SpaceX and cis-lunar Space Tourism

[meekGee]

Up till now, we really only talked about SpaceX in the context of ISS Taxi, comsats, and Mars.

With Dragon V2 coming up, and Bigelow at the unveiling event, and interpreting comments by Elon regarding the moon, it's a fair question:

Suppose a VC puts up the funds to do a space tourism company.   Trips to LEO, GTO, and lunar-free-return.   "In high volume, single-digit-Million".    Will people put down $10-$20M for a trip?

[pathfinder_01]

Given that Russia has sold an few tickets to the ISS at that price possibly yes, but being able to turn an profit at that price is still far away. The falcon heavy at the moment still goes for $77 million to $135 mill and odds are you won't be able to fit 7 people on that mission and some of the Dragon's systems are going to need to be upgraded.

[A_M_Swallow]

A version of the Dragon able to land and take off from the Moon would be useful.

It does not need protection against re-entry but will need protecting against back-draft from its own engines.  Very long legs will protect the spacecraft against not having a flame trench and the extreme cold of the ground during lunar nights.  A much larger fuel tank to perform the round trip without refuelling.

[king1999]

The current price is $500m with one person already signed up (need 2 for a mission using Soyuz).
I would think the FH/Dragon can do 3 person, each for $100m initially. When the re-usability is proved, it can certainly goes down to $10-20m range for 10 re-uses of FH and Dragon.

[sanman]

If Musk can bring down the cost of taking people to LEO by a wide margin, then it seems axiomatic that there could be some comparable lowering of the cost to take people to the Moon.

Musk and other multi-planetarists may not see the Moon as being terraformable or ocean-izable or icecap-meltable as Mars is, according to their far-flung ambitious timelines. But let's face it, for the near-to-medium term, the Moon is no less habitable than Mars. Right now, Mars is a vast airless megadesert, and so is the Moon. Yes, Mars has water, but the amount of water on the Moon isn't insignificant either.

So if you have to pick between 2 vast airless megadeserts, then go for the one that's mere days away, rather than for the one that requires months of travel time.

Musk wants spaceflights to become routine, numbering in thousands of flights per year by 2030. Well, that's more likely to happen by luring potential customers with the exotic-yet-nearby destination of the Moon, as compared to the very-exotic-and-very-far destination of Mars. Lower the difficulty barrier, and more trips become possible at lower cost. The famous "Forcing Function" then continues its work at faster pace.

The Moon is lower-hanging fruit than Mars is, even if Mars is the better-quality fruit in the long run.

Use the Moon to lure more customers into spending on trips there, and then re-invest that money into the better-quality equipment that will be required to reach faraway Mars and live that much farther away from the support of Mother Earth.

[spacetraveler]

^ Completely agree. Musk has said he wants moving to Mars to cost 500k. Well I think there are a heck of a lot more people that would pay more than that for a flight to the moon (even just a flyby) than there are who would pay 500k to permanently move to Mars.

[ArbitraryConstant]

I don't know about tourism, but I think the Bigelow approach of sovereign customers will inevitably happen if transportation gets cheap enough. Even if SpaceX has no particular interest in the moon, they'll launch anyone that can pay.

[Geron]

I wonder if dragon v2 with full tanks has enough delta v to land on and then take off from the moon.

If so then a dragon could be parked in lunar orbit, do lunar rendezvous with incoming dragon with tourists, and be the shuttle to and from the surface.

I bet bigelow is pretty excited about dragon v2!

[Owlon]

I wonder if dragon v2 with full tanks has enough delta v to land on and then take off from the moon.

If so then a dragon could be parked in lunar orbit, do lunar rendezvous with incoming dragon with tourists, and be the shuttle to and from the surface.

I bet bigelow is pretty excited about dragon v2!

Almost certainly not. That requires something around 4 km/s of delta-V, which means propellant would have to be something like 80% of Dragon's mass. In other words, assuming an empty Dragon weighs 5000 kg, it would have to weigh about 25000 kg loaded with propellant. Dragon most likely only carries 2-3 tons of propellant.

A dragon with an extensively modified trunk carrying fuel and acting as a descent/ascent stage could probably do it, but that's a major engineering project.

[meekGee]

In my mind, the minute you bring up a moon landing, costs explodes again, since nothing that SpaceX has done addresses EVAs, lunar environment, etc - nevermind just the added mass for the added dV.

But the added complexity for a lunar free return is (in comparison) low, and the added value (in comparison to Earth orbit) is high.

So I think there's a sweat spot there.

For SpaceX, the extra complexity of BEO HSF is "on the way to Mars", so they'll be getting paid to develop things they need anyway.  Which is Elon's favorite MO.

For the tourism company, there's a nice upramp, from LEO (with stock DV2), to GTO (better view) to Lunar free return.   

Just like with the son-of-teledesic, I am sure that more than one VC has done this math and had dinner with Elon about it.

[Coastal Ron]

Given that Russia has sold an few tickets to the ISS at that price possibly yes, but being able to turn an profit at that price is still far away. The falcon heavy at the moment still goes for $77 million to $135 mill and odds are you won't be able to fit 7 people on that mission and some of the Dragon's systems are going to need to be upgraded.

All the space tourists that have flown on the Soyuz have gone to a space station and spent time there (i.e. the ISS).  The goal of the tourists was not to fly on the Soyuz, but to stay on the ISS - the Soyuz was just a means to an end.

So sure someone could rent a Dragon V2 flight, but without a destination I doubt they will get many takers.

And just a note about the price.  Musk stated at the Dragon V2 unveiling that they have quoted a price to NASA less than $20M per seat.  When the crew version of the Dragon was first announced Musk stated that the cost would be as low as $20M per seat, but only if all 7 seats were purchased (i.e. $140M for the total flight).  And that's on a Falcon 9, not a Falcon Heavy.

Also Musk stated that you could fly 7 passengers and extra cargo, so no upgrades are needed.

Taking into account that the Dragon will only be certified for LEO operations to start, and that space tourists are paying to go to a destination in space, not just to orbit LEO in a capsule with six other people, unless the ISS is going to be hosting a lot of tourists I'm not sure how successful a space tourism company could be.

[QuantumG]

So sure someone could rent a Dragon V2 flight, but without a destination I doubt they will get many takers.

I asked Eric Anderson and Richard Garriott about that at SpaceVision 2007 and they said they already had customers for short flights. Most high net worth individuals don't have time to go the station for weeks. The problem is supply.

[Wigles]

Spacex would need to hire some pilots to fly those rich people around the moon.

Cis-lunar cruise spaceship pilot, best job in the world?

[TrevorMonty]

V2 should be able to support 3-4 crew for lunar fly by,  but sharing ( this includes bodily functions ) a small capsule with 3-4 strangers for a week!  If they added extra accommodation module eg old cargo dragon or modified Cygnus, that make trip more enjoyable, plus give extra life support. This extra module may allow a crew of 7.

[su27k]

I think they'll let Bigelow take the lead here, Bigelow has always been focused on the moon, and they have plans for tugs for pushing BA 330 around. SpaceX will probably just provide LEO transportation.

[Joel]

I wonder if dragon v2 with full tanks has enough delta v to land on and then take off from the moon.

