Next Small Step: RP-1 Career Series

[Wiseman]

In this episode, I talk about reusable landers, and make a request to the community - if you've got a config for a realistic reusable lander, send it to me! Then, we wrap up the Moon landing mission, and check in on the Martian Moonhopper!

 

Edited May 14, 2021 by Wiseman

[Spaceman.Spiff]

1 hour ago, Wiseman said:

config for a realistic reusable lander,

I’ll see if I can make one later tonight. It will probably be an RL10 Lunex derivative. 

Maybe with slightly reduced thrust and ISP with increased mass to compensate for its restart capability. 

The RL10 can theoretically ignite as many times as necessary, and is limited by the amount of electricity required to do so. It’s a very good engine for landing. 

[jimmymcgoochie]

OK, hear me out for a moment:

KTDU plus generic thrusters.

KTDU does most of the work during the descent, generic thrusters with a TWR of just above 1 (or below 1 but also chunky RCS with a bit of throttling, fore by throttle switched on and toggleable with an action key) using the same fuel do the final touchdown, KTDU does the ascent, generics for rendezvousing and so on in orbit to save ignitions. I haven’t tried it myself, but I see no reason why it wouldn’t work.

[Spaceman.Spiff]

48 minutes ago, jimmymcgoochie said:

OK, hear me out for a moment:

KTDU plus generic thrusters.

KTDU does most of the work during the descent, generic thrusters with a TWR of just above 1 (or below 1 but also chunky RCS with a bit of throttling, fore by throttle switched on and toggleable with an action key) using the same fuel do the final touchdown, KTDU does the ascent, generics for rendezvousing and so on in orbit to save ignitions. I haven’t tried it myself, but I see no reason why it wouldn’t work.

An RL10 based architecture would have the advantage of possible ISRU usage. 

I suppose the density of UDMH and NTO as well as the storability would be good for a large propellant depot in lunar orbit. 

[jimmymcgoochie]

10 hours ago, Spaceman.Spiff said:

An RL10 based architecture would have the advantage of possible ISRU usage. 

I suppose the density of UDMH and NTO as well as the storability would be good for a large propellant depot in lunar orbit. 

I looked into water to hydrolox ISRU systems a while ago and until you unlock the big ISRU in one of the last life support/ISRU nodes it’s not practical even on Mars where water is more readily available than the Moon.

It would take years to produce enough propellant for a single Moon landing because the rate of water electrolysis is so low, plus you have to either find or transport the water and deal with two weeks of continuous darkness every month.

Storable propellants can’t be made, but they also don’t boil off and require smaller tanks. A suitable rocket could throw 50 tons or more into Lunar orbit, enough fuel for multiple Moon landings; once the 50 ignitions on the KTDU run out, swap it out for another one with KIS/KAS.

[Spaceman.Spiff]

7 hours ago, jimmymcgoochie said:

I looked into water to hydrolox ISRU systems a while ago and until you unlock the big ISRU in one of the last life support/ISRU nodes it’s not practical even on Mars where water is more readily available than the Moon.

It would take years to produce enough propellant for a single Moon landing because the rate of water electrolysis is so low, plus you have to either find or transport the water and deal with two weeks of continuous darkness every month.

Storable propellants can’t be made, but they also don’t boil off and require smaller tanks. A suitable rocket could throw 50 tons or more into Lunar orbit, enough fuel for multiple Moon landings; once the 50 ignitions on the KTDU run out, swap it out for another one with KIS/KAS.

Alright, I’m convinced your idea is better.
 

Thanks for explaining it to me, I’m still fairly new to RP1 and Kerbalism. 

[Wiseman]

Thank you both for the excellent discussion! I think the KTDU+generics idea is doable right now, which is a plus for it. I was hoping for an easy one-size-fits-all engine config, but not adding any new parts is probably a good thing, especially in teaching folks how to use the systems provided. I'll see what I can come up based on that in a future episode!

Meanwhile, let's see about dragging home the 9GB sitting in orbit of Mars!

 

[Wiseman]

First, the Mars Exploration System is headed back home! Hopefully it goes well when it finally arrives. Then, let's work on our communications network again... again. For the last time? Maybe? Look, x-band is challenging. Then, it's August 20, 1977 - time for the launch of Voyager 2!

 

 

[Spaceman.Spiff]

24 minutes ago, Wiseman said:

Then, it's August 20, 1977 - time for the launch of Voyager 2!

That should be fun!!

I wonder if you can do the Pluto flyby….

[jimmymcgoochie]

There’s an RSS config for distant object enhancement, you can find it on the RO/-1 GitHub. It makes the planets have the right colours from a distance so Mars is red, Earth is blue etc. which is much better than everything being white blobs.

[Wiseman]

Ooh, I love the idea of properly-colored DOE. That'll be helpful since we're sending Voyagers 1 and 2 on their way!

