Author Topic: ARCA (Read 152454 times)

launchwatcher · « **Reply #100 on:** 01/21/2021 01:28 pm »

Quote from: Steven Pietrobon on 01/16/2021 01:47 am

Quote from: xyv on 01/16/2021 12:35 am
For an orbital attempt with an engine that leaked before the test last time and still didn't go boom!
The engine did not leak as far as I know. It was the composite propellant tank that leaked. This was replaced with a spherical tank which looks to have been successfully tested with the engine.

Given how much pressure the tank needs to endure in ARCA's device, this is a distinction without a difference; what looks like the propellant tank has a role more like the thrust chamber of a conventional liquid rocket engine, or the casing of a solid rocket motor.

Steven Pietrobon · « **Reply #101 on:** 01/22/2021 04:12 am »

New video. Planning for test next week, depending on the weather. The test will be a short hop using the landing engine (small aerospike engine at the base of the main aerospike engine). Dry mass is 269 kg. It will be loaded with 200 kg of propellant for the test.

EgorBotts · « **Reply #102 on:** 01/22/2021 11:34 am »

According to the replies under their video on youtube, they call it "take off and landing" but it will not actually land, simply hang with the help of the cables.
It could actually more look like a static fire than anything else.

Steven Pietrobon · « **Reply #103 on:** 02/01/2021 05:02 am »

Three new videos from ARCA. They are building two vehicles for the orbital mission in June is called "Mission 10". They also plan on building a kick stage. Test of the first stage using the landing engine is planned for latter this week.

ncb1397 · « **Reply #104 on:** 02/12/2021 07:50 pm »

Episode 6/7/8...

They state in episode 8 a figure of 700 kgf or ~1550 lbf (~ 7 kN). For comparison, the electron first stage is 51,000 lbf. Previously in the ecorocket presentation, they mention a mass of 4,400 kg for the rocket. So, looks subscale (they need at least 6.5x more thrust to clear the pad).

Steven Pietrobon · « **Reply #105 on:** 02/13/2021 02:22 am »

Quote from: ncb1397 on 02/12/2021 07:50 pm

They state in episode 8 a figure of 700 kgf or ~1550 lbf (~ 7 kN). For comparison, the electron first stage is 51,000 lbf. Previously in the ecorocket presentation, they mention a mass of 4,400 kg for the rocket. So, looks subscale (they need at least 6.5x more thrust to clear the pad).

Only the landing engine has a thrust of 6.9 kN. The big main engine (the aerospike engine above the landing engine) has much greater thrust.

The did an 11 second test at 4.4 kN, but has thrust instability due to the vortex created at the valve from the large tank above. The fix is to have a separate smaller tank for the landing engine.

Fmedici · « **Reply #106 on:** 02/28/2021 04:56 am »

Their first launch in June will be from undersea according to the last post on their Facebook page:

Quote

EcoRocket will launch from undersea, in June 2021, through an innovative procedure. In this way we will achieve an exceptional launch flexibility virtually from any sea or ocean, without being dependent of a fixed launch pad.

soltasto · « **Reply #107 on:** 02/28/2021 10:08 am »

They literally used the Sea Dragon scenery from For All Mankind...
Stealing work from Apple doesn't seem smart...

https://twitter.com/TurbulentSphere/status/1365816403987734537

Anyways, the June date is simply not going to happen. They make it sound like launching from the sea is easier, when in reality it's much harder. Leaving aside the of course the fact that they have no chance of going orbital with that rocket for so many other technical reasons.

Lars-J · « **Reply #108 on:** 02/28/2021 05:35 pm »

This sea launch gambit - which won’t happen - is their latest shifting goalposts stage. The moment they get “close” to when real progress needs to be shown (actual flights), they shift gears.

The only “undersea launch” they will demonstrate (much later) is to have have something buoyant tied down underwater, then they cut the cord and it pops up, briefly. Victory declared.

CameronD · « **Reply #109 on:** 02/28/2021 11:20 pm »

Quote from: Lars-J on 02/28/2021 05:35 pm

This sea launch gambit - which won’t happen - is their latest shifting goalposts stage. The moment they get “close” to when real progress needs to be shown (actual flights), they shift gears.

The only “undersea launch” they will demonstrate (much later) is to have have something buoyant tied down underwater, then they cut the cord and it pops up, briefly. Victory declared.

Well, it would certainly be entertaining to watch. Can't wait!

Steven Pietrobon · « **Reply #110 on:** 05/02/2021 07:35 am »

Some forward looking statements by ARCA. Price per kg is $9,750.

"We'll launch the first satellite in 2021. This puts us years ahead of the competition.
Despite out achievements we kept the development cost under $1 million.
The expected cost per launch is at $390,000 for 40 kg of payload.
We plan to deliver 10 launches in the first year of commercial operations."

Steven Pietrobon · « **Reply #111 on:** 05/02/2021 07:38 am »

They're still saying June for their first launch attempt. That's only one to two month's away.