If so then a dragon could be parked in lunar orbit, do lunar rendezvous with incoming dragon with tourists, and be the shuttle to and from the surface.

I bet bigelow is pretty excited about dragon v2!

Almost certainly not. That requires something around 4 km/s of delta-V, which means propellant would have to be something like 80% of Dragon's mass. In other words, assuming an empty Dragon weighs 5000 kg, it would have to weigh about 25000 kg loaded with propellant. Dragon most likely only carries 2-3 tons of propellant.

A dragon with an extensively modified trunk carrying fuel and acting as a descent/ascent stage could probably do it, but that's a major engineering project.

If you could have most of the descent burn be performed by a (later crashing) upper stage, you could cut that number in half. For 2 km/s delta-v and 235 s isp, you get a pmf of 58 %.

[douglas100]

Dragon is not designed to land people on the Moon. That needs a separate specially designed lander. There is no evidence that SpaceX plans to develop one. See meekGee's post.

And anyway, this thread is about tourist flights around the Moon. And SpaceX do have the potential hardware to do that with FH and Dragon.

[Burninate]

I would really like to see a Dragon 2.0 combined with a comfy Bigelow module that is in the mid-range (~70m^3), with a cupola mounted on the end, launched from a single Falcon Heavy, into a Lunar Free Return trajectory, with no transition to orbit, and 5 out of 7 seats marked 'tourist'...

But the math just doesn't seem to work out for my mass estimates of the above payload, about 20 tons, to launch on a Falcon Heavy capable of only 53T IMLEO, on what I would expect to be relatively low specific impulse hypergolic Draco thrusters.

BEAM is already in production and only 1.5T, but it's a fairly tiny module for 7 people to share, as is the Dragon.  I suppose it beats Soyuz at least...

What's the specific impulse of a Draco engine?

[Mongo62]

I would really like to see a Dragon 2.0 combined with a comfy Bigelow module that is in the mid-range (~70m^3), with a cupola mounted on the end, launched from a single Falcon Heavy, into a Lunar Free Return trajectory, with no transition to orbit, and 5 out of 7 seats marked 'tourist'...

But the math just doesn't seem to work out for my mass estimates of the above payload, about 20 tons, to launch on a Falcon Heavy capable of only 53T IMLEO, on what I would expect to be relatively low specific impulse hypergolic Draco thrusters.

A Bigelow BA330 would mass about 20 mt, and a dry Dragon v2 about 5 mt (I'm guessing it's a bit more than a dry Dragon v1). If a single FH can launch about 16 mt into TLI, then two launches using LEO rendezvous could presumably send about 32 mt, leaving around 7 mt for consumables including propellant, and passengers. This would be more than enough for a full 7-passenger free return trajectory, with plenty of elbow room on the (disposable?) BA330.

Would there be sufficient available propellant to brake the Dragon+BA330 into lunar orbit, and later send the Dragon by itself back to Earth? The delta V required is not a huge amount, but they would not have a huge amount of propellant to work with either.

If the numbers don't work out (and I suspect that they don't), then what about sending an unmanned BA330 plus propulsion module into lunar orbit using two FH launches and LEO rendezvous, and later using single FH launches to send Dragons with crew and consumables to rendezvous with the lunar BA330 and some time later return to Earth?

[Burninate]

I would really like to see a Dragon 2.0 combined with a comfy Bigelow module that is in the mid-range (~70m^3), with a cupola mounted on the end, launched from a single Falcon Heavy, into a Lunar Free Return trajectory, with no transition to orbit, and 5 out of 7 seats marked 'tourist'...

But the math just doesn't seem to work out for my mass estimates of the above payload, about 20 tons, to launch on a Falcon Heavy capable of only 53T IMLEO, on what I would expect to be relatively low specific impulse hypergolic Draco thrusters.

A Bigelow BA330 would mass about 20 mt, and a dry Dragon v2 about 4 mt (I'm guessing it's about the same as a Dragon v1). If a single FH can launch about 16 mt into TLI, then two launches using LEO rendezvous could presumably send about 32 mt, leaving around 8 mt for consumables including propellant, and passengers. This would be more than enough for a full 7-passenger free return trajectory, with plenty of elbow room on the (disposable?) BA330.

Would there be sufficient available propellant to brake the Dragon+BA330 into lunar orbit, and later send the Dragon by itself back to Earth? The delta V required is not a huge amount, but they would not have a huge amount of propellant to work with either.

If the numbers don't work out (and I suspect that they don't), then what about sending an unmanned BA330 plus propulsion module into lunar orbit using two FH launches and LEO rendezvous, and later using single FH launches to send Dragons with crew and consumables to rendezvous with the lunar BA330 and some time later return to Earth?

A Lunar free return trajectory alone costs you around 3250 - 3350 m/s.  This is a lot.  Assume a need for some amount in reserve for maneuvering, 3500ms/ total.  These are the dry:wet (payload) mass fractions for that 3500m/s implied by various specific impulses, and the max payload that suggests for a 53 ton (with optimistic crossfeed functionaity) Falcon Heavy launch:
330s 33.9% 18.0T
300s 30.4% 16.1T
270s 26.7% 14.2T
240s 22.6% 12.0T

LEO -> LLO -> LEO is about a 6.8km/s mission (numbers not optimized for free return, which likely costs slightly more).
Similar numbers for 7km/s dV:
330s 11.5% 6.10T
300s 9.26% 4.91T
270s 7.11% 3.77T
240s 5.11% 2.71T

Iterate this *again* if you want to add on the (slightly more than) 3500/s dV, and the landing gear, and the heavy high-thrust engines, required to actually land on the Lunar surface.  A lunar return really is not that much 'closer' dV-wise than a Mars return.

[Burninate]

I will present another tourist mission concept for you though:

The Lunar Cruise
After burning initially on a free return trajectory, a crew capsule + inflatable hab transfer into a highly elliptical Lunar orbit on the order of 24 hours orbital period (compare to minimum LLO period: ~2 hours).  Every morning, the tourists wake up to begin another very close Lunar approach, and get a very good look at the terminator.  The cruise lasts ~4 weeks, the passengers get to see the Lunar surface from all sides, and by the end, the orbit is aligned such that a low-dV transfer back to Earth is possible.

12 cruise windows per year, each several days long (the constraint being full daylight during the closest approach).  The inflatable hab burns up in the atmosphere.  The Dragon comes down to a spaceport pad.

Semimajor axis for 24hr orbit calculated at 9750km.
Periapsis: However close ops dares, plausibly even closer than a LLO, which has to deal with masscons.
Apoapsis: 16000km above the surface, a vew of the night side of the Moon.

Does anyone have the tools to calculate how much additional dV this would require on top of the free return trajectory?  I'm hoping something on the order of hundreds, rather than thousands, of meters per second?

[Dave G]

... odds are you won't be able to fit 7 people on that mission and some of the Dragon's systems are going to need to be upgraded.

For a Lunar free return, what specifically would need to be upgraded?

[cryptoanarchy]

... odds are you won't be able to fit 7 people on that mission and some of the Dragon's systems are going to need to be upgraded.

For a Lunar free return, what specifically would need to be upgraded?

