RSS - Challenges of Mars Missions

[stratochief66]

I am working on a mission to Mars in RSS/RO. My planned mission architecture is most similar to Mars Direct.

http://www.marspapers.org/papers/Zubrin_1991.pdf

I am aiming to perform each mission using 2 SLS-like launchers. The primary hurdles I have found to carrying this out are the Mars Entry, Decent, and Landing (EDL) and in-situ resource utilization (ISRU) production and storage. Both of these challenges break down into a number of separate issues, most of which I have made at least a cursory attempt to resolve.

I intend to lay out each of those challenges and note down my solutions to them as they are resolved. I also plan to store and organize a number of documents pertaining to these challenges here. At first, I will be focus on the workings of the craft that will land unmanned, fill its tanks using fuel made on Mars, and fly back to Earth with a crew. This craft is similar to the MAV as seen in 'The Martian', except it is expected to go all the way from Mars' surface to Earth.

 

A: Mars EDL (Entry, Decent, and Landing):

1. Lifting entry body design
2. Propulsive final decent
3. Possible HAID/Ballute usage
4. Direct entry
5. Site targeting: FAR, Mechjeb & Trajactories?

 

So, I plan to leaf each of these out at a later time, but for now I will lay out the basics. My craft will be 30-60T when it reaches Mars. Some of that will make up the bus for powering and controlling the craft between the Trans-Mars Injection (TMI) and this point. To save on mass, I intend to enter the atmosphere directly from this trajectory, rather than braking into Mars orbit first. Most of my tests have been performed with a decent from Mars orbit, but I have performed some as well from this trajectory (thanks Hyperedit!) By offsetting the payload mass slightly and leading with a heat shield (not at max ablator capacity) I will be able to generate some lift, allowing the craft to slow down before entering propulsive decent. I have had success in achieving an L/D factor of 0.15 - 0.35 with this method. I expect fitting my final craft into a shape that can fit on this shield will be quite challenging. I predict that targetting will be the greatest challenge. I may need to learn and use kOs in order to accomplish 2 landings within 100m of each other

I have performed some tests using the ballute from Inline Ballutes by riocrokite. I have found them to be quite functional, but further testing is required to see what value they might provide above that of just a blunt lifting body. I found found a few very useful and interesting videos on this topic, including this one from a Langley Research Centre presentation on Mars Entry, Descent and Landing with Humans.

 

B: Mars ISRU (In-Situ Resource Utilization):

1. Feedstock - LH2 from Earth, CO2 from Mars' atmosphere
2. Conversion - Sabatier & RWGS
3. Storage - Tanking & Cryogenic Cooling
4. Energy - Radioisotope thermoelectric generator (RTG)

 

There are many pathways to produce rocket fuels by leveraging native martian resources. A few of those paths are detailed in this paper by Pioneer Astro. I have added some parts to the RealISRU mod to represent the RWGS pathway as shown on page 15 of this document. To produce 1 tonne of methane & liquid oxygen (LO2) fuel per day will require a 375 kW power source. I currently plan to use a RTG to generate this energy, but I have yet to find a source for what such a large RTG would weigh. In this process, liquid hydrogen is brought from Earth to be used as feedstock for methane (LCH4) fuel. The hydrogen could potentially be sourced from local martian water, but I don't plan to add that functionality to RealISRU right now. My understanding is that substantial amounts of water would need to be taken from the ground, which would further require a ground distribution map of this resource on Mars. My intended fuel path could be carried out from any landing site, regardless of the availability of ground resources.

My greatest challenge at the moment is the tanking and cryogenic cooling of fuel produced. Due to liquid hydrogen's (LH2) low density, it takes a not insubstantial amount of tank volume to bring enough LH2 to Mars The required hydrogen doesn't have a great deal of mass, but the additional tanks required to bring it might. To combat this, Pioneer Astro suggests that some tanks be used to carry LH2 from Earth, and then later be filled with LO2 or LCH4 as fuel is produced and LH2 is consumed. Currently, RealFuel tanks do not support changing the contents while in flight. Secondly, the stock thermal system & radiators appear unable to chill fuels to their cryogenic point. LO2 boils at 90.2K and LCH4 boils at 111.7K, LH2 at 20.3K. HeatPump appears capable of providing cooling, but so far I can only get it to chill tanks when the radiators are surface attached. Starwaster mentioned that it is capable of cooling a non-surface attached part, but it sounded like it would be a targeted part, and not the dozen or so RealFuel tanks I intend to use in the craft.

