Stock Mars Landing

[sneakeypete]

I\'d just cheat and use an existing IRL study.

Something like TROY?

The issue, I think, isn\'t so much the method of getting yourself/fuel to the planet. There\'s that, and numerous other proposals. What i find, however, in all of them, is that they have some magic vehicle which is able to land on mars (with/without refueling on the surface). and then return to orbit. I\'ve not heard any proposals on the feasibility of constructing such a rocket.

[DrBurst]

Here is the names I came up with. These are all bassed around the latin name for war, bellum.

kellum and kerrum.

[Temstar]

I\'ve been coming up with prototypes of the craft I will need for a manned mission to Planet L

3 vehicles will be launched, one with heavy lifter, one medium lifter and one light lifter.

1. Orbital Tanker / Propellant Deport

2. Interplanetary Maneuvering Stage

3. Planetary Excursion Module

IMS and PEM are launched with additional boosters which coupled with their own engine will take them to Low Kerbin Orbit. Once in orbit, the IMS and PEM will dock in turn with the orbital tanker to refill their fuel tanks.

the PEM will then dock with the rear docking collar of the IMS. Once hard docked the IMS will fire its main engines for a Hohmann transfer orbit to Planet L. Upon arrival at Planet L, IMS will then turn around for a retro burn to settle down in low orbit above Planet L.

The assumption is that Planet L is a Mars like planet - surface gravity 0.4G (Mun is 0.16G), surface atmosphere pressure 0.5% of Kerbin\'s atmosphere pressure at sea level. Parachute only landing is not possible but the rarefied atmosphere and reduced gravity makes it much easier to reach orbit than Kerbin. My PEM when tested on Kerbin can easily reach 60,000m apoapsis after jettisoning parallel stage, so the same craft should have enough fuel for powered descent + return to orbit on a 0.4G planet with almost no atmosphere.

PEM undocks from the IMS and make a parachute assisted powered descent to Planet L\'s surface. RCS fuel usage should be minimal since parachute will reduce lateral movements. Once there the Kerbalnauts will get out for EVA, pick up some rocks, plant a flag and whatnot. Once EVA is complete PEM then takes off from the surface, staging once descent/ascent stage is out of fuel and reach orbit to redock with IMS. If things really go pear shaped the IMS\'s own spacecraft stage can undock from the boosters, catch the drifting PEM and bring it back with it\'s own forward docking arm.

Once PEM is hard docked IMS then makes another Hohmann transfer orbit burn back to Kerbin with a retroburn in LKO. PEM is filled enough fuel for deorbit burn and deorbits. Then IMS forward spacecraft stage separates from the IMS boosters and makes it\'s own deorbit burn.

The IMS boosters are left in LKO. I\'ve sized it with enough tankage that it should be able to attempt a Hohmann transfer orbit to outer gas giant planets so it will be a waste to just let it burn up. With the IMS boosters in orbit a future interplanetary mission only needs to send another PEM, a small control spaceship to dock with IMS booster stage and another orbital tanker to have enough hardware.

The orbital tanker fuel tank is also designed to be able to separate with the space tug. Once a tanker is empty the tug can leave the empty tank in space for conversion into a wet workshop space station with the tug itself returns to Kerbin.

[sneakeypete]

Wait, the real mars\' atmosphere is only 0.5% of earths?

That\'s a lot less than i thought.

[VincentMcConnell]

That\'s why Mars is almost a vacuum. We need to terraform it.

[Endeavour]

Here is the names I came up with. These are all bassed around the latin name for war, bellum.

kellum and kerrum.

Kerrum reminds me more of Ferrum, as in the element Iron. Which makes sense since the red color of mars is supposed to be rusted iron.

[AlternNocturn]

rusted iron

'Oxidized iron'. 'Rusted iron' is redundant. Why does this even matter to me? No idea.

OT: I have a feeling patched conics will help a lot with getting to other planets, although I forsee myself utilizing MechJeb for the first few launches to the new planets until I can feel confident enough to do it myself. According to earlier replies to my post the 'Wait until planet comes up over Kerbin\'s limb and burn' method won\'t work for objects in orbit around Kerbol, only objects orbiting the same object you\'re orbiting. In that case I believe heavy use of Minmus to perform Orbital slingshots will be the only way to do repeated missions there without using too much fuel.

[PakledHostage]

In that case I believe heavy use of Minmus to perform Orbital slingshots will be the only way to do repeated missions there without using too much fuel.

I disagree. I\'ve compared Delta-V requirements for a few different interplanetary trajectories and it doesn\'t take much more Delta-V to get into an interplanetary trajectory than it does to get to the Mun. And that\'s without the added complexity of a gravitational assist from the Mun or Minmus.

