Sign in to follow this  
KAL 9000

Titan Sample Return Concept

Recommended Posts

So, I'm not exactly sure why you would want samples from Titan, or why NASA or ESA or SpaceX or whatever would fund it, but ANYWAY, I came up with a concept/idea for a sample return mission to Titan using existing or in development rockets/hardware. I worked out some of the details, and here it is: 

The mission consists of 2 spacecraft: A lander that lands on Titan and delivers the samples to Titan orbit, and an orbiter that picks up the samples from Titan orbit and returns them to Earth orbit. Due to the necessary size of such craft, a transfer stage would have to be assembled in Earth orbit. The transfer stage is a Delta IV Heavy or Falcon Heavy configuration (3 identical cores). Each core is a Space Shuttle External Tank with the middle one's nose flattened to allow the payload to attach there. All of the tanks' bottoms are also flattened for engine attachment. The engines are Centaur engines like the ones on the upper stage of an Atlas V. To save weight, the tanks are launched empty (by an SLS Block II) and fueled in orbit by later launches. The outer tanks perform the trans-Saturn injection burn and any course corrections needed, then decouple. The middle tank performs Saturn orbital insertion and maneuvers to Titan, and finally performs Titan orbit insertion before decoupling. The tanks would have to be fitted with special equipment to stop the liquid hydrogen and liquid oxygen from boiling off en route. 

The Titan lander has 2 main sections: the surface module and the ascent module. The surface module performs operations on Titan and collects the samples, while the ascent module returns them to Titan orbit. After going through reentry and decoupling its heat shield, it lands on parachutes, which are incredibly effective in Titan's thick atmosphere and low gravity. The surface module contains an RTG for power, while the ascent module is only its own separate spacecraft for a few days at most, so it can rely on battery power. After collecting samples, the ascent module takes off and returns to Titan orbit. The ascent module is a two-stage rocket, small-ish but having enough Delta-V to reach Titan orbit and rendezvous with the orbiter. The lower stage is powered by a SpaceX Merlin 1D engine modified to use liquid methane and liquid oxygen as propellants to aid ISRU (due to liquid methane's abundance on Titan). The engine has also been modified to function in Titan's thick atmosphere. The upper stage is powered by a modified Russian-made S5.98M engine, which runs on Nitrogen Tetroxide and UDMH.

The orbiter is designed to return the samples to Earth. After being released from the transfer stage, its main propulsion comes from a cluster of three 445 Newton engines, burning Nitrogen Tetroxide and MMH. Each engine is the same model as the engines on the Cassini spacecraft, although they have been upgraded to have a higher ISP. The mission can still be completed with one engine failing and only 2 operational. The orbiter is powered by an RTG

Mission Plan:

3 Launches for Transfer Stage 01 - Launch Vehicle: SLS Block II 

Transfer Stage 01 Assembled in orbit.

5 Fueling Launches - Launch Vehicle: Falcon Heavy 

Transfer Stage 01 Fueled.

Lander Launch - Launch Vehicle: SLS Block II 

Lander docks with Transfer Stage 01 

Lander - Trans-Saturn Injection Burn 

3 Launches for Transfer Stage 02 - Launch Vehicle: SLS Block II 

Transfer Stage 02 Assembled in orbit. 

5 Fueling Launches - Launch Vehicle: Falcon Heavy 

Transfer Stage 02 Fueled.

Orbiter Launch - Launch Vehicle: SLS Block I 

Orbiter - Trans-Saturn Injection Burn 

Lander - Jupiter Gravity Assist 

Orbiter - Jupiter Gravity Assist 

Lander - Saturn Orbital Insertion 

Lander - Titan SOI Entered, Transfer Stage 01 Decouples 

Lander - Titan EDL 

Lander - Touchdown

Orbiter - Saturn Orbital Insertion 

Orbiter - Titan Orbital Insertion, Transfer Stage 02 Decouples 

Lander - Samples Collected 

Lander - Titan Ascent 

Lander - Rendezvous With Orbiter 

Lander & Orbiter - Docking, Combined Spacecraft is formed 

Lander Surface Module & Combined Spacecraft - Science Operations until Saturn -> Earth Launch Window 

Combined Spacecraft - Science Operations cease, Trans-Earth Injection Burn 

Lander Surface Module - Science Operations until Contact Is Lost 

Combined Spacecraft - Earth Orbital Insertion 

Combined Spacecraft - Rendezvous with a Dragon or Soyuz 

Combined Spacecraft - Sample Transfer 

Combined Spacecraft - RTG Moved To Dragon or Soyuz 

Combined Spacecraft - Shutdown 

Dragon or Soyuz - RTG transferred to a Progress tug 

Dragon or Soyuz - Earth EDL, Samples delivered to a lab 

Progress Tug - Crashes Into Moon, RTG is now safely disposed of 

--Samples analyzed in lab, end of mission when contact is lost with Lander Surface Module-- 

 

Please give me some feedback on this!

