Author Topic: Going back to the Moon *really* fast.  (Read 10525 times)

Offline sevenperforce

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Re: Going back to the Moon *really* fast.
« Reply #40 on: 03/09/2018 09:18 PM »
Quote
2. aerobrake into Earth orbit; or
Not to mention that #2 will require a heat shield every bit as beefy as #1

Is this true?
Yes, you need to slow down from 11km/s, from lunar freefall, not 8km/s from LEO eventually, but going from that velocity to GTO is about 1km/s, and in principle you can do it then as slowly as you like (modulo radiation).

Annoyingly, I keep hitting paywalls when I try to find papers of the heating of the shuttle over time, and aerodynamic drag.
You really need to do it in one go, thanks to old Van Allen. So that's around 3 km/s. My gut is that the peak heating will not be substantially lower than it would be for direct entry, because you are going to have to dip awfully low in the atmosphere to avoid skipping out with a high apogee. I don't recall what perigee altitude the Apollo missions targeted, but it couldn't have been much lower than Zond 5, which did skip out.

Offline rakaydos

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Re: Going back to the Moon *really* fast.
« Reply #41 on: 03/10/2018 04:57 AM »
Quote
2. aerobrake into Earth orbit; or
Not to mention that #2 will require a heat shield every bit as beefy as #1

Is this true?
Yes, you need to slow down from 11km/s, from lunar freefall, not 8km/s from LEO eventually, but going from that velocity to GTO is about 1km/s, and in principle you can do it then as slowly as you like (modulo radiation).

Annoyingly, I keep hitting paywalls when I try to find papers of the heating of the shuttle over time, and aerodynamic drag.
You really need to do it in one go, thanks to old Van Allen. So that's around 3 km/s. My gut is that the peak heating will not be substantially lower than it would be for direct entry, because you are going to have to dip awfully low in the atmosphere to avoid skipping out with a high apogee. I don't recall what perigee altitude the Apollo missions targeted, but it couldn't have been much lower than Zond 5, which did skip out.

You know, we COULD do something about the van allen belts...
https://en.wikipedia.org/wiki/Van_Allen_radiation_belt#Proposed_removal

Offline raketa

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Re: Going back to the Moon *really* fast.
« Reply #42 on: 03/10/2018 06:24 AM »
Give Spacex 1B every year for BFR development.

Offline john smith 19

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Re: Going back to the Moon *really* fast.
« Reply #43 on: 03/10/2018 07:41 AM »
Give Spacex 1B every year for BFR development.
Because "giving" $1Bn a year to the SLS contractor has worked so well so far (over the last 14 years).
Hint. COTS Cargo was done under the NASA Space Act Agreement mechanism. Dragon 2 (or crewed Dragon) under FAR section 22, as is SLS. You might like to compare the implementation time frames.

Perhaps you should read the OP for this thread again.
« Last Edit: 03/10/2018 07:43 AM by john smith 19 »
BFS. The worlds first Methane fueled FFORSC engined CFRP structured A380 sized aerospaceplane tail sitter capable of flying in Earth and Mars atmospheres. BFR. The worlds biggest Methane fueled FFORSC engined CFRP structured booster for BFS. First flight to Mars by end of 2022. Forward looking statements. T&C apply. Believe no one. Run your own numbers. So, you are going to Mars to start a better life? Picture it in your mind. Now say what it is out loud.

Offline Oli

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Re: Going back to the Moon *really* fast.
« Reply #44 on: 03/10/2018 11:04 AM »
I don't see the point of going back to the Moon "really fast".

If the goal is not to establish a permanent outpost on the Moon, I'd rather see "sorties" to asteroids and the Martian moons. I'm starting to think this reorientation towards the Moon is a mistake.

Offline speedevil

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Re: Going back to the Moon *really* fast.
« Reply #45 on: 03/10/2018 11:43 AM »
I don't see the point of going back to the Moon "really fast".

If the goal is not to establish a permanent outpost on the Moon, I'd rather see "sorties" to asteroids and the Martian moons. I'm starting to think this reorientation towards the Moon is a mistake.

In principle, the Moon has a place that Mars does not - namely a week away, not a couple of years away.

If you have wholly reusable vehicles, neglecting delta-v, you can put a hundred times more cargo on the Moon than Mars in a year, with the same capital investment, with no need to develop ISRU for the Moon.

