Vanamonde

Blue Origin thread. (New, replacing lost thread.)

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8 minutes ago, mikegarrison said:

Isn't that the same thing? An electrical trigger that lights off a small solid pyro charge, thus "augmented"?

Whoops, I missed the "augmented" bit. Just saw "don't seem to use a chemical ignition system".

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8 hours ago, kerbiloid said:

As I can get, the question was: can we feed the same engine without modification with methane or hydrogen in turn.

RD-701 is a sample of engine which can be, absolutely unmodified, fed by pure hydrogen or kerosene with hydrogen mixture.
It has 2x2 MN on sea level and 2x0.8 MN in vacuum, this is absolutely normal thrust for launch vehicle (though it was designed for a spaceplane).

So, as I have written, such switchable engine probably anyway requires LH2 among the components (because it's used as a cooling agent), but it can definitely consume both hydrogen and hydrocarbons.

The idea of methane usage is just to use cheaper and denser fuel than hydrogen when possible, not "or-or". 
Here we can see an implemented example of engine which can be fed mostly with hydrocarbons, using hydrogen as admixture. 
Maybe not purist enough, but does exactly what is required.

Additionally, it can switch right in the flight just due to its construction. Just combine cryotanks in required proportion.

And I'll reiterate... That's because the RD-701 was designed to do that. You could absolutely design an engine that would happily run on hydrogen, methane, or even a mix of both at the same time. But you cannot just feed methane into, say, an RS-68 or a BE-3, and expect it to go well. You could certainly modify the engine to run on it, though the changes could be somewhat extensive.

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The Aerojet LR87 (Titan booster engine) was tested with all 3 major propellant mixtures used at the time.

LR87 was N2O4/Aerozine-50 (hypergolic), and they also made a LR87 LH2 burning hydrogen, and the LR87-3 which was kerlox (and flew many times).

These were variants, however, not the same engine run with different props.

Edited by tater
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^^ Yeah, it was.

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Quote

Bezos: The only way that I can see to deploy this much financial resource is by converting my Amazon winnings into space travel. That is basically it. Blue Origin is expensive enough to be able to use that fortune. I am liquidating about $1 billion a year of Amazon stock to fund Blue Origin. And I plan to continue to do that for a long time. Because you're right, you're not going to spend it on a second dinner out. That's not what we are talking about. I am very lucky that I feel like I have a mission-driven purpose with Blue Origin that is, I think, incredibly important for civilization long term. And I am going to use my financial lottery winnings from Amazon to fund that.

 

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So I guess it's like I said -- Blue Origin is Bezos's "building libraries" phase, where now that he has made all this money he tries to spend it on something.

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18 minutes ago, mikegarrison said:

So I guess it's like I said -- Blue Origin is Bezos's "building libraries" phase, where now that he has made all this money he tries to spend it on something.

I always put it as this is Bezo's "F you" money, lol, but I guess that's the same thing.

His vision and Musk's are actually pretty close in some ways. Bezos is if anything more aimed at the "cosmic endowment" of humanity, but there is a lot of overlap, particularly in the gut reaction statements of both that they think that a seeking, exploring culture is always better than stasis.

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On 5/1/2018 at 9:04 PM, sevenperforce said:

 

You can't use spark ignition for kerolox engines but it works great for hydrolox engines and should work well enough for methalox...or, at least, full-flow staged-combustion methalox. I don't know if it will work for ORSC.

I think they will use something comparable to the TJI (Turbulent Jet Ignition) currently applied in Formula1 engines.

Basically, a small prechamber with a spark plug and injector. Gaseous methane would work flawlessly with it.

At ignition, shaped flame jets are injected into the main combustion chamber.

http://www.mahle-powertrain.com/en/experience/mahle-jet-ignition/

 

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39 minutes ago, Hesp said:

I think they will use something comparable to the TJI (Turbulent Jet Ignition) currently applied in Formula1 engines.

Basically, a small prechamber with a spark plug and injector. Gaseous methane would work flawlessly with it.

At ignition, shaped flame jets are injected into the main combustion chamber.

http://www.mahle-powertrain.com/en/experience/mahle-jet-ignition/

 

Keep in mind the difference between piston engines and continuously burning engines like turbines and rockets. With piston engines you need to re-ignite the combustion every cycle, in a precisely timed way. With continuously burning engines, you only need to relight it if you have turned it off.