 

Edited by KAL 9000

Share this post


Link to post
Share on other sites

The shuttle external tank is designed to be outside of the rocket during launch. It also is not produced anymore, I see no real benefit to using it instead of designing a new tank. Also I see no reason to jettison the rtg, you could just send the orbiter to a neo instead.

Share this post


Link to post
Share on other sites
23 minutes ago, insert_name said:

The shuttle external tank is designed to be outside of the rocket during launch. It also is not produced anymore, I see no real benefit to using it instead of designing a new tank. Also I see no reason to jettison the rtg, you could just send the orbiter to a neo instead.

I know what it was used for, and you make a point. I just thought it might be easier to modify an existing design then to create a new one. Plus, the SLS is planned to use a modified Shuttle ET for its core stage fuel tank, so production will restart anyway. The orbiter is only designed to get from Titan to Earth, so I doubt it would have the fuel to get to a NEO, and I doubt the general population would approve of a RADIOACTIVE ISOTOPE in an orbit that would eventually decay and possibly crash into a populated area :wink:.

Edited by KAL 9000

Share this post


Link to post
Share on other sites

The "factory" is Michaud, and it's busy making SLS. Shuttle tanks are not a thing, and won't be.

Share this post


Link to post
Share on other sites
6 minutes ago, tater said:

The "factory" is Michaud, and it's busy making SLS. Shuttle tanks are not a thing, and won't be.

I edited my post :wink:. You could also just use an SLS tank instead.

Edited by KAL 9000

Share this post


Link to post
Share on other sites

I'd then say real life isn't KSP. If it's to use SLS parts, then make it an SLS launch (or 2, or whatever).

Share this post


Link to post
Share on other sites
1 hour ago, tater said:

I'd then say real life isn't KSP. If it's to use SLS parts, then make it an SLS launch (or 2, or whatever).

All too true. Hey, that gives me a thought: Can an SLS get an empty SLS tank into orbit? According to NASA's Trajectory planner, a round-trip with the orbiter would take like 15 km/s of Delta-V, and that's just for Saturn and back, not counting any Titan maneuvers! That also includes a final Earth orbit insertion, because I highly doubt that any heat shield ever designed can survive a reentry at 25 km/s relative velocity to Earth. I'm just assuming 10 km/s for a standard Earth orbit velocity. I also doubt that an SLS could launch one payload with that much Delta-V... It doesn't really matter what tank it uses, you're gonna need to assemble the transfer stage in orbit.

Share this post


Link to post
Share on other sites

I would assume the answer is "no." Even if the mass is such that you could loft an empty tank mass, it's the 2d stage, not the core that's putting the thing into orbit. Any mission design needs to fit under the fairing, and be within the mass limits.

Share this post


Link to post
Share on other sites

This looks like a mighty mission:) 

Hard bits

- Jupiter assist tx - 6600 m/s hohmann ?

- Titan ascent - 7600 m/s ******  nope appears to be more like 3800 m/s *******

- Earth return tx - 4250 m/s ? (3000 to saturn assist then burn 1250(x4 oberth effect)? for 5000m/s hohmann)

Good bits

- Jupiter assist 

- aerobrake at titan 

- isru on titan surface

I can understand wanting to use hydrogen+zero-boiloff for transfer/insertion stages.

With titans thick atmos, propulsive landing fuel might cost less kgs than parachutes.

 

One question : why are use hypergolics on the your ascent vehicle upper?

the s98 is a cool engine but seems strange when you are already doing methane isru for the lower stage.

You could try methane all the way home to earth in two or three stages. Direct style instead of orbital rv.

 

Interesting to compare all-hypergolics (apollo style) to all-methane+isru to your hydrolox/methane/hg combo.

What delta-v's are you using for transfers, insertions and surface parts of the mission?

