NASA defends decision to restart RS-25s

[fredinno]

http://www.nasaspaceflight.com/2016/01/nasa-defends-restart-rs-25-production/

NASA explains why it rejected proposals for an alternate engine for SLS (apparently one 'unnamed, small company, who had not produced engines before' had proposed their own SLS engine.)

This explanation was apparently done to help prevent a protest by that company on not having a competitive SLS engine contract. (I think this was a similar situation to the competitive SLS Advanced Booster contract being given to Orbital ATK without a competition).

According to NASA, the proven RS-25 was about 40 percent cheaper to implement- and a new engine used for SLS following the consumption of the existing RS-25 engine stockpile was also rejected, as this would mean the rocket would have to be modified to accommodate the engine, increasing cost, and potentially causing delays.

[silversliver]

1 hour ago, fredinno said:

 (apparently one 'unnamed, small company, who had not produced engines before' had proposed their own SLS engine.)

"Hi, we're a new company, we never built a rocket before, and we want to propose this engine to you, NASA, the biggest space agency in the world, for your actually more important project, the SLS."

 

 

.............yes?

[fredinno]

8 minutes ago, silversliver said:

"Hi, we're a new company, we never built a rocket before, and we want to propose this engine to you, NASA, the biggest space agency in the world, for your actually more important project, the SLS."

 

 

.............yes?

It actually might have been Blue Origin, though, as during the designing of SLS, they had not actually built an engine. They're doing pretty well with BE-3 and BE-4, last time I checked.

[silversliver]

5 minutes ago, fredinno said:

It actually might have been Blue Origin, though, as during the designing of SLS, they had not actually built an engine. They're doing pretty well with BE-3 and BE-4, last time I checked.

Yes they're doing well but their original plan was to flew a manned rocket in 2010. Then 2012.

Now is 2016 and the first UNMANNED launch is just happened.

Great ambitions but you can't compete with who has decades of experience.

[fredinno]

5 minutes ago, silversliver said:

Yes they're doing well but their original plan was to flew a manned rocket in 2010. Then 2012.

Now is 2016 and the first UNMANNED launch is just happened.

Great ambitions but you can't compete with who has decades of experience.

They can with cost. BE-3 is much less expensive than RL-10 (which costs an arm and a leg), and can both be used for upper stages- and BE-4 is a serious threat to AR-1.

[Kryten]

 Blue were building their own engines well before the SLS program started. They were flying a vehicle with them nearly ten years ago.

[silversliver]

10 minutes ago, fredinno said:

and BE-4 is a serious threat to AR-1

For this we need the launch of Vulcan, than we can see.

I would feel more safe with an engine like the RS-25 that flew for 135 missions with an reliability rate of 99,95% than a new engine under development.

[saabstory88]

2 hours ago, fredinno said:

They can with cost. BE-3 is much less expensive than RL-10 (which costs an arm and a leg), and can both be used for upper stages- and BE-4 is a serious threat to AR-1.

RL-10 is an expander cycle engine with a very high ISP. Blue Origin has not released the exact ISP of the BE-3, but it is likely closer to the 436s predicted on the J2-S engine. This would seriously reduce the performance of something like a Centaur upper stage, not increase it.

[fredinno]

4 hours ago, Kryten said:

 Blue were building their own engines well before the SLS program started. They were flying a vehicle with them nearly ten years ago.

Source? BE-3 was pre-SLS, and I can't find anything on BE-2 and BE-1.

2 hours ago, saabstory88 said:

RL-10 is an expander cycle engine with a very high ISP. Blue Origin has not released the exact ISP of the BE-3, but it is likely closer to the 436s predicted on the J2-S engine. This would seriously reduce the performance of something like a Centaur upper stage, not increase it.

So? Vulcan actually is more powerful than Atlas (if the BE-4 option is used). It has extra payload capacity to spare, why not use it to save costs?

[Exoscientist]

On January 5, 2016 at 3:48 PM, fredinno said:

http://www.nasaspaceflight.com/2016/01/nasa-defends-restart-rs-25-production/

NASA explains why it rejected proposals for an alternate engine for SLS (apparently one 'unnamed, small company, who had not produced engines before' had proposed their own SLS engine.)

This explanation was apparently done to help prevent a protest by that company on not having a competitive SLS engine contract. (I think this was a similar situation to the competitive SLS Advanced Booster contract being given to Orbital ATK without a competition).

According to NASA, the proven RS-25 was about 40 percent cheaper to implement- and a new engine used for SLS following the consumption of the existing RS-25 engine stockpile was also rejected, as this would mean the rocket would have to be modified to accommodate the engine, increasing cost, and potentially causing delays.

 

 Running the numbers, with the upgraded thrust of the Merlin 1D, the F9 boosters could serve as the side boosters on the SLS, i.e., two would have sufficient thrust for liftoff. Then you could make the SLS reusable a la the Falcon Heavy by returning the side boosters to the launch site and recovering the SLS core out at sea by barge landing.

 Get a reusable super heavy lift system.

  Bob Clark

[sgt_flyer]

2 hours ago, Exoscientist said:

 

 Running the numbers, with the upgraded thrust of the Merlin 1D, the F9 boosters could serve as the side boosters on the SLS, i.e., two would have sufficient thrust for liftoff. Then you could make the SLS reusable a la the Falcon Heavy by returning the side boosters to the launch site and recovering the SLS core out at sea by barge landing.

 Get a reusable super heavy lift system.

  Bob Clark

 

Only two F9 first stages ? Make that 4... Even with the lower fuel mass thanks to the higher ISP.

1x Falcon 9 1.1 full thrust : 6806kN of thrust

1x 5 segment SRB booster : 16000kN of thrust.

Besides,

RS-25s are not restartable inflight. - an engine has to be designed from the beginning to be restartable inflight.

besides, the core stage would have to sustain much higher reentry speeds than a F9H core stage  at the time of separation.

(falcon 9 1st stages have a 180s burn time (without fuel crossfeed draining the side boosters faster)

- so you're looking for a burn time around 300s max for the core stage. SLS core stage (stretched ET with 4 RS-25s) you're going to be much closer to 400s of burn time for the core stage. The difference in speed is going to be quite high for reentry  

Edited January 10, 2016 by sgt_flyer

[Exoscientist]

 True about higher reentry speeds. But that is also true for the Falcon Heavy central core stage.

 Note a side booster does not have to equal the thrust of another side booster to improve performance (payload). It can do it by having higher Isp and being lightweight.

 

  Bob Clark

Edited January 10, 2016 by Exoscientist

[StrandedonEarth]

Hmmm, now how do I plug F9 cores, 5seg SRB's, and SLS cores into KER, to see what gives more dV in the end?

[fredinno]

1 hour ago, StrandedonEarth said:

Hmmm, now how do I plug F9 cores, 5seg SRB's, and SLS cores into KER, to see what gives more dV in the end?

An SLS core will almost certainly give more Delta V, no questions asked. A 4-seg SRB will be able to go just short of LEO, provided you can control ts trajectory. Meanwhile, a Falcon 9 core has payload capacity of ~5-10 T, and SLS core w/ Atlas 1.5 staging= 50T to LEO.