When I setup the RealISRU parts I disabled boiloff for the realfuel tanks. In case you want to do something similar, by setting this value to 190 or something, I will be disabling LOX boiloff on that specific tank as long as the ambient temperature is below 190K. Example. Since the point of this project is to research the real life challenges of a human Mars mission and utilize realistic and probable solutions, I choose not to continue wasting time right now fighting with the issues of both stock and HeatPump radiators. 

 

Update March 9th:
My RealISRU parts are live! Working nicely (with boiloff disabled) and a test craft made from stock/RO and procParts. Feel free to use it and create your own improved craft and mission profiles: https://github.com/jbengtson/RealISRU

Edited March 9, 2016 by stratochief66

[Nightside]

Great mission, I've been vaguely planning something similar, but you've laid out the challenges well.

Do you need such fast fuel production? I guess you have to weigh the cost of refrigerating the LH₂ vs powering the converters.

[stratochief66]

The Pioneer Astro document estimates the energy demands of production at order of magnitude intervals. The 1 tonne of fuel per day is the largest amount, and it might find use in my final fully Mars Direct craft, which has to be big enough to hold supplies for 2-4 astronauts return coast to Earth, which is months of supplies. Currently, I find such speedy propellant production to be useful for quickly verifying that things are being produced as desired, in the right ratios, etc. With my current test craft this rate of production can fill it up in roughly a month, so much faster than is actually necessary. Once I have things tuned and accurate for these modules I will probably make the parts for one notch down, so 100kg/day. My actual final goal is whatever will fill it up in under a year, similar to actual Mars ISRU proposals.

Also, my first video is up for this! I was planning to follow along with videos as a resolve major problems, or possibly one to discuss the problem and another where I resolve it. I got a bit ahead in my development, so there will be a few videos in quick succession to catch that side of things up.
 

 

Edited February 29, 2016 by stratochief66

[Laie]

What bugged me most when trying to build a (far less ambitious) Mars mission was the inability to bring things into shape. The way KSP works, vessels tend to become tall towers or sprawling assemblies of radial mounts. Moving the engine into the lander while utilizing the room around it, rather than have it dangle below and bridging the gap with long stilts, is not an easy task.

375kW seems.... ambitious? RTGs are horribly inefficient, on the order of 5-10%, so you'd need to bring a ~5MW heat source to start with. The concepts I've heard of presume that power demands in excess of a kW or two would justify some kind of heat engine. If the machine is supposed to be maintenance-free, stirling engines are the only solution I'm aware of (not that anyone has done this yet; but apparently stirling engines are the only devices one can reasonably expect to keep going for a couple of years).

As to hydrogen storage, I recall coming across a NASA document where they described using a standard off-the-shelf cryocooler to keep a largish hydrogen tank from boiling. On the photograph the tank appeared to be of about S-IVB size, but it was a ground installation with (presumably) excellent insulation. It took a little less than 30W of cooling to reach zero boiloff.

Both stirling engine and cryocooling were no more than proof-of-concept. I can't recall seeing any figures as to weight, size, or anything else beyond "it works in the lab".

[Laie]

Update to add:

http://www.shicryogenics.com/wp-content/uploads/2015/09/RDK-500B-Datasheet.pdf  -- cryocooler 40W@20K; needs ~9kW, weighs 125kg. Requires cooling water, so you'd presumably need an ordinary ISS-style radiator on top of that.

[stratochief66]

14 hours ago, Laie said:

Update to add:

http://www.shicryogenics.com/wp-content/uploads/2015/09/RDK-500B-Datasheet.pdf  -- cryocooler 40W@20K; needs ~9kW, weighs 125kg. Requires cooling water, so you'd presumably need an ordinary ISS-style radiator on top of that.

