Author Topic: Rocket Lab Neutron rocket - Discussion  (Read 408991 times)

Offline whitelancer64

Re: Rocket Lab Neutron rocket - Discussion
« Reply #1480 on: 09/28/2022 08:42 pm »
*snip*
And today we can develop engines faster and cheaper than before. In the long run it could be a better choice.

I don't know if that's true. 6-10 years from concept to first flight attempt has been approximately how long it takes to develop a rocket engine since the 1960s.

I think the perception that we can develop engines faster comes from all the small launch companies. I think the reality is that we've always developed smaller engines faster.

Smaller engines somewhat faster, larger engines take longer, yeah.

As examples, both the RL-10 and the J-2 took about 6 years from start of development to first launch. The F-1 took about 10 years.

The SpaceX Merlin 1A was 6 years.

Rocket Lab's Rutherford took 4 years, as an example of a smaller engine taking less time.
« Last Edit: 09/28/2022 08:44 pm by whitelancer64 »
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Offline trimeta

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Re: Rocket Lab Neutron rocket - Discussion
« Reply #1481 on: 09/28/2022 09:23 pm »
The engines have such different roles that it is a bit of a compromise to force one engine to do everything.
Actually, during the Investor Day presentation, Beck seemed to be saying that the requirements for a second-stage engine and a first-stage engine capable of propulsive landing are similar. E.g., if you've given your first-stage engines enough throttle range that you can land the stage by lighting up one of the nine at minimum throttle, that's about what you'd need for the second-stage engine anyway.

Offline Kaputnik

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Re: Rocket Lab Neutron rocket - Discussion
« Reply #1482 on: 09/28/2022 10:18 pm »
The engines have such different roles that it is a bit of a compromise to force one engine to do everything.
Actually, during the Investor Day presentation, Beck seemed to be saying that the requirements for a second-stage engine and a first-stage engine capable of propulsive landing are similar. E.g., if you've given your first-stage engines enough throttle range that you can land the stage by lighting up one of the nine at minimum throttle, that's about what you'd need for the second-stage engine anyway.

Sure it's possible to get the thrust requirement to match up, you just need to use the right number of engines.
You could also have a dedicated landing engine on the first stage (he talked about that in the very early Neutron days).
But fundamentally one engine design is being reused and the other is being expended. In the emerging launch market the disposable upper stage cost is going to be a huge driver for Neutron's costs, and it makes sense for its engine to be as cheap as possible. A constraint which does not apply to the first stage.
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Online matthewkantar

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Re: Rocket Lab Neutron rocket - Discussion
« Reply #1483 on: 09/29/2022 04:08 am »
But fundamentally one engine design is being reused and the other is being expended. In the emerging launch market the disposable upper stage cost is going to be a huge driver for Neutron's costs, and it makes sense for its engine to be as cheap as possible. A constraint which does not apply to the first stage.

Wait a sec, there is an expendable upper stage on Neutron?

Online TrevorMonty

Re: Rocket Lab Neutron rocket - Discussion
« Reply #1484 on: 09/29/2022 04:47 am »
But fundamentally one engine design is being reused and the other is being expended. In the emerging launch market the disposable upper stage cost is going to be a huge driver for Neutron's costs, and it makes sense for its engine to be as cheap as possible. A constraint which does not apply to the first stage.

Wait a sec, there is an expendable upper stage on Neutron?
That was RL plan from day one but they are not discounting reuseable US. The problem with reuseable US in this LV class high payload penalty, suddenly a 13t LV becomes 10t at a guess. If $kg is $2k then that is $6M of lost performance which could pay for expendable US that doesn't need refurbishing.


« Last Edit: 09/29/2022 04:50 am by TrevorMonty »

Offline trimeta

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Re: Rocket Lab Neutron rocket - Discussion
« Reply #1485 on: 09/29/2022 06:31 am »
But fundamentally one engine design is being reused and the other is being expended. In the emerging launch market the disposable upper stage cost is going to be a huge driver for Neutron's costs, and it makes sense for its engine to be as cheap as possible. A constraint which does not apply to the first stage.

Wait a sec, there is an expendable upper stage on Neutron?
That was RL plan from day one but they are not discounting reuseable US. The problem with reuseable US in this LV class high payload penalty, suddenly a 13t LV becomes 10t at a guess. If $kg is $2k then that is $6M of lost performance which could pay for expendable US that doesn't need refurbishing.
Of course, not every payload uses the full capacity of the rocket. And rockets are priced (for customers) per launch, not per kg -- you don't get a discount for using less than full capacity. So even if a reusable upper stage drops the downstream-landing payload to 10t (which actually sounds optimistic to me), that may be worth it for missions not fully utilizing the vehicle's capabilities.

