Blue Origin Thread (merged)

[sojourner]

I could see them at some point in the future retiring Falcon 9 and Merlin and replacing it with a single stick 5 raptor rocket using lessons learned from Falcon and ITS. It would be a true second gen reusable.

[Frozen_Heart]

24 minutes ago, sojourner said:

I could see them at some point in the future retiring Falcon 9 and Merlin and replacing it with a single stick 5 raptor rocket using lessons learned from Falcon and ITS. It would be a true second gen reusable.

I was thinking the same but single stick 9 Raptors, with a single Raptor vacuum second stage. Pretty much an upscaled Falcon 9.

 

Looking at the numbers puts it at a similar liftoff thrust to the Falcon Heavy, but more efficient and with a much better second stage.

[mikegarrison]

4 hours ago, Bill Phil said:

What if those smaller engines are just as reliable individually than the larger ones? Then it's better to have more. Engine out is great, but too many engines can be a huge issue. Five is a good number. It certainly saved the Saturn V at least once. But engines that are too big are also problematic, like the F-1's combustion instability. We were able to make the engine work by fooling around with the injector assembly. The Russians noticed this issue and so they made multiple chambers run off of one set of pumps for that very reason.

They would have to be *more* reliable to make up the difference. Because to get the same launch reliability with more engines, you need each engine to be more reliable.

The first question is whether you need to worry about T/W ratio. If the engine fails too soon, it can deal a fatal blow to your T/W unless you purposely design your other engines with an excess of thrust. But after not too long in the flight, your T/W is no longer a major concern. In fact, you may be wanting to intentionally shut down some engines like the Saturn V did. So if an engine fails then, you are probably fine. You may have to burn a little longer, but you'll get there. The big issue is if it fails right at takeoff, when you are heaviest and thrusting directly against gravity. So either you need to overthrust your engines by 1+1/N times or you need to accept that a shutdown right after launch is a failure.

If you overdesign your engines to be able to handle the 1+1/N thrust, then yes, it's good to have a higher N (more engines). But you need to consider whether you want to pay that cost on every flight just to avoid the occasional failure. If your engines are reliable enough, then you are more likely to accept a lower N. Because of course every fewer engine improves your engine reliability by 1/(N+1), too. So it's a trade.

And if you are designing your engines to have 1/N too much thrust, then they are heavier and more expensive than they need to be.

Perhaps more importantly, every time you have an engine failure that means you are dragging that dead engine along for the ride. So everything has to be designed with more margin. If you can improve your reliability enough to allow you to cut back on your redundancy, then you save cost on *every* successful mission.

Airplanes went through this trade. They have pretty nearly settled on two engines as being the best choice given the current situation. Yes, you have to put large enough engines on so that if one fails during takeoff you can still limp through a climb enough to gain speed and altitude sufficient to return to the airport. And for the very largest airplanes, like the A380 or 747, the technology to make engines that big (so that it could climb with just one of them) doesn't economically exist yet. So for those airplanes, they go with four engines. But engines are expensive, and failure rates are extremely low, and so almost every other modern airliner has only two engines.

Edited April 8, 2017 by mikegarrison

[mikegarrison]

4 hours ago, Exoscientist said:

 You left out the ironic smiley face there!

I always figured that if Jane Austen or William Shakespeare could make themselves understood without smiley faces, then I should learn to do so as well.

[RedKraken]

6 hours ago, cantab said:

I doubt it. Methane is rather lower density than kerosene, so the rocket would hold less fuel unless it's substantially enlarged. And if you're going to change the engines and the structure so much, it's not really a Falcon 9 any more. Also, Falcon 9 lands on one Merlin on low thrust, one Raptor would be three times as powerful and that makes the landing require more precision. And if you replace nine Merlins with three Raptors, what does that do to your engine-out capability.

No, Falcon 9 will keep using Merlins. Raptors are bigger engines for a bigger rocket.

Maybe.

but Spacex would be wasting a great opportunity to make money while practicing methalox operations.