 

Thankfully the paper comes with estimates for the power consumption and needs of they cryogenic cooling. The tricky part seems to be getting it it actually work in the KSP engine, even at no or low timewarp. In further inspection I found that I was pulling the incorrect electrical requirement values for my setup. So outside of cryogenic cooling I appear to need 175 kW to produce 1 tonne of fuel per day, a lowly 17.5 kW for 0.1 tonne per day.

Cooling for the ISS, or anything in a vacuum is very difficult. Thankfully, Mars is not a vacuum, plus I have the martian ground to use as a heatsink.

Edited March 1, 2016 by stratochief66

[Starwaster]

On 2/27/2016 at 7:59 PM, stratochief66 said:

RealHeat appears capable of providing cooling, but so far I can only get it to chill tanks when the radiators are surface attached. Starwaster mentioned that it is capable of cooling a non-surface attached part, but it sounded like it would be a targeted part, and not the dozen or so RealFuel tanks I intend to use in the craft.

Your text mentions 'RealHeat' in several places, which is entirely different than and unrelated to the link provided for 'Heat Pumps'. Heat Pumps has nothing to do with Real Heat at all

[stratochief66]

Good catch Starwaster. Tired brains make strange errors. Editted.

[Lothaar]

I have been looking into Mars and the various plans to get there and stay there.

I like the idea of orbital fuel storage/production stations and have been working on a few designs to use in LEO and LMO.

As such. boil off is my first and foremost problem. Today I plan to play with Starwaster's heat pumps to get a feel for its default capabilities. I may as you did, adjust temp values for boil off to get a working model so I can then focus on the ideal size for the core module and component tanks.

ISRU and its capabilities will inform a lot on the best type and size of an orbital fuel storage/production station for LMO. It is great to see someone is already working out how ISRU will function on the surface.

Orbital fuel storage/production stations will only really reduce my launch weights on Earth and Mars. ISRU will still be essential to maintain the LMO station fuels stores.

My hope is to have orbital fuel stations reduce needed complexity and weight of surface launched/landed systems to increase the safety and reliability of these systems. This will however require a specialist craft to ferry fuel from the surface to the LMO fuel station to bridge gaps in production.

I may try to leave the majority of hydrogen in LMO and just ferry up carbon dioxide and do most of the processing in orbit. Just produce enough fuel on the surface to attain LMO for the transports and fuel ferries. It will increase start up time for  the system, but once running, should be more efficient as a lot of hydrogen mass will not be delivered to the surface, nor the resulting fuel from its incorporation into fuel production lifted to LMO.

I am still in early planning, but excited to see someone else working on things that will help my overall goals of stable Martian systems on the surface and in orbit.

 

 

[winged]

Hi, stratochief, I just saw your recent video, sorry for the offtop but could you provide the link to download these Mars ground textures created by KillAshley? They're gorgeous looking. Thanks in advance.

Edited March 7, 2016 by winged

[stratochief66]

On 3/3/2016 at 5:30 PM, Lothaar said:

I have been looking into Mars and the various plans to get there and stay there.

I like the idea of orbital fuel storage/production stations and have been working on a few designs to use in LEO and LMO.

As such. boil off is my first and foremost problem. Today I plan to play with Starwaster's heat pumps to get a feel for its default capabilities. I may as you did, adjust temp values for boil off to get a working model so I can then focus on the ideal size for the core module and component tanks.

ISRU and its capabilities will inform a lot on the best type and size of an orbital fuel storage/production station for LMO. It is great to see someone is already working out how ISRU will function on the surface.

Orbital fuel storage/production stations will only really reduce my launch weights on Earth and Mars. ISRU will still be essential to maintain the LMO station fuels stores.

My hope is to have orbital fuel stations reduce needed complexity and weight of surface launched/landed systems to increase the safety and reliability of these systems. This will however require a specialist craft to ferry fuel from the surface to the LMO fuel station to bridge gaps in production.

I may try to leave the majority of hydrogen in LMO and just ferry up carbon dioxide and do most of the processing in orbit. Just produce enough fuel on the surface to attain LMO for the transports and fuel ferries. It will increase start up time for  the system, but once running, should be more efficient as a lot of hydrogen mass will not be delivered to the surface, nor the resulting fuel from its incorporation into fuel production lifted to LMO.