Edited by RedKraken

Share this post


Link to post
Share on other sites

I calculated Delta-V using two amazing tools: NASA's Trajectory Browser and KSP RO

Yeah, this would definitely fall in the "Super-Flagship"-class.

Share this post


Link to post
Share on other sites
4 hours ago, tater said:

I would assume the answer is "no." Even if the mass is such that you could loft an empty tank mass, it's the 2d stage, not the core that's putting the thing into orbit. Any mission design needs to fit under the fairing, and be within the mass limits.

You *could* build a larger fairing.

Share this post


Link to post
Share on other sites

Personally, I'd prefer a modified SpaceX BFR, with landing legs on the core and any tank modifications needed to land the core+booster on Titan.

SSTO the modified core to earth staging orbit, send up the ITS return craft (set up for Titan ISRU, uncluding refueling the booster), dock and refuel both in orbit (many flights), and send it to titan.

Since it's unmanned, a saturn aerocapture may be plausable even without a proper heat shield on the BFR core- no need to worry about  mission duration or saturn's radiation belts. Saturn aerocapture  to titan aerocapture (over several passes) should limit the Delta V needed for capture, entry, desent and landing.

Then refuel, BFR to ITS to earth return.

Share this post


Link to post
Share on other sites

At such an investment, I'm beginning to seriously wonder why the transfer tug isn't nuclear-electric. Thus it can slowly decelerate into Titan orbit in advance of the lander's arrival.

Also, given the plethora of methane to go around, I wonder if it would be possible to create an airbreathing rocket with just the oxidizer onboard.

Share this post


Link to post
Share on other sites
3 hours ago, DDE said:

Also, given the plethora of methane to go around, I wonder if it would be possible to create an airbreathing rocket with just the oxidizer onboard.

Oxidizer is the heavier part of the propellant. You need four times the oxygen as you need methane by mass. Even if atmosphere was pure methane, it'd still be easier to build an airbreather rocket on Earth than on Titan, and we haven't even done that. The actual concentration of methane on Titan is less than 2% in atmosphere, which is bellow the flammability limit. Even if you add oxygen, it simply won't burn. To build an engine, you'll need a precooler and a centrifuge compressor stage to condense and separate methane from nitrogen, then send nitrogen to a high bypass fan and use methane-rich fraction to power the engine. This is pretty complex. And while this might work for something like a jet engine, it'd make for a terrible rocket.

On the other hand, it might just about make sense to simply land the ascent stage with empty fuel tank and use a condenser to extract methane from atmo to fill it up before ascent. It's not a huge saving overall, but the 10%-20% weight reduction you may squeeze out of it is not bad, and might be worth the complexity and additional point of failure.

The reason I'm suggesting condensing methane is because a) it's already really close to dew, and b) you'll get much higher purity that way than trying to pump stuff from lakes. It will be easier to build a condenser than a proper filtration system with a pump, and might actually take less energy to fill the tanks.

Edited by K^2

Share this post


Link to post
Share on other sites
4 hours ago, DDE said:

At such an investment, I'm beginning to seriously wonder why the transfer tug isn't nuclear-electric. Thus it can slowly decelerate into Titan orbit in advance of the lander's arrival.

Also, given the plethora of methane to go around, I wonder if it would be possible to create an airbreathing rocket with just the oxidizer onboard.

Good point... I'm just proposing a concept using technology and hardware we either already have or is in development. Sadly, nuclear-electric propulsion isn't actually being researched by NASA or any space agency at the present time. As for the odd mix of propellants and engines, I'm trying to maximize efficiency: i.e. hypergolics are better in a vacuum, but methalox is better in an atmosphere. ISRU could be done by extracting methane from the atmosphere instead, but an airbreathing rocket on Titan would need a RIDICULOUS amount of air scoops. No matter what, you're gonna need to bring oxidizer with you, unless you plan to collect ice on Titan (and on Titan, ice is literally as hard as rock... In fact, it IS rock there) and electrolyze it. 

 

9 hours ago, Rakaydos said:

Personally, I'd prefer a modified SpaceX BFR, with landing legs on the core and any tank modifications needed to land the core+booster on Titan.

SSTO the modified core to earth staging orbit, send up the ITS return craft (set up for Titan ISRU, uncluding refueling the booster), dock and refuel both in orbit (many flights), and send it to titan.

