Author Topic: Rocket Labs vs. SpaceX  (Read 28032 times)

Offline john smith 19

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Re: Rocket Labs vs. SpaceX
« Reply #60 on: 06/11/2018 06:21 am »
We should expect their prices to come down once their launch rate (after internal use, e.g., Starlink) approaches or exceeds the rate of sales, and not before.
It also depends if their customers have a supply chain that can actually be sped up to mfg their payloads more quickly.  The satellite industry has been in "hand built" mode for decades.
Quote from: Exastro
It strikes me as likely that the market is a lot more elastic at the low end (especially cubesats) than the high end (large GTO).
Why?

IIRC small sats can be built for $100k. They can fly as secondary payloads on Ariane 5 or Atals V for prices around that mark. Buy all six slots and you can build a probe around that.

But what are Rockelab charging. 50x that? Pegasus launches are around $40m.
You need a compelling  case to really benefit from have a whole (expendable) LV to yourself.


Quote from: Exastro
That seems a little strong.  SX found a solution using grid fins, but that doesn't preclude the possibility of doing it without them. 
Not really.
You might like to review the sort of concepts looked at for booster recovery from the 1960's onward. There have been quite a few. Most of them were basically "If NASA gives us enough money we can do this."
Well they couldn't.

Quote from: Exastro
In a high-risk business with big R&D and capital barriers to entry, expendable's reduced the time and cost to get something flying could easily be more attractive than reusable's marginal cost reduction.
Here's a shocker. If you build what you always built you tend to get what you always got.

The interesting implication of this is that the F9 booster is not that much different to any other LRE booster on a TSTO rocket.

IOW this could  be done by any 1st stage, if the mfgs were prepared to take the risk with their own money of making the necessary mods.

Let's see which of them will.
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Offline envy887

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Re: Rocket Labs vs. SpaceX
« Reply #61 on: 06/11/2018 01:34 pm »
Quote from: Exastro
In a high-risk business with big R&D and capital barriers to entry, expendable's reduced the time and cost to get something flying could easily be more attractive than reusable's marginal cost reduction.
Here's a shocker. If you build what you always built you tend to get what you always got.

The interesting implication of this is that the F9 booster is not that much different to any other LRE booster on a TSTO rocket.

IOW this could  be done by any 1st stage, if the mfgs were prepared to take the risk with their own money of making the necessary mods.

Let's see which of them will.

Not exactly. Every liquid rocket booster is 100% built around a specific liquid rocket engine. The problem for other manufacturers isn't their boosters, it's their engines. Who is going to do a 6-year, billion-dollar program for new engines with their own money? And then redesign the booster to use those new engines?

Electron would likely be fairly straightforward to upgrade for RTLS, since it has multiple engines that can probably be modified for deep throttling (electric pumps) and restart (spark igniter) without much trouble, and a reasonably large upper stage depressing the staging velocity. But Ariane 6 or Vulcan? Not happening, even if they wanted to.

Offline edkyle99

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Re: Rocket Labs vs. SpaceX
« Reply #62 on: 06/11/2018 04:25 pm »
Electron would likely be fairly straightforward to upgrade for RTLS, since it has multiple engines that can probably be modified for deep throttling (electric pumps) and restart (spark igniter) without much trouble, and a reasonably large upper stage depressing the staging velocity. But Ariane 6 or Vulcan? Not happening, even if they wanted to.
Electron is too small to retrofit for first stage recovery.  This is a tiny rocket, by previous standards.  It only weighs 12.55 tonnes at liftoff.  That is less than half of the weight of a Falcon 9 first stage with no propellant loaded.  It is also less than half the GLOW of a Falcon 1.  Electron can only lift 150 kg to sun synchronous low earth orbit.  That capability would be lost, probably all of it, to the needs of a propulsive-stage-recovery system added to the existing stage. 

To maintain its listed capability while adding stage recovery, Electron would have to grow substantially in liftoff mass, which would in turn require much more liftoff thrust, which either means a new higher thrust engine or a larger number of existing engines (at least a dozen, maybe more) on what would have to be a fatter, taller stage.
There's also the question about the reuse of the composite pressurized tanks.

 - Ed Kyle   
« Last Edit: 06/11/2018 04:52 pm by edkyle99 »

Offline envy887

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Re: Rocket Labs vs. SpaceX
« Reply #63 on: 06/11/2018 05:46 pm »
Electron would likely be fairly straightforward to upgrade for RTLS, since it has multiple engines that can probably be modified for deep throttling (electric pumps) and restart (spark igniter) without much trouble, and a reasonably large upper stage depressing the staging velocity. But Ariane 6 or Vulcan? Not happening, even if they wanted to.
Electron is too small to retrofit for first stage recovery.  This is a tiny rocket, by previous standards.  It only weighs 12.55 tonnes at liftoff.  That is less than half of the weight of a Falcon 9 first stage with no propellant loaded.  It is also less than half the GLOW of a Falcon 1.  Electron can only lift 150 kg to sun synchronous low earth orbit.  That capability would be lost, probably all of it, to the needs of a propulsive-stage-recovery system added to the existing stage. 