This pretty much does not apply as an advantage to launch vehicles with long cadences, or ones where you have to salvo lots of launchers for one-off missions.

It does not apply if you use the normal set of main contractors as you are going to blow any conceivable budget even with free launch trying to design ten thousand tons of payload.

Versus launching a one-off demonstration payload at the moon with perhaps a ton of useful payload for $10B or so, and simply encouraging most of traditional aerospace further into revenue optimisation which got us here to begin with - giving $1B/year to SpaceX seems like a pretty solid plan.

We need to work out how to make vastly cheaper payloads, as step 0.
Several providers are attempting to radically lower the cost of launch with wholly reusable vehicles.
If even one of them achieves it, and we don't know how to make payloads at under $10M/ton, then it's pretty pointless.
That is the fundamental 'technological' leap that is needed - not how to do Apollo 2.






Offline john smith 19

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Re: Going back to the Moon *really* fast.
« Reply #46 on: 03/10/2018 09:43 PM »
We need to work out how to make vastly cheaper payloads, as step 0.
..
That is the fundamental 'technological' leap that is needed - not how to do Apollo 2.
Yes that's the weak link in this plan.   :(

It's believed Dragon 2 can be converted to operate on the Moon but OrionMPCV is the PoR (and it's incomplete. It still needs the SM from the ESA) for BEO operations.

Based on Orions development budget (c $400m/tonne) cutting the development cost to $1m/tonne would be a massive cut in development costs.

I'm not sure if anyone has a handle on how to do this.  :(

I guess what I can't get my head around is that the NASA publishes all the standards such systems have to meet, so why does it seem to take so long and require so many changes after the design has been agreed (IE when changes will be most expensive and take the longest to implement) ?
BFS. The worlds first Methane fueled FFORSC engined CFRP structured A380 sized aerospaceplane tail sitter capable of flying in Earth and Mars atmospheres. BFR. The worlds biggest Methane fueled FFORSC engined CFRP structured booster for BFS. First flight to Mars by end of 2022. Forward looking statements. T&C apply. Believe no one. Run your own numbers. So, you are going to Mars to start a better life? Picture it in your mind. Now say what it is out loud.

Offline daveklingler

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Re: Going back to the Moon *really* fast.
« Reply #47 on: 03/12/2018 05:34 PM »
I attempted to work this while walking dogs this morning, not optimal, but I *think* it gets pretty close. It requires plenty of ground mods.

Falcon Heavy launches full Centaur + Dragon into elliptical orbit.
Second Falcon Heavy with full Xeus docks with Centaur 1 and does a second burn to use up any residual prop.
Centaur 1 continues burn to LLO. Xeus goes to surface and back.
Any residual prop is transferred to Xeus, then Xeus does TOI. Dragon returns home.

Thoughts:
1. Using a Xeus can save a lot of mass.
2. Using FH either to carry LH/LOX tanks or full Centaurs uses its capabilities better.
3. Using elliptical orbits cuts required delta vee.
4. Using chilled propellants might even make a big difference.

* Can't remember whether a Xeus has enough prop to make it off the lunar surface to TOI without topping off.
« Last Edit: 03/12/2018 05:52 PM by daveklingler »

Offline john smith 19

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Re: Going back to the Moon *really* fast.
« Reply #48 on: 03/12/2018 08:45 PM »
I attempted to work this while walking dogs this morning, not optimal, but I *think* it gets pretty close. It requires plenty of ground mods.

Falcon Heavy launches full Centaur + Dragon into elliptical orbit.
Second Falcon Heavy with full Xeus docks with Centaur 1 and does a second burn to use up any residual prop.
Centaur 1 continues burn to LLO. Xeus goes to surface and back.
Any residual prop is transferred to Xeus, then Xeus does TOI. Dragon returns home.

Thoughts:
1. Using a Xeus can save a lot of mass.
2. Using FH either to carry LH/LOX tanks or full Centaurs uses its capabilities better.
3. Using elliptical orbits cuts required delta vee.
4. Using chilled propellants might even make a big difference.