Offline Steven Pietrobon

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Re: Rocket Lab Neutron rocket - Discussion
« Reply #1486 on: 09/29/2022 06:40 am »
Of course, not every payload uses the full capacity of the rocket. And rockets are priced (for customers) per launch, not per kg -- you don't get a discount for using less than full capacity.

Not always true. SpaceX charged NASA $50.3M to launch IXPE, $11.7M less than the standard price of $62M.

https://www.nasa.gov/press-release/nasa-awards-launch-services-contract-for-groundbreaking-astrophysics-mission/
« Last Edit: 09/29/2022 06:41 am by Steven Pietrobon »
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Offline trimeta

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Re: Rocket Lab Neutron rocket - Discussion
« Reply #1487 on: 09/29/2022 06:52 am »
Of course, not every payload uses the full capacity of the rocket. And rockets are priced (for customers) per launch, not per kg -- you don't get a discount for using less than full capacity.

Not always true. SpaceX charged NASA $50.3M to launch IXPE, $11.7M less than the standard price of $62M.

https://www.nasa.gov/press-release/nasa-awards-launch-services-contract-for-groundbreaking-astrophysics-mission/
People often cite that example, but that feels a lot more like "specifically trying to undercut (or at least, go head-to-head with) Pegasus XL" than "a trend of SpaceX offering a discount for reduced payloads." And before you mention SpaceX's bid to use Starship for NASA's TROPICS missions, that one was basically "let us carry an experimental payload on Starship's first launch": they needed to launch Starship anyway, might as well see if someone would pay them for it. Again, not representative.

Offline M.E.T.

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Re: Rocket Lab Neutron rocket - Discussion
« Reply #1488 on: 09/29/2022 07:54 am »
Of course, not every payload uses the full capacity of the rocket. And rockets are priced (for customers) per launch, not per kg -- you don't get a discount for using less than full capacity.

Not always true. SpaceX charged NASA $50.3M to launch IXPE, $11.7M less than the standard price of $62M.

https://www.nasa.gov/press-release/nasa-awards-launch-services-contract-for-groundbreaking-astrophysics-mission/
People often cite that example, but that feels a lot more like "specifically trying to undercut (or at least, go head-to-head with) Pegasus XL" than "a trend of SpaceX offering a discount for reduced payloads." And before you mention SpaceX's bid to use Starship for NASA's TROPICS missions, that one was basically "let us carry an experimental payload on Starship's first launch": they needed to launch Starship anyway, might as well see if someone would pay them for it. Again, not representative.

Well,  I suggest people prepare for a lot more “undercutting” once would-be competitors try to get off the ground. Question then is - how many “undercutting” examples are required to constitute a trend.

« Last Edit: 09/29/2022 07:55 am by M.E.T. »

Offline tbellman

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Re: Rocket Lab Neutron rocket - Discussion
« Reply #1489 on: 09/29/2022 08:18 am »
Of course, not every payload uses the full capacity of the rocket. And rockets are priced (for customers) per launch, not per kg -- you don't get a discount for using less than full capacity.

Not always true. SpaceX charged NASA $50.3M to launch IXPE, $11.7M less than the standard price of $62M.

https://www.nasa.gov/press-release/nasa-awards-launch-services-contract-for-groundbreaking-astrophysics-mission/

But IXPE was actually a somewhat demanding launch, since it was to an equatorial LEO orbit, requiring a significant dogleg maneuver.  That necessitated a downrange landing, not a return to launch site landing, despite the very low mass of the payload.

An example where customers actually have a per-kilogram price is SpaceX's rideshare program, which is advertised as $1.1M for 200kg to SSO with additional mass at $5.5k/kg.  Of course, that's because SpaceX expects to fill up the remaining capacity from other customers, so the rocket is usually reasonably fully loaded.

A better example of different prices depending on used capacity, and how much of the rocket can be recovered, is probably Falcon Heavy.  A Falcon Heavy launch with RTLS landings of the side boosters has an advertised price of $97M, a fully expended launch I think is $165M, and one which expends the center core but recovers the side boosters is somewhere inbetween (and that probably has different prices depending on if they can RTLS the side boosters or if a downrange landing, using both their barges, is needed).  That model matches reasonably well a hypothetical future evolved Neutron with reusable upper stage, where customers can chose to spend extra to get more capacity by having the upper stage expended.