To maintain its listed capability while adding stage recovery, Electron would have to grow substantially in liftoff mass, which would in turn require much more liftoff thrust, which either means a new higher thrust engine or a larger number of existing engines (at least a dozen, maybe more) on what would have to be a fatter, taller stage.
There's also the question about the reuse of the composite pressurized tanks.

 - Ed Kyle

To get the same payload, it would need a larger booster with either uprated or additional engines. But who says 100 kg to SSO isn't enough? And if most of the penalty is for boostback/entry fuel, they could just expend the booster and use that fuel up if they really needed the extra performance. Even on a small rocket, booster dry mass trades at much less than 1:1 with payload. Probably more like 1:10. So take 50 kg off the payload and apply 500 kg to the booster dry mass for recovery. The whole booster probably masses around 500 kg as it is...

The smaller vehicle is helped by drag on the way down, as terminal velocity is likely low enough for at least a subsonic landing burn. The smaller, lighter booster will also need far less protection at reentry due to the lower ballistic coefficient.

Or it might be small enough to airhook or net the whole thing. It's far smaller and lighter than a F9 fairing, and a parachute is probably a lot lighter than legs and landing fuel.

Offline edkyle99

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Re: Rocket Labs vs. SpaceX
« Reply #64 on: 06/11/2018 06:36 pm »
The whole booster probably masses around 500 kg as it is...
Much heavier than that I expect.  The engines alone with electric motor pumps and batteries are together going to weigh something like 300 to 450 kg.  My guess for first stage burnout mass is roughly 950 kg, which would include residuals.

 - Ed Kyle 
« Last Edit: 06/11/2018 06:38 pm by edkyle99 »

Offline envy887

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Re: Rocket Labs vs. SpaceX
« Reply #65 on: 06/11/2018 07:50 pm »
The whole booster probably masses around 500 kg as it is...
Much heavier than that I expect.  The engines alone with electric motor pumps and batteries are together going to weigh something like 300 to 450 kg.  My guess for first stage burnout mass is roughly 950 kg, which would include residuals.

 - Ed Kyle

Old RocketLab interview suggests a 1090 kg total dry mass, of which 15-20% is probably the fairing and upper stage. So 950 kg is probably a lot closer than 500 kg. But adding 500 kg for recovery hardware seems pretty excessive for such a small stage, they could probably do it for less than half that.

http://www.parabolicarc.com/2014/07/29/rocket-lab-announces-small-satellite-launcher/

That still lighter and a lot smaller than the F9 fairing half. And it appears they have quite a bit of excess thrust already, if they deem a stage stretch worthwhile. Liftoff TWR is about 1.55.


Offline hkultala

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Re: Rocket Labs vs. SpaceX
« Reply #66 on: 06/11/2018 07:58 pm »
The whole booster probably masses around 500 kg as it is...
Much heavier than that I expect.  The engines alone with electric motor pumps and batteries are together going to weigh something like 300 to 450 kg.  My guess for first stage burnout mass is roughly 950 kg, which would include residuals.

 - Ed Kyle

Old RocketLab interview suggests a 1090 kg total dry mass, of which 15-20% is probably the fairing and upper stage. So 950 kg is probably a lot closer than 500 kg. But adding 500 kg for recovery hardware seems pretty excessive for such a small stage, they could probably do it for less than half that.

http://www.parabolicarc.com/2014/07/29/rocket-lab-announces-small-satellite-launcher/

That still lighter and a lot smaller than the F9 fairing half. And it appears they have quite a bit of excess thrust already, if they deem a stage stretch worthwhile. Liftoff TWR is about 1.55.

Though stretch would also mean bigger and heavier batteries.

But of course, those bigger and heavier batteries would not be a problem, it would just mean slightly worse performance improvement from the stretch than what most other rockets get.

Offline TrevorMonty

Re: Rocket Labs vs. SpaceX
« Reply #67 on: 06/11/2018 09:38 pm »
For reuse to be viable downrange recovery with mid air capture would give less performance loss. Have to factor in reentry heat shielding and damage, its take SpaceX quite while to get this right. Also operational cost of helicopter and its support ship. It maybe possible with southward launches from Mahia to use land based helicopter which would be huge saving.

Offline brainbit

Re: Rocket Labs vs. SpaceX
« Reply #68 on: 06/11/2018 10:33 pm »
If SpaceX can get the fairings back to the ocean can Rocket Lab get there 1st stage rocket back to a lake? fresh water will not do such damage to the used rocket and as it is so much smaller than an F9 and flying from  NZ where space is less congested it may be safe?? Given sufficient warning. Don't know but I would give it a try  :) :)

Offline deruch

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Re: Rocket Labs vs. SpaceX
« Reply #69 on: 06/11/2018 10:41 pm »
What i'm really curious about is how Rocket Labs can:

2. Absorb the battery weight penalty (for the rutherford engine)

and still be competitive.....

