ARCA

[Lars-J]

And the training was just a crane holding the mock-up above water in horizontal position? [Borat]Great success![/Borat]

[ncb1397]

And the training was just a crane holding the mock-up above water in horizontal position? [Borat]Great success![/Borat]

No, the rocket was lowered into the water...

[Asteroza]

Is the rocket they're floating the flight article, or the boilerplate version? (pun intended)

[CameronD]

In that video they mention "August 16-30" as their target date for launch.

[russianhalo117]

Is the rocket they're floating the flight article, or the boilerplate version? (pun intended)

A future KSP2 DLC.

[Lars-J]

And the training was just a crane holding the mock-up above water in horizontal position? [Borat]Great success![/Borat]

No, the rocket was lowered into the water...

Thanks! I had assumed that images attached to their Facebook post would show the most significant part of the test, but I guess not.

They did at least show a mechanism (with release?) for holding the “rocket” vertical. Although very unstable.

My earlier prediction remains… they’ll do another test where they release it to pop up out of the water, maybe with an unguided lit first stage, then declare victory and move the goalposts to the next idea.

[Davidthefat]

Have they even showed that their water rocket produced more thrust than what their two stage weighs? I remember last time, it looked like it didn't produce sufficient amount of thrust for even 1 stage.

[darkenfast]

It will also be interesting to see how low that thing floats when it's fueled. Unless they have separate flotation, it will be way deeper. I'm not sure how that will affect the already low-performance of the first stage.

[daedalus1]

It will also be interesting to see how low that thing floats when it's fueled. Unless they have separate flotation, it will be way deeper. I'm not sure how that will affect the already low-performance of the first stage.

It'll sink as the density will be above 1.

[ncb1397]

It will also be interesting to see how low that thing floats when it's fueled. Unless they have separate flotation, it will be way deeper. I'm not sure how that will affect the already low-performance of the first stage.

It'll sink as the density will be above 1.

I assume you mean 1 t/cubic meter. Technically this is salt water though, so somewhat higher water density could be expected (1 - 1.05 t/cubic meter). They may leave air pockets in each tank. They could also rely on the temperature of the water in the first 2 stages to help maintain bouyancy or air bags after up-righting. Plenty of ways to solve this I think.

[daedalus1]

Also no one has suggested a way of superheating water in a pressure tank surrounded by a cold ocean.

[Asteroza]

Also no one has suggested a way of superheating water in a pressure tank surrounded by a cold ocean.

You don't? I assumed most of the superheated water would be provided externally via a boiler mounted on deck? Otherwise you are putting heating elements on the rocket, making it even heavier...

[trimeta]

Also no one has suggested a way of superheating water in a pressure tank surrounded by a cold ocean.

You don't? I assumed most of the superheated water would be provided externally via a boiler mounted on deck? Otherwise you are putting heating elements on the rocket, making it even heavier...

I thought "putting heating elements on the rocket" was exactly what they were doing. With the only concession to weight savings being that the first stage doesn't use onboard batteries for power, but rather heats those elements using electricity provided by ground support equipment. I'm not sure about the second stage, I know having onboard batteries to provide electricity was discussed at one point, but I don't know if the current three-stage design uses that or ground-supplied electricity for the second stage.

[daedalus1]

It will also be interesting to see how low that thing floats when it's fueled. Unless they have separate flotation, it will be way deeper. I'm not sure how that will affect the already low-performance of the first stage.

It'll sink as the density will be above 1.

I assume you mean 1 t/cubic meter. Technically this is salt water though, so somewhat higher water density could be expected (1 - 1.05 t/cubic meter). They may leave air pockets in each tank. They could also rely on the temperature of the water in the first 2 stages to help maintain bouyancy or air bags after up-righting. Plenty of ways to solve this I think.

So far we've got a low isp engine with only partially filled tanks (so it doesn't sink), heating the water to superheated with electic elements while submerged in a cold ocean lol. If this thing gets more than 100 feet in the air it'll be a miracle.
This is a scam.

[edzieba]

The fundamental principle of thrust from phase transition is not 'fake' (take a fluid heated to almost boiling by ground power, then give it the last few joules needed to boil by electric heaters from onboard power as it enters the nozzle) but pretty much all the operations wrapped around that core concept by Arca are not those conducive to actually achieving anything useful. ISP is awful, so your booster needs to be very very big indeed to compensate for being so exceedingly dumb in order to even hope to achieve orbit (let alone with a payload).

[Beratnyi]

The fundamental principle of thrust from phase transition is not 'fake' (take a fluid heated to almost boiling by ground power, then give it the last few joules needed to boil by electric heaters from onboard power as it enters the nozzle) but pretty much all the operations wrapped around that core concept by Arca are not those conducive to actually achieving anything useful. ISP is awful, so your booster needs to be very very big indeed to compensate for being so exceedingly dumb in order to even hope to achieve orbit (let alone with a payload).

