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It's nothing yet except for a statement of intention: we aspire to become the next SpaceX and hope to raise the interest of investors that can't access SpaceX s

by yholio 6y ago

It's nothing yet except for a statement of intention: we aspire to become the next SpaceX and hope to raise the interest of investors that can't access SpaceX stock. There is no talk about the engines, it's quite clear that the Rutherford won't cut it (Electron already uses 9 of them). So they have to either buy or develop an engine, expensive in time or money. The mega-constellation sweet spot argument is not really convincing, if you have a reusable mega rocket with a relightable second stage (like SpaceX plans), you can hit multiple planes in a single launch. The 8 ton class is probably just the largest they can afford to plan at this stage.

Robotbeat 6y ago
I disagree. For mega constellations it’s about cost per kg to orbit, and for reusable it’s about launch rate. If you build too big, your launch rate isn’t high enough to get the full advantage of reuse. I think Starship is awesome, but even Falcon 9 is so big it leaves some room for something a bit smaller. 8 tons is in the Soyuz/R7 range, which is what the other megaconstellation is using. And it has had well over 1000 launches and still holds the record (in the 70s and 80s) of the most number of launches per year for a single rocket type, which makes it a good target class for size of a reusable rocket. 8 tons is about where Falcon 9 v1.0 started out, by the way. How many customers wish they had that built the smaller falcon 5. Additionally, a smaller rocket is useful for some human spaceflight applications. If you only need to launch two astronauts in orbit to fix a satellite, it’d be nice to have a smaller rocket option. An 8 ton first stage reusable rocket is also big enough to eventually have a reusable upper stage and still carry a a couple astronauts, their space suits, a small (Gemini-sized) vehicle (possibly integrated with the reusable upper stage), and some tools and parts to repair the satellite. Launch costs could in principle be less than $1 million, which is about the propellant costs alone for Starship. Starship is awesome. But we don’t have JUST 757s and 777s. We also have smaller utility aircraft. I’ve long thought that something just under 10 tons, partially or fully reusable, is a good market opportunity. Makes a lot more sense than tiny rockets for megaconstellations.
- DennisP 6y ago
  But we do have just airplanes that are 100% reusable. So far, Rocket Lab only talks about reusing the first stage; second-stage reuse is hard, and a huge cost savings. But maybe until Starship gets the launch rate to reach its potential, there's room for smaller rockets with disposable upper stages. SpaceX is banking on the space industry expanding well beyond megaconstellations, but that will take a few years. By the time we get there, maybe other companies will manage reusable upper stages too.
  - Robotbeat 6y ago
    Right. Having a decent sized reusable first stage on Neutron gives RocketLab the option of a reusable upper stage down the road. It’s pretty tough to justify going for full reuse before you have even accomplished partial reuse. Something similar to the recovery method of Electron’s first stage would be appropriate for a reusable upper stage. (And at one time, SpaceX was planning it for Falcon 9’s upper stage... ballute/heatshield and parachute for Falcon 9 upper stage recovery).
- CarVac 6y ago
  > If you build too big, your launch rate isn’t high enough to get the full advantage of reuse. But if you throw away second stages, your rate of reuse goes waaay down. I don't think an 8-ton lift vehicle is going to achieve second stage reuse.
  - Robotbeat 6y ago
    On the contrary, there are MORE viable methods for reuse with a smaller vehicle. They can do mid-air recovery with such an upper stage, for instance, but no hope of that with a Starship-sized upper stage.
    - CarVac 6y ago
      More ways to land, but the performance penalty of heat shielding will be crippling on a smaller stage.
sandworm101 6y ago
>> The mega-constellation sweet spot ... multiple planes in a single launch. Mega-constellations are exactly the type of project that doesn't need multiple planes. They require multiple sat in each plane, meaning one rocket full of small sats can go to one plane and dump them all. I suspect something has been lost in translation. I think they mean to say that the relightable engines will allow access to different altitudes on a single launch, multiple orbits within a single plane.
- Sanzig 6y ago
  Depends on the plane. Inclination changes are expensive, so if you want different inclinations, it almost always makes sense to use a separate launch vehicle for each inclination you want to target. However, the longitude of the ascending node (Ω) is perturbed by the earth's oblateness, and the rate of Ω precession is a function of the semi-latus rectum (p) and the inclination (i). If you adjust the orbit altitude to tweak p, you can adjust the precession rate to swing the plane around to where you want it. This takes a while (months), and you of course need some sort of propulsion on the spacecraft to return you to your target altitude after the maneuver, but if the launch vehicle can drop you into the higher/lower altitude above/below the target plane rather than doing that on-board the spacecraft, the delta-v cost is halved.
  - sandworm101 6y ago
    I would call that on-orbit maneuvers rather than part of the launch process. This rocket will drop the sat off at the contracted orbit and fly away. Multiple engine firings will mean separate customers can get at best separate altitudes.
api 6y ago
Rutherford is really reliable. Why not use like 27 of them? Is there some reason that this is inherently bad? It would probably be less efficient to use lots of small engines, but perhaps the reduced cost of using an already existing engine that you can mass produce would make up for it.
- vermontdevil 6y ago
  Batteries. Imagine all the weight.
- yholio 6y ago
  Rutherford is only a 26 KN engine. An original Merlin 1 engine was 340 KN, so you would need 15 Rutherfords for each Merlin. A total of 135 engines for a rocket comparable to the original Falcon 9 which they are targeting.
  - api 6y ago
    Yeah I guess we tried lots of engines once, though that was a long time ago: https://en.wikipedia.org/wiki/N1_(rocket) https://en.wikipedia.org/wiki/N1_(rocket)
    - cnlevy 6y ago
      The N1's first stage had 30 engines, not much more than the Falcon Heavy which has 27
    - Already__Taken 6y ago
      Read the launch history most of it the engines weren't the problem. *edit control was the problem, it just happens to be connected to parts of the engines.
    - nickik 6y ago
      The Falcon Heavy has 27 engines and works fine. Its not the number of engines that is the problem. The problem is how efficient is your engine, how is the Trust-to-Weight ratio. To do a reusable launcher you need to be really damn efficient on every part of the rocket. Elon explains this pretty well in the talks he gave around 2014.
MichaelMoser123 6y ago
interesting if the Neutron will use electric-pump-fed engines, is this a concept that is scalable to bigger engines?
- Gibbon1 6y ago
  I read a paper that indicated you can build them to any arbitrary size. Electric feed pump designs don't get worse as they get bigger. But turbo pumps have better performance at large sizes than electric feed pumps. However the paper also assumed a fixed weigh battery pack. On the second stage electron tosses one of it's battery packs overboard. Also raw performance isn't as critical for the first stage. One other thing, electric feed has much simpler plumbing than a turbo pump feed. Ans: Maybe, but I have no idea.
  - MichaelMoser123 6y ago
    Interesting, do you have a link to that paper? I guess the regular engines that are running inefficient fuel cycles to power the fuel pumps aren't too weight efficient either, due to the inefficiencies of these fuel cycles. Interesting why this approach wasn't tried earlier.
    - Gibbon1 6y ago
      Took a bit of searching but I found it again. https://www.aacademica.org/hernan.emilio.tacca/9.pdf https://www.aacademica.org/hernan.emilio.tacca/9.pdf If I remember correctly simple turbo pump feed engines have to run using a lot of excess fuel. Simple designs just dump the turbine exhaust overboard. That represents a fair amount of wasted energy. Advanced designs feed the exhaust back into the engine. I think they also scavenge some energy from cooling the nozzle.
      - MichaelMoser123 6y ago
        thanks!