I think paying customers would want more space.  Two or three customers only and one pilot.  I think SpaceX would have several groups willing to pay the higher price.  With two customers the Dragon would be comfortable enough and there would be no need for a habitation module. 

[Herb Schaltegger]

The ECLSS will almost certainly need to be upgraded.  A 6 hour rendezvous profile is one thing - a week in transit to and from the Moon is something else - you need active THC (temperature and humidity control); the ability to either filter and purify the condensate to drink it or provision to vent it; the ability to store/vent urine; food storage; solid waste storage and/or disposal; provision for expendable LiOH cartridge storage or a LOT more power and mass for active CO2 removal ...

[Mongo62]

The ECLSS will almost certainly need to be upgraded.  A 6 hour rendezvous profile is one thing - a week in transit to and from the Moon is something else - you need active THC (temperature and humidity control); the ability to either filter and purify the condensate to drink it or provision to vent it; the ability to store/vent urine; food storage; solid waste storage and/or disposal; provision for expendable LiOH cartridge storage or a LOT more power and mass for active CO2 removal ...

From the Dragon v2 unveiling: "It'll be capable of carrying seven people - seven astronauts for several days." Would this mean that it has a capacity of 14 to 21 person-days of life support and consumables? (Assuming that "several days" means 2-3 days.) With a three-person load, that would be 5-7 days. Apollo 13, which of course used a free-return trajectory, lasted a bit under 6 days from launch to splashdown. So if my assumption is true, then a Dragon v2 with a pilot and two paying passengers on a Lunar free-return voyage could indeed sustain the people on board for the duration of the trip. I would want to increase the margin of safety though, if this is feasible.

[Herb Schaltegger]

From the Dragon v2 unveiling: "It'll be capable of carrying seven people - seven astronauts for several days." Would this mean that it has a capacity of 14 to 21 person-days of life support and consumables? (Assuming that "several days" means 2-3 days.) With a three-person load, that would be 5-7 days. Apollo 13, which of course used a free-return trajectory, lasted a bit under 6 days from launch to splashdown. So if my assumption is true, then a Dragon v2 with a pilot and two paying passengers on a Lunar free-return voyage could indeed sustain the people on board for the duration of the trip. I would want to increase the margin of safety though, if this is feasible.

Maybe. My concern is that not all ECLSS requirements scale equally and smoothly up and down as you add or remove crew-days to the mission profile; some things are just more granular than that. It really bugs me when I see armchair experts talk about "installing an ECLSS" like it's plugging a cable box into your TV.  It ain't nearly that simple in practice.

[yg1968]

Up till now, we really only talked about SpaceX in the context of ISS Taxi, comsats, and Mars.

With Dragon V2 coming up, and Bigelow at the unveiling event, and interpreting comments by Elon regarding the moon, it's a fair question:

Suppose a VC puts up the funds to do a space tourism company.   Trips to LEO, GTO, and lunar-free-return.   "In high volume, single-digit-Million".    Will people put down $10-$20M for a trip?

In the Bigelow report, Bigelow offered NASA transportation around the Moon. But if Soyuz is offering it for $150M, you have to expect it to cost about 3 times as much as a LEO flight. The trip would be on a FH and Dragon would have to be slightly upgraded. 

http://www.nasaspaceflight.com/2014/02/affordable-habitats-more-buck-rogers-less-money-bigelow/

[QuantumG]

In the Bigelow report, Bigelow offered NASA transportation around the Moon. But if Soyuz is offering it for $150M, you have to expect it to cost about 3 times as much as a LEO flight. The trip would be on a FH and Dragon would have to be slightly upgraded.

I'd expect the price to be completely unrelated to Soyuz.. it's a completely different system by a completely different company in a completely different country, after all.

[yg1968]

In the Bigelow report, Bigelow offered NASA transportation around the Moon. But if Soyuz is offering it for $150M, you have to expect it to cost about 3 times as much as a LEO flight. The trip would be on a FH and Dragon would have to be slightly upgraded.

I'd expect the price to be completely unrelated to Soyuz.. it's a completely different system by a completely different company in a completely different country, after all.

Yes I know but I am saying that it's likely to cost at least 3 times as much as a SpaceX LEO flight because of distance, less astronauts, FH price, etc.

[Dave G]

... odds are you won't be able to fit 7 people on that mission and some of the Dragon's systems are going to need to be upgraded.

For a Lunar free return, what specifically would need to be upgraded?

I think paying customers would want more space.  Two or three customers only and one pilot.  I think SpaceX would have several groups willing to pay the higher price.  With two customers the Dragon would be comfortable enough and there would be no need for a habitation module.

Could they use the upper stage tanks as a hab module?  What if it were hydrolox?

[spacetraveler]

... odds are you won't be able to fit 7 people on that mission and some of the Dragon's systems are going to need to be upgraded.

For a Lunar free return, what specifically would need to be upgraded?

I think paying customers would want more space.  Two or three customers only and one pilot.  I think SpaceX would have several groups willing to pay the higher price.  With two customers the Dragon would be comfortable enough and there would be no need for a habitation module.

Could they use the upper stage tanks as a hab module?  What if it were hydrolox?

SpaceX has no interest in hydrolox. They seem to be pursuing methane.

[meekGee]

The condition I'd imagine they'd put up for participating in this is that it will not be a distraction.

So my guess, as much as you can do with a modified DV2, on a FH.   So maybe crew of 4, and the back region converted to storage and facilities for an extended flight, but that's about it.

Docking with Bigelow - sure - if Bigelow can take care of his stuff himself, which is far from proven at this point.

[ChrisWilson68]

If Musk can bring down the cost of taking people to LEO by a wide margin, then it seems axiomatic that there could be some comparable lowering of the cost to take people to the Moon.

Musk and other multi-planetarists may not see the Moon as being terraformable or ocean-izable or icecap-meltable as Mars is, according to their far-flung ambitious timelines. But let's face it, for the near-to-medium term, the Moon is no less habitable than Mars. Right now, Mars is a vast airless megadesert, and so is the Moon. Yes, Mars has water, but the amount of water on the Moon isn't insignificant either.

So if you have to pick between 2 vast airless megadeserts, then go for the one that's mere days away, rather than for the one that requires months of travel time.

Musk wants spaceflights to become routine, numbering in thousands of flights per year by 2030. Well, that's more likely to happen by luring potential customers with the exotic-yet-nearby destination of the Moon, as compared to the very-exotic-and-very-far destination of Mars. Lower the difficulty barrier, and more trips become possible at lower cost. The famous "Forcing Function" then continues its work at faster pace.

The Moon is lower-hanging fruit than Mars is, even if Mars is the better-quality fruit in the long run.

Use the Moon to lure more customers into spending on trips there, and then re-invest that money into the better-quality equipment that will be required to reach faraway Mars and live that much farther away from the support of Mother Earth.

I agree that there are some advantages for tourism of the Moon versus Mars.  But I don't agree that "for the near-to-medium term, the Moon is no less habitable than Mars".  Mars is dry, but the Moon is drier, and that matters.  Mars has little atmosphere, but the Moon has far less, and that matters.  Methane can be produced fairly easily on Mars.  Try that on the Moon.  Mars also has more gravity.  We don't really know the long-term health effects of either Mars' or the Moon's gravity, but Mars gravity is closer to Earth's, so it may well be that Mars is significantly better for your health.  Mars has a day-night cycle similar to Earth's.  The Moon doesn't, and it is hard to bake in the direct sun for two weeks, then shiver through a two-week night.