Since it's unmanned, a saturn aerocapture may be plausable even without a proper heat shield on the BFR core- no need to worry about  mission duration or saturn's radiation belts. Saturn aerocapture  to titan aerocapture (over several passes) should limit the Delta V needed for capture, entry, desent and landing.

Then refuel, BFR to ITS to earth return.

I'm just gonna say, the first ITS WILL explode violently, killing everyone aboard... It's a rocket straight out of KSP! It will take a while, at least until 2050, until it's actually ready.

Share this post


Link to post
Share on other sites

Sounds like a lot of launch... I mean, if this is unmanned, even the lander (+ orbiter) can be done in one go by SLS Block I or IB (I guess dV requirement until landing doesn't differ much to those by Jupiter Icy Moon Explorer, after all it doesn't take lots of dV to go a bit farther when you already gone pretty elliptical right), but ofc this is my initial rambling.

RSS dV map, anyone ?

Edited by YNM

Share this post


Link to post
Share on other sites

I think you underestimate the boiloff problem, I think the insertion stage should not use H2. CH4 still yields a pretty good Isp.

www.projectrho.com/public_html/rocket/enginelist.php

"However, this is the highest performance of any chemical rocket using fuels that can be stored indefinitely in space. Chemical rockets with superior specific impulse generally use liquid hydrogen, which will eventually leak away by escaping between the the molecules composing your fuel tanks. Liquid methane and liquid oxygen will stay put."

The transfer to Titan is a long time. The mass savings on tankage and cooling and insulation and not having propellant escape will likely outweigh the inferior Isp.

377 vs 336 for your hypergolics... maybe you'd want your orbiter return stage to be a methane-lox design too.

For Titan ascent, you'd definitely want to use an air augmented rocket... use that N2 as working mass. My guess is you'd probably be able to get 600+ effective Isp that way.

Still, at this point, its worth looking into ISRU... and maybe you ditch the orbiter... the point of an orbiter is you don't waste fuel bringing your return fuel down and back up again.... but what if you brought no return fuel? The ground is very icy... water ice. Titan is very cold, insulation for LH2 won't need to be as substantial...

Maybe just land an RTG, cooling equipment, empty tanks, and some drills. Return on a 2 stage H2-O rocket fueled from ISRU, with the lower stage having the ducting needed for an air augmented rocket.

Direct return after ISRU fueling, no orbital rendevous, return using the maximum Isp rocket you can, mass savings proportionately get passed on to lower stages (this heavily depends on the mass of the ISRU!)

Share this post


Link to post
Share on other sites

I can't comment on the rocket science part of it since my knowledge of sending rockets to another planet's moon starts and ends with KSP. But from the chemist's perspective, why bring samples back? You will need to keep them at cryogenic temperatures the entire time they are in transit, and once they get to the surface. Not an impossible task, but difficult. As soon as it warms to room temperature, probably even 0 C, it will be destroyed. There are some tests that can be very useful that are almost impossible to do on Titan (like taking an NMR spectrum), but it might be easier to just launch the equipment to Titan and really do everything in situ rather than risk altering your sample.

Share this post


Link to post
Share on other sites
34 minutes ago, todofwar said:

I can't comment on the rocket science part of it since my knowledge of sending rockets to another planet's moon starts and ends with KSP. But from the chemist's perspective, why bring samples back? You will need to keep them at cryogenic temperatures the entire time they are in transit, and once they get to the surface. Not an impossible task, but difficult. As soon as it warms to room temperature, probably even 0 C, it will be destroyed. There are some tests that can be very useful that are almost impossible to do on Titan (like taking an NMR spectrum), but it might be easier to just launch the equipment to Titan and really do everything in situ rather than risk altering your sample.

There are many scientific advantages to having samples available to all the best labs on Earth. As for keeping the samples cold, I think we'll have no problem, considering the ships will be in the FRICKING OUTER SOLAR SYSTEM for most of the time, where it's so cold that ice is harder than rock.

Share this post


Link to post
Share on other sites
10 hours ago, KerikBalm said:

For Titan ascent, you'd definitely want to use an air augmented rocket... use that N2 as working mass. My guess is you'd probably be able to get 600+ effective Isp that way.

Very interesting. Oniks on titan.

Ramjets are heavy (sabre twr 14 in atmos) but in 0.17g this starts to look better (twr 82).  if u can double the isp, nobody cares if the engine is 3 or 4 times heavier (except if u are sending it empty from earth...then u care about extra mass) The fuel mass still dominates the mass ratio. The low temps (-180 deg C) will allow u to build lighter than for an earth ramjet too.