You dont use the full-size 3MN raptor on falcon9. You would use the 1MN test article, modified for merlin-replacement and production.

A methalox falcon (70mx3.66m) using the test article(1MN,334-361s) would lift more than the falconFT (23t), about 25t.

I've been knee-deep in falcon spreadsheets for the last couple of weeks.

I will tidy it up and post for the hordes to savage.

This is not new stuff ... this is the earliest coverage i have found : 

(methalox falcon 9 from 2014) 

(more methalox falcons...check the falcon6) 

(propellant densities from steve pietrobon)

Methane(0.438kg/L) is lower density than kero(0.827kg/L)....

but the bulk density of chilled metholox (0.9kg/L) is 83% percent of chilled kerolox(1.1kg/L).

Why? Because at a ratio of 3.8 oxidiser to 1 fuel, the oxidiser (at 1.25kg/L) dominates the combined density. Even at ratio 3.5, the fraction is 80%.

(The merlin 1D O/F ratio is about 2.35:1 going by the data from spaceflight101)

You got plenty of propellant. Just not enough for 9 1MN engines.

So you use 7. You keep the middle engine for a very soft raptor landing.

The tanks stay 3.66m diameter and Al-Li because thats what you are set up to make.

Weirdly, the kerolox tanks sizes are really close to what the methalox rocket needs.

If you kept the dimensions fixed (70m x 3.66m), same dry masses, adjust the internal bulkheads slightly...

a 460t MethFalc7 with 9197m/s lifts 25t to LEO expendable. TWR ~1.41 liftoff.

swap in a vacuum raptor 1.2MN 380s to your upper stage.....now you are lifting 28t expendable.

For comparison, a 70x4.3m 634t MethFalc9 with 9175m/s lifts 37t. TWR 1.32. 

The deltav split is 4100/5100. Not optimal but ok.

If you take 2m from the first stage length, and add to the second stage, you get back to the 3700/5400 split of the falcon9FT.

Of course, integrating the methane is going to a challenge.

New plumbing for autogen pressure system, rip out the helium. Wack in hotgas reservoirs connected to the raptor heat exchangers. Replace the nitro rcs thrusters with methane thrusters. Insulate the hotgas system from the cryoprops. The methane tank will be about -170centigrade, much colder than the kero(-7C), but closer to the lox temp of -207C. Other engineering stuff. Propellant feeds to the new engines.

Actual tank engineers or learned colleagues could help out here.

All this requires a new launch site. You dont want to interrupt  current F9 operations.

And a ton of other stuff. Not quick or easy.

But could be very profitable testing of your methalox capabilities.

 

 

Edited April 8, 2017 by RedKraken
use same dry mass as falcon9FT

[RedKraken]

38 minutes ago, Frozen_Heart said:

I was thinking the same but single stick 9 Raptors, with a single Raptor vacuum second stage. Pretty much an upscaled Falcon 9.

 

Looking at the numbers puts it at a similar liftoff thrust to the Falcon Heavy, but more efficient and with a much better second stage.

Big Fat Falcon (3MN raptors, 9+1, on a 70mx8.4m, 2000t vehicle) lifts 115t to leo expendable.

Now that would be something to see. The booster landing would be magnificent.

Much softer landing with the center raptor.

* possibly 5 or 10m taller with the 8.4m fairing

[wumpus]

2 hours ago, sojourner said:

I could see them at some point in the future retiring Falcon 9 and Merlin and replacing it with a single stick 5 raptor rocket using lessons learned from Falcon and ITS. It would be a true second gen reusable.

It would have to be as inexpensive in all conditions as the Falcon 9 (but only after the cost saving of shutting down an extra production line) *and* allow landing to be as reliable - i.e. having the raptor throttle down at least twice as far as the falcon.  Otherwise it would be similar to the "3 engine landing" without shutting down the extra engines (or more accurately, shutting down the center instead of the sides) at the landing.