All of these have big effects in the near and medium term, not just when we're ready to terraform.

[Mader Levap]

All of these have big effects in the near and medium term, not just when we're ready to terraform.

Cost is all that matters. I can bet large sum of money on this:
- 500k ticket to Moon will be achieved way, way earlier (possibly decades) than 500k ticket to Mars. Well, duh.
- Flying to Mars will always (read: in any sensibly predictable future) be many order of magnitude more costly than flying to Moon.
It is enough and Mars Firsters should get over this. They already lost to laws of physics already before start of whole debacle Moon vs Mars.

Conclusion: Musk will have to settle for retirement on Moon. He simply was born too early to die on Mars (not on impact, of course). Such is life.

[InfraNut2]

The ECLSS will almost certainly need to be upgraded.  A 6 hour rendezvous profile is one thing - a week in transit to and from the Moon is something else - you need active THC (temperature and humidity control); the ability to either filter and purify the condensate to drink it or provision to vent it; the ability to store/vent urine; food storage; solid waste storage and/or disposal; provision for expendable LiOH cartridge storage or a LOT more power and mass for active CO2 removal ...

From the Dragon v2 unveiling: "It'll be capable of carrying seven people - seven astronauts for several days." Would this mean that it has a capacity of 14 to 21 person-days of life support and consumables? (Assuming that "several days" means 2-3 days.) With a three-person load, that would be 5-7 days. Apollo 13, which of course used a free-return trajectory, lasted a bit under 6 days from launch to splashdown. So if my assumption is true, then a Dragon v2 with a pilot and two paying passengers on a Lunar free-return voyage could indeed sustain the people on board for the duration of the trip. I would want to increase the margin of safety though, if this is feasible.

"several" means around 7. So about a week with full crew.

I think have also seen/heard 7-10 days, but I might remember wrong. I do not know if that includes the extra (likely optional) O2 (+air?) tanks in the top of the trunk, that the DV2 kremlinology thread seem to have revealed, or if that is part of an additional long-duration option.

[meekGee]

All of these have big effects in the near and medium term, not just when we're ready to terraform.

Cost is all that matters. I can bet large sum of money on this:
- 500k ticket to Moon will be achieved way, way earlier (possibly decades) than 500k ticket to Mars. Well, duh.
- Flying to Mars will always (read: in any sensibly predictable future) be many order of magnitude more costly than flying to Moon.
It is enough and Mars Firsters should get over this. They already lost to laws of physics already before start of whole debacle Moon vs Mars.

Conclusion: Musk will have to settle for retirement on Moon. He simply was born too early to die on Mars (not on impact, of course). Such is life.

Medar, this is an old, old argument. 

Of course travel to the moon is cheaper.  But for the reasons CW68 counted above (and more), a long duration stay on Mars is cheaper.

We will have tourists around the moon, and maybe even on the moon, before we'll have any person in Mars orbit.   But we will have a Mars colony a lot sooner.  As a matter of fact, I see a moon colony as about as difficult as a space colony.

Since this thread is about LEO/lunar tourism, we're all good though.

[RanulfC]

I agree that there are some advantages for tourism of the Moon versus Mars.  But I don't agree that "for the near-to-medium term, the Moon is no less habitable than Mars".  Mars is dry, but the Moon is drier, and that matters.  Mars has little atmosphere, but the Moon has far less, and that matters.  Methane can be produced fairly easily on Mars.  Try that on the Moon.  Mars also has more gravity.  We don't really know the long-term health effects of either Mars' or the Moon's gravity, but Mars gravity is closer to Earth's, so it may well be that Mars is significantly better for your health.  Mars has a day-night cycle similar to Earth's.  The Moon doesn't, and it is hard to bake in the direct sun for two weeks, then shiver through a two-week night.

All of these have big effects in the near and medium term, not just when we're ready to terraform.

"Terraforming" aside the fact that the Moon is so much closer to Earth is a big factor that kind of makes it stand out very much over Mars. Granting the various "differences" you've pointed out, I'll point out that travel time and round-trip time and energy tend to "trump" Mars as a destination if they are "compared" straight up against each other. Degrees of "difficulty" don't necessarily lead to actual "advantages" and "disadvantages" when compared directly AND all other factors are considered. In the end what a lot of folks who "favor" Mars over any other destination end up not realizing is that when comparing "advantages" and "disadvantges" among various locations are by their nature rather "subjective" to the ones doing the argument. Change a single "factor" and the "argument" tends to boil down to "because I say so" more than anything else

But as meekGee points out this is an old, old argument, one that "I" personally think is rather silly. We're not going to make the "final choice" here on these forums and really "I" don't see there being a "choice" other than we're either GOING to colonize space or we are NOT going to do so with no in-between or differention between "destinations" in space. All or nothing. It's a "no-brainer" not worth expending effort over.

Tourism, specifically "Cis-Lunar" tourism is something different and I'm of the opinion that EM specifically isn't interested in such an effort. The "main" question of the day is however would he be "willing" to sell D-V2 flights to LEO in order to facilitate such efforts? From a business point of view it would make little sense for him (and SpaceX) to NOT support such efforts, but I don't see (frankly I've never seen any "real" efforts) him actually offering such services himself or "selling" equipment to be used for such efforts.

By that I mean where as SpaceX would offer launch services for whomever was organizing such a business, I don't see them selling D-V2's or engines/tanks/etc to such a business. I'm thinking that outside offering the flights to and from LEO everthing else would not be within SpaceX's business model at the moment. (This would change if MCT were capable of being used for Lunar transport as well but it remains to be seen WHAT its capabilities are going to be )

Randy

[Lar]

The moon is closer from a travel time, and communication perspective but it's not that much closer from a deltaV perspective, as upthread analysis shows. 

[ChrisWilson68]

All of these have big effects in the near and medium term, not just when we're ready to terraform.

Cost is all that matters. I can bet large sum of money on this:
- 500k ticket to Moon will be achieved way, way earlier (possibly decades) than 500k ticket to Mars. Well, duh.
- Flying to Mars will always (read: in any sensibly predictable future) be many order of magnitude more costly than flying to Moon.
It is enough and Mars Firsters should get over this. They already lost to laws of physics already before start of whole debacle Moon vs Mars.

Conclusion: Musk will have to settle for retirement on Moon. He simply was born too early to die on Mars (not on impact, of course). Such is life.

If flying to Mars will always be "many orders of magnitude" more costly than flying to the Moon, why is it that unmanned orbiters and landers on Mars haven't been many orders of magnitude more costly than those going to the Moon?

Nobody is disputing that getting to Mars is harder.  The question is the trade-off between harder-to-reach Mars and harder-to-live on Moon.  There's no one answer to that question.  It depends on the goals and scale of the project.

[guckyfan]

Nobody is disputing that getting to Mars is harder. 

Actually I do, to some extent. Going to the moon and back is harder delta-v wise if there is fuel ISRU on Mars and not on Luna. And that too will be much easier on Mars. Of course there is always the longer flight time to Mars as an obstacle.

