Questions

[Guest]

47 minutes ago, PB666 said:

Anything can be a final burn to orbit

ehehehehe.jpg

47 minutes ago, PB666 said:

Let me clarify this so I don't get a pedantic response.

That's a good idea.

47 minutes ago, PB666 said:

Maybe ULA doesn't want to redesign a stage and things its just cheaper to Jimmy it into orbit with non-optimal equipment.

Oh, for sure. My issue here is you saying it doesn't work when it clearly does, efficiently, I might add, on the manufacturing and cost front.

[Green Baron]

Looking at the mere data of the engine it seems quite well suited for the last push. Could have a little less around the waist.

Let me play the fool: and for the last 1-2km/s ... if the alternative is falling back down :-)

[PB666]

1 hour ago, regex said:

ehehehehe.jpg

That's a good idea.

Oh, for sure. My issue here is you saying it doesn't work when it clearly does, efficiently, I might add, on the manufacturing and cost front.

Delta III second stage works fine, Delta IV second stage might work fine for a MEO orbit its a waste for LEO. [corrected]

The RL10b-2 is a known thing, its only 277 kg, adding a second engine like the Russians do in similar circumstances is tried and true practice.

Edited December 11, 2017 by PB666

[Guest]

1 minute ago, PB666 said:

The RL10b-2 is a known thing, its only 277 kg, adding a second engine like the Russians do in similar circumstances is tried and true practice.

I'm sure there's a cost/benefit analyst job just waiting for you at ULA.

[PB666]

59 minutes ago, Green Baron said:

Looking at the mere data of the engine it seems quite well suited for the last push. Could have a little less around the waist.

Let me play the fool: and for the last 1-2km/s ... if the alternative is falling back down :-)

I can come up with a design easily that does not need and RL10-b2 and a cheaper on that uses Kerosene and Oxygen. RL10-b2 is a space engine, it really not a go to orbit engine unless your payload in small.

In fact why it took me so long to test the configurations was that all my rockets overshot the target velocity, I had to take the first stage apart and reduce the engines in them. lol.

[DDE]

9 hours ago, PB666 said:

The RL10b-2 is a known thing, its only 277 kg, adding a second engine like the Russians do in similar circumstances is tried and true practice.

Starliner and its Atlas V-?22 called.

[PB666]

17 hours ago, regex said:

I'm sure there's a cost/benefit analyst job just waiting for you at ULA.

OK,  . . . .

A lighter launch rocket, 3-RL10b-2 on the back 40 tons into orbit (The addition of 12 tons of payload for the cost of 2 RL10b-2) it can easily be justified by a lower weight in the launch rocket (plus 800 dV of cryo left).

RL10s are not like SSME, they are a pretty simple engine.

 

[Guest]

1 hour ago, PB666 said:

OK,  . . . .

A lighter launch rocket, 3-RL10b-2 on the back 40 tons into orbit (The addition of 12 tons of payload for the cost of 2 RL10b-2) it can easily be justified by a lower weight in the launch rocket (plus 800 dV of cryo left).

RL10s are not like SSME, they are a pretty simple engine.

 

I wonder why ULA doesn't offer that option but does offer a standard Delta-IV Heavy launch to 200km orbit?

E: I mean, given everything you've said it's the most inefficient thing they could be doing. Earlier you even claimed they really couldn't be doing it which is my main point of contention since they clearly can. I'm not arguing efficiency of engines and thrust here, but you're very wrong to state that a single RL-10b-2 isn't an engine that can make the final push to orbit with a large load.

Edited December 12, 2017 by regex

[PB666]

1 hour ago, regex said:

I wonder why ULA doesn't offer that option but does offer a standard Delta-IV Heavy launch to 200km orbit?

E: I mean, given everything you've said it's the most inefficient thing they could be doing. Earlier you even claimed they really couldn't be doing it which is my main point of contention since they clearly can. I'm not arguing efficiency of engines and thrust here, but you're very wrong to state that a single RL-10b-2 isn't an engine that can make the final push to orbit with a large load.

The reason is quite simple. The difference between the two engines is too great, the RS68A is a very very powerful engine, its great, fantastic, with two booster really great .. . . Its practically the only engine I use now. . . . . but the RL10b-2 is also a really great space engine meaning 95% V_orb to hyperbolic , but you need something in between to burn efficiently to orbit. This is why I brought up the discussion earlier about the RD150. If the D4H had a intermediate stage consisting of RD150 engines it would be the rocket to beat, PL to orbit would almost double.

The three stages of ULA combined at launch produce 100x the thrust of the RL10b-2 where as the upper stage is 1/5th the total weight. a differential ratio of 1:20.
The falcon 9 produces 10 times the thrust in the first than the second and the but the first stage is 549 whereas the second stage is 111, a differential ratio of 1:2.
Thats a pretty big difference. A wide difference like that puts more work on the core. Note that the Falcon9 (expendible) gets 22t  into orbit versus DH4 gets 28 t

Unless ULA changes there configuration SpaceX is going to beat ULA, for the same sized or smaller rocket eventually they will get a higher payload into orbit.

 

 

Edited December 12, 2017 by PB666

[Guest]

13 minutes ago, PB666 said:

Unless ULA changes there configuration SpaceX is going to beat ULA, for the same sized or smaller rocket eventually they will get a higher payload into orbit.

Well that's their problem, but you're still wrong saying that the RL-10b-2 can't get things to orbit.

[PB666]

They can use whatever they want, I won't use an RL10-b2 to lift 28t to orbit , its simply a waste.