Author Topic: ARCA Space Corporation  (Read 11686 times)

Online sevenperforce

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Re: ARCA Space Corporation
« Reply #40 on: 04/04/2017 12:30 PM »
HTP is also cheaper than LOX, and while it has its own handling challenges, it's less challenging from a materials standpoint than LOX.

I'm pretty sure rocket grade HTP is more expensive than LOX. 85% HTP costs $8.27/kg in a 30 kg lot, although should come down for higher volumes. Google says that LOX is $0.16/kg.

http://www.peroxidepropulsion.com/hydrogen-peroxide.php

With a propellant mass of 15,640 kg and a mixture ratio of 8.2 to 1 (the same as the British Gamma engine), that gives a HTP mass of 13,940 kg and a upper bound of the cost of $115,284.
Well, color me surprised.

Well, Electron also isn't SSTO, so it has far more margin to play with.
A fair point. Taking the dry mass of nine battery packs and pumps all the way to orbit probably would have tanked the efficiency advantage.

Plus, doesn't the electron need helium pressurant anyway to maintain ullage pressure?

Offline Davidthefat

Re: ARCA Space Corporation
« Reply #41 on: 04/05/2017 10:34 PM »
Their latest "plan" to use tanks as habitats once in orbit...

https://www.facebook.com/arcaspace/photos/a.225583008331.177238.225552438331/10155952223343332/?type=1&theater

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Online Gliderflyer

Re: ARCA Space Corporation
« Reply #42 on: 04/06/2017 01:11 AM »
Their latest "plan" to use tanks as habitats once in orbit...

https://www.facebook.com/arcaspace/photos/a.225583008331.177238.225552438331/10155952223343332/?type=1&theater

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While I am a fan of wet workshops, this is laughable. Those tanks are only ~5 feet in diameter. As depicted, I doubt a person could even fit through the docking port.
I tried it at home

Offline GWH

Re: ARCA Space Corporation
« Reply #43 on: 04/06/2017 01:58 PM »
Quote from: sevenperforce
A fair point. Taking the dry mass of nine battery packs and pumps all the way to orbit probably would have tanked the efficiency advantage.

Plus, doesn't the electron need helium pressurant anyway to maintain ullage pressure?

The whole trade is based on the increased mass required for thicker tank walls for all the propellant at a higher pressure,  not just a couple helium bottles. That mass is going to orbit in either scenario.

Offline josespeck

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Re: ARCA Space Corporation
« Reply #44 on: 04/08/2017 04:12 PM »
Quote from: sevenperforce
A fair point. Taking the dry mass of nine battery packs and pumps all the way to orbit probably would have tanked the efficiency advantage.

Plus, doesn't the electron need helium pressurant anyway to maintain ullage pressure?

The whole trade is based on the increased mass required for thicker tank walls for all the propellant at a higher pressure,  not just a couple helium bottles. That mass is going to orbit in either scenario.

What is the equation for tank thickness?.
What is the thickness of the Falcon9 tank and other?.

Offline Katana

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Re: ARCA Space Corporation
« Reply #45 on: 04/09/2017 03:03 AM »
Looking for red flags in these specs:

Length: 16 m
Diameter: 1.5 m
Dry mass: 550 kg
Launch mass: 16,290 kg
Payload mass: 100 kg
Engine: Pressure-fed linear aerospike
Nozzle: 80:1 expansion ratio, 80% cut
Engine coolant & pressurant: Liquid helium
Number of chambers: 16
Nozzle cooling: Ablative + RP-1 film
Propellant: HTP + RP-1
Burn duration: 272 s
Thrust (SL): 22,920 kgf
Thrust (vac): 33,500 kgf
Isp (SL): 230 s
Isp (vac): 314 s
Propellant flow rate: 100 kg/s
Mixture ratio: 7.46:1
Tank pressure: 20 barg
Chamber pressure: 16 barg

Gas generator pump fed , not pressure fed.
https://en.m.wikipedia.org/wiki/Executor_(rocket_engine)

Offline catdlr

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Re: ARCA Space Corporation
« Reply #46 on: 04/10/2017 04:55 PM »
This one-of-a-kind rocket is designed to reach space in just 5 minutes

Tech Insider

Published on Apr 10, 2017
This rocket is about to change space travel. The Haas 2CA rocket is designed by the ARCA Space Corporation. It's set to be the cheapest rocket of its kind and could get to space faster and cheaper than similar rockets, today.

https://www.youtube.com/watch?v=hcjXvjYRLRE?t=001

Tony De La Rosa

Online matthewkantar

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Re: ARCA Space Corporation
« Reply #47 on: 04/10/2017 05:19 PM »
This seems to be a CG illustration of a linear aerospike on a pallet jack?

Offline ChrisWilson68

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Re: ARCA Space Corporation
« Reply #48 on: 04/10/2017 06:05 PM »
This one-of-a-kind rocket is designed to reach space in just 5 minutes

Tech Insider

Published on Apr 10, 2017
This rocket is about to change space travel. The Haas 2CA rocket is designed by the ARCA Space Corporation. It's set to be the cheapest rocket of its kind and could get to space faster and cheaper than similar rockets, today.

Wow, Tech Insider just believed all the fantasy ARCA claimed without any attempt to verify any of it or get opinions from outside experts.  Sad.  They present themselves as journalists, but clearly there's no journalism going on here.

The focus on 5 minutes to orbit instead of 8 is also really bizarre -- as if that matters in any way whatsoever.

