraction of the energy needed to get to orbit, but there doesn’t seem to be a path.
Lots of vlogs, tho....

[Steven Pietrobon]

While not as adamant as Lars-J I am confounded as to how Arca expects to fly.
From where does the power come?

They are using very hot water. The water is heated using electrical power from the ground. Read their updated white paper for more information.

https://www.arcaspace.com/docs/ARCA_LAS_White_Paper_January_14_2020_Issue_2.pdf

The LAS25D nozzle engine had an Isp of 17 seconds while the LAS25DA aerospike engine has an Isp of 20 seconds, which I calculate to be a 17.6% increase. The paper says the plan is to increase Isp to 60 seconds.

[ncb1397]

While not as adamant as Lars-J I am confounded as to how Arca expects to fly.
From where does the power come?

They are using very hot water. The water is heated using electrical power from the ground. Isp ranges from 50 to 60 seconds Read their white paper for more information.

https://www.arcaspace.com/docs/ARCA_LAS_White_Paper_January_14_2020_Issue_2.pdf

With 60 seconds of isp and a mass ratio of 5 to 1, you can get ~1 km/s out of the stage or ~2200 mph. The falcon 9 often stages at a speed of about 4500 mph. It technically would work as a booster stage, but you need something different for the upper stage(s). If you already got to a high enough altitude, the altitude compensating aerospike already did its job and everything after that could use a specialized vacuum nozzle.

[Steven Pietrobon]

Please tell me, Steven, what makes them credible in your mind?

I think they are genuine in their intentions, like many space enthusiasts, but whether they will succeed, only time will tell. Anyway, I think its interesting watching their progress, warts and all.

[ncb1397]

Please tell me, Steven, what makes them credible in your mind?

According to some news articles posted online, there was some contention that they were or may have been responsible for the Schiaparelli lander failure (think they probably got cleared because it doesn't match what I have heard about the cause of the failure). In which case, they have done more on Mars than SpaceX has.

[ChrisWilson68]

The ARCA aerospike engine has 15% greater Isp compared to their bell nozzle engine.

Then they didn't design their engine with a bell nozzle correctly.

The advantage of an aerospike is that it can do well at different altitudes.  At sea level, a bell nozzle engine designed for sea level has no reason it would do worse than an aerospike.  Their pictures make it clear that they were testing both on the ground at ambient atmospheric pressure.

[ncb1397]

The ARCA aerospike engine has 15% greater Isp compared to their bell nozzle engine.

Then they didn't design their engine with a bell nozzle correctly.

The advantage of an aerospike is that it can do well at different altitudes.  At sea level, a bell nozzle engine designed for sea level has no reason it would do worse than an aerospike.  Their pictures make it clear that they were testing both on the ground at ambient atmospheric pressure.

Ground level and sea level aren't necessarily the same thing and bell nozzles that start at sea level aren't necessarily optimized for sea level. This was done most likely somewhere in Romania, which has an elevation between 0 and 2.5 kilometers. You are right though in saying that at some elevation, the bell nozzle likely matches or exceeds the toroidal aerospike (their figures likely only apply to the atmospheric pressure at the location of their test).

[su27k]

Please tell me, Steven, what makes them credible in your mind?

According to some news articles posted online, there was some contention that they were or may have been responsible for the Schiaparelli lander failure (think they probably got cleared because it doesn't match what I have heard about the cause of the failure). In which case, they have done more on Mars than SpaceX has.

You mean ignoring the fact that SpaceX has sent a car well past Mars orbit, or the fact that SpaceX provided NASA with supersonic retro-propulsion data applicable to large Mars lander and saved NASA tens of millions of dollars?

If we want to keep this thread sane, it's best to avoid crazy claims like yours.

[ParabolicSnark]

Please tell me, Steven, what makes them credible in your mind?

According to some news articles posted online, there was some contention that they were or may have been responsible for the Schiaparelli lander failure (think they probably got cleared because it doesn't match what I have heard about the cause of the failure). In which case, they have done more on Mars than SpaceX has.

You mean ignoring the fact that SpaceX has sent a car well past Mars orbit, or the fact that SpaceX provided NASA with supersonic retro-propulsion data applicable to large Mars lander and saved NASA tens of millions of dollars?

If we want to keep this thread sane, it's best to avoid crazy claims like yours.

Was anyone reading their post as a serious assertion that Arca is contributing more towards Mars exploration? Seemed pretty clear it was akin to a Bezos "I got a reusable rocket to space first" jab: technically true, but just technically.

[Steven Pietrobon]

Everyone, now that we have a dedicated thread for ARCA, can we please just stick with the technical side of their progress? That is just concentrate on their engines and rockets and avoid the non-technical comments. Otherwise, this thread will get locked tout suite and I'll have to go post updates in the general thread. :-)

[edzieba]

Is the ARCA 'boiler rocket' operating as a simple resistojet (water in tank is e.g. 99°C, passes through the heating element to raise it to 100°C and release the expanding steam to produce thrust) or as a controlled BLEVE (water in tank heated well above 100°C and pressurised, pressure release triggering phase transition to produce steam and thrust)?