I am still in early planning, but excited to see someone else working on things that will help my overall goals of stable Martian systems on the surface and in orbit.

 

 

Excellent plans!

I hope you made some progress with the heat pumps, they really are good and useful. I used them for a Saturn S-II & S-IVb based manned transfer vehicle test that ended up just fiddling with thermal properties. The heat pumps worked well for parts they were surface attached to, so perfectly for those monolithic tanks. I had to change around and test a number of the thermal properties of the tank, heat pumps and rads to achieve zero boil-off, but I couldn't do so realistically, I was just able to get a very crude feel for the variables at play (part temp, surface temp, radiatorMax, radiatorHeadroom, partTemp, maxTemp) and how they interacted. If you have any questions about that feel free to post here! I'm not currently actively tackling the problem myself, but I'd be happy to share with you what I know (or think I know) and try to drag @Starwaster and @NathanKell into the mix if needed

@Starwaster mentioned a method to target which part is to be cooled at some point, but I didn't quite understand it. If you need that he might be able to explain it again or point you in the right direction.

On 3/7/2016 at 3:30 AM, winged said:

Hi, stratochief, I just saw your recent video, sorry for the offtop but could you provide the link to download these Mars ground textures created by KillAshley? They're gorgeous looking. Thanks in advance.

*Disclaimer Disclaimer! Work In Progress, Work In Progress! No support provided by anybody!*

@Theysen has also been working on some scatterer files specifically tailored for Venus and Mars that are also very WIP, even though I think they look quite good, he might share them at some point soon.

https://github.com/KillAshley/RealSolorSystemTextures
https://github.com/KillAshley/RealSolarSystem
 

@KillAshley should also be pinged, since it is his work. 

*Disclaimer Disclaimer! Work In Progress, Work In Progress! No support provided by anybody!*

 

Edit:
@winged it appears some or all of those textures may have made it to the actual RSS repo, but not release yet. I am still trying to get them working though, I keep getting an odd "cannot click on things in VAB" issue/
https://github.com/KillAshley/RealSolarSystem/commits/master

Edited March 9, 2016 by stratochief66

[stratochief66]

I want to brainstorm some precursor missions that would make sense to test the technology and leading up to a full, manned Mars Direct style mission. I like the idea of ambitious precursor missions that allowing testing/proving of multiple enabling technologies at once. The of the major enabling technologies I see myself being able to prove out at this point at:

* Multi-ton lifting body EDL
* Surface ISRU
* Ascent to Mars orbit

I believe I could design a small craft, not too much larger than the largest craft already placed on the surface of Mars, that is capable of landing the small form ISRU units on the surface and powering them via the sun. Effectly, the same scale as the current RealISRU test craft 10. I don't want to make the single craft too ambitious, so I would only size it sufficiently to return to Mars orbit, but not to return the sample to Earth. If that mission runs successfully, the surface samples from this craft could be transferred to a second craft that returns them to Earth, or an Ion craft could be sent along with the craft, capable of sending the sample back to Earth.

The second precursor mission would be an unmanned dress rehearsal of the ascent craft used for Mars Direct. It would also include hardware capable of sample return, possibly some small rovers as well. This craft would use RTGs for power and the 100 class ISRU hardware. It would fuel up over roughly a year, sending a man scale heat shielded capsule (with a small solar support bus w/RCS) on an Earth return trajectory for sample return. This might end up being mostly roleplay, since without learning Infernal Robotics (IR) I don't see an unmanned method to pass surface samples from a rover or science package into the return capsule. I am also notoriously terrible at rover design.

An obvious but exceptionally challenge will be proving that I can land 2 craft within 100 metres of each other. That is something I would like to do before committing humans to a mission, but I can't think of a way to add more value and science to doing this. Perhaps a twin mission, like the twin Mars Exploration rovers? If just one succeeds, it still demonstrates the ISRU and surface sample return missions. Or, the second vehicle landed could be my prototype second Mars Direct vehicle (the habitat and outbound manned vehicle, currently undesigned). a rover & automation could use that habitat to attempt to remotely farm food or perform surface biology experiments, or even basic secondary ISRU like metallurgy and fabrication? Or, it could just be a straight landing of a Hab, intended for potential use in a future human mission?