(Personally, I suspect that redesigning the upper stage of Neutron to be recoverable will reduce payload enough that a redesign of the entire rocket will be the better choice for Rocket Lab.  But I'm not betting my hat on it. :) )

(And as an aside, $50.3M was the (estimated) total cost for NASA for launching IXPE, but that includes things outside of the launch contract with SpaceX ("other mission-related costs"; see this post by Jim).  The actual price charged by SpaceX was $42M: https://forum.nasaspaceflight.com/index.php?topic=48510.msg1967914#msg1967914.)

Online TrevorMonty

Re: Rocket Lab Neutron rocket - Discussion
« Reply #1490 on: 09/29/2022 10:00 am »
This SpaceX stuff needs to move to "Neutron vs F9R and SS" thread thats what it is for.

Offline Kaputnik

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Re: Rocket Lab Neutron rocket - Discussion
« Reply #1491 on: 09/29/2022 12:34 pm »
*snip*
And today we can develop engines faster and cheaper than before. In the long run it could be a better choice.

I don't know if that's true. 6-10 years from concept to first flight attempt has been approximately how long it takes to develop a rocket engine since the 1960s.

I think the perception that we can develop engines faster comes from all the small launch companies. I think the reality is that we've always developed smaller engines faster.

Smaller engines somewhat faster, larger engines take longer, yeah.

As examples, both the RL-10 and the J-2 took about 6 years from start of development to first launch. The F-1 took about 10 years.

The SpaceX Merlin 1A was 6 years.

Rocket Lab's Rutherford took 4 years, as an example of a smaller engine taking less time.

Good data points.
In an ideal world the Rutherford team would have moved straight on to Archimedes.
Is there any evidence that developing engines has beginner, if not faster, at least cheaper and with reduced team sizes?
I know the advantages of 3D printing can be overblown at times, but rapid prototyping is surely where it shines? This must have led to some sort of real world benefits?

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Offline sevenperforce

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Re: Rocket Lab Neutron rocket - Discussion
« Reply #1492 on: 09/30/2022 12:35 am »
Slight modification to my earlier pixel counting approach, now with estimated tank volumes.

The volumetric split on the upper stage is assumed to be equal to that on the booster, and all spherical caps are assumed to be perfect spherical caps.

I hope you're accounting that the curvature adius of the caps along the vehicle axis is 373/2 while sideways it's 617/2

I.e. I hope you're assuming the caps are actually not spherical but ellipsoidal, based on a an rotationally symmetric ellipsoid with the short diameter 373cm and both identical long diameters of 617cm.

The values are based off your pixel counts.
How sure are you that the caps are ellipsoidal rather than spherical? There appears to be a pretty sharp angle at the seam between the cap and the ring section.

But yes, if they are ellipsoidal caps then my tank volumes will be slightly low.

Unless they want to develop two totally different thrust class engines no easy way to avoid F9 and Electron's well proven 9+1 combination. The other alternative is engine that can throttle down to 20-30% but that is big ask for large booster engine.
Even if you do a landing engine that can throttle down to 20-30%, it's still going to be overweight for your upper stage.

The real alternative, if you're willing to dev two different thrust class engines, is to use 1-2 large engines on your booster and 1-2 smaller engines on the upper stage, with 1-2 upper-stage engines acting as first-stage verniers on ascent and as landing engines. For example, SpaceX could have fielded a "Falcon 4" with a booster powered by two Merlin 1Cs and two sea-level optimized Kestrels on the booster and an upper stage powered by two Vacuum-optimized Kestrels. Or if ULA wanted to make a reusable, stretched Delta IV (which is obviously dumb but for other reasons) they could upgrade the DCSS to use two RL-10s and also attach a pair of RL-10A-5s to the sides of the booster to provide extra umph on ascent and landing thrust on landing.

Online TrevorMonty

Re: Rocket Lab Neutron rocket - Discussion
« Reply #1493 on: 09/30/2022 09:14 am »
Slight modification to my earlier pixel counting approach, now with estimated tank volumes.

The volumetric split on the upper stage is assumed to be equal to that on the booster, and all spherical caps are assumed to be perfect spherical caps.