The question is the trade-off between harder-to-reach Mars and harder-to-live on Moon.  There's no one answer to that question.  It depends on the goals and scale of the project.

Agree. You can support a research station on the moon with lower cost transport but a larger size settlement or colony is much harder on  the moon due to the harsh conditions.

[meekGee]

and with that very good summary, we can move past the moon-mars debate because there is no "Mars" in the title or the thread.

[Owlon]

Is it feasible to use a single FH to launch a Dragon V2 on a lunar free return trajectory with a small BEAM or Cygnus sort of hab module in the trunk that could then be ejected and docked with? This would have 3-5 crew/passengers. Ideally it would involve as close to zero modification and new development as possible.

Other than improved communications hardware and maybe power upgrades, what modifications might be needed for such a Dragon mission? A new navigation system? It sounds like the planned ECLSS could support this sort of mission.

The cost with a fully expendable FH at $135 million, a $20 million hab module, and a roughly $20 million per mission cost of a reusable modified Dragon flying five crew comes out to $35 million per person ($175 million total). That could come down a lot if:
a) FH has the performance to reuse the side boosters on a launch like this
b) the extra hab module is cheaper (NASA is paying ~$18 million for BEAM)
c) Dragon has a lower effective per-mission cost due to more reuses, or
d) some combination of the above.

Am I overlooking anything major?

[MP99]

The moon is closer from a travel time, and communication perspective but it's not that much closer from a deltaV perspective, as upthread analysis shows.

As a Moon-firster, this suggests to me that SpaceX's architecture for Mars could be relatively efficient at delivering payloads to the Moon. (With Gucky's caveat re Lunar ISRU).

As I see it, SpaceX won't do the Moon themselves just because they want to concentrate their resources on Mars.

But, once they start to build their Mars architecture, I believe that companies like Golden Spike will take the opportunity to buy services based on that hardware for Moon missions.

They'll just have to accept that they won't be able to buy a launch during Mars conjunction or opposition. But, it will provide a paying customer for the infrastructure between Mars missions.

With SpaceX providing the infrastructure, business will see an opportunity to go to the Moon with lower risk than Mars, and the chance for a more rapid return on investment. Tourism will be a part of this, encouraged by the fact that risks are lower when they're just one user of the architecture, since that architecture will mature as it sees more and more use.

Cheers, Martin

[Burninate]

Is it feasible to use a single FH to launch a Dragon V2 on a lunar free return trajectory with a small BEAM or Cygnus sort of hab module in the trunk that could then be ejected and docked with? This would have 3-5 crew/passengers. Ideally it would involve as close to zero modification and new development as possible.

Other than improved communications hardware and maybe power upgrades, what modifications might be needed for such a Dragon mission? A new navigation system? It sounds like the planned ECLSS could support this sort of mission.

The cost with a fully expendable FH at $135 million, a $20 million hab module, and a roughly $20 million per mission cost of a reusable modified Dragon flying five crew comes out to $35 million per person ($175 million total). That could come down a lot if:
a) FH has the performance to reuse the side boosters on a launch like this
b) the extra hab module is cheaper (NASA is paying ~$18 million for BEAM)
c) Dragon has a lower effective per-mission cost due to more reuses, or
d) some combination of the above.

Am I overlooking anything major?

No, I don't think you are overlooking anything serious, though BEAM is rather small to make an especially comfortable habitat, and the next step up Bigelow has made concepts of is the too-heavy BA-330.  Myself, I wonder what people might pay for a single brief Lunar flyby versus several very low passes.  There's also a question about whether you might want to actually berth/dock a hab module from launch rather than doing an Apollo-style spin-around docking with something from the trunk once in orbit.

{Free return} is much easier than {low orbit & return} is much easier than {landing & return}.

I can foresee financial difficulties, even if SpaceX manages to make everything reusable,  burning up a comfortable-sized hab on every mission.  Perhaps with magnetoshell aerobraking, after detaching you could perch it back in LEO (and indeed, build a space station out of these slightly-used modules), but so long as they're expendable, there's incentive to get as much value out of them as possible.

What do you think of this compromise?

I will present another tourist mission concept for you though:

The Lunar Cruise
After burning initially on a free return trajectory, a crew capsule + inflatable hab transfer into a highly elliptical Lunar orbit on the order of 24 hours orbital period (compare to minimum LLO period: ~2 hours).  Every morning, the tourists wake up to begin another very close Lunar approach, and get a very good look at the terminator.  The cruise lasts ~4 weeks, the passengers get to see the Lunar surface from all sides, and by the end, the orbit is aligned such that a low-dV transfer back to Earth is possible.

12 cruise windows per year, each several days long (the constraint being full daylight during the closest approach).  The inflatable hab burns up in the atmosphere.  The Dragon comes down to a spaceport pad.

Semimajor axis for 24hr orbit calculated at 9750km.
Periapsis: However close ops dares, plausibly even closer than a LLO, which has to deal with masscons.
Apoapsis: 16000km above the surface, a vew of the night side of the Moon.

Does anyone have the tools to calculate how much additional dV this would require on top of the free return trajectory?  I'm hoping something on the order of hundreds, rather than thousands, of meters per second?

Alternately, maybe detach the hab in a highly elliptical Lunar orbit, which would allow you to build up a station there.     A BEAM + berthing nexus + minimal ion propulsion for the hab would allow your Lunar passengers to spend a few days getting to Lunar orbit in cramped conditions, then rendezvous with the hab for an eventually luxurious number of cubic meters, then climb back in the Dragon to return, leaving the hab behind to build up the station.  Bonus: Detaching the hab in high-elliptical lunar orbit saves you a little dV.

[guckyfan]

Alternately, maybe detach the hab in a highly elliptical Lunar orbit, which would allow you to build up a station there.     A BEAM + berthing nexus + minimal ion propulsion for the hab would allow your Lunar passengers to spend a few days getting to Lunar orbit in cramped conditions, then rendezvous with the hab for an eventually luxurious number of cubic meters, then climb back in the Dragon to return, leaving the hab behind to build up the station. 

This raises some questions with me.

Would such an orbit be sufficiently stable so you can leave a station there?

Docking needs a minimum weight of the two vehicles so they can dock. For Apollo to dock with the lunar lander it needed the lander still attached to the stage to generate enough resistance for the docking mechanism. How much does the LIDS need? Could a sufficiently heavy station be put in place with a Falcon Heavy?

I would not be too concerned with the cost of a BEAM. A Falcon Heavy sending a Dragon to the moon would lose the central core and the second stage at least, at much higher cost than a BEAM. If the BEAM allows 4 or 5 passengers instead of 2 it is well worth it.
I do remember Gwynne Shotwell said at some occasion they have considered mounting an inflatable volume on top of Dragon to provide more space. So not even docking would be required. Just the ability to drop it before reentry. They have not given it much thought though.

Bonus: Detaching the hab in high-elliptical lunar orbit saves you a little dV.

Actually it saves a lot ov delta-V compared to LLO. Maybe enough to do it with a stock Dragon?