* Can't remember whether a Xeus has enough prop to make it off the lunar surface to TOI without topping off.
Saving mass is not a priority. Saving time would be. Remember it's 966 days to the next Presidential election. Xeus I think is too long term.  :(

Prop cooling, even with LH2, has been demonstrated. If you avoid going full slush you can get a significant volume reduction without the issues of 2 phase flow. 

IIRC Centaur has been hosted on a number of LV's over the decades, so FH (stage diameters permitting) could host it as well. Centaur as an EDS sounds quite viable.

I think people have self imposed constraints they will only use specific mfg hardware. This is not a real constraint. If it's for sale and it can get the job done that's reasonable.

Nice bit of lateral thinking.
« Last Edit: 03/12/2018 08:47 PM by john smith 19 »
BFS. The worlds first Methane fueled FFORSC engined CFRP structured A380 sized aerospaceplane tail sitter capable of flying in Earth and Mars atmospheres. BFR. The worlds biggest Methane fueled FFORSC engined CFRP structured booster for BFS. First flight to Mars by end of 2022. Forward looking statements. T&C apply. Believe no one. Run your own numbers. So, you are going to Mars to start a better life? Picture it in your mind. Now say what it is out loud.

Offline daveklingler

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Re: Going back to the Moon *really* fast.
« Reply #49 on: 03/14/2018 04:38 AM »
Saving mass is not a priority. Saving time would be. Remember it's 966 days to the next Presidential election. Xeus I think is too long term.  :(

Well...to be accurate, more than a few days is too long term.  For that matter, if you're relying on a certain someone's lunar ambitions, those have long since been superseded by a big parade.

Quote
IIRC Centaur has been hosted on a number of LV's over the decades, so FH (stage diameters permitting) could host it as well. Centaur as an EDS sounds quite viable.

Yeah, I've been playing with Centaur and Xeus.  Centaur works really, really well as an EDS, and the combo is even better. Centaur is half the mass of an equivalent storable, as ULA points out.  Centaur and RL-10 really are both hard to top in the space hardware kit catalog.

FH can almost put a fully-loaded Centaur in TLI, so that's what I'm fooling with right now.

Offline john smith 19

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Re: Going back to the Moon *really* fast.
« Reply #50 on: 03/14/2018 06:18 AM »
Yeah, I've been playing with Centaur and Xeus.  Centaur works really, really well as an EDS, and the combo is even better. Centaur is half the mass of an equivalent storable, as ULA points out.  Centaur and RL-10 really are both hard to top in the space hardware kit catalog.

FH can almost put a fully-loaded Centaur in TLI, so that's what I'm fooling with right now.
I'll skip over and "parade" ambitions but your approach is sort of what I was thinking of.

2 Points to consider would be.
1) The Block 5 F9 upgrade is coming. I guess there will be some kind of thrust increase as well, since presumably that's what they will move toward for the boosters.
2) What happens if you load the Centaur propellant up to the current FH maximum payload? No vehicle mods for payload increase, just what's already demonstrated?
BFS. The worlds first Methane fueled FFORSC engined CFRP structured A380 sized aerospaceplane tail sitter capable of flying in Earth and Mars atmospheres. BFR. The worlds biggest Methane fueled FFORSC engined CFRP structured booster for BFS. First flight to Mars by end of 2022. Forward looking statements. T&C apply. Believe no one. Run your own numbers. So, you are going to Mars to start a better life? Picture it in your mind. Now say what it is out loud.

Offline daveklingler

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Re: Going back to the Moon *really* fast.
« Reply #51 on: 03/15/2018 06:19 PM »
Yeah, I've been playing with Centaur and Xeus.  Centaur works really, really well as an EDS, and the combo is even better. Centaur is half the mass of an equivalent storable, as ULA points out.  Centaur and RL-10 really are both hard to top in the space hardware kit catalog.

FH can almost put a fully-loaded Centaur in TLI, so that's what I'm fooling with right now.

Making no allowances for boiloff or sunshades and some optimistic estimates for crew and cargo (6t for Xeus kit, hab conversion, suitports, crew and equipment), this closes:

1. FH RTLS launches Centaur with docking ring (no transfer passage necessary) to LEO. 
2. Another FH RTLS launches Xeus with a similar docking ring to LEO. Xeus and Centaur dock.
3. Falcon 9 launches Dragon to LEO. Dragon makes rendezvous with Centaur-Xeus combo, and crew transfers to Xeus.
4. Dragon is left in LEO. Centaur burns most of its props, then separates and returns to LEO near the orbiting Dragon.
5. Xeus continues direct to lunar surface. Astronauts get out, plant flag, etc., hop back into Xeus, which...
6. ...returns them to LEO, where they rendezvous with Dragon, disembark and go home.
7. Centaur and Xeus re-dock and remain in LEO, where they wait for FH tanker to arrive and send them on another mission.