Online Welsh Dragon

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Re: ARCA Space Corporation
« Reply #49 on: 04/10/2017 07:17 PM »
Bit disingenuous to use footage of XRS-2200 when talking about their engine. Anyone would think they've testfired it already.

Offline ringsider

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Re: ARCA Space Corporation
« Reply #50 on: 04/10/2017 08:20 PM »
This one-of-a-kind rocket is designed to reach space in just 5 minutes

Tech Insider

Published on Apr 10, 2017
This rocket is about to change space travel. The Haas 2CA rocket is designed by the ARCA Space Corporation. It's set to be the cheapest rocket of its kind and could get to space faster and cheaper than similar rockets, today.

Wow, Tech Insider just believed all the fantasy ARCA claimed without any attempt to verify any of it or get opinions from outside experts.  Sad.  They present themselves as journalists, but clearly there's no journalism going on here.

The focus on 5 minutes to orbit instead of 8 is also really bizarre -- as if that matters in any way whatsoever.
This is why PR like this and the stories put out by Vector are so insidious. Now any serious company will be held to this "benchmark" by less well-informed investors, making genuine technology look worse.

These people hurt themselves and everybody else.

Offline Steven Pietrobon

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Re: ARCA Space Corporation
« Reply #51 on: 04/11/2017 07:18 AM »
The focus on 5 minutes to orbit instead of 8 is also really bizarre -- as if that matters in any way whatsoever.

It helps a lot, since gravity losses are reduced, meaning less delta-V is required to reach orbit.
Akin's Laws of Spacecraft Design #1:  Engineering is done with numbers.  Analysis without numbers is only an opinion.

Offline as58

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Re: ARCA Space Corporation
« Reply #52 on: 04/11/2017 01:48 PM »
I'm starting to think that ARCA is actually a video/CGI production company that likes to advertise by making videos of fanciful rockets.

Online envy887

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Re: ARCA Space Corporation
« Reply #53 on: 04/11/2017 02:26 PM »
The focus on 5 minutes to orbit instead of 8 is also really bizarre -- as if that matters in any way whatsoever.

It helps a lot, since gravity losses are reduced, meaning less delta-V is required to reach orbit.

The higher acceleration needed to reach orbit faster is apparently just due to the higher thrust of a SSTO, which has a TWR of 3 to 6 in the flight regime where a TSTO upper stage has a TWR of 0.6 to 0.9.

But the SSTO has considerably worse mass fractions compared to a TSTO after staging, so the reduced gravity loss isn't a net win: payload as a fraction of GLOM is still very low. And burnout acceleration is extremely high... 10 to 15g, perhaps higher if unthrottled?

Offline Davidthefat

Re: ARCA Space Corporation
« Reply #54 on: 04/11/2017 04:22 PM »
I'm starting to think that ARCA is actually a video/CGI production company that likes to advertise by making videos of fanciful rockets.

The CGI isn't even that good honestly...

Offline ChrisWilson68

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Re: ARCA Space Corporation
« Reply #55 on: 04/11/2017 04:48 PM »
The focus on 5 minutes to orbit instead of 8 is also really bizarre -- as if that matters in any way whatsoever.

It helps a lot, since gravity losses are reduced, meaning less delta-V is required to reach orbit.

That's at best an internal advantage, not an external advantage.  What I mean is that at best that helps them with something else that would matter to a payload.  For example, if it meant less propellant, maybe that means less cost.  It's the less cost that actually matters.  So taking less time to get to orbit isn't by itself something that matters, it's, at best, an aid in something else that actually matters.  So it's not something that justifies being trumpeted as an advantage of ARCA's proposed launch system.  If it helps them lower costs, let them claim the lower costs.

As another poster pointed out, this is just one factor and optimizing for lower time to orbit might bring disadvantages that more than make up for the reduced gravity losses.  Other launch providers have made different trade-offs, so others seem to think it's better to have the higher gravity losses in exchange for other benefits.

Online FutureSpaceTourist

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Re: ARCA Space Corporation
« Reply #56 on: 04/20/2017 06:31 AM »

Offline ChrisWilson68

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Re: ARCA Space Corporation
« Reply #57 on: 04/20/2017 08:07 AM »
Another ARCA piece:

http://krqe.com/2017/04/18/new-mexico-rocket-seeks-historic-first/

The article says "Between the engine and the fuels, Popescu says his engine is 30 percent more fuel efficient than today’s traditional engines."  Anyone have any idea how they justify that?

That unbelievable claim comes right after the article says, "ARCA also does away with cryogenic fuels, the traditional super-cold liquid hydrogen and oxygen used by many space vehicles today. Instead, the Haas 2CA will use kerosene and hydrogen peroxide, which do not need to be kept cold."  Which seems to imply that they're claiming 30% better Isp than hydrolox for kerosene and hydrogen peroxide.

Offline Steven Pietrobon

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Re: ARCA Space Corporation
« Reply #58 on: 04/21/2017 06:44 AM »
The article says "Between the engine and the fuels, Popescu says his engine is 30 percent more fuel efficient than today’s traditional engines."  Anyone have any idea how they justify that?

Maybe they meant impulse density? HTP/Kero can be have up to 15% greater impulse density than LOX/Kero.
Akin's Laws of Spacecraft Design #1:  Engineering is done with numbers.  Analysis without numbers is only an opinion.

Online savuporo

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Re: ARCA Space Corporation
« Reply #59 on: 04/21/2017 06:56 AM »
Maybe they meant impulse density? HTP/Kero can be have up to 15% greater impulse density than LOX/Kero.

I don't think that's what they meant. I highly doubt anyone of that team speaks rocket.
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