There was supposed to be a "Falcon 5" but it was removed either to reduce the manufacturing complexity (and thus all launch data applied to their only [falcon 9] rocket).  It is fairly obvious that it would be fairly difficult to land a "falcon 5" rocket with the throttle limitations of falcon 9.  I don't know if that was the only reason it was scrapped, or if the cost savings didn't add up (it couldn't be cheaper than a used flight proven Falcon 9).

[sevenperforce]

If I was designing a next-gen Raptor-based RLV, I'd do a composite body 3.66m in diameter with just four SL Raptors in the base. I think the Raptor has low enough throttle. Upper stage would be oversized, large enough to make orbit on its own if not for the Vac nozzle, and land biconically using pressure-fed methalox thrusters pressurized off the Raptor. Upper stage could fly with an integrated Dragon 3 or with a cargo bay.   

[sojourner]

2 hours ago, wumpus said:

It would have to be as inexpensive in all conditions as the Falcon 9 (but only after the cost saving of shutting down an extra production line) *and* allow landing to be as reliable - i.e. having the raptor throttle down at least twice as far as the falcon.  Otherwise it would be similar to the "3 engine landing" without shutting down the extra engines (or more accurately, shutting down the center instead of the sides) at the landing.

There was supposed to be a "Falcon 5" but it was removed either to reduce the manufacturing complexity (and thus all launch data applied to their only [falcon 9] rocket).  It is fairly obvious that it would be fairly difficult to land a "falcon 5" rocket with the throttle limitations of falcon 9.  I don't know if that was the only reason it was scrapped, or if the cost savings didn't add up (it couldn't be cheaper than a used flight proven Falcon 9).

I'm not talking about building a Falcon 5 and putting Raptors on it. I'm talking about building a whole new rocket based on 5 raptors for the first stage and scaling everything to take advantage of that.  It would end up being a bigger rocket with a larger payload.

[Skylon]

(Looks for references to ITS booster landing legs, finds only pictures of KSP recreations) Okay next question, is the ITS landing on its engines? Isn't this Krazy KSP stuff?

And would the ITS booster ever launch anything other than the ship? I haven't run any numbers, but I am pretty sure this could launch a sufficiently sized centrifuge? (Imagines huge fairings)

Edited April 9, 2017 by Skylon

[Frozen_Heart]

1 hour ago, Skylon said:

(Looks for references to ITS booster landing legs, finds only pictures of KSP recreations) Okay next question, is the ITS landing on its engines? Isn't this Krazy KSP stuff?

And would the ITS booster ever launch anything other than the ship? I haven't run any numbers, but I am pretty sure this could launch a sufficiently sized centrifuge? (Imagines huge fairings)

ITS is apparently going to be landing in the launch clamps therefore not needing landing legs...

 

Yeah i think that's crazy too.

[Nibb31]

2 hours ago, Skylon said:

(Looks for references to ITS booster landing legs, finds only pictures of KSP recreations) Okay next question, is the ITS landing on its engines? Isn't this Krazy KSP stuff?

The concept is for the ITS to land into a cradle, which is supposed to dispense of needing legs. It's a crazy idea, and like many of their other ideas, might be scrapped when it starts flying.

2 hours ago, Skylon said:

And would the ITS booster ever launch anything other than the ship? I haven't run any numbers, but I am pretty sure this could launch a sufficiently sized centrifuge? (Imagines huge fairings)

The booster doesn't reach orbit and certainly doesn't come back from orbit. If it launches anything else, that thing is going to need an upper stage.

6 hours ago, sojourner said:

I'm not talking about building a Falcon 5 and putting Raptors on it. I'm talking about building a whole new rocket based on 5 raptors for the first stage and scaling everything to take advantage of that.  It would end up being a bigger rocket with a larger payload.

What market is there for a larger payload ?

[Skylon]

23 minutes ago, Nibb31 said:

-Snippety snip

What market is there for a larger payload ?