There's some flexibility in this process because the FH isn't really being fully used. The Centaur tug can impart about 2.3 km/sec to a fully-loaded Xeus. I think positioning the stack a little higher or moving to a more elliptical orbit could make up for some of the boiloff or other deficiencies.

Using Centaur and Xeus as a tug system this way opens up the way for a lot of other missions. Xeus can deliver about 5 tons to the lunar surface, reusable, or 10 tons and remain on the surface.

One idea would be to deliver a hab and a power system, along with a couple of micro rovers equipped with remote-operated front-end loader blades. The rovers bury the hab and prep it for the arrival of the astronauts, who come on the third mission. 

Everything is reusable in this scenario. Each successive mission requires a Falcon Heavy tanker (20 tons of props each for the Centaur and Xeus) and a Falcon 9 to bring a Dragon for crewed missions. A cargo payload could possibly come up in the Dragon's trunk.

2 Points to consider would be.
1) The Block 5 F9 upgrade is coming. I guess there will be some kind of thrust increase as well, since presumably that's what they will move toward for the boosters.

If FH really does become more capable, the biggest improvement I see would be in the direct-to-lunar-surface cargo missions growing in capability by a ton or two. But FH is already pretty useful as a tanker and big enough to deliver a full Centaur to LEO.

Quote
2) What happens if you load the Centaur propellant up to the current FH maximum payload? No vehicle mods for payload increase, just what's already demonstrated?

Not sure what you mean here, given that the Centaur only holds 20 tons of propellant, unless you're asking what happens when Centaur becomes an ACES.  But yes, an ACES 73 used as a tug would be pretty spectacular.  A bigger and more capable Xeus would be nice, as well.

Note that Centaur will already be human-rated, and Masten is already toward the end of a SAA with NASA on Xeus.
« Last Edit: 03/15/2018 06:27 PM by daveklingler »

Online TrevorMonty

Re: Going back to the Moon *really* fast.
« Reply #52 on: 03/15/2018 08:00 PM »
Dave can you break your Centuar and Xeus vehicle masses down. I've worked similar missions and ended up with minimum of 100t LOX/LH per trip. NB round trip is 12km/s.

Offline sevenperforce

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Re: Going back to the Moon *really* fast.
« Reply #53 on: 03/15/2018 09:54 PM »
I confess I don't entirely understand. If Dragon 2 has heat shields rated for entry from cislunar space, why not take it at least to high-elliptic Earth orbit, if not all the way to lunar orbit?

Offline A_M_Swallow

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Re: Going back to the Moon *really* fast.
« Reply #54 on: 03/15/2018 10:35 PM »
{snip}
Note that Centaur will already be human-rated, and Masten is already toward the end of a SAA with NASA on Xeus.

c/end of a SAA/start of a SAA/

Masten Space are currently developing the XL-1 100kg payload lander and testing everything on the XL-1T.

XEUS is "System Concept Design Review 3" by September 2019 - that sounds like early paperwork not metal bending.

Online TrevorMonty

Re: Going back to the Moon *really* fast.
« Reply #55 on: 03/15/2018 11:24 PM »
{snip}
Note that Centaur will already be human-rated, and Masten is already toward the end of a SAA with NASA on Xeus.

c/end of a SAA/start of a SAA/

Masten Space are currently developing the XL-1 100kg payload lander and testing everything on the XL-1T.

XEUS is "System Concept Design Review 3" by September 2019 - that sounds like early paperwork not metal bending.
There be some flight testing in their somewhere for Xeus. Masten wanted to test out vertical takeoff and land with varies simulated fuel loads. Mainly to develop flight software and how to handle fuel moving around in tanks. The landing thrusters may even be different engines and even fuels compared to flight version.

For flight version plan was to use multiple LOX/LH landing engines, fed from their own small tanks. These tanks were filled from main tanks just before landing and take off.



