Author Topic: ARCA  (Read 132928 times)

Offline ncb1397

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Re: ARCA
« Reply #20 on: 02/04/2020 01:41 pm »
Is the ARCA 'boiler rocket' operating as a simple resistojet (water in tank is e.g. 99C, passes through the heating element to raise it to 100C and release the expanding steam to produce thrust) or as a controlled BLEVE (water in tank heated well above 100C and pressurised, pressure release triggering phase transition to produce steam and thrust)?

In this video at ~5:30...



They show a boiling point diagram with pressure vs temperature to explain the temperature of the tank. This suggests they pressurize the tank and then keep the bulk liquid below the boiling point at that pressure. Evaporation then occurs when the pressure drops.

Online launchwatcher

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Re: ARCA
« Reply #21 on: 02/04/2020 03:56 pm »
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. :-)
Steven,

One thing which IMHO discourages focused technical discussion is posting videos without adding any text of your own.

Wherever you post these videos, can you at least give us a paragraph or two abstract with the key claims and numbers from each video?   

Offline ringsider

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Re: ARCA
« Reply #22 on: 02/05/2020 06:30 am »
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. :-)
Genuine question: why just tech? These forums are general discussion, so as long as it's on topic and factual what is the issue discussing financing, business, customers, founders etc? That's like saying "no talking about Elon Musk" in a SpaceX forum.
« Last Edit: 02/05/2020 06:30 am by ringsider »

Offline Danirode

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Re: ARCA
« Reply #23 on: 02/05/2020 11:46 am »
In their White Paper they say that the booster will separate @3000m and at ~mach1.2. What kind of performace boost do they expect to obtain for the second stage? How much dV will it spare to te second stage?

Also, they are investing money in developing a first stage that will bring the LV to just 3km in height, I know that the design is much (much much) simpler than a traditional first stage rocket, but yet, it seems that they are spending money for a very little gain in terms of performance.

Offline niwax

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Re: ARCA
« Reply #24 on: 02/05/2020 07:12 pm »
In their White Paper they say that the booster will separate @3000m and at ~mach1.2. What kind of performace boost do they expect to obtain for the second stage? How much dV will it spare to te second stage?

Also, they are investing money in developing a first stage that will bring the LV to just 3km in height, I know that the design is much (much much) simpler than a traditional first stage rocket, but yet, it seems that they are spending money for a very little gain in terms of performance.

It has the same ring to it as air launch startups. They release at lower speed but higher altitude and I have same questions about them. All of the air launch concept so far have still thrown away multiple stages, making them not much better than any other two-stage rocket launched from a dirt pad.
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Re: ARCA
« Reply #25 on: 02/05/2020 07:34 pm »
In their White Paper they say that the booster will separate @3000m and at ~mach1.2. What kind of performace boost do they expect to obtain for the second stage? How much dV will it spare to te second stage?

Also, they are investing money in developing a first stage that will bring the LV to just 3km in height, I know that the design is much (much much) simpler than a traditional first stage rocket, but yet, it seems that they are spending money for a very little gain in terms of performance.

It sounds like the same kind of benefit as any strap-on booster. This is just a steam rocket rather than a solid booster.

From the white paper: "Regarding ARCAs Haas 2CA SSTO rocket, this vehicle was designed with the capability to put 100kg into LEO in a single stage, for a take-off mass of 16,000 kg. The use of a 18,000kg LAS 50E booster would offer a reduction of mass of the Haas 2CA rocket from 16t to 6t, while keeping the payload capability. Another example is also related to the Haas 2CA rocket. Adding a 40t LAS 200E booster to the existing configuration would increase the payload capability of the rocket from 100 kg to 700 kg"
"One bit of advice: it is important to view knowledge as sort of a semantic tree -- make sure you understand the fundamental principles, ie the trunk and big branches, before you get into the leaves/details or there is nothing for them to hang on to." - Elon Musk
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Offline ncb1397

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Re: ARCA
« Reply #26 on: 02/05/2020 08:52 pm »
In their White Paper they say that the booster will separate @3000m and at ~mach1.2. What kind of performace boost do they expect to obtain for the second stage? How much dV will it spare to te second stage?

Also, they are investing money in developing a first stage that will bring the LV to just 3km in height, I know that the design is much (much much) simpler than a traditional first stage rocket, but yet, it seems that they are spending money for a very little gain in terms of performance.

It has the same ring to it as air launch startups. They release at lower speed but higher altitude and I have same questions about them. All of the air launch concept so far have still thrown away multiple stages, making them not much better than any other two-stage rocket launched from a dirt pad.

Just compare the size and payload capability of launcher one compared to electron. Launcher one is about 50% bigger by volume but has 130% more max payload to orbit.  That is with staging at subsonic speeds. This sounds like it is targeted for somewhere between mach 1 and 2 so the benefit will be even greater (if they can get it to work).

edit: Just to do a gut check, the energy density of 250 degrees C water is about 300 watt hours per kilogram. About the same or better than lithium ion batteries. So, it makes about as much sense as Musk's VTOL supersonic electric plane. Or to look at this another way, the kinectic energy equivalent of the same 300 watt hour per kilogram density is an object moving at 1.5 km/s.
« Last Edit: 02/05/2020 09:25 pm by ncb1397 »

Offline Steven Pietrobon

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Re: ARCA
« Reply #27 on: 07/31/2020 10:50 am »
ARCA have posted 19 situation reports on their Mission 9 flight in the last three weeks. Here's the first one.