by yholio 6y ago

Robotbeat 6y ago

I disagree. For mega constellations it’s about cost per kg to orbit, and for reusable it’s about launch rate. If you build too big, your launch rate isn’t high enough to get the full advantage of reuse. I think Starship is awesome, but even Falcon 9 is so big it leaves some room for something a bit smaller. 8 tons is in the Soyuz/R7 range, which is what the other megaconstellation is using. And it has had well over 1000 launches and still holds the record (in the 70s and 80s) of the most number of launches per year for a single rocket type, which makes it a good target class for size of a reusable rocket. 8 tons is about where Falcon 9 v1.0 started out, by the way. How many customers wish they had that built the smaller falcon 5. Additionally, a smaller rocket is useful for some human spaceflight applications. If you only need to launch two astronauts in orbit to fix a satellite, it’d be nice to have a smaller rocket option. An 8 ton first stage reusable rocket is also big enough to eventually have a reusable upper stage and still carry a a couple astronauts, their space suits, a small (Gemini-sized) vehicle (possibly integrated with the reusable upper stage), and some tools and parts to repair the satellite. Launch costs could in principle be less than $1 million, which is about the propellant costs alone for Starship. Starship is awesome. But we don’t have JUST 757s and 777s. We also have smaller utility aircraft. I’ve long thought that something just under 10 tons, partially or fully reusable, is a good market opportunity. Makes a lot more sense than tiny rockets for megaconstellations.