But terrestrial ramjets only operate well between mach 1 and mach 6 (330m/s to 2000m/s). Will this differ much with titans low grav, 1.45atmos and N2?

Starting to think the extra dry mass sent from earth is not worth the dv gain for half the ascent. I could be wrong. Tanks tend to be larger mass component than engines.

Edited by RedKraken

Share this post


Link to post
Share on other sites
9 hours ago, KAL 9000 said:

There are many scientific advantages to having samples available to all the best labs on Earth. As for keeping the samples cold, I think we'll have no problem, considering the ships will be in the FRICKING OUTER SOLAR SYSTEM for most of the time, where it's so cold that ice is harder than rock.

Thing is, the ship will be generating heat and outer space happens to be a fantastic insulator to trap it in, which is why radiating heat is always a concern. Now, it's probably a surmountable challenge but it needs considering. Also, bringing it in for re entry will require keeping it cold the whole way down. Again, probably can be done. Still, I have a hard time figuring out what to do with that sample that couldn't be done with a heavy lander.

Share this post


Link to post
Share on other sites

Ok.... in RO 1.1.3 with my ITS lander, i only used 4000m/s to ascend from titans surface to 1000x1000km.

?? my dv map says 7600 ??

is this a bad estimate?  RO data appears to be sound.

Info about the map here https://www.reddit.com/r/space/comments/1ktjfi/deltav_map_of_the_solar_system/

MJ reads 1.35m/s2 gravity, 1.55 atmos, density 5.5 kg/m3 at surface.... all good.

3 SL raptors all the way....didnt turn on the vacs

Surface start at 150t/2100t dry/fueled no cargo. twr 3.2, 8100m/s (sl) 8730m/s (vac)

orbital vel is 1570m/s so i used about 2430m/s in losses.

It was a rough gravity turn (40%) starting a 10km ending at 250km.

I had to burn an ap at 1500km cause titan was clawing it down, even out at 600km. 600km is low orbit.

i had mechjeb limit my q to 29kpa, so it was slow going off the surface 110 - 150 m/s in the first 20km.

Edited by RedKraken

Share this post


Link to post
Share on other sites
7 hours ago, RedKraken said:

But terrestrial ramjets only operate well between mach 1 and mach 6 (330m/s to 2000m/s). Will this differ much with titans low grav, 1.45atmos and N2

In terms of bulk atmospheric composisition, it should be very similar to Earth. 80% N2 vs 98% N2. The colder atmosphere should make the max mach a little higher, as its heating of the atmosphere when compressed in a jet engine that is a major problem (hence sabre precoolers).

Also one should note that we have Ramjets... and Scramjets... the 2nd havingthe addition of "supersonic combusting" because the ramjet doesn't slow air down to subsonic speed in the chamber for combustion. In our case, we don't care about combusting fuel with the atmosphere. The combustion happens in the combustion chamber of the rocket engine, whose exhaust is mixed with the ramcompressed air. As far as I know, an air augmented rocket should keep operating to scramjet speeds just fine (with air augmentation, it can also operate in vacuum conditions). Also we should note that orbital velocity for titan is ~2 km/second.

Mach 6 would just about get you to orbital velocity for Titan.

 

Quote

Starting to think the extra dry mass sent from earth is not worth the dv gain for half the ascent. I could be wrong. Tanks tend to be larger mass component than engines.

Well, the engine would be heavier... yes, but unlike Earth, you'd be getting useful thrust augmentations for basically the whole way to orbit, not just the first 1/4 of the way. Also the engine mass would scale to some degree with the ship mass. A small ascent vehicle means less mass in ducting for the air augmented rocket.

I haven't done the calculations, but I suspect if these things are tantalizingly close to paying off on Earth, that on Titan they'd easily beat the competition (since, again, they provide useful augmentation basically the entire way to orbit).

We also would have to consider if ISRU is/is not going to be used. If its not going to be used, then we need to consider the mass of the ascent vehicle tanks and fuel vs the increased engine mass. If ISRU is going to be used, we consider the increased engine mass vs the greater tankage mass and more robust ISRU equipment since more fuel would need to be processed.

Share this post


Link to post
Share on other sites
This thread is quite old. Please consider starting a new thread rather than reviving this one.

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Sign in to follow this