I hope you're accounting that the curvature adius of the caps along the vehicle axis is 373/2 while sideways it's 617/2

I.e. I hope you're assuming the caps are actually not spherical but ellipsoidal, based on a an rotationally symmetric ellipsoid with the short diameter 373cm and both identical long diameters of 617cm.

The values are based off your pixel counts.
How sure are you that the caps are ellipsoidal rather than spherical? There appears to be a pretty sharp angle at the seam between the cap and the ring section.

But yes, if they are ellipsoidal caps then my tank volumes will be slightly low.

Unless they want to develop two totally different thrust class engines no easy way to avoid F9 and Electron's well proven 9+1 combination. The other alternative is engine that can throttle down to 20-30% but that is big ask for large booster engine.
Even if you do a landing engine that can throttle down to 20-30%, it's still going to be overweight for your upper stage.

The real alternative, if you're willing to dev two different thrust class engines, is to use 1-2 large engines on your booster and 1-2 smaller engines on the upper stage, with 1-2 upper-stage engines acting as first-stage verniers on ascent and as landing engines. For example, SpaceX could have fielded a "Falcon 4" with a booster powered by two Merlin 1Cs and two sea-level optimized Kestrels on the booster and an upper stage powered by two Vacuum-optimized Kestrels. Or if ULA wanted to make a reusable, stretched Delta IV (which is obviously dumb but for other reasons) they could upgrade the DCSS to use two RL-10s and also attach a pair of RL-10A-5s to the sides of the booster to provide extra umph on ascent and landing thrust on landing.
A short high G deceleration burn uses less fuel than long low G burn, which means more powerful landing engine the better to certain extent. 

Offline edzieba

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Re: Rocket Lab Neutron rocket - Discussion
« Reply #1494 on: 09/30/2022 09:20 am »
Slight modification to my earlier pixel counting approach, now with estimated tank volumes.

The volumetric split on the upper stage is assumed to be equal to that on the booster, and all spherical caps are assumed to be perfect spherical caps.

I hope you're accounting that the curvature adius of the caps along the vehicle axis is 373/2 while sideways it's 617/2

I.e. I hope you're assuming the caps are actually not spherical but ellipsoidal, based on a an rotationally symmetric ellipsoid with the short diameter 373cm and both identical long diameters of 617cm.

The values are based off your pixel counts.
How sure are you that the caps are ellipsoidal rather than spherical? There appears to be a pretty sharp angle at the seam between the cap and the ring section.

But yes, if they are ellipsoidal caps then my tank volumes will be slightly low.

Unless they want to develop two totally different thrust class engines no easy way to avoid F9 and Electron's well proven 9+1 combination. The other alternative is engine that can throttle down to 20-30% but that is big ask for large booster engine.
Even if you do a landing engine that can throttle down to 20-30%, it's still going to be overweight for your upper stage.

The real alternative, if you're willing to dev two different thrust class engines, is to use 1-2 large engines on your booster and 1-2 smaller engines on the upper stage, with 1-2 upper-stage engines acting as first-stage verniers on ascent and as landing engines. For example, SpaceX could have fielded a "Falcon 4" with a booster powered by two Merlin 1Cs and two sea-level optimized Kestrels on the booster and an upper stage powered by two Vacuum-optimized Kestrels. Or if ULA wanted to make a reusable, stretched Delta IV (which is obviously dumb but for other reasons) they could upgrade the DCSS to use two RL-10s and also attach a pair of RL-10A-5s to the sides of the booster to provide extra umph on ascent and landing thrust on landing.
A short high G deceleration burn uses less fuel than long low G burn, which means more powerful landing engine the better to certain extent.
You can relight main(s) + verniers for majority of deceleration, then shut down mains and keep verniers running for terminal control and the last few tens of m/s of deceleration. Similar to Falcon's  1 > 3 > 1 burn sequences.

Offline edzieba

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Re: Rocket Lab Neutron rocket - Discussion
« Reply #1495 on: 09/30/2022 09:37 am »

Offline sevenperforce

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Re: Rocket Lab Neutron rocket - Discussion
« Reply #1496 on: 09/30/2022 03:16 pm »
I hope you're accounting that the curvature adius of the caps along the vehicle axis is 373/2 while sideways it's 617/2

I.e. I hope you're assuming the caps are actually not spherical but ellipsoidal, based on a an rotationally symmetric ellipsoid with the short diameter 373cm and both identical long diameters of 617cm.