[LouScheffer]

Docking needs a minimum weight of the two vehicles so they can dock. For Apollo to dock with the lunar lander it needed the lander still attached to the stage to generate enough resistance for the docking mechanism

The ascent stage of the lander (the lightest part) docked with the CSM just fine in lunar orbit.

[Burninate]

Alternately, maybe detach the hab in a highly elliptical Lunar orbit, which would allow you to build up a station there.     A BEAM + berthing nexus + minimal ion propulsion for the hab would allow your Lunar passengers to spend a few days getting to Lunar orbit in cramped conditions, then rendezvous with the hab for an eventually luxurious number of cubic meters, then climb back in the Dragon to return, leaving the hab behind to build up the station. 

This raises some questions with me.

Would such an orbit be sufficiently stable so you can leave a station there?

Very low lunar orbit for completely passive spacecraft is perturbed by an unevenly spherical distribution of mass - 'Mass concentrations' or 'masscons' sprinkled over the surface, which only certain specific inclinations are safely balanced between.  Deviations in the terrain closest to an orbiter during periapsis can affect the altitude of apoapsis significantly.  In this case, though, the orbiter spends very little time in close proximity to the terrain, and the apoapsis has an inordinately high amount of 'give' before it starts crashing into mountains.  I suspect you wouldn't have to worry about masscons at all - to the extent that you could fly lower than people actually in LLO dare to go, since they have to integrate the orbital deviations caused by the terrain perturbations over 360 degrees times large numbers of orbits.  Any slight deviation can be corrected for using tractable amounts of ion thrusters for station keeping - like our GSO commsats have to do to deal with lunar perturbations.

Bonus: Detaching the hab in high-elliptical lunar orbit saves you a little dV.

Actually it saves a lot ov delta-V compared to LLO. Maybe enough to do it with a stock Dragon?

Never going to LLO saves a lot of delta V.  Getting to the Moon, inserting in a small burn, then sticking to a high elliptical orbit that lasts about four weeks, then transferring back to Earth in a small burn at just the right orbital phase (as you're going at close to escape velocity at periapsis, in the direction you would want to go to transfer, already), is what makes it delta V efficient.  BEAM itself is a pretty small/light hab - only 1.5 tons for 16 m^3 is what Bigelow is claiming.  Add another ton for a 4-way docking nexus and a small ion thruster or two for stationkeeping, , and you're up to 2.5 tons on top of the Dragon.  That's not a lot, compared to the mass of the Earth descent module (Dragon) and service module (trunk), because the Lunar periapsis burn to transfer back to Earth is in theory a small one.  What it would buy you if you left the hab in high lunar orbit is, if you run this mission again a year later, you can insert into the same trajectory, rendezvous, and get to use the same hab again, as part of a 2-BEAM station, and the next year, a 3-BEAM station.  If BEAM's mass is manageable but the volume is unfortunately low, using a bunch of them should quickly allow for a fairly comfortable station, relative to the alternative;  It doesn't require advanced aerocapture tech to be developed, it doesn't require a larger more comfortable, expensive inflatable to burn up every cruise, and it doesn't limit the cruise to a level of privacy and claustrophobia that most billionaires won't tolerate.

Concept, I dub thee 'Earthrise Lunar Cruise' and 'Earthrise Lunar Station'.

[Sean Lynch]

I can imagine a future when spindly propulsion modules are printed, assembled and fueled in LEO, joined to inflatable taxi habs that fly to stations in eccentric orbits that have the delta v's required...each leg of the journey having it's own mission specific requirements which won't require the mass of a heat shield and structural rigidity of a reentry pressure vessel.

[AncientU]

Alternately, maybe detach the hab in a highly elliptical Lunar orbit, which would allow you to build up a station there.     A BEAM + berthing nexus + minimal ion propulsion for the hab would allow your Lunar passengers to spend a few days getting to Lunar orbit in cramped conditions, then rendezvous with the hab for an eventually luxurious number of cubic meters, then climb back in the Dragon to return, leaving the hab behind to build up the station. 

This raises some questions with me.

Would such an orbit be sufficiently stable so you can leave a station there?

Very low lunar orbit for completely passive spacecraft is perturbed by an unevenly spherical distribution of mass - 'Mass concentrations' or 'masscons' sprinkled over the surface, which only certain specific inclinations are safely balanced between.  Deviations in the terrain closest to an orbiter during periapsis can affect the altitude of apoapsis significantly.  In this case, though, the orbiter spends very little time in close proximity to the terrain, and the apoapsis has an inordinately high amount of 'give' before it starts crashing into mountains.  I suspect you wouldn't have to worry about masscons at all - to the extent that you could fly lower than people actually in LLO dare to go, since they have to integrate the orbital deviations caused by the terrain perturbations over 360 degrees times large numbers of orbits.  Any slight deviation can be corrected for using tractable amounts of ion thrusters for station keeping - like our GSO commsats have to do to deal with lunar perturbations.

Bonus: Detaching the hab in high-elliptical lunar orbit saves you a little dV.

Actually it saves a lot ov delta-V compared to LLO. Maybe enough to do it with a stock Dragon?

Never going to LLO saves a lot of delta V.  Getting to the Moon, inserting in a small burn, then sticking to a high elliptical orbit that lasts about four weeks, then transferring back to Earth in a small burn at just the right orbital phase (as you're going at close to escape velocity at periapsis, in the direction you would want to go to transfer, already), is what makes it delta V efficient.  BEAM itself is a pretty small/light hab - only 1.5 tons for 16 m^3 is what Bigelow is claiming.  Add another ton for a 4-way docking nexus and a small ion thruster or two for stationkeeping, , and you're up to 2.5 tons on top of the Dragon.  That's not a lot, compared to the mass of the Earth descent module (Dragon) and service module (trunk), because the Lunar periapsis burn to transfer back to Earth is in theory a small one.  What it would buy you if you left the hab in high lunar orbit is, if you run this mission again a year later, you can insert into the same trajectory, rendezvous, and get to use the same hab again, as part of a 2-BEAM station, and the next year, a 3-BEAM station.  If BEAM's mass is manageable but the volume is unfortunately low, using a bunch of them should quickly allow for a fairly comfortable station, relative to the alternative;  It doesn't require advanced aerocapture tech to be developed, it doesn't require a larger more comfortable, expensive inflatable to burn up every cruise, and it doesn't limit the cruise to a level of privacy and claustrophobia that most billionaires won't tolerate.

Concept, I dub thee 'Earthrise Lunar Cruise' and 'Earthrise Lunar Station'.

A BA-330 or two (a.k.a., a commercial station) at EML-1 or 2 would be long-term stable, advance the NASA BEO agenda, and allow for access to any return path desired without awaiting phasing of a high elliptical orbit.  EML-1 is located on the way to the Moon and EML-2 only adds 15% to the journey length.  Each require less delta-v than LLO.

[Burninate]

EML2 or EML1 would be a more convenient place to put a station in terms of ops, but at 60,000km from the Moon, the Moon is 3 degrees across instead of 140 degrees across, as it is from 100km.  If the mission is to put tourists in close proximity to the Moon, the Lagrange points don't work.

What I don't quite get is what EML points offer operationally over LEO, for any mission except perhaps efficient SEP unmanned bulk transport, and as short-term maneuver keyholes for interplanetary missions.

