Space X Style Landing Burn

[thevegimobil]

Hey guys!

I wonder if I can get your thoughts on how best to execute the Space X launch profile. I have a stock a like Falcon 9 that I am really proud of.

However... I can't seem to determin the best and most effecient way to burn back to the launch pad. I find that I have to sacrifice so much Stage 1 dV that it makes the 1st stage less useful to orbit, it leaves too much work to the second stage. I wonder what the most effecient was of burning back to KSC is in your opinions? In order to get an efficient enough flight I have to burn at a shallow angle, but that means loads more horizontal velocity to burn back on to reverse my course to the space centre. I have a landing site on the island to the North West of KSC which is perfectly placed for this type of launch, though its still pretty close and I would love to hear your thoughts. I am saving a lot of delta V for the landing burn at this stage and would like to fine tune my launches before working on my Falcon Heavy variant!

 

C

[p1t1o]

You may be trying to return too much mass, try shifting some 1st stage dV to the 2nd stage. You'll get an earlier seperation, and more room for correction in the 2nd stage.

It may not be strictly SpaceX but you could try a few parachutes to save dV on the descent, unless that jars too much with your "powered landing" sensibilities. 

And try as much as possible to do most of your rocket-enabled slowing down at the last minute, a "suicide burn" uses the least dV for touchdown.

If you're getting desperate, reducing the payload mass will of course improve performance at all levels.

[thevegimobil]

Thanks! Yeah that's a good idea re moving mass up the stages. Though I want to be as reuseable as possible so wouldnt want to bump too much up a stage.

Interesting comment on the powered landing sensibilities I hate the idea of parachutes!!

[Snark]

Moving to Gameplay Questions.

[invision]

since your going to land it and recover it just use more fuel as it only going to cost you fuel which is cheap.

also use airbrakes and it should slow you down enough you only need about 10 real seconds of fuel to kill off the last bit of speed.

[Human Person]

2 hours ago, thevegimobil said:

it leaves too much work to the second stage.

That‘s what these lazy Falcon 1st stages always do, leave most of the work for the 2nd stage!

just kidding, I’f you want the first stage to do more, simply make it bigger.

 

For the boostback burn, there‘s a really useful mod called Trajectories.

 

For the landing burn: practice. I haven‘t found an easy way of doing it!

Edited January 26, 2018 by Physics Student

[A_name]

Also consider making the first stage booster an SSTO, pretty achievable in stock Kerbin. That way you only need to leave enough Dv for deorbiting (anywhere between 200-500 m/s depending on your orbit), making the entry burn and the landing burn. It will save you all the Dv needed to boost back. The thing is, with stock Kerbin, because of the low orbital velocity (compared to IRL Earth) it's often actually cheaper in terms of Dv to continue on into orbit than to boost back.

[Spricigo]

27 minutes ago, A_name said:

Also consider making the first stage booster an SSTO, pretty achievable in stock Kerbin. That way you only need to leave enough Dv for deorbiting (anywhere between 200-500 m/s depending on your orbit), making the entry burn and the landing burn. It will save you all the Dv needed to boost back. The thing is, with stock Kerbin, because of the low orbital velocity (compared to IRL Earth) it's often actually cheaper in terms of Dv to continue on into orbit than to boost back.

Agree with the idea, differ in the reasoning.

Rather than how much extra deltaV it takes, the question is if we can save Funds with even with the extra deltaV required to bring the booster back.

That said, our ascending trajectory will be more efficient, since we don't need to worry about going too far away from the launch site to have a good recovery rate. Also (assuming we recover only the 1st stage) we have more to recover to begin with. And finally, it can be much simpler to setup, since we don't need to worry about switching vessels during atmospheric flight or landing the booster before upper stage start to fall down.