See, tons of options. I'm curious of people's opinions of the validity of these tests, or other potential missions that could also serve to prove the technologies required for the future human mission.

[Starwaster]

By default, heat pump parts only target the parent part to which they are attached. To make them target a specific node attached part you need to specify the attach node as follows

In the following example, any parts attached to node_stack_bottom and node_stack_latch would receive cooling. Note Heat Pump doesn't limit cooling to the heatTransfer value. In addition to that, it also will provide enough cooling to neutralize however much heat penetrated into the tank interior. (so, skin <-> part influx + heatTransfer = amount of cooling applied * (parent part + attach node targets))

The rate specified for ElectricCharge is ok for stock but Realism Overhaul environments should use a value of 114 ec / watt of heat removed

	MODULE
	{
		name = ModuleHeatPump

		heatTransfer = 0.078
		heatConductivity = 0.0039

		RESOURCE
		{
			name = ElectricCharge
			rate = 1
		}      
		HEATPUMP_NODE
		{
			name = latch
		}
		HEATPUMP_NODE
		{
			name = bottom
		}
	}

 

[Lothaar]

Thanks for that snip Starwaster. This will remove a lot of constraints on design and allow for much better stowed positions for heat pumps.

 

I have been playing with boil off and it is not an easy problem regarding game mechanics. The persistence of the boil off effect, cooling, and heat reduction/increase all perform differently at different time scales and active/inactive states. Often times, temps can be lowered, but then are stuck there and will not raise even when cooling is disengaged. While I can simulate a synchronized state of these variables, it is through cfg editing, and only pertains to one environment and does not scale. As such, I may just ignore and instead, adjust some temps in tank configs, and still design with radiators/heatpumps to the proportions/power needed. So when we get them working, it will not require major changes in layouts.

 

With boil off on the back burner and station design not having any other major issues, I will now focus on refining the ferry design for LMO to surface, surface to LMO and surface to surface operations.The ferry design will also inform a lot on how the station will be set up.

I started playing with your EDL craft setup stratochief66. It helped me with a few design elements in my ferry. It will have two variants; one for cargo/fuel/materials and one for crew. 

Both variants will have on-board ISRU and will use full propulsion ascent/decent profiles. I have played with balutes, chutes, heatshields, and air brakes. They all add complexity in, flight profile, design, parts, staging and utilization. They also are more difficult to employ where repeated trips to the same place on the planet surface will be required. A full propulsion set up will lend more to simplicity, safety and accuracy.

Even with the need to import more fuel and fuel precursors to various gravity potentials, I think this will be a viable craft until ice/water can be produced on the surface. Then the ferry will either get an increase in payload with the removal of LqdHydrogen mass or a substantial reduction in overall mass while still maintaining current operational ranges.

I have tested an 72 ton (10tn cargo or crew/LS) ferry. It has about 5k deltaV for testing (to be reduced later once flight profiles and fueling station locations are dialed in). I can land from an orbit of 200km fairly well now and have a few decent profiles worked out. It has enough LqdHydrogen to refuel with ISRU and then can easily attain 200km orbit again.

 

I am working with the basic RO RSS install and I only use RO modified stock and procedural parts. ISRU and heat pumps are my two part pack additions for my current testing. Happy to share my fuel station and ferry craft files.

So great to have all these modifications. I am so excited to be able to develop real martian infrastructure in Kerbal. ISRU has bridged some major gaps that until now I could only get past with honor-system/role play/hyper-edit.

[stratochief66]

@Lothaar it sounds like you have made enough progress to spin off your own thread! You could post about your mission objectives and accomplished goal, as well as epic screenshot galleries and your craft files. I look forward to seeing and possibly using your craft

Edit:

Also, Starwaster's "114 ec / watt of heat removed" would be in a vacuum. I haven't yet researched what the rate would be on the surface of Mars, but it would be much lower since surface cryogenic radiators would have access to convective and conductive heat transfer, not just radiative.