The ARCA approach is very smart for the following reasons:
1) This makes it very easy to make an SSTO, since it is not entirely correct to take into account the water stages
2) Water stages are actually cheap analogs of non-rocket launch systems such as space cannon, spin launch, hypersonic air launch, etc.
3) This allows you to reduce the rocket launch noise to a minimum, which will greatly help in P2P transportation
4) It becomes very easy to ensure reusability when you do not have intense chemical reactions in the engine and there are no turbo pumps.
5) The cost of developing and operating water stages is incredibly cheap, since there is no complex thermodynamics, explosion hazard, toxic, cryogenics, etc.

[joek]

The ARCA approach is very smart for the following reasons:
1) This makes it very easy to make an SSTO, since it is not entirely correct to take into account the water stages
2) Water stages are actually cheap analogs of non-rocket launch systems such as space cannon, spin launch, hypersonic air launch, etc.
...

Stages are stages, regardless of the technology. The "water stages" are stages. This is not, nor will ever be, SSTO any more than Virgin Orbit would be considered SSTO (assuming they could get to a single stage). Get rid of the "water stages" and you might have an SSTO argument; otherwise not.

[Beratnyi]

The ARCA approach is very smart for the following reasons:
1) This makes it very easy to make an SSTO, since it is not entirely correct to take into account the water stages
2) Water stages are actually cheap analogs of non-rocket launch systems such as space cannon, spin launch, hypersonic air launch, etc.
...

Stages are stages, regardless of the technology. The "water stages" are stages. This is not, nor will ever be, SSTO any more than Virgin Orbit would be considered SSTO (assuming they could get to a single stage). Get rid of the "water stages" and you might have an SSTO argument; otherwise not.

Think of this as a task of using electricity for the initial overclocking of the SSTO. This can be done in several ways:
1) Use a complex, expensive and ineffective electromagnetic cannon to fire a rocket with large overloads
2) Use a centrifuge to spin the rocket to a crazy rotation and launch, again with large overloads
3) Use an ultra-expensive array of lasers to heat the propellant in the rocket tank
4) Use an electric supersonic aircraft for air launch, which is still pure fantastic
5) Use a composite tank with water heated to 250C and under a pressure of 40 atmospheres. After starting, lower the tank by parachute, refill with water and use again
I think it becomes obvious which way is the smartest.

[Redclaws]

The ARCA approach is very smart for the following reasons:
1) This makes it very easy to make an SSTO, since it is not entirely correct to take into account the water stages
2) Water stages are actually cheap analogs of non-rocket launch systems such as space cannon, spin launch, hypersonic air launch, etc.
...

Stages are stages, regardless of the technology. The "water stages" are stages. This is not, nor will ever be, SSTO any more than Virgin Orbit would be considered SSTO (assuming they could get to a single stage). Get rid of the "water stages" and you might have an SSTO argument; otherwise not.

Think of this as a task of using electricity for the initial overclocking of the SSTO. This can be done in several ways:
1) Use a complex, expensive and ineffective electromagnetic cannon to fire a rocket with large overloads
2) Use a centrifuge to spin the rocket to a crazy rotation and launch, again with large overloads
3) Use an ultra-expensive array of lasers to heat the propellant in the rocket tank
4) Use an electric supersonic aircraft for air launch, which is still pure fantastic
5) Use a composite tank with water heated to 250C and under a pressure of 40 atmospheres. After starting, lower the tank by parachute, refill with water and use again
I think it becomes obvious which way is the smartest.

Ok, but……. It’s a stage.  It’s literally a set of tanks full of something used to propel the rocket which is dropped while other parts of it continue.

[Beratnyi]

The ARCA approach is very smart for the following reasons:
1) This makes it very easy to make an SSTO, since it is not entirely correct to take into account the water stages
2) Water stages are actually cheap analogs of non-rocket launch systems such as space cannon, spin launch, hypersonic air launch, etc.
...

Stages are stages, regardless of the technology. The "water stages" are stages. This is not, nor will ever be, SSTO any more than Virgin Orbit would be considered SSTO (assuming they could get to a single stage). Get rid of the "water stages" and you might have an SSTO argument; otherwise not.

Think of this as a task of using electricity for the initial overclocking of the SSTO. This can be done in several ways:
1) Use a complex, expensive and ineffective electromagnetic cannon to fire a rocket with large overloads
2) Use a centrifuge to spin the rocket to a crazy rotation and launch, again with large overloads
3) Use an ultra-expensive array of lasers to heat the propellant in the rocket tank
4) Use an electric supersonic aircraft for air launch, which is still pure fantastic
5) Use a composite tank with water heated to 250C and under a pressure of 40 atmospheres. After starting, lower the tank by parachute, refill with water and use again
I think it becomes obvious which way is the smartest.

Ok, but……. It’s a stage.  It’s literally a set of tanks full of something used to propel the rocket which is dropped while other parts of it continue.

The rocket stages are different. For example, a hydrogen-oxygen stage with a turbopump closed cycle engine is very different from a kerosene-peroxide stage with a pressure-fed engine. The second option is to make the SSTO almost impossible without the initial acceleration and the water stage is the best option for this.