Offline A_M_Swallow

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Re: Going back to the Moon *really* fast.
« Reply #56 on: 03/16/2018 12:09 AM »
{snip}
Note that Centaur will already be human-rated, and Masten is already toward the end of a SAA with NASA on Xeus.

c/end of a SAA/start of a SAA/

Masten Space are currently developing the XL-1 100kg payload lander and testing everything on the XL-1T.

XEUS is "System Concept Design Review 3" by September 2019 - that sounds like early paperwork not metal bending.
There be some flight testing in their somewhere for Xeus. Masten wanted to test out vertical takeoff and land with varies simulated fuel loads. Mainly to develop flight software and how to handle fuel moving around in tanks. The landing thrusters may even be different engines and even fuels compared to flight version.

For flight version plan was to use multiple LOX/LH landing engines, fed from their own small tanks. These tanks were filled from main tanks just before landing and take off.




XEUS will probably need the ability to rendezvous with spacecraft and spacestations, to dock, undock, refuel, pick up a cargo, release a cargo, support long range communications and navigation equipment. These can be tested in LEO.

Online TrevorMonty

Re: Going back to the Moon *really* fast.
« Reply #57 on: 03/16/2018 02:27 AM »
{snip}
Note that Centaur will already be human-rated, and Masten is already toward the end of a SAA with NASA on Xeus.

c/end of a SAA/start of a SAA/

Masten Space are currently developing the XL-1 100kg payload lander and testing everything on the XL-1T.

XEUS is "System Concept Design Review 3" by September 2019 - that sounds like early paperwork not metal bending.
There be some flight testing in their somewhere for Xeus. Masten wanted to test out vertical takeoff and land with varies simulated fuel loads. Mainly to develop flight software and how to handle fuel moving around in tanks. The landing thrusters may even be different engines and even fuels compared to flight version.

For flight version plan was to use multiple LOX/LH landing engines, fed from their own small tanks. These tanks were filled from main tanks just before landing and take off.




XEUS will probably need the ability to rendezvous with spacecraft and spacestations, to dock, undock, refuel, pick up a cargo, release a cargo, support long range communications and navigation equipment. These can be tested in LEO.
Initial cargo ones will most likely be expendable, launch fully fuelled lander and payload to LEO under Vulcan or NG fairing.

Until there is low cost lunar fuel cargo landers will be expendable. Reuseable crew version can live with higher fuel prices.
« Last Edit: 03/16/2018 02:27 AM by TrevorMonty »

Offline john smith 19

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Re: Going back to the Moon *really* fast.
« Reply #58 on: 03/16/2018 09:04 PM »
Yeah, I've been playing with Centaur and Xeus.  Centaur works really, really well as an EDS, and the combo is even better. Centaur is half the mass of an equivalent storable, as ULA points out.  Centaur and RL-10 really are both hard to top in the space hardware kit catalog.

FH can almost put a fully-loaded Centaur in TLI, so that's what I'm fooling with right now.

Making no allowances for boiloff or sunshades and some optimistic estimates for crew and cargo (6t for Xeus kit, hab conversion, suitports, crew and equipment), this closes:

1. FH RTLS launches Centaur with docking ring (no transfer passage necessary) to LEO. 
2. Another FH RTLS launches Xeus with a similar docking ring to LEO. Xeus and Centaur dock.
3. Falcon 9 launches Dragon to LEO. Dragon makes rendezvous with Centaur-Xeus combo, and crew transfers to Xeus.
4. Dragon is left in LEO. Centaur burns most of its props, then separates and returns to LEO near the orbiting Dragon.
5. Xeus continues direct to lunar surface. Astronauts get out, plant flag, etc., hop back into Xeus, which...
6. ...returns them to LEO, where they rendezvous with Dragon, disembark and go home.
7. Centaur and Xeus re-dock and remain in LEO, where they wait for FH tanker to arrive and send them on another mission.

There's some flexibility in this process because the FH isn't really being fully used. The Centaur tug can impart about 2.3 km/sec to a fully-loaded Xeus. I think positioning the stack a little higher or moving to a more elliptical orbit could make up for some of the boiloff or other deficiencies.