The batteries are not completely dead weight.  They avoid the need to run some of the fuel through the gas generator, which will raise the ISP compared to a gas-generator cycle like the Merlin.  The details of this trade would require some thought, but it's definitely not as bad as just adding the mass of the batteries.
Here's some people who have given this some thought: Performance assessment of electrically driven pump-fed LOX/kerosene cycle rocket engine: Comparison with gas generator cycle  They conclude:
Quote
Under the same operating conditions for both cycles, the hypothetical LEO mission analysis revealed that the ElecPump cycle has a payload capability that is only 2.1% to 3.1% less than that of the GG cycle for the 3 MPa case.
See also ELECTRIC FEED SYSTEMS FOR LIQUID PROPELLANT ROCKET ENGINES for similar conclusions

So a relatively small performance hit, but a drastic simplification of the engine.

Those are interesting papers, thanks for linking.  They give a great overview of the general considerations/trades being done on comparing turbopumped and electropumped engines, but for the discussion of the Rutherford upper stage engine in particular, their conclusions aren't quite that relevant because Electron uses battery "staging" on the upper stage.  i.e. They split their batteries into multiple packs and then jettison the spent ones in a fashion very similar to serial staging in rockets.  So, RocketLabs significantly reduce their Mass Ratio penalty and can likely also gain additional performance benefits by reducing their battery cooling mass flow requirements if they limit the flow to only the battery packs in operation at any one time, etc.  Of course, as well as some mass considerations, this requires adding some complexity back into the system.
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Offline speedevil

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Re: Rocket Labs vs. SpaceX
« Reply #70 on: 06/11/2018 11:06 pm »
As a note Over in the electric pumped rocket cycle thread are some rough calculations I did on a F9 clone with Rutherford engines.

In short - if you take a F9, and replace the Merlins with Rutherfords, you lose four tons payload to LEO, and two or so tons to GEO.

Slight modifications (ditch most of the rutherfords on S2 as you get to 20 tons mass) may get it closer to one ton penalty.

It is also unclear if you can't lose other weights in the stage, potentially reducing this penalty.
If Rocketlabs was to go with reusable there are several reasonable arguments as to why it may be easier than F9.
Starting with much better throttleability and thruster response (50-100% step in thrust should be well under 100ms), and much, much more divided thrust for S1, with no need for gimballing potentially.

Offline Spudley

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Re: Rocket Labs vs. SpaceX
« Reply #71 on: 06/12/2018 08:31 pm »
As a note Over in the electric pumped rocket cycle thread are some rough calculations I did on a F9 clone with Rutherford engines.

In short - if you take a F9, and replace the Merlins with Rutherfords, you lose four tons payload to LEO, and two or so tons to GEO.

Slight modifications (ditch most of the rutherfords on S2 as you get to 20 tons mass) may get it closer to one ton penalty.

It is also unclear if you can't lose other weights in the stage, potentially reducing this penalty.
If Rocketlabs was to go with reusable there are several reasonable arguments as to why it may be easier than F9.
Starting with much better throttleability and thruster response (50-100% step in thrust should be well under 100ms), and much, much more divided thrust for S1, with no need for gimballing potentially.

It's an interesting comparison, but remember that Rutherford is a brand new engine, while Merlin has had several major upgrades through it's life. It's reasonable to compare early version Merlins, or assume that Rutherford could be similarly upgraded. Also, it's reasonable to assume improvements in battery technology will allow for weight reductions for Rutherford over time.

Offline john smith 19

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Re: Rocket Labs vs. SpaceX
« Reply #72 on: 06/16/2018 06:27 pm »
That still lighter and a lot smaller than the F9 fairing half. And it appears they have quite a bit of excess thrust already, if they deem a stage stretch worthwhile. Liftoff TWR is about 1.55.
Interesting. IIRC that's pretty sporty by modern commercial LV standards.

OTOH gravity losses are the biggest element of loss in an ascent, so getting horizontal faster can pay big dividends.

Incidentally IIRC Electron is even smaller than Black Arrow, the British LV that put the Prospero satellite up in 1971.  AFAIK Black Arrow was considered tiny by the standards of the time.
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Offline Nomadd

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Re: Rocket Labs vs. SpaceX
« Reply #73 on: 06/16/2018 07:19 pm »
 It would be funny to see them partner with Tesla. There would be nobody better to improve battery efficiency and packaging. They know quite a bit about electric motors too.
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Offline high road

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Re: Rocket Labs vs. SpaceX
« Reply #74 on: 06/19/2018 03:06 pm »
It would be funny to see them partner with Tesla. There would be nobody better to improve battery efficiency and packaging. They know quite a bit about electric motors too.

And both of them need to be successful at mass production in order to succeed ;-)

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