[guckyfan]

Docking needs a minimum weight of the two vehicles so they can dock. For Apollo to dock with the lunar lander it needed the lander still attached to the stage to generate enough resistance for the docking mechanism

The ascent stage of the lander (the lightest part) docked with the CSM just fine in lunar orbit.

You are right.

[meekGee]

Thinking as a tourist, most of the value is in going around the moon, even once.   Doing it 5 times, meh.  Flying real low - now that's something.

Comfort is nice, (e.g. toilet), but not much more.  These are "adventurer tourists". Hardship is part of the trip. (as is risk). 

[Mader Levap]

Post moved here, per meekGee suggestion.

[meekGee]

Part of me wants to delete Moon/Mars posts after my previous warning.
Part of me wants to argue back.
Another part says, meh, just ask them again to drop that argument.
Part of me is busy today.

The first part won.


Mader - copy your post for posterity, and start a Moon-vs-Mars thread with it.  We can argue there.
I'll be back in an hour to trim.

Cheers

[TrevorMonty]

The biggest issue I had with habitat module for flyby was having to dock with it once in space. Guckyfan stated that SpaceX had considered launching Dragon with deflated Beam module already docked. This leaves trunk free for extra fuel and oxygen. The only problem I see with this would be Dragon's max abort weigh.

[A_M_Swallow]

Somewhere along the line it becomes financially viable to make a chemical tug to push the Dragon around.  The tug would basically be a lunar lander with big fuel tanks and a docking port.

[Owlon]

The biggest issue I had with habitat module for flyby was having to dock with it once in space. Guckyfan stated that SpaceX had considered launching Dragon with deflated Beam module already docked. This leaves trunk free for extra fuel and oxygen. The only problem I see with this would be Dragon's max abort weigh.

Having an inflatable module pre-docked would likely be a better option in the long run, but a BEAM derivative in the trunk might need much less development; it could potentially just be essentially BEAM with a docking port instead of berthing port.

[ChrisWilson68]

The biggest issue I had with habitat module for flyby was having to dock with it once in space. Guckyfan stated that SpaceX had considered launching Dragon with deflated Beam module already docked. This leaves trunk free for extra fuel and oxygen. The only problem I see with this would be Dragon's max abort weigh.

Having an inflatable module pre-docked would likely be a better option in the long run, but a BEAM derivative in the trunk might need much less development; it could potentially just be essentially BEAM with a docking port instead of berthing port.

Why the fear of docking in space?  It seems like a pretty mature technology by now.

[TrevorMonty]

For beam to dock it would need a propulsion system, also how do extract it from trunk without a robotic arm.

[ChrisWilson68]

For beam to dock it would need a propulsion system, also how do extract it from trunk without a robotic arm.

Just basic attitude stabilization.  No need for a robotic arm, just release it and have Dragon move itself and the trunk off of it.

Adding a few cold gas thrusters to the inflatable habitat module seems a much smaller change than having the Falcon 9/Dragon stack have to lift off with a big new something screwed onto the nose.  The pad abort and max-Q abort tests, at a minimum would have to be redone with the habitat attached.

[douglas100]

Agree 100%.

I think having another module mounted on the nose of the Dragon makes abort extremely difficult, if not impossible. With this configuration the module would have to be protected by a fairing and would have to separate after the abort to allow the parachutes to deploy safely. Essentially you would have a larger version of Soyuz. It would  be a new spacecraft requiring significant development.

I agree with Chris about docking. This is a mature technology. It has been done hundreds of times. You could even emulate Apollo's conops for transposition and docking. The BEAM module would be mounted on the FH's upper stage and the trunk would act merely as a fairing. The Dragon separates and turns through 180 degrees. The upper stage would provide stability using its own thrusters as the Dragon moves in and docks. Then the stage separates and we're on our way.

[TrevorMonty]

Good points about the aerodynamics of BEAM module attached to Dragon and cold gas thrusters to simplify propulsion.
Assuming Dragon can meet all life support demands of the trip, the BEAM only needs to provide a empty room which will be disposed of at end of the trip.

The issue of not overloading the Dragons max abort weight,  could be solved by having 2 trunks. In an abort the top (lightly loaded) trunk stays with Dragon while lower trunk with bulk of payload eg BEAM, external tanks stays with LV.

 

[douglas100]

Good points about the aerodynamics of BEAM module attached to Dragon and cold gas thrusters to simplify propulsion.
Assuming Dragon can meet all life support demands of the trip, the BEAM only needs to provide a empty room which will be disposed of at end of the trip.

The issue of not overloading the Dragons max abort weight,  could be solved by having 2 trunks. In an abort the top (lightly loaded) trunk stays with Dragon while lower trunk with bulk of payload eg BEAM, external tanks stays with LV.

True, but if you follow the "Apollo solution" BEAM is not in the trunk, but only covered by it. During an abort the Dragon and trunk would separate as "usual" leaving BEAM behind mounted on the upper stage. This solves the overloading during abort problem without needing the extra complexity of two trunks.  However, there might be clearance issues during such an "energetic" separation event.

[Elmar Moelzer]

True, but if you follow the "Apollo solution" BEAM is not in the trunk, but only covered by it. During an abort the Dragon and trunk would separate as "usual" leaving BEAM behind mounted on the upper stage. This solves the overloading during abort problem without needing the extra complexity of two trunks.  However, there might be clearance issues during such an "energetic" separation event.

Do we know for sure that the trunk HAS to stay attached to the capsule during an abort? It seems rather odd to me. I would expect that it could optionally be left behind, unless it is needed to stabilize the capsule somehow.
Also: What about a reusable orbital tug to go between the moon and LEO (launched with a single FH) and then a separate launch (or several F9R launches) for crew and fuel. It would increase the initial cost, but could be cheaper and more flexible in the long term.

[douglas100]

From Elmar Moelzer

Do we know for sure that the trunk HAS to stay attached to the capsule during an abort? It seems rather odd to me. I would expect that it could optionally be left behind, unless it is needed to stabilize the capsule somehow.

I'm assuming that the trunk and its fins are needed for aerodynamic stability during the first part of an abort if it takes place when there is still a substantial atmosphere (Otherwise, what are the fins for? They're not needed as radiators.) If that's not the case, then things are simplified.

Also: What about a reusable orbital tug to go between the moon and LEO (launched with a single FH) and then a separate launch (or several F9R launches) for crew and fuel. It would increase the initial cost, but could be cheaper and more flexible in the long term.

We can come up with more complicated missions involving multiple launches, of course. I was thinking in terms of the simplest possible mission, which I think is the kind most likely to happen first in terms of tourism.

[meekGee]

The fins confuse me.

During the first part of the abort, there's so much input from the SDs that that fins can't passively stabilize the capsule if the SDs are not doing their job.

Maybe after thrust is cut, in the "coast" phase - but then why burn the SDs to depletion?

I actually think that rather than being Fins, they are "pre-deployed, launch-proof" solar cells/radiators - basically they are shaped like fins so that they can survive launch and still give added area on orbit.  They don't really act as stabilizers.

Of course, I admit, why carry the trunk then?  Maybe it helps move the c.m. back, and THAT adds stability - since this property is magnified by the acceleration the SDs provide.