Edited March 11, 2016 by stratochief66

[Starwaster]

17 minutes ago, stratochief66 said:

@Lothaar it sounds like you have made enough progress to spin off your own thread! You could post about your mission objectives and accomplished goal, as well as epic screenshot galleries and your craft files. I look forward to seeing and possibly using your craft

Edit:

Also, Starwaster's "114 ec / watt of heat removed" would be in a vacuum. I haven't yet researched what the rate would be on the surface of Mars, but it would be much lower since surface cryogenic radiators would have access to convective and conductive heat transfer, not just radiative.

Actually it's 114 watts of electricity per watt of heat (using RF/RO, EC would be kw, so rate would be set to 114 kwe / kwt. I kind of screwed that up there)

And that's regardless of environment. 114 watts period. That's the cost to move the heat to the radiators.

Edited March 11, 2016 by Starwaster

[Lothaar]

Yes, it would seem I have my own momentum now; I will make a thread later this week to record my progress.

 

If I find any new setups or solutions to cryo ill post in here.

 

I am trying to find a good way to share decent and ascent profiles so when craft are shared, people can have a good starting point for setting up fight profiles. I am trying to avoid gdoc and data entry methods for poster and user.

 

Also, regarding the engines you are using. For those engines will there feasibly be more powerful variants in real life to model from, or are those 66kn version about a beefy as they will get, and larger craft will just need to use more of them? I am not finding this to be a major limitation, I just thought I would ask about multi ignition, deep throttle, methane/LqdOxygen, engines that will have100-200kn thrust capability. I know the RL-10 has a methane variant, but it is not much more powerful and has a less favorable ratio of methane/LqdOxygen to match ISRU production ratios.

 

 

Edited March 11, 2016 by Lothaar

[stratochief66]

1 hour ago, Lothaar said:

 

I am trying to find a good way to share decent and ascent profiles so when craft are shared, people can have a good starting point for setting up fight profiles. I am trying to avoid gdoc and data entry methods for poster and user.
 

Also, regarding the engines you are using. For those engines will there feasibly be more powerful variants in real life to model from, or are those 66kn version about a beefy as they will get, and larger craft will just need to use more of them? I am not finding this to be a major limitation, I just thought I would ask about multi ignition, deep throttle, methane/LqdOxygen, engines that will have100-200kn thrust capability. I know the RL-10 has a methane variant, but it is not much more powerful and has a less favorable ratio of methane/LqdOxygen to match ISRU production ratios.

 

 

Issue 1: Place the info in the description text for the craft? ie. under where you name it, you get a little window.

Issue 2: My 66kn engine is pretty much the CECE, with a slightly different mixing ratio. With SE-RWGS you can achieve any amount of oxygen you want, but the paper provides specifics for energy consumption and ISRU hardware masses for the ratio I went with. If you're willing to guestimate a bit you can probably make a different version of my ISRU unit(s) that output a different ratio. Or, you could create a seperate unit to produce the additional oxygen requested. I might re-visit that once my craft starts to come together and I make modular life support producing ISRU units.

There is/was fairly little demand for methane powered engines, particularly deep throttling ones, until recently. If you want to go bigger, the SpaceX Raptor is definitely bigger.

[Lothaar]

Yes I have noticed the utter lack of methane powered engines in current development. The raptor is a bit much. I am looking for a total thrust package in the 500-600 kn range. This would be for craft up to 70tn.

I am going to poke around and see what other engines I can find. For now, your CECE is working great. A bit deeper throttle would be nice, but I don't want to start tinkering with every variable that is not to my liking.  That will quickly take me into fantasy land.

I am going to try to only use realistic stats, but man what I would not give for some higher isp. What do you think the isp of these types of methane engines will top out at over the next decade or two? high 300s or maybe break 400 or is that getting past limits inherit to the fuels themselves? I am very unfamiliar with the gains yet to be had in efficiency for modern spacecraft engines.

 

 

[stratochief66]

17 hours ago, Lothaar said:

Yes I have noticed the utter lack of methane powered engines in current development. The raptor is a bit much. I am looking for a total thrust package in the 500-600 kn range. This would be for craft up to 70tn.