DennisP 6y ago
But we do have just airplanes that are 100% reusable. So far, Rocket Lab only talks about reusing the first stage; second-stage reuse is hard, and a huge cost savings. But maybe until Starship gets the launch rate to reach its potential, there's room for smaller rockets with disposable upper stages. SpaceX is banking on the space industry expanding well beyond megaconstellations, but that will take a few years. By the time we get there, maybe other companies will manage reusable upper stages too.
- Robotbeat 6y ago
  Right. Having a decent sized reusable first stage on Neutron gives RocketLab the option of a reusable upper stage down the road. It’s pretty tough to justify going for full reuse before you have even accomplished partial reuse. Something similar to the recovery method of Electron’s first stage would be appropriate for a reusable upper stage. (And at one time, SpaceX was planning it for Falcon 9’s upper stage... ballute/heatshield and parachute for Falcon 9 upper stage recovery).
CarVac 6y ago
> If you build too big, your launch rate isn’t high enough to get the full advantage of reuse. But if you throw away second stages, your rate of reuse goes waaay down. I don't think an 8-ton lift vehicle is going to achieve second stage reuse.
- Robotbeat 6y ago
  On the contrary, there are MORE viable methods for reuse with a smaller vehicle. They can do mid-air recovery with such an upper stage, for instance, but no hope of that with a Starship-sized upper stage.
  - CarVac 6y ago
    More ways to land, but the performance penalty of heat shielding will be crippling on a smaller stage.

sandworm101 6y ago

>> The mega-constellation sweet spot ... multiple planes in a single launch. Mega-constellations are exactly the type of project that doesn't need multiple planes. They require multiple sat in each plane, meaning one rocket full of small sats can go to one plane and dump them all. I suspect something has been lost in translation. I think they mean to say that the relightable engines will allow access to different altitudes on a single launch, multiple orbits within a single plane.

Sanzig 6y ago
Depends on the plane. Inclination changes are expensive, so if you want different inclinations, it almost always makes sense to use a separate launch vehicle for each inclination you want to target. However, the longitude of the ascending node (Ω) is perturbed by the earth's oblateness, and the rate of Ω precession is a function of the semi-latus rectum (p) and the inclination (i). If you adjust the orbit altitude to tweak p, you can adjust the precession rate to swing the plane around to where you want it. This takes a while (months), and you of course need some sort of propulsion on the spacecraft to return you to your target altitude after the maneuver, but if the launch vehicle can drop you into the higher/lower altitude above/below the target plane rather than doing that on-board the spacecraft, the delta-v cost is halved.
- sandworm101 6y ago
  I would call that on-orbit maneuvers rather than part of the launch process. This rocket will drop the sat off at the contracted orbit and fly away. Multiple engine firings will mean separate customers can get at best separate altitudes.

api 6y ago

Rutherford is really reliable. Why not use like 27 of them? Is there some reason that this is inherently bad? It would probably be less efficient to use lots of small engines, but perhaps the reduced cost of using an already existing engine that you can mass produce would make up for it.

vermontdevil 6y ago
Batteries. Imagine all the weight.
yholio 6y ago
Rutherford is only a 26 KN engine. An original Merlin 1 engine was 340 KN, so you would need 15 Rutherfords for each Merlin. A total of 135 engines for a rocket comparable to the original Falcon 9 which they are targeting.
- api 6y ago
  Yeah I guess we tried lots of engines once, though that was a long time ago: https://en.wikipedia.org/wiki/N1_(rocket) https://en.wikipedia.org/wiki/N1_(rocket)
  - cnlevy 6y ago
    The N1's first stage had 30 engines, not much more than the Falcon Heavy which has 27
  - Already__Taken 6y ago
    Read the launch history most of it the engines weren't the problem. *edit control was the problem, it just happens to be connected to parts of the engines.
  - nickik 6y ago
    The Falcon Heavy has 27 engines and works fine. Its not the number of engines that is the problem. The problem is how efficient is your engine, how is the Trust-to-Weight ratio. To do a reusable launcher you need to be really damn efficient on every part of the rocket. Elon explains this pretty well in the talks he gave around 2014.

MichaelMoser123 6y ago

interesting if the Neutron will use electric-pump-fed engines, is this a concept that is scalable to bigger engines?

Gibbon1 6y ago
I read a paper that indicated you can build them to any arbitrary size. Electric feed pump designs don't get worse as they get bigger. But turbo pumps have better performance at large sizes than electric feed pumps. However the paper also assumed a fixed weigh battery pack. On the second stage electron tosses one of it's battery packs overboard. Also raw performance isn't as critical for the first stage. One other thing, electric feed has much simpler plumbing than a turbo pump feed. Ans: Maybe, but I have no idea.
- MichaelMoser123 6y ago
  Interesting, do you have a link to that paper? I guess the regular engines that are running inefficient fuel cycles to power the fuel pumps aren't too weight efficient either, due to the inefficiencies of these fuel cycles. Interesting why this approach wasn't tried earlier.
  - Gibbon1 6y ago
    Took a bit of searching but I found it again. https://www.aacademica.org/hernan.emilio.tacca/9.pdf https://www.aacademica.org/hernan.emilio.tacca/9.pdf If I remember correctly simple turbo pump feed engines have to run using a lot of excess fuel. Simple designs just dump the turbine exhaust overboard. That represents a fair amount of wasted energy. Advanced designs feed the exhaust back into the engine. I think they also scavenge some energy from cooling the nozzle.
    - MichaelMoser123 6y ago
      thanks!