Alternative - and fun trajectories!

[Sorabh]

I was muddling through the internet yesterday, and saw some pretty fun trajectories for Mars exploration:

Following the above trajectory, a Mars exploration mission would have been possible with two, maximum three Saturn V launches.

Hyperbolic orbit rendezvous, is it possible in KSP?

[NSEP]

2 hours ago, Sorabh said:

I was muddling through the internet yesterday, and saw some pretty fun trajectories for Mars exploration:Hyperbolic orbit rendezvous, is it possible in KSP?

It may be hard, but not impossible. If you plan everything well enough you can do it. 

Hey, new challenge idea!

[wumpus]

7 hours ago, Sorabh said:

I was muddling through the internet yesterday, and saw some pretty fun trajectories for Mars exploration:

 

Following the above trajectory, a Mars exploration mission would have been possible with two, maximum three Saturn V launches.

Hyperbolic orbit rendezvous, is it possible in KSP?

Powered swingby burn (H₂/O₂).  That looks like hydrolox and not peroxide to me.  I don't think storing hydrogen for 8 months was possible in 1960s/early 70s tech.  Maybe with "space race funding" still in place they could have managed it, but the one project that requires similar tech (James Webb telescope) seems infinitely delayed.

I wonder how big the 6-9 month habitat is.  Skylab was the size of the TLI fuel tank (I think it *was* a retrofitted tank and definitely fit in its place on a Saturn V) which would be my go-to habitat (presumably most of the engineering was already done for Skylab).  That doesn't leave much room on the other 2.

[Sorabh]

 

1 hour ago, wumpus said:

Powered swingby burn (H₂/O₂).  That looks like hydrolox and not peroxide to me.

Although Hydrogen peroxide can be used as a monopropellant( decomposing it into hydrogen and oxygen and then igniting it),  its more useful as an oxidiser. Although only the British rocket Black Arrow used a Kerosene/ peroxide mixture. 

Thats because H₂O₂ decomposes into  H₂ and O₂with evolution of heat. This evolved heat then further quickens the process of dissosciation.  Soon, the gaseous byproducts would exert stress on the fuel tank, and if not vented out. There'Bs no way peroxide will last for the transit time in space....

1 hour ago, wumpus said:

I wonder how big the 6-9 month habitat is.  Skylab was the size of the TLI fuel tank (I think it *was* a retrofitted tank and definitely fit in its place on a Saturn V) which would be my go-to habitat (presumably most of the engineering was already done for Skylab).  That doesn't leave much room on the other 2.

Also, for a 6 person crew(Minimum crew for Mars) a 150m³ of habitable space is required. Skylab had almost 320 cubic metres of habitable space (Much fuel tank, such space!) which would be twice of what they really need!

So launches will be like this:

1. Launch Hab and propulsion bus
2. Launch Ascent stage of MEV
3. Launch first part of descent  stage 
4. Launch second part of descent stage.

The entire MEV(Mars Excursion Module) weighs around 80 tons, so for individual launches they might not use a Saturn V.. Maybe a smaller booster.

Sources:

1.  Habitable volume: https://ston.jsc.nasa.gov/collections/trs/_techrep/TM-2015-218564.pdf
2. Peroxide behaviour: 
3. MEV weight: I read it long ago, cant really remember which document...

[YNM]

9 hours ago, Sorabh said:

Hyperbolic orbit rendezvous, is it possible in KSP ?

It's even possible in real life, although :

- Cost lots and lots of propellant

- Must be very precise and direct (not when things are only carried out half an hour later !)

[Sorabh]

14 minutes ago, YNM said:

Cost lots and lots of propellant

But we are only accelerating a relatively small Ascent module to hyperbolic trajectory. Far less fuel required than accelerating the entire vehicle to that velocity. Also, they wont be doing any capture burn so propellant saved there too!

 

18 minutes ago, YNM said:

Must be very precise and direct (not when things are only carried out half an hour later !)

The descent stage is given a 500 m/s boost when it separated, so theres a 20 day time gap. Although yes, if you missed once, there might be another chance....

[YNM]

11 minutes ago, Sorabh said:

But we are only accelerating a relatively small Ascent module to hyperbolic trajectory. Far less fuel required than accelerating the entire vehicle to that velocity. Also, they wont be doing any capture burn so propellant saved there too!

Yeah - but that still means bigger things, bigger carrier, bigger booster... oh hang on...

12 minutes ago, Sorabh said:

The descent stage is given a 500 m/s boost when it separated, so theres a 20 day time gap. Although yes, if you missed once, there might be another chance....

Ah... mistook for a robotic mission or something.

 

In case of manned mission what you're saying is a bit like when they saved that Martian.

[Sorabh]

8 minutes ago, YNM said:

Yeah - but that still means bigger things, bigger carrier, bigger booster... oh hang on...

