Rocket Lab Neutron rocket - Discussion

[ZachF]

https://twitter.com/RocketLab/status/1862220940391977080


It really is going to be interesting to see what kind of mass ratios they can get with a CF balloon upper stage supported from above. Will probably be counteracted a bit by a large Archimedes engine which doesn't look like it has a very good TWR. from a structural standpoint it's hard to see what could beat this though.

My guess is 3% (1500kg) dry mass. Stage is 50mt wet.
Tanks 400kg, engine 750kg (conservative 1:100 TWR), 350kg for structure avionics etc

100 isn't really conservative for Archimedes, if anything that's probably the opposite... It's probably more like 70-80 TWR, and the vac 60-70.

RD-180 is only in the 80 range, and that's with a fuel ~30% more dense. Physically, the powerhead on the Arichimedes is almost comically large.

I'll try to do a comparison drawing later today.

[TrevorMonty]

Here is size comparision to Rutherford.

https://images.app.goo.gl/DsMF6knyGtnm1fMk6

[ZachF]

Here is size comparision to Rutherford.

https://images.app.goo.gl/DsMF6knyGtnm1fMk6

Here's what I'm talking about with Archimedes having a gigantic powerhead; very rough physical size comparison between Archimedes and Raptor 3:

[TrevorMonty]

Here is size comparision to Rutherford.

https://images.app.goo.gl/DsMF6knyGtnm1fMk6

Here's what I'm talking about with Archimedes having a gigantic powerhead; very rough physical size comparison between Archimedes and Raptor 3:

Amount and type of metal in powerheads should be considerably different as they are operating at different  pressures and power levels.

[DanClemmensen]

Here is size comparision to Rutherford.

https://images.app.goo.gl/DsMF6knyGtnm1fMk6

Here's what I'm talking about with Archimedes having a gigantic powerhead; very rough physical size comparison between Archimedes and Raptor 3:

Amount and type of metal in powerheads should be considerably different as they are operating at different  pressures and power levels.

True, but I think the big difference may be that Raptor 3 is its third iteration while Archimedes is its first iteration. Compare Archimedes to Raptor 1.

[ZachF]

Here is size comparision to Rutherford.

https://images.app.goo.gl/DsMF6knyGtnm1fMk6

Here's what I'm talking about with Archimedes having a gigantic powerhead; very rough physical size comparison between Archimedes and Raptor 3:

Amount and type of metal in powerheads should be considerably different as they are operating at different  pressures and power levels.

I very much doubt Archimedes weighs more than Raptor 3, but my point is that it's probably not a very high TWR engine. The very first thing I noticed about the engine was "dang, that's a big powerhead"

Raptor 3 weighs 1,525kg, my guess is Archimedes probably weighs ~1,000kg, roughly double the weight of Merlin-1D+. That gives it a TWR of ~75, which is roughly the same as the RD-180 or 1C version of Merlin. That probably puts the Archimedes vac at 1100-1200kg.

Here's the M1D+ (470kg) added in, which has a similar chamber pressure and makes ~14% more thrust.

[ZachF]

Here's BE-4 added in... as you can see, the Archimedes powerhead is almost as large as BE4, kinda curious what the reason is for it.

EDIT- found a better Archimedes picture with less fisheye distortion

[TrevorMonty]

Yesterday's youtube investor interview with Peter and Adam. Also on main thread. I followed Dave G first so here is his version. Peter talked a bit on engine testing and future development.

Current V1 is going through flight certification testing. Just like Raptor future versions will be cheaper to build or/and have more performance.
I'd expect new versions very few years along with Neutron block upgades. Every flight will be carrying customer payloads so new versions will have to be flight certified before flying.

[ZachF]

I've been doing pixel measures of some of the recent Neutron cutaways, and it looks like they have shifted a lot of the weight to the upper stage, which makes sense. It looks like the fuel ratio between upper and lower stages is around 3.75:1 (F9 is 4:1). Also lessens the problem of an overpowered upper stage.


GTOW of 480t is known.

My guess for masses are:

S1 fuel: 338t
S1 empty: 35.5t

S2 fuel: 90t
S2 empty: 3.5t

Payload: 13t
GTOW: 480t

 

[ZachF]

Yesterday's youtube investor interview with Peter and Adam. Also on main thread. I followed Dave G first so here is his version. Peter talked a bit on engine testing and future development.

Current V1 is going through flight certification testing. Just like Raptor future versions will be cheaper to build or/and have more performance.
I'd expect new versions very few years along with Neutron block upgades. Every flight will be carrying customer payloads so new versions will have to be flight certified before flying.

There's a lot of room in Neutron for future upgrades.

-Higher pressure/thrust
-Lengthening/stretching
-Superchilling propellant

probably easy 50% increase in payload there

I also suspect they will try to use HIAD and parachutes eventually (ultra low weight upper stage will help here) and go full reuse, combined with the upgrades above they could probably maintain the current pauyload capacity while doing it.

[TrevorMonty]

I've been doing pixel measures of some of the recent Neutron cutaways, and it looks like they have shifted a lot of the weight to the upper stage, which makes sense. It looks like the fuel ratio between upper and lower stages is around 3.75:1 (F9 is 4:1). Also lessens the problem of an overpowered upper stage.


GTOW of 480t is known.

My guess for masses are:

S1 fuel: 338t
S1 empty: 35.5t

S2 fuel: 90t
S2 empty: 3.5t

Payload: 13t
GTOW: 480t

I get about 7.5km/s for S2 with 13t payload which is about right for staging with reuseable booster.