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Well, if there is a system that allows you to relight your engine an indefinite number of times, why not use it over "old style" solutions that impose a hard limit? (see Falcon heavy splashdown and TEA/TEB exhaustion)

The capability of repeated/precisely timed ignition is only an advantage from my point of view, complexity of the system doesn't change much.

If the trend is to go towards rocket engine reusability and fast turnaround, a technology (and mindset) transfer from automotive sector would be a great step forward. Cost isn't a barrier for sure, with aerospace budgets you can pick the most advanced solutions and still have a bargain.

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22 hours ago, MaverickSawyer said:

But you cannot just feed methane into, say, an RS-68 or a BE-3, and expect it to go well.

Was I going to do that? Did I in a single word mention RS-68 or BE-3?
The question was "can a hydrogen engine be fueled with methane". As we can see thanks to RD-701 - yes. 
So, this is a good and healthy example.

Can an existing LH2 engine (say, BE-3) run on methane? Definitely not, at least because its cooling system wouldn't allow.
 

Edited by kerbiloid

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1 hour ago, kerbiloid said:

Was I going to do that? Did I in a single word mention RS-68 or BE-3?
The question was "can a hydrogen engine be fueled with methane". As we can see thanks to RD-701 - yes. 
So, this is a good and healthy example.

Can an existing LH2 engine (say, BE-3) run on methane? Definitely not, at least because its cooling system wouldn't allow.
 

No, the original question was if you can run an engine designed to use hydrogen as it's ONLY fuel on methane without modifications, not if an engine could be designed to happily run on both. A question, btw, that you have finally answered in the post I've quoted.

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On 4/29/2018 at 3:48 PM, MaverickSawyer said:

Depends on the dry mass of the first stage. BE-4 is certainly capable of throttling down to ~50% rated power and remaining stable, which is interesting given the fact that the engine is an ox-rich staged combustion cycle. So that means about 250k lbs thrust on landing.

So I wasted spent a ton of time analyzing pictures and trying to scale NG to find a tank to fuel correlation that made sense to no avail. Then I realized that doing this by thrust, ISP, and dV, I could probably get a ballpark much easier. Super Rough estimate: 250 t - 125 t just based on thrust and the knowledge that BE-4 can throttle to 50% so the minimum that the dry mass can be is 50% of the BE-4 SLT otherwise it can't hover. 

Spoiler

The slightly longer version of how I got to this is using a single BE-4 SL thrust of 2400 kN. At 50% throttle, the 1:1 TWR gives a mass of approximately 125 t so this is the absolute minimum assuming that the BE-4 is stable at 50% throttle. There's probably some margin on this and even if it's fuel, I'd say that just ends up being part of the dry mass calculation anyway.

On the high side, you need a 1:1 TWR to hover, which they are currently doing with NS, so 250t is the max. Again, you'd probably need some margin since you're fighting gravity and you don't really want to suicide burn starting with less than 1:1.

That being said, if the lower stage is 250 t at stage separation and the booster touches down just as the mass gets to 125 t, it uses about 2175 - 2400 m/s of dV. The discrepancy is with how you calculate dV: vacuum vs SL ISP, the values I used are found here. Also, 250 t... at stage separation... have I mentioned this thing is huge yet? The New Glenn booster, at stage separation, will probably weigh as much as an Atlas V booster FULLY FUELED.

Now the next question, is this reasonable? By my estimate, on both the low side and high side, yes. I find myself continually adjusting my spreadsheet to principally give a conservative result based on assumptions. Basically, regardless of how I calculate landing dV (thus fuel), the numbers work out to something that seems reasonable. 

How much fuel is needed for landing? I really have no idea. Well, if the requirement for booster recovery is 2.2(ish) km/s, you get booster separation masses 397 t - 372 t and dry masses in the 212 t - 172 t range; assuming you have a landing mass that corresponds to approximately 75% of throttle maximum for 1 engine.

Simplest ballpark answer: 187.5 t this is the ground level TWR mass of 75% throttle, given the 2400 kN of thrust. I probably didn't need to waste spend as much time on this as I did but vanity prevailed and I didn't really get the good estimate I wanted.