The values are based off your pixel counts.
How sure are you that the caps are ellipsoidal rather than spherical? There appears to be a pretty sharp angle at the seam between the cap and the ring section.

But yes, if they are ellipsoidal caps then my tank volumes will be slightly low.
I went back and calculated for ellipsoidal tank caps, and while the lower (assumed CH4) booster tank volume somewhat intuitively remains the same, the upper (assumed LOX) booster tank volume goes up from 238.3 cubic meters to 255.4 cubic meters, bringing the apparent mixture ratio up from 2.99 to to 3.2 which is still surprisingly fuel-rich but not as severely as before. So good call there.

Booster propellant mass goes up, from 363 tonnes to 382 tonnes, and upper stage prop mass goes up from 84 to 90 tonnes.

In the design proposed in December of last year, they claimed a GLOW of 480 tonnes and total liftoff thrust of 5.96 MN (a liftoff TWR of 1.27:1). Now, the vehicle has been stretched (from 40 meters to nearly 43 meters) and engine thrust has gone down while engine count and total liftoff thrust has gone up. If we assume the same liftoff TWR, then that's 532 tonnes GLOW which is a total dry mass percentage of 11.1%. Not too bad, considering engines and recovery accoutrements. If TWR has gone up a little then the dry mass percentage will be lower.

Even if you do a landing engine that can throttle down to 20-30%, it's still going to be overweight for your upper stage.

The real alternative, if you're willing to dev two different thrust class engines, is to use 1-2 large engines on your booster and 1-2 smaller engines on the upper stage, with 1-2 upper-stage engines acting as first-stage verniers on ascent and as landing engines. For example, SpaceX could have fielded a "Falcon 4" with a booster powered by two Merlin 1Cs and two sea-level optimized Kestrels on the booster and an upper stage powered by two Vacuum-optimized Kestrels. Or if ULA wanted to make a reusable, stretched Delta IV (which is obviously dumb but for other reasons) they could upgrade the DCSS to use two RL-10s and also attach a pair of RL-10A-5s to the sides of the booster to provide extra umph on ascent and landing thrust on landing.
A short high G deceleration burn uses less fuel than long low G burn, which means more powerful landing engine the better to certain extent.
Yes, for sure. The limit here is going to be stresses on the vehicle...at some point, even doing a 1-3-1 burn will overstress the structure.

But there are other considerations, too. For example, if your upper stage engine doubles as your booster landing engine, then it is the only one that needs to be restartable in-air, which can save complexity and weight. You are then able to use larger and potentially more efficient primary engines on your first stage. A pair of RD-180s could replace the entire outer ring of Merlin 1Ds on Falcon 9, leaving a single Merlin in the center for the landing burn. Granted, they would weigh more, but the added thrust and increased specific impulse would probably make up for it.

Online TrevorMonty

Re: Rocket Lab Neutron rocket - Discussion
« Reply #1497 on: 09/30/2022 04:05 pm »
The 11% dry mass isn't unrealistic as Electron is close to 5% ie 92% fuel Beck comment + 2% payload. Extra dry mass from increase diameter is offset by not needing fuel for reentry burn.

Upper stage dry mass should be well under 5% probably close to 2.5%. Which would be impossible if it wasn't totally encapsulated by booster.
« Last Edit: 09/30/2022 04:06 pm by TrevorMonty »

Online TrevorMonty

Re: Rocket Lab Neutron rocket - Discussion
« Reply #1498 on: 10/16/2022 10:27 am »
Been studying maps and images of Wallops Island looks like Neutron will be just south of Pad 0-B. Which is Minotaur's pad.

Electron is south side of large water tower that supports Antares launches there is only about 100m between 2 pads. All google maps and earth satellite images are 2016 so before Electron pad was built.

Not sure where Neutron factory is but moving 7m LVs on roads in this area shouldn't be problem. Just look SpaceX SS videos to see how it can be done.


Edit. Just watch today's Peter Beck NSF interview. Neutron launch pad is just south of Electron. Picture shows Minotaurs pad between Neutron's landing and launch pads.

« Last Edit: 10/17/2022 12:41 am by TrevorMonty »

Online TrevorMonty

Re: Rocket Lab Neutron rocket - Discussion
« Reply #1499 on: 10/22/2022 10:31 pm »
New factory is chicken farm on corner of 803 and radar rd. So straight 6km drive to beach on private road.
I'd expect the early Neutrons to be return to factory for inspection and upgrades between launches.

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