For example, getting out to 1.5 times Kerbin\'s orbital radius (i.e. out to 20 million km from Kerbol) from a 100 km high parking orbit above Kerbin only requires ~180 m/s more Delta-V than it takes to get to the Mun from that same orbit. And if the new planet has an atmosphere, then we will be able to use aerobraking upon arrival to save even more fuel.

But I think the strongest argument that we won\'t need to use a gravitational assist from the Mun or Minmus to get to any new planets comes from the example set by real-life Mars missions. Curiosity didn\'t require a lunar slingshot to send it on its way to Mars.

[Temstar]

Problem with using gravitational assist in this case, other than the small amount of assist the low gravity of Mun and Minmus can provide is launch window. A direct Hohmann transfer orbit to another planet will happen multiple times each Kerbin year. If you had to also get Mun and/or Minmus in position for an assist than the window considerably narrows depending on the length of the Munar month.

[Temstar]

There\'s one thing that\'s been bugging me about lander designs. Namely why did the Apollo LM use two separate engines, one for descent and one for ascent? Seems like a waste of fuel to carry that ascent engine as deadweight down to the lunar surface. In comparison the tiny Soviet LK lander could also carry two people to the lunar surface and then rejoin LOK waiting in lunar orbit. It manages to do this while only weighing 1/3 as much as the Apollo LM by (among other things) using the same engine for both descent and ascent, leaving only its landing legs on the lunar surface.

Is there any reason for this particular design for the Apollo LM? It definitely wasn\'t because LM descent engine couldn\'t be restarted because Apollo 13 manage to fire its descent engines multiple times for free return trajectory and course corrections.

[RC1062]

Fuel may be wasted going down, but on return it hasn\'t got the dead weight of the legs.

I suppose it is an egotistical thing aswell, you\'re leaving something behind that will remain for centuries.

[Nibb31]

There\'s one thing that\'s been bugging me about lander designs. Namely why did the Apollo LM use two separate engines, one for descent and one for ascent? Seems like a waste of fuel to carry that ascent engine as deadweight down to the lunar surface. In comparison the tiny Soviet LK lander could also carry two people to the lunar surface and then rejoin LOK waiting in lunar orbit. It manages to do this while only weighing 1/3 as much as the Apollo LM by (among other things) using the same engine for both descent and ascent, leaving only its landing legs on the lunar surface.

Is there any reason for this particular design for the Apollo LM? It definitely wasn\'t because LM descent engine couldn\'t be restarted because Apollo 13 manage to fire its descent engines multiple times for free return trajectory and course corrections.

The LK lander only had room for one person, the other cosmonaut would have stayed in the modified Soyuz (the LOK). It was designed to only stay on the surface for a few hours and couldn\'t have stayed several days like the LEM.

The LK was also much more basic. For example, the LK didn\'t have any proper docking hardware: the cosmonaut would have transferred between the LK and the LOK by EVA. The whole docking process was precarious and involved sticking a hook on the LOK into one of the 100 holes in a special plate on the top of the LK.

The difference in engine design comes from the fact that the LOK had a different mission profile.

- The Apollo CSM used its SPS engine for LOI, and then the LM descent engine performed the deorbit burn, the braking, and the final descent burns. Therefore the descent stage was quite large, which made it beneficial to shed its mass and the empty tankage for the ascent.

- The LOK/LK used a single Blok D stage for LOI, deorbit, and braking. The Blok D was designed as a crasher stage and was only jettisoned before the final descent burn. The LK\'s Blok E only had to do that final touchdown burn, so its tanks were pretty much full when it touched the ground.

In fact, in both cases, the number of burns is identical and 3 engines were involved in the lunar stack.

- Apollo: SPS (LOI, TEI), LM-Descent (Deorbit, Braking, Descent), LM-Ascent (Ascent)

- LOK/LK: Blok-D (LOI, Deorbit, Braking), Blok-E (Descent-Ascent), and LOK (TEI)

There are advantages and drawbacks to both approaches. The Russian way results in a smaller lander, but a system that drops a crasher stage isn\'t a very good idea if you plan to build a moon base or if you want to preserve the area that you are exploring.

On the other hand, the US astronauts had more room to move about and had more margins, which allowed them a longer stay and more equipment like the lunar rover on the SIM bay experiments in the later missions. The Soviet cosmonauts would have had to remain seated in the LOK descent module for the entire mission, with only a short stay on the lunar surface for one cosmonaut.

[PakledHostage]

Very interesting write-up, Nibb31! Thanks for sharing.