 

[jimmymcgoochie]

@Wiseman it's not on the RO/RP-1 github, it's here:

https://github.com/MOARdV/DistantObject/tree/master/Alternate Planet Color Configs/Real Solar System (default)/DistantObject

Or on CKAN, it says compatible to 1.7.x but it works in 1.11.1 with no issues for me.

[Wiseman]

Another Apollo launch, another milestone. This time, four crew in space! Then, lots of orbital station shenanigans!

 

 

[Wiseman]

We've put together a new Mars Exploration System, and hopefully it'll even work this time. Well, the old one accomplished amazing things! But we have more objectives yet to meet on the red planet...

 

 

[jimmymcgoochie]

That’s odd, the DOE config worked for me. Did you delete the default config?

[Wiseman]

I did, I deleted and replaced. I'll give it another shot with a fresh download. In the meantime, let's prepare the way for some real homesteading, by landing our very first lunar base module! Also, let me know what I should call it!

 

 

[Spaceman.Spiff]

1 hour ago, Wiseman said:

I did, I deleted and replaced. I'll give it another shot with a fresh download. In the meantime, let's prepare the way for some real homesteading, by landing our very first lunar base module! Also, let me know what I should call it!

 

 

Trident. 
To remember what we could have had 

It would be cool to see more extensive lunar colonization though. Not sure if you’re interested in that. 

Edited June 5, 2021 by Spaceman.Spiff

[jimmymcgoochie]

NTRs aren’t as useful as you think, the combination of low density hydrogen and high engine mass means you need some absolutely MASSIVE tanks to get anywhere with a meaningful payload; radiators are really heavy too which makes things worse, plus the engines throttle up/down very slowly. They have a lot of restarts though, and can throttle down quite far compared to e.g. the J2.

On an unrelated note- Basey McBaseFace 

[jimmymcgoochie]

On the subject of reusable landers, I decided to put my money where my mouth is and make one:

It's based on a Moon lander I've already been using but with a single stage design. One KTDU-425 plus four 2.2kN generic thrusters set to UDMH+NTO to match fuel types, Al-Cu integral tanks and the advanced Mk1 lander can which has two seats. I'm using tech level 5 solar panels for power and 6 RCS and generic thrusters, but it should work with lower tech levels with a little bit less delta-V, but that won't be an issue as this thing is completely overbuilt with a massive fuel margin:

Landed from a 30km orbit, then launched back to a 50km orbit with over 1km/s to spare- and that was before I rebalanced the fuels as seen in the first screenshot. It'll probably require 15 tons of fuel per round trip, plus life support and fuel cell resources as needed.

Weird trick- the lander can has pressurised tanks, so put a bit of fuel in that and set the fuel priority to drain it after the main tanks and you don't actually need the main tank to be pressurised, saving a lot of weight.

[Wiseman]

On 6/5/2021 at 12:50 AM, jimmymcgoochie said:

NTRs aren’t as useful as you think...

Aw boo, really? Is there not a break-even point where they get to be more efficient than hydrolox? I'll admit I tried to make my Mercury orbiter craft using an NTR, took one look at the numbers and swapped in the russian staged combustion hydrolox engine instead.  I was really hoping that at some point in the tech tree they make sense at the very least for long-duration missions. I gotta imagine for something big and heavy like a crewed Mars mission it would be useful, yeah? Maybe?

Also, love the proof of concept on that lander design! Given what I'm dealing with in the next episode re: landing at my Moon base, this whole Apollo LEM thing is just not sustainable. I'll have to build something similar!

Anyways! Despite the short episode, we're getting a lot done! Crew returning from Orblab 3, a new (Russian!) engine unveiled and tested, and not one, but two spacecraft entering the Jovian system!

 

 

[jimmymcgoochie]

@Wisemanyou say “proof of concept”, I say “new workhorse of my lunar fleet” . I fully intend to use that lander as soon as it’s built.

[Wiseman]

The (yet unnamed) Moon base crew has arrived at Lunette station! But it looks like I failed to consider the latitude of the base and the way that the rotation of the Moon would move it relative to the orbit of the station... Let's hope we've got enough snacks to wait for the launch window!

 

 

[Wiseman]

After waiting for the latitude of the Moon base to line up with our orbit, we're finally ready to descend to the surface, and inhabit the first lunar outpost!

 

 

[jimmymcgoochie]

Kerbalism counts anything above 90kPa as fully pressurised, not entirely sure if that also applies in RO but I haven’t seen anything that says it’s not so you should be fine for a while.

Have fun with that lander! 

[Wiseman]

As the title says, the veteran of the space program is back for another ride on the Apollo stack! But first, let's send out a resupply vehicle to Lunette station to deal with pressurization issues.