Akin's Laws of Spacecraft Design #1:  Engineering is done with numbers.  Analysis without numbers is only an opinion.

Offline Steven Pietrobon

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Re: ARCA
« Reply #28 on: 07/31/2020 10:55 am »
They've built a large dynamic test stand.

Roll control thrusters.

LAS 25DA engine.

Tank connected to engine. They plan to perform tethered vertical ascent and landing in the test stand to calibrate thruster control.

Flight Command Centre?!

Roll control thrusters on main engine.

Flight Readiness Review on 8 August.

Connecting the heater elements.
« Last Edit: 07/31/2020 11:37 am by Steven Pietrobon »
Akin's Laws of Spacecraft Design #1:  Engineering is done with numbers.  Analysis without numbers is only an opinion.

Offline xyv

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Re: ARCA
« Reply #29 on: 08/02/2020 12:55 am »
Is this still a water/steam rocket?  But back to (sort of)  the aerospike - in this case radially symmetric.  Glad to see these guys back...they're fun to watch and don't burn through anywhere near the cash that Vector did...meaning they can hopefully entertain for longer.

Offline ChrisWilson68

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Re: ARCA
« Reply #30 on: 08/02/2020 02:34 am »
An aerospike for an engine that will only operate from the ground to an altitude of 3 km?  Did I get that right?

That doesn't make any sense.

Offline Steven Pietrobon

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Re: ARCA
« Reply #31 on: 08/02/2020 04:22 am »
Yes, this is still a water/steam bottle rocket.

Yes, the altitude reached by these boosters is only 3 km just before separation. The velocity at separation is 390 m/s. Read their white paper to see how their system works.

https://www.arcaspace.com/docs/ARCA_LAS_White_Paper_January_14_2020_Issue_2.pdf
Akin's Laws of Spacecraft Design #1:  Engineering is done with numbers.  Analysis without numbers is only an opinion.

Offline brickmack

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Re: ARCA
« Reply #32 on: 08/02/2020 05:52 pm »
That paper is amazing. My favorite part was when they mention commonality between this vehicle and ArcaBoard.

Offline Davidthefat

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Re: ARCA
« Reply #33 on: 08/07/2020 03:50 am »
That paper is amazing. My favorite part was when they mention commonality between this vehicle and ArcaBoard.

So they are controlling the rocket with an Arduino?

Offline Steven Pietrobon

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Re: ARCA
« Reply #34 on: 08/12/2020 03:50 am »
Several more reports have been posted, to 24. Pitch and yaw control is achieved using differential thrust from the aerospike engine. The flight readiness review (FRR) has been delayed from 8 August to 17 August, as hot weather is limiting work on the vehicle to six hours per day (6 am to 12 pm).
Akin's Laws of Spacecraft Design #1:  Engineering is done with numbers.  Analysis without numbers is only an opinion.

Offline Steven Pietrobon

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Re: ARCA
« Reply #35 on: 09/01/2020 09:02 am »
Motor has been lifted into the stand and secured, with power and signal connections connected to the base. The FRR is scheduled for next week.

Akin's Laws of Spacecraft Design #1:  Engineering is done with numbers.  Analysis without numbers is only an opinion.

Offline GWH

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Re: ARCA
« Reply #36 on: 09/01/2020 10:17 pm »
I'm not following this super close... but is there plan to do a "hot fire" (steamy fire?) with the vehicle secured to the ground with ropes? Then more ropes on the side to stabilize it? All of which is in or very close to the exhaust path?

Offline Gliderflyer

Re: ARCA
« Reply #37 on: 09/01/2020 11:07 pm »
I'm not following this super close... but is there plan to do a "hot fire" (steamy fire?) with the vehicle secured to the ground with ropes? Then more ropes on the side to stabilize it? All of which is in or very close to the exhaust path?

Looks like it, but it shouldn't be too big of a problem (depending on the rope). I don't know how hot they are running, but I bet it is under 500K in the tank. It will cool rapidly as it expands, so by the time it gets to the end of the spike it could be down to around 212F.
I tried it at home

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Re: ARCA
« Reply #38 on: 09/02/2020 03:53 am »
I'm not following this super close... but is their plan to do a "hot fire" (steamy fire?) with the vehicle secured to the ground with ropes? Then more ropes on the side to stabilize it? All of which is in or very close to the exhaust path?
Given how flimsy the "test stands" look are you surprised by this?

Offline GWH

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Re: ARCA
« Reply #39 on: 09/02/2020 04:43 am »
Given how flimsy the "test stands" look are you surprised by this?

The only thing that really surprises me is that they still exist.

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