What stage 1 1/2 means?

[Pawelk198604]

I know that Atlas rocket that launched Mercury spacecraft was 1 1/2 stage but what that means?

Edited February 28, 2016 by Pawelk198604

[SargeRho]

The Atlas drops 2 of its engines in flight, but it doesn't drop a full stage. Hence 1 1/2 stage.

[Pawelk198604]

11 minutes ago, SargeRho said:

The Atlas drops 2 of its engines in flight, but it doesn't drop a full stage. Hence 1 1/2 stage.

 

Thanks

 

[Bill Phil]

It drops engines, but not tanks.

[Nothalogh]

Similarly, I've seen droptank designs called 1.5 stage

[Bill Phil]

15 minutes ago, Nothalogh said:

Similarly, I've seen droptank designs called 1.5 stage

A stage is usually engines and a tank.

[fredinno]

8 hours ago, Bill Phil said:

A stage is usually engines and a tank.

So if either is dropped, that's a 1/2 stage.

[Pawelk198604]

I wonder does is any video showing how Mercury Atlas separating this engine ? 

[Nibb31]

There were plans for a 1.5 stage Saturn V variant, using a modified "S-IB" that would jettison 4 of its F-1 engines to reach orbit with 20-ton payload.

http://lostinthisspace.blogspot.fr/2013/01/s-1d-first-stage.html

[sevenperforce]

15 minutes ago, Nibb31 said:

There were plans for a 1.5 stage Saturn V variant, using a modified "S-IB" that would jettison 4 of its F-1 engines to reach orbit with 20-ton payload.

http://lostinthisspace.blogspot.fr/2013/01/s-1d-first-stage.html

That's beautiful.

I concur with what the commenters said: the Shuttle is undoubtedly the most awe-inspiring, aesthetically breathtaking, mission-capable thing we've ever put into space, but WOW was it a waste of money.

I wonder how recovery would have gone with that ring.

[fredinno]

7 hours ago, Nibb31 said:

There were plans for a 1.5 stage Saturn V variant, using a modified "S-IB" that would jettison 4 of its F-1 engines to reach orbit with 20-ton payload.

http://lostinthisspace.blogspot.fr/2013/01/s-1d-first-stage.html

http://www.spacelaunchreport.com/sls2.html

This concept would have used a 1 1/2 stage SLS core to replace Ares 1. It was never truely considered because NASA was told to have 100t rockets to LEO, not the 30T of this rocket. Still cool though, and would have been pretty quick to develop, by the looks of it.

[sevenperforce]

More efficient than the 1.5-stage design, though also more complicated, is the variable-ratio tripropellant liquid-fueled engine. Design an engine that can burn two different types of fuel (typically LH2 and RP1, though other combinations are possible) along with a single oxidizer. Most importantly, design the engine such that it will be able to vary the fuel and oxidizer ratios infinitely while maintaining maximum efficiency. 

That way, you can start your launch with a high proportion of RP-1 for maximum thrust, then vary the ratio slowly to more and more LH2 as your thrust requirements drop, increasing specific impulse.

Putting the RP1 in a drop tank makes this design even better. 

[fredinno]

2 hours ago, sevenperforce said:

More efficient than the 1.5-stage design, though also more complicated, is the variable-ratio tripropellant liquid-fueled engine. Design an engine that can burn two different types of fuel (typically LH2 and RP1, though other combinations are possible) along with a single oxidizer. Most importantly, design the engine such that it will be able to vary the fuel and oxidizer ratios infinitely while maintaining maximum efficiency. 

That way, you can start your launch with a high proportion of RP-1 for maximum thrust, then vary the ratio slowly to more and more LH2 as your thrust requirements drop, increasing specific impulse.

Putting the RP1 in a drop tank makes this design even better. 

I imagine the engine structure would be one engineering acheivement.

[Ten Key]

12 hours ago, Pawelk198604 said:

I wonder does is any video showing how Mercury Atlas separating this engine ? 

As far as I know, there weren't any cameras aboard those rockets. This is the best I could find. It's an Atlas-Agena launch, but the rocket is essentially the same as the one they used for Mercury launches. 

https://youtu.be/xerPh9-IZ4I?t=4m40s

You really can't see much.

The Atlas D booster engines were on a skirt-like structure at the base of the rocket. The skirt had a hole in the middle for the central sustainer engine. Roughly two minutes into the flight the skirt dropped away, leaving the central engine burning.

 

 

This engine arrangement allowed the rocket to ignite all three engines on the launch pad and avoided the problem of having to start an engine in flight. 

[Mitchz95]

^ That seems like the kind of thing you'd see in KSP, not real life.

[sevenperforce]

1 hour ago, fredinno said:

I imagine the engine structure would be one engineering acheivement.

A dazzling one. Any tripropellant design is an engineering nightmare; an efficient one ever so much more so. 

[Pawelk198604]

I wonder does any of you tried 1 1/2 stage in KSP, my rocket always had 2 stages.

[SargeRho]

I've used a 1 1/2 stage rocket, that drops 2 engines once it's light enough.

[justidutch]

It works quite well on spaceplanes that just can't quite get to orbit on their own

[Nothalogh]

10 hours ago, Pawelk198604 said:

I wonder does any of you tried 1 1/2 stage in KSP, my rocket always had 2 stages.

I've used them before, a swivel and two thuds on decouplers

[fredinno]

9 hours ago, justidutch said:

9 hours ago, justidutch said:

It works quite well on spaceplanes that just can't quite get to orbit on their own

It works quite well on spaceplanes that just can't quite get to orbit on their own

Why would you? It wouldn't result in much improvement in payload capacity.

[magnemoe]

12 hours ago, Pawelk198604 said:

I wonder does any of you tried 1 1/2 stage in KSP, my rocket always had 2 stages.

Some of my huge interplanetary ships back in 0.9x had an skipper to help the LV-N doing the end of gravity turn, the interplanetary ship was here upper stage and was refuled in LKO, drop skiper at 2.2 km/s. 
Drop tanks are very nice everywhere and is used a lot. Both for interplanetary missions and for landers, You can take one Kerbal from LKO to Mun landing and back on one 909 and drop tanks, Stage during Mun transfer, landing and accent. 
Accent also dump legs. 

[kerbiloid]

On 01.03.2016 at 4:58 PM, Nibb31 said:

There were plans for a 1.5 stage Saturn V variant, using a modified "S-IB" that would jettison 4 of its F-1 engines to reach orbit with 20-ton payload.

http://lostinthisspace.blogspot.fr/2013/01/s-1d-first-stage.html

Amazing picture!

If the quad were reusable, that's how an EvilScientist / KerbalDarkLord personal rocketship would look like.
Launching from the DarkCitadel, returning all stages onto the platform of the cargo elevator at the citadel's backyard to be reattached and refueled.
 

[Frybert]

On 3/3/2016 at 10:35 AM, Pawelk198604 said:

I wonder does any of you tried 1 1/2 stage in KSP, my rocket always had 2 stages.

Early in my RP-0 save I used this a lot. I have since gone back to more traditional staging however as it made it much easier to know TWR and DV. Also, stock fuel tanks in KSP are much heavier than IRL tanks for the amount of fuel they hold, so you're almost always going to be wanting to dump some tankage with your engines. The atlas used a very lightweight 'balloon' tank, so tank mass wasn't as big of an issue.