[Endeavour]

Nibb31, I think that anywhere else that many acronyms would completely lose anyone trying to read it but not here!

[VincentMcConnell]

The DPS made two burns, Nibb.

DOI and PDI.

Descent Orbit Insertion: Dropped the LM\'s pericynthion down to only 10,000 feet or something like that.

Powered Descent Initiation.: A continuous burn that lasted several minutes all the way until six feet before the footpads touched the surface. When the probes made contact, on all missions but Apollo 11, the DPS shut down.

[Temstar]

I rewired my lander to be able to drop the parallel boosters in two pairs and then tested it launching from KSC. It nearly managed to make LKO, only something like 80m/s off, less if I used RCS thrusters too.

Assuming this 'Mars' planet really does have 0.4G and thin atmosphere the same craft should have no problem making a parachute assisted powered descent and then take off SSTO.

[PakledHostage]

Assuming this 'Mars' planet really does have 0.4G and thin atmosphere the same craft should have no problem making a parachute assisted powered descent and then take off SSTO.

You\'re a man of my own heart. I\'m also trying to maximise the efficiency of my launches and orbital manoeuvres in preparation for when another planet is added to the game. My plan is to fly a few unmanned probes to the planet first to gather information about its mass, the nature if its atmosphere, etc. I figure I should be able to send a probe on a one-way trip from KSC to the new planet using a 7-8 LFT stack (so long as it is within ~2 Kerbin orbital radii of Kerbol). When I\'m ready to fly a manned mission, I\'m hoping to be able to use a combination of crew transfer/rendezvous to minimise the necessary size of my rockets. I\'m also hoping that we\'ll have to make some allowances for re-entry heating by then. If we want to use aerobraking to save fuel (depending on how aggressive we want to be about it, of course), then there should be a cost in the form of needing to carry a heat sheild.

If you haven\'t already done so, check out the Mini-challenge: max altitude with this supplied spacecraft challenge, the Shoot for the Sun! challenge as well as the Economy of design challenge. All three are good examples of the type of efficiencies that are possible.

[scotty110]

http://www.buildtheenterprise.org/

the guy behind that site believes thats the kind of ship that needs to be built to get to mars in 90 days and it can be done with today\'s technology.

[AlternNocturn]

But I think the strongest argument that we won\'t need to use a gravitational assist from the Mun or Minmus to get to any new planets comes from the example set by real-life Mars missions. Curiosity didn\'t require a lunar slingshot to send it on its way to Mars.

Well, maybe slingshots won\'t work for our Martian analogue, but what about farther out planets?

[PakledHostage]

Well, maybe slingshots won\'t work for our Martian analogue, but what about farther out planets?

I don\'t think I said it won\'t work... What I tried to say is that I didn\'t think it was worth the trouble. It might be an interesting exercise to figure out how much of a fuel savings we\'d achieve by using a gravity assist from the Mun or Minmus, but I think that is all it would be: An interesting exercise. I don\'t think that the handful of m/s Delta-V that we’d gain would warrant the restricted launch window.

[Apotheosist]

I believe any ship that is capable of a double mun return trip could go to Mars and back. Attached is one of designs to make as small a rocket capable of this. And it worked, my first mars mission will probably use a similar ship design. The second return ship uses just 3 tanks, and used landing legs for separation, which is no longer possible in .15. Need to modify a little.

[Temstar]

So I thought about this quote:

The issue, I think, isn\'t so much the method of getting yourself/fuel to the planet. There\'s that, and numerous other proposals. What i find, however, in all of them, is that they have some magic vehicle which is able to land on mars (with/without refueling on the surface). and then return to orbit. I\'ve not heard any proposals on the feasibility of constructing such a rocket.

And then I looked at my lander, which comes just short of achieving Kerbin Orbit, and I thought to myself:

Challenge accepted

So here it is, the uprated version of Planetary Excursion Module, using the good old Kerbal motto of 'MOAR BOOSTERS' now easily capable of achieving Kerbin orbit from KSC.

Next test will involve strapping a booster underneath that thing and shooting it up to ohh say 100,000m and then perform a parachute assisted powered descent back to KSC, then once on the ground take off and achieve LKO under the lander\'s own power. If that Planetary Excursion Module can do a landing followed by a take off to Kerbin orbit I say it\'s ready for landing on Mars.

[Lord Wasteland]

In reality, the lander would undock from a ship which would carry it to Mars.

[Temstar]

In reality, the lander would undock from a ship which would carry it to Mars.

I got that covered too:

Just need docking to refuel this guy from a tanker and then dock the PEM to the rear and we\'ll be on our way to Mars

[Ferrit]

Holy Jeb that is cool! 8)