Fmedici · « **Reply #112 on:** 05/02/2021 05:02 pm »

Updates on EcoRocket. I'm even more curious to see it fly.

https://twitter.com/StarshipFairing/status/1388840813971611650

Craftyatom · « **Reply #113 on:** 05/02/2021 06:08 pm »

Quote from: Steven Pietrobon on 05/02/2021 07:35 am

"We'll launch the first satellite in 2021. This puts us years ahead of the competition.
Despite out achievements we kept the development cost under $1 million.
The expected cost per launch is at $390,000 for 40 kg of payload.
We plan to deliver 10 launches in the first year of commercial operations."

Well, never let anyone say that they weren't dreaming big enough.
The development cost is a good data point; it seems to fit with what we've seen.
I hope they do make a launch attempt this year - would be interesting one way or another. That said, and as others have intimated, I'm skeptical of that schedule based on past performance. Testing means results, and the results aren't always good.

trimeta · « **Reply #114 on:** 05/02/2021 08:01 pm »

Quote from: Fmedici on 05/02/2021 05:02 pm

Updates on EcoRocket. I'm even more curious to see it fly.

https://twitter.com/StarshipFairing/status/1388840813971611650

Did they add an extra stage less than two months before their alleged first launch? I think Lars-J summarized their strategy well, always moving the goalposts when it looks like they should have been able to make at least some visible progress on their previous plan.

matthewkantar · « **Reply #115 on:** 05/02/2021 08:43 pm »

Looks like SodaStream^tm has gotten into the launch biz.

Andy Bandy · « **Reply #116 on:** 05/03/2021 12:23 am »

ARCA is the a legacy of the Ansari X Prize. It competed, somehow it still exists despite producing very little. The other legacy is SpaceShipTwo, still trying to carry space tourists almost 17 years later.

trimeta · « **Reply #117 on:** 05/03/2021 10:14 pm »

Someone over on Reddit calculated the delta-v for the new three-stage EcoRocket Produs 2.1, based on the numbers from their latest video. This user concluded that largely due to the underperforming third stage (which is pressure-fed keroxide with a bell nozzle, not a steam-powered aerospike), they're coming in at under 75% the delta-v they'd need to achieve orbit. IANARS, so I can't verify this myself, but if so it rather undermines claims that they'll reach orbit by June. Oddly enough, this user says that the two-stage EcoRocket seemed to be significantly closer (over 90% the delta-v needed to reach orbit), but it had a substantially larger keroxide final stage.

ncb1397 · « **Reply #118 on:** 05/04/2021 12:43 am »

Quote from: trimeta on 05/03/2021 10:14 pm

Someone over on Reddit calculated the delta-v for the new three-stage EcoRocket Produs 2.1, based on the numbers from their latest video. This user concluded that largely due to the underperforming third stage (which is pressure-fed keroxide with a bell nozzle, not a steam-powered aerospike), they're coming in at under 75% the delta-v they'd need to achieve orbit. IANARS, so I can't verify this myself, but if so it rather undermines claims that they'll reach orbit by June. Oddly enough, this user says that the two-stage EcoRocket seemed to be significantly closer (over 90% the delta-v needed to reach orbit), but it had a substantially larger keroxide final stage.

yeah, using the same ISP numbers of 319 and 80 used in that reddit post and saying they need 9250 m/s+, I get a payload of 2 kg...

ln((2+180)/(2+16)) * 9.8 * 319 + ln((2+180+820)/(2+180+80)) * 9.8 * 80 + ln((2+180+820+4020)/(2+180+820+420)) * 9.8 * 80 = 9274 m/s

Although, if we give ARCA the benefit of the doubt and suggest that all dry mass numbers are rounded up and the wet mass is rounded down. And we also use 90 for water isp and 329 for kerosene+peroxide isp.... I get a payload of about 6-7 kg...

ln((6+184.9)/(6+15.5)) * 9.81 * 329 + ln((6+184.9+824.9)/(6+184.9+75)) * 9.81 * 90 + ln((6+184.9+824.9+4024.9)/(6+184+824.9+415)) * 9.81 * 90 = 9344 m/s

If we go even farther and suggest they are using an equatorial launch site, they probably only need 9 km/s even. That should bump them up to 8-9 kg.

Although, the 11,300 kgf liftoff thrust and 5020 kg liftoff weight is rather high at >2 thrust to weight at launch. So, maybe those rules of thumb in terms of delta-v required to reach LEO don't exactly apply. You really only need about 7.3 km/s of additional velocity if you launch from the equator. The difference between the 9 km/s and the 7.3 km/s is usual aero and gravity losses.

edit: Here we go for burn times. I get mass flow rates for first stage flight of 125 kg/second. That means the 3600 kg of propellant in the first stage would be consumed in ~29 seconds(assuming for simplicity static thrust and isp of 90). For second stage flight, I get mass flow rates of ~18 kg/second which means the second stage burn time is ~41 seconds. Third stage flight would be 1.2 kg/second and burn times of 137 seconds. Total is 207 seconds or 3.5 minutes. That is quick ride to orbit. For reference, just looked at the last starlink mission to LEO and SECO-1 was at 9 minutes or so. So, maybe they totally miss their payload numbers but arguably all they have to do is put a tennis ball or equivalent into orbit to turn heads.

Steven Pietrobon · « **Reply #119 on:** 05/08/2021 04:48 am »

Latest video. They will be launching from "in" the Black Sea! Second launch is planned for September 2021.