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Go Grasshopper! :D

bigdad84

By bigdad84
in Science & Spaceflight

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Psycix

Psycix

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So who said buzzing the tower was't realistic?

I'm happy to see stuff like this. I love spaceX! Can't wait for the launch of the 5th of september where they will fly the F9 v1.1 stage with Merlin 1D engines for the first time and attempt to grasshopper land it over water before splashdown.

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bigdad84

bigdad84

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So who said buzzing the tower was't realistic?

I'm happy to see stuff like this. I love spaceX! Can't wait for the launch of the 5th of september where they will fly the F9 v1.1 stage with Merlin 1D engines for the first time and attempt to grasshopper land it over water before splashdown.

Me either! If how Musk interprets it to be, you will be able to launch, recover, and launch again in as little as 10 hours...

Ahem... More space debris :wink:

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Motokid600

Motokid600

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Posted
So who said buzzing the tower was't realistic?

I'm happy to see stuff like this. I love spaceX! Can't wait for the launch of the 5th of september where they will fly the F9 v1.1 stage with Merlin 1D engines for the first time and attempt to grasshopper land it over water before splashdown.

Simply beautiful. Psycix you said they were going to grasshopper land it and splash it into the water? Doesn't that defeat the purpose? I have a hard time understand how this thing is going to work in general so im just trying to wrap my head around it. Will they make the rocket come to a stop just above the water pretending as if it was the surface? That's cool I guess, but its not the launch pad.

So..the 1.1 stage is the liquid boosters for the Falcon heavy, yes? I cant for the life of me imagine how this thing is going to burn to sub-orbital speeds, turn around before/at apoapsis and go right back. And have the leftover fuel to do it. The only way I can imagine this is if the booster completes an orbit and burns retrograde.

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Eric S

Eric S

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Simply beautiful. Psycix you said they were going to grasshopper land it and splash it into the water? Doesn't that defeat the purpose?

It's a test to make sure it's at least semifunctional before trying to bring it down near any expensive facilities.

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Nibb31

Nibb31

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Posted (edited)
Simply beautiful. Psycix you said they were going to grasshopper land it and splash it into the water? Doesn't that defeat the purpose? I have a hard time understand how this thing is going to work in general so im just trying to wrap my head around it. Will they make the rocket come to a stop just above the water pretending as if it was the surface? That's cool I guess, but its not the launch pad.

So..the 1.1 stage is the liquid boosters for the Falcon heavy, yes? I cant for the life of me imagine how this thing is going to burn to sub-orbital speeds, turn around before/at apoapsis and go right back. And have the leftover fuel to do it. The only way I can imagine this is if the booster completes an orbit and burns retrograde.

There are several steps to reusing a first stage. First you need to demonstrate that you can actually restart the Merlin engine, which isn't exactly trivial, especially when it is facing the airflow. Then, you need to demonstrate that it can actually decelerate and land. Then you want to test the actual launch profile, which is different from an expendable launch. You also need to test navigation systems and avionics. And finally, you want to test the "throwback" manoeuver, which is the extra burn that puts the rocket on a RTLS (Return To Launch Site) trajectory. Before throwing the first stage back to the launch site, you want to make sure that it can actually land safely and not crash into a populated area. After that, you need to do extensive testing to make sure that the first stage wasn't damaged, buckled, or bent, in the process. The whole thing might turn out to be not practical at all. They don't really know.

Because rockets are expensive, they will be testing each of these individual steps on actual commercial launches (I assume that customers get a discount for the extra risk or payload loss). The first stages are assumed to be expendable, so after they have done their job, instead of ditching them, they will try out some of their new systems to find out if the RTLS manoeuver is actually practical before actually risking sending one back to the launch pad that might crash into the VAB. Each step actually decreases payload fraction (a reusable F9R will have a payload of approximately 7mt to LEO instead of 11mt for the F9 1.1), so if you are testing on launches that are paid by a customer, it makes sense to minimise payload loss by only testing parts of the RTLS system each time.

Edited by Nibb31
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nhnifong

nhnifong

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First you need to demonstrate that you can actually restart the Merlin engine, which isn't exactly trivial, especially when it is facing the airflow.

They could also leave it on a low throttle setting while they steer the first stage around.

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Nibb31

Nibb31

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It's not really a good idea to have your first stage thrusting (even on minimal thrust) during separation of the second stage. You really want to cut off your engine before the separation event, clear the first stage and then start your second stage engine when you are at a safe distance from the first stage to not damage it with the plume. If your first stage is on low throttle, you risk recontacting and damaging something, which could be catastrophic.

And then, after the RTLS burn, the first stage will be falling down ballistically with the nozzle facing a hypersonic airflow for several minutes before reaching terminal velocity. I'm pretty sure that the plan is to let the atmosphere do its job and to restart the Merlin only at the last minute to save propellant. Restarting a rocket engine in those conditions is pretty much unprecedented and unknown.

Edited by Nibb31
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Nibb31

Nibb31

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I remember reading that an uncontrolled ballistic trajectory would make the first stage impact between 200 and 300 km downrange. I assume that the first flights of a modified F9 expendable first stage will be about trying to restart the central Merlin engine and attempting a soft splashdown in that area. Once they get that figured out, they will start doing tests involving navigation and pinpoint splashdown before going for a full RTLS landing.

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magnemoe

magnemoe

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Because rockets are expensive, they will be testing each of these individual steps on actual commercial launches (I assume that customers get a discount for the extra risk or payload loss). The first stages are assumed to be expendable, so after they have done their job, instead of ditching them, they will try out some of their new systems to find out if the RTLS manoeuver is actually practical before actually risking sending one back to the launch pad that might crash into the VAB. Each step actually decreases payload fraction (a reusable F9R will have a payload of approximately 7mt to LEO instead of 11mt for the F9 1.1), so if you are testing on launches that are paid by a customer, it makes sense to minimise payload loss by only testing parts of the RTLS system each time.

No extra risk for the customers, except the new updated software and the rcs on first stage but new engines is probably more dangerous, yes it will be some reduction in payload because an heavier first stage however they always carry some spare fuel,

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