Umm, please elaborate?

I mean English is not my first language..

Edited December 11, 2017 by Sorabh

[YNM]

1 hour ago, Sorabh said:

Umm, please elaborate?

I mean English is not my first language..

Well, rocket equation 101.

[Sorabh]

Tsiolkovsky is literally my display pic......  Dont need to remind me of that one...

No I meant, how do you think a mission whose major component will just flyby be more massive than a mission whose entire spacecraft will burn for insertion and then again for ejection?

Maybe there is a communication gap here..

[Nuke]

12 hours ago, Sorabh said:

Hyperbolic orbit rendezvous, is it possible in KSP?

ive done it

[Sorabh]

@Nuke Your 5 stars are testament to your achievement! Congrats!

But have you attempted the 'Crocco' trajectory? (Burn only once at Kerbin and set a Kerbin- Duna- Kerbin free return orbit...)

Edited December 11, 2017 by Sorabh

[Green Baron]

14 hours ago, Sorabh said:

Hyperbolic orbit rendezvous, is it possible in KSP?

Sure, try to catch an asteroid in Kerbin's SOI ... as a training

Edited December 11, 2017 by Green Baron

[StrandedonEarth]

9 minutes ago, Green Baron said:

Sure, try to catch an asteroid in Kerbin's SOI ... as a training

Been there, done that, added them to my LKO space casino. 

[Sorabh]

1 hour ago, Green Baron said:

Sure, try to catch an asteroid in Kerbin's SOI ... as a training

Oh.. But in Kerbin's SOI, even if you rendezvous with the asteroid on hyperbolic trajectory, you know that by burning retrograde you will fall back in Kerbin's orbit. 

But once my ascent module docks with my spaceship moving at escape velocity in Duna's SOI, how do I make sure that it will fall back in Kerbin's SOI after departure?

1 hour ago, StrandedonEarth said:

Been there, done that, added them to my LKO space casino. 

Congratulation on the new attraction! 

[Laie]

15 hours ago, Sorabh said:

Hyperbolic orbit rendezvous, is it possible in KSP?

Absolutely. The main drawback is that you have exactly one attempt. I don't know how much that matters in practical terms, but it certainly sounds risky.

[DAL59]

So to get this straight, the ship separates in to three sections.  One flybys Mars, another enters orbit, and the lander descends and ascends 20 days ahead, then docks with the orbiter.  When the flyby piece passes Mars again, they do a hyperbolic rendezvous and return.  

[Sorabh]

The ship is separates into 2 parts, the Mars Transfer Vehicle and the Mars Excursion Vehicle 

MEV separates from MTV and gets a 500m/s 'kick'

This lets it reach Mars 20 days earlier. The MEV aerocaptures into orbit first and then descends as a single unit.

After surface mission is over in 20 days, MTV is now overhead, in a hyperbolic orbit. The crew gets in the ascent stage and kicks to orbit.

It then accelerates to match MTV velocity, they dock and then after a 800m/s of boost, they are on their way to a Venus Swingby.

Using the Venus Swingby, they will sheat off their orbital velocity and fall to Earth's SOI. @DAL59

[Zeiss Ikon]

18 hours ago, Sorabh said:

Hyperbolic orbit rendezvous, is it possible in KSP?

That (including bringing enough fuel to direct or park thousands of tonnes of rock) is exactly what you're doing if you intercept an asteroid that's blundered into Kerbin's SOI.  Unless it's temporarily captured by a Mun encounter, any asteroid that comes from outside Kerbin's SOI is on an escape trajectory (though the game sometimes incorrectly reports them as "orbiting Kerbin" with an apoapsis above the SOI limit).

[Nuke]

8 hours ago, Sorabh said:

@Nuke Your 5 stars are testament to your achievement! Congrats!

But have you attempted the 'Crocco' trajectory? (Burn only once at Kerbin and set a Kerbin- Duna- Kerbin free return orbit...)

unfortunately no. but ive been playing around with kerbal star systems and old boom boom. when the kraken ate most of my ship leaving jeb stranded between stars on a rather flat trajectory, i opted to send a repair mission (good thing i had kis installed). i sent a ship with bunch of replacement parts and between the two craft rebuilt a new ship one peice at a time while in transit. the result had an odd configuration, the secondary propulsion was pointing in a direction different than the orion drive. so id have to turn around to trim my manuvers out. 

ksp doesnt seem to like to show you intercepts on open trajectories for some reason, but if you create a node, and then create a second node near the intercept, and indicator will display letting you tune that orbit to the point where you can get within 50k of a moon in the system. stopping in time is a different matter entirely with my transit velocity is around 80000m/s.

 

and honestly i dont know where those stars came from.

Edited December 12, 2017 by Nuke