I am going to poke around and see what other engines I can find. For now, your CECE is working great. A bit deeper throttle would be nice, but I don't want to start tinkering with every variable that is not to my liking.  That will quickly take me into fantasy land.

I am going to try to only use realistic stats, but man what I would not give for some higher isp. What do you think the isp of these types of methane engines will top out at over the next decade or two? high 300s or maybe break 400 or is that getting past limits inherit to the fuels themselves? I am very unfamiliar with the gains yet to be had in efficiency for modern spacecraft engines.

 

 

There are actual limitations in the chemistry. No matter how high your combustion chamber pressure is, or well tuned your nozzle design is, there are limits. If you check page 9 of this document, they list the maximum they expect to get, which might be the chemical limits, I'm not sure. Depending on where you want the extra throttling, you could consider putting your engines into a could of symmetry groups and using an action group to leave some of them off entirely, or shut some of them off when you really want deeper throttling. If the maximum throttle down per engine is 30%, but only half of your engines are running then you have effectively throttled to 15%

[Lothaar]

Yes, I have broken them into 4 pairs across a set of 8 and now I have the throttle control I need. I always forget about engine grouping. I did add extended action groups for ease of control, but I needed that anyway to finish out fully equipped craft operation. I'm just trying to keep mods to an absolute minimum.

 

How is your progress on landing two craft in close proximity? Even with full propulsion decent profiles I am having trouble achieving this. This seems, to me, to be one of the most important problems in developing true surface infrastructure. I am curious how much the need for accuracy will influence craft design.

I understand with center of mass offset and a large enough heat shield one can get a good amount of lift, L/D (0.3+)  and with craft rotation can use that to kind of steer the craft. Will this be enough or do you think you will need to have a move evasive way of interacting with the atmosphere to achiever greater flight path control?

 

[stratochief66]

@Lothaar I haven't had any time to work on it since my last video, busy busy.

 

I am hoping to be able to get 'close enough' using roll control -> directional lift to target a previous landing site, but I am very skeptical as well if it will be enough. i fully expect to have to make some serious kOS code to achieve my goal. I will have to 'one shot' the landing site from a flyby velocity of 6-8 km/s, and I'm pretty sure I can only see predicted landing sites using MechJeb or Trajectories once I enter Mars' SOI.

 

The Trajectories mod is damn useful IF you are willing to use an old version of FAR back when Trajectories would function with FAR. Particularly since you are using a ballistic and propulsive craft, that should be very useful once you get used to telling Trajectories how to work (ie. inform it you plan to come in retrograde. If I were trying to do that (which I might try, as I think targeting the same site with your craft would be easier than with mine) I would fire the engines shortly in orbit to target the landing site, then only trigger a suicide burn near the last second and burn all the way down to the landing area.

I have even half seriously considered putting wheels on my first landing craft, so I could bring it closer to the human landing party during the year or so of their surface mission before the ascent to orbit.  

Edited March 14, 2016 by stratochief66

[Lothaar]

Can you imagine the added stress of always wondering and hoping your return vehicle will make it to your location.

"Dangit Bob, stop using battery power to link in and check on the DAVs mobile progress; It will get here when it gets here."

[stratochief66]

Found a fission reactor to research more deeply. 100kW electric, 400kW thermal for 0.5T, what a deal!

 

https://en.wikipedia.org/wiki/Safe_Affordable_Fission_Engine

[Lothaar]

So funny, I was looking in to the systems on this chart

https://www.google.com/imgres?imgurl=http://a.static.trunity.net/images/121224/400x218/scale/&imgrefurl=http://www.eoearth.org/view/article/154970/&h=218&w=400&tbnid=tlgqdROn7ipgoM:&docid=A-2d5LnVUyB1_M&ei=z-jpVtbvNMTjmAGC8IzgAw&tbm=isch&ved=0ahUKEwiWk7flqsbLAhXEMSYKHQI4AzwQMwggKAMwAw

and also the homer15/25

SAFE seems to be the best in terms of power and weight.

 

Edited March 16, 2016 by Lothaar