Spoiler

So, I mentioned previously that this estimate stacks many assumptions on top of each other. Here they are:

  • Pad Mass: 1660 t - 996 t, based on pad TWR
  • Pad TWR: range analyzed: 1.05 - 1.75
  • Upper stage mass: 351 t, pretty reasonable estimate based on previous effort. This includes the payload fairing since it's shown deploying after stage separation.
  • Upper stage dV: 6592 m/s, based on previous work with some adjustments to be a bit more conservative. 
  • Exhaust Velocity (for dV calculations): 3138 m/s - 3481 m/s (320 s - 355 s, SL and Vac respectively)
  • LEO dV: 10 000 m/s - 9300 m/s, I'm assuming this is going to LEO for comparison purposes. I don't really know what the worst case would be.
  • Payload fairing: 5704 kg, really this was a very conservative estimate based on the Atlas V 5 meter fairing. I could probably figure out the mass of the NG 5 meter fairing (which is actually 5.25 m OD) but for the marginal weight savings it might have, it's probably not worth Blue Origin's time developing or using it so it wasn't considered. Square/cube law strikes again.

All in all, based on the numbers I came up with, I think Blue Origin might be sandbagging their performance. For the lower stage, tankage + aerodynamics (wings and control surfaces) + engines = < 50 t. I'm still missing fuel margin and landing equipment as major items but dry/wet leaves a ton of room for these. 

 

Edited by Racescort666

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This probably doesn't have a good answer, but...

Does anybody know what Blue Origin's plan for developing landing capability for New Glenn is? Considering their general approach, it seems like they're going to try and land boosters from the get-go. On the other hand, it took years of launching and testing for SpaceX to get landing technology to work, and years more to use what they had learned to build a properly re-usable booster. Does BO plan a similar iterative approach, or are they going to try and design the whole thing up front? The latter seems more likely, based on their company philosophy, but it also doesn't jibe with what we've seen of reusable vehicle development so far.

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They could always fly suborbitally from their ranch in TX for a bit.

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4 hours ago, IncongruousGoat said:

This probably doesn't have a good answer, but...

Does anybody know what Blue Origin's plan for developing landing capability for New Glenn is? Considering their general approach, it seems like they're going to try and land boosters from the get-go. On the other hand, it took years of launching and testing for SpaceX to get landing technology to work, and years more to use what they had learned to build a properly re-usable booster. Does BO plan a similar iterative approach, or are they going to try and design the whole thing up front? The latter seems more likely, based on their company philosophy, but it also doesn't jibe with what we've seen of reusable vehicle development so far.

They are scaling up from New Shepard. It will be impressive if they can manage that without any crashes at first, but I would not consider that totally impossible. Especially since NG is said to be capable of hovering so they can do grasshopper like test flights with the real booster.

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14 hours ago, IncongruousGoat said:

On the other hand, it took years of launching and testing for SpaceX to get landing technology to work, and years more to use what they had learned to build a properly re-usable booster.

As far as we know, Blue Origin landed and then actually reused (several times) their very first New Shepard. So maybe it's a little premature to assume they can't do it with New Glenn.

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16 minutes ago, mikegarrison said:

As far as we know, Blue Origin landed and then actually reused (several times) their very first New Shepard. So maybe it's a little premature to assume they can't do it with New Glenn.

During the first flight, the booster stage crashed and was not recovered due to a failure of hydraulic pressure in the vehicle control system during the descent.

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42 minutes ago, sevenperforce said:

During the first flight, the booster stage crashed and was not recovered due to a failure of hydraulic pressure in the vehicle control system during the descent.

Oh yeah? So the one that made the first landing was the second booster? Well that kind of undercuts my comment pretty effectively.

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4 minutes ago, mikegarrison said:

Oh yeah? So the one that made the first landing was the second booster? Well that kind of undercuts my comment pretty effectively.

Maybe a little.

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Landing a tiny suborbital rocket is a lot easier than landing a giant SHLV on a moving barge ship, so I don't think they'll succeed on their first try (especially considering the new shephard failure mentioned earlier).

 

However, I think they will get it a bit faster than SpaceX did, in part thanks to how they land: Instead of performing the most efficient possible suicide burn, rhey hover over the landing site for a few seconds. This makes it easier to do, with greater room for error. It won't take them too long.

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