Using Centaur and Xeus as a tug system this way opens up the way for a lot of other missions. Xeus can deliver about 5 tons to the lunar surface, reusable, or 10 tons and remain on the surface.

One idea would be to deliver a hab and a power system, along with a couple of micro rovers equipped with remote-operated front-end loader blades. The rovers bury the hab and prep it for the arrival of the astronauts, who come on the third mission. 

Everything is reusable in this scenario. Each successive mission requires a Falcon Heavy tanker (20 tons of props each for the Centaur and Xeus) and a Falcon 9 to bring a Dragon for crewed missions. A cargo payload could possibly come up in the Dragon's trunk.

2 Points to consider would be.
1) The Block 5 F9 upgrade is coming. I guess there will be some kind of thrust increase as well, since presumably that's what they will move toward for the boosters.

If FH really does become more capable, the biggest improvement I see would be in the direct-to-lunar-surface cargo missions growing in capability by a ton or two. But FH is already pretty useful as a tanker and big enough to deliver a full Centaur to LEO.

Quote
2) What happens if you load the Centaur propellant up to the current FH maximum payload? No vehicle mods for payload increase, just what's already demonstrated?

Not sure what you mean here, given that the Centaur only holds 20 tons of propellant, unless you're asking what happens when Centaur becomes an ACES.  But yes, an ACES 73 used as a tug would be pretty spectacular.  A bigger and more capable Xeus would be nice, as well.

Note that Centaur will already be human-rated, and Masten is already toward the end of a SAA with NASA on Xeus.
I thought Centaur was heavier than that.  Obviously the block 5 upgrade should give some additional payload, but that's TBD.

Reusability should help costs down (not a priority, but good to have). ULA tests have shown they can cut boiloff by 1/2 with pulsed settlement thrusting.  Current longest mission a Centaur has run is 12 hours but I'm not sure if the baseline insulation could do better but it's never had to. So good up to a day? IIRC that's still a bit short for doing mid course correction burns, let alone a landing.

IMHO the complete absence of any in space support infrastructure left by Apollo is part of the reason it's proved so difficult to move BEO for so long.
BFS. The worlds first Methane fueled FFORSC engined CFRP structured A380 sized aerospaceplane tail sitter capable of flying in Earth and Mars atmospheres. BFR. The worlds biggest Methane fueled FFORSC engined CFRP structured booster for BFS. First flight to Mars by end of 2022. Forward looking statements. T&C apply. Believe no one. Run your own numbers. So, you are going to Mars to start a better life? Picture it in your mind. Now say what it is out loud.

Offline daveklingler

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Re: Going back to the Moon *really* fast.
« Reply #59 on: 03/17/2018 04:16 PM »
Dave can you break your Centuar and Xeus vehicle masses down. I've worked similar missions and ended up with minimum of 100t LOX/LH per trip. NB round trip is 12km/s.

Hi Trevor.

I haven't had time yet to sit down and rework this, but the short answer is that I had initially been using expendable Falcon Heavies and I think I might have erroneously kept the 2.74 km/s aerobraking return instead of changing it back to 5.93 km/s for lunar surface to LEO.  So...it doesn't close.  Sorry!

I did leave out 1.7 mt of propellants; Centaur carries 20.85 mt and not the 20 mt I was using in my calculations, so adding that back in might help. I also used a single RL-10, assuming I'd have to go back later and check to make sure that would work.

Refilling the tug in LEO and doing another rendezvous for the return trip might close it, or using more of the Falcon Heavy's capability, or using more elliptical orbits.  I putzed around with ACES mass ratios a little bit yesterday and that was impressive. There's very little added tank mass for the additional propellant that ACES carries. But we're not using ACES in this exercise.

My initial problem with using two Falcon Heavies as expendables was that it worked great for cargo but I couldn't figure out how to get crew aboard. That required the crew to come up aboard a capsule. Using a CST-100 launch would bring up an empty Centaur, but that didn't seem to help anything.

Well, if I get some time this weekend I'll work it around some more. And I can always go back to the expendable Falcon Heavies, but the idea of making everything reusable was pretty appealing.

EDIT: I haven't checked to see what happens if you keep the FH second stage attached after crew rendezvous and use it to throw either the full stack or just the Xeus. That might be good for a few km/s.
« Last Edit: 03/17/2018 04:33 PM by daveklingler »