Maybe launching hundreds of satellites at once? Or launching large modules for interplanetary motherships. I guess we don't see larger payloads because we can't launch them. Plus spacex may eventually want a destination for their dragon other than the ISS they could even try to build a 'space hotel' or something of the sort. Then there would be more interest.

Also they could practise landing larger boosters, though I'm not sure if it is harder or not

Edited April 9, 2017 by Skylon

[Scotius]

To need bigger payloads (thus, bigger rockets) we would need to start doing serious stuff in space. Mining, construction, big stations with more than a dozen people onboard at any time. Permanent manned bases on the Moon and beyond. Which puts it couple of decades away. And only if this Space Renaissance we are apparently witnessing doesn't fizzle out prematurely.

[tater]

Launching "all the things!" in one go doesn't give you a launch cadence that justifies the notion of a less expensive (per launch) reusable craft.

There's a chicken and egg issue here, you need loads of launches to make new economies of scale work, and you need a reason to go to justify loads of launches.

[wumpus]

2 hours ago, tater said:

Launching "all the things!" in one go doesn't give you a launch cadence that justifies the notion of a less expensive (per launch) reusable craft.

There's a chicken and egg issue here, you need loads of launches to make new economies of scale work, and you need a reason to go to justify loads of launches.

There's also the issue of finding enough satellites that want the same angle of inclination.  Spacex already has plans for a "many bird" communication relay, but likely can fit all the satellites for one inclination on a Falcon Heavy.  You aren't going to fix angles of inclination as willy-nilly as you can in KSP.

[Kerbal01]

FH flight Hardware on the test stand! https://mobile.twitter.com/NASASpaceflight/status/850900133441130496?ref_src=twsrc^google|twcamp^serp|twgr^tweet

[sevenperforce]

8 hours ago, Nibb31 said:

What market is there for a larger payload ?

Yeah, this is the sticking point for me. I'd be interested to see Raptor's ridiculously good specific impulse and TWR being used for smaller payloads, like a fully-reusable mini-ITS that could fly either with an integrated crew capsule or with a cargo bay.

A Raptor-based upper stage can use the autogenous pressurization gas with the planned methalox thrusters for a feather-light landing.

Edited April 9, 2017 by sevenperforce

[cantab]

A telescope with an aperture of several hundred metres could read 12 point text from Low Earth Orbit. I can think of a few organisations that would find that useful. Probably they would build an interferometric array not a single insane mirror, but it would still be a Big Thing.

OK, that's a silly example. But I think in general the spy agencies will have the money and the will to take advantage of a big payload capacity to orbit.

Edited April 10, 2017 by cantab

[mikegarrison]

10 minutes ago, cantab said:

A telescope with an aperture of several hundred metres could read 12 point text from Low Earth Orbit.

... unless it was cloudy that day.

[RedKraken]

Crikey...some really good falcon 9 systems detail here :

https://www.reddit.com/r/spacex/comments/64ew8x/falcon_9_a_systems_overview/

[pyrosheep]

How do plans for increasing the number of satellites in orbit get account for space debris/Kessler effect? 

Or is this problem just overblown?

[Rakaydos]

18 minutes ago, pyrosheep said:

How do plans for increasing the number of satellites in orbit get account for space debris/Kessler effect? 

Or is this problem just overblown?

It's more a problem at, ironically, the higher altitudes. At low altitudes the dangerous schrapnel that sustanes a kessler cascade has too much drag to stay in orbit, and falls back to earth.

And the satelites arnt actually that close together. Imagine if there were only 40,000 cars in the entire world, roughly equally far apart.

[Skylon]

What is the reason for having more satellites? Is there no way you could increase the capacity of a satellite while increasing the mass? Does a bigger satellite equal less satellites? I imagine not

Does Elon Musk still want to have their first mars mission in 3 year's time? So the 2020 vision?

Edited April 10, 2017 by Skylon

[Wjolcz]

1 hour ago, Skylon said:

Does Elon Musk still want to have their first mars mission in 3 year's time? So the 2020 vision?

It's the current plan, I believe.