 

[sublimemarsupial]

The fins confuse me.

During the first part of the abort, there's so much input from the SDs that that fins can't passively stabilize the capsule if the SDs are not doing their job.

Maybe after thrust is cut, in the "coast" phase - but then why burn the SDs to depletion?

I actually think that rather than being Fins, they are "pre-deployed, launch-proof" solar cells/radiators - basically they are shaped like fins so that they can survive launch and still give added area on orbit.  They don't really act as stabilizers.

Of course, I admit, why carry the trunk then?  Maybe it helps move the c.m. back, and THAT adds stability - since this property is magnified by the acceleration the SDs provide.

The fins may help stabilize the roll axis, which the SuperDracos do not have very much control authority in (as opposed to the pitch and yaw axes).

[Elmar Moelzer]

The fins confuse me.

Welcome to the club! (we need a beer smiley).

We can come up with more complicated missions involving multiple launches, of course. I was thinking in terms of the simplest possible mission, which I think is the kind most likely to happen first in terms of tourism.

You are right of course. I keep thinking too much about architecture and long term goals. For a short term, simple proof of "we can do it mission", it might be easier to do it all in one launch.
That said, I don't quite understand the need for the Beam module. Just send less people (if all you want is make it work and you don't worry about anything else too much). Dragon is housing 7 people quite comfortably. If you took 4 of those seats out, you would free a lot of room for extra equipment (and a toilet of sorts) and you might be able to increase the operational timeframe a little bit. Might safe some weight as well, especially if you think about the added weight of a Beam.

[Elmar Moelzer]

The fins may help stabilize the roll axis, which the SuperDracos do not have very much control authority in (as opposed to the pitch and yaw axes).

If they are needed for that, how do they control the roll for powered landings?

[douglas100]

We can come up with more complicated missions involving multiple launches, of course. I was thinking in terms of the simplest possible mission, which I think is the kind most likely to happen first in terms of tourism.

You are right of course. I keep thinking too much about architecture and long term goals. For a short term, simple proof of "we can do it mission", it might be easier to do it all in one launch.
That said, I don't quite understand the need for the Beam module...

I think you're right, it probably isn't necessary for a "minimalist" mission. But if one were to be carried, then I think the "Apollo solution" is a straightforward way of doing it.

[Burninate]

The fins confuse me.

Welcome to the club! (we need a beer smiley).

We can come up with more complicated missions involving multiple launches, of course. I was thinking in terms of the simplest possible mission, which I think is the kind most likely to happen first in terms of tourism.

You are right of course. I keep thinking too much about architecture and long term goals. For a short term, simple proof of "we can do it mission", it might be easier to do it all in one launch.
That said, I don't quite understand the need for the Beam module. Just send less people (if all you want is make it work and you don't worry about anything else too much). Dragon is housing 7 people quite comfortably. If you took 4 of those seats out, you would free a lot of room for extra equipment (and a toilet of sorts) and you might be able to increase the operational timeframe a little bit. Might safe some weight as well, especially if you think about the added weight of a Beam.

Dragon is housing 7 heavily screened volunteer NASA astronauts wearing space suits and diapers, planning on being in that situation for at most about 2 days, but more likely about six hours.  There's only 10m^3 of air ("pressurized volume") in the whole vehicle, before considering cargo or increased life support needs.  A Lunar free return trajectory is a ~6 day maneuver.  The average *coffin* has about 0.9m^3 of airspace - that's less than 2 coffins per person.

For comparison: the Shuttle, which flew comparable crews, had 74.3m^3 of pressurized volume, and the Soyuz flies 3 people in 7.5m^3 (2.5m^3 in the landing module, which essentially everybody remarks is claustrophobic/uncomfortable, but which they're only confined to for hours at a time).

Tourists are going to want more.  Treat the Dragon as a place to launch from and reenter the atmosphere, and no more, for that purpose - even with a diminished crew of 4 it's as cramped as Soyuz.

[douglas100]

The fins confuse me.

During the first part of the abort, there's so much input from the SDs that that fins can't passively stabilize the capsule if the SDs are not doing their job.

If the abort takes place from the pad or at low altitude, that may be true. But at high speed--maxQ for example, the capsule itself would not not aerodynamically stable nose forward. Its centre of mass is so positioned that it would tend to tumble to blunt end forward when released into the air stream.  You don't want that if you're trying to get away from a speeding LV. Now if the Dracos and SD's are powerful and can react fast enough to overcome these aerodynamic forces, no problem. However, my take is that SpaceX have modeled this and have almost certainly done wind tunnel tests and have decided that aerodynamic stabilization is required.

I actually think that rather than being Fins, they are "pre-deployed, launch-proof" solar cells/radiators - basically they are shaped like fins so that they can survive launch and still give added area on orbit.  They don't really act as stabilizers.

If they don't act as stabilizers they don't need four. Only two carry solar cells. If that was their only purpose two could be omitted. I don't buy the radiator argument. There is a large area on the antisolar side of the trunk for radiators.

Let's not overthink this. I suggest that the fins are exactly what they appear to be: aerodynamic stabilizers.

[Elmar Moelzer]

Dragon is housing 7 heavily screened volunteer NASA astronauts wearing space suits and diapers, planning on being in that situation for at most about 2 days, but more likely about six hours. 

That's why I suggested to do a lunar mission with only 3 people on board, instead of 7.

There's only 10m^3 of air ("pressurized volume") in the whole vehicle, before considering cargo or increased life support needs.  A Lunar free return trajectory is a ~6 day maneuver.  The average *coffin* has about 0.9m^3 of airspace - that's less than 2 coffins per person.

Again, I was talking 3 people, not 7. That would more than double the room per person.
Also Dragon was said to be able to remain autonomous for up 10 days. So with reduced crew and additional supplies it might be doable. Sure it would not be comfortable, but I was told that this was meant as an example for a "minimum mission" kind of thing.

Tourists are going to want more.

Hence my suggestion of a separately launched orbital tug, which could have significantly more living space (and would be reusable and probably cheaper in the long term). But for a "minimal mission", I think just the Dragon should be fine.

[ChrisWilson68]

What about a reusable orbital tug to go between the moon and LEO (launched with a single FH) and then a separate launch (or several F9R launches) for crew and fuel. It would increase the initial cost, but could be cheaper and more flexible in the long term.

Yes, I agree that's the way to go in the long term.  There should be specialized reusable vehicles (such as Dragon V2, but others could also fill the role) that only transport people between the Earth's surface and LEO.  At LEO, people should transfer to vehicles that stay in space and are resused, no matter where they're going or staying.

I hope we get to that long-term way of thinking sooner rather than later.  Falcon 9/Falcon Heavy/Dragon represents that way of thinking -- make the Earth-to-orbit-and-back system reusable and do many flights.  Falcon 9 and Falcon Heavy are perfect for bringing up lots of propellant and supplies on many flights.  SLS is the opposite approach, where nothing is reusable, flight rates are low, and we have no leverage to scale anything.

Having a habitat launched with a Dragon is a step in the wrong direction, in my opinion -- a step toward the throw-it-away mindset.

[Space Ghost 1962]

The fins confuse me.

During the first part of the abort, there's so much input from the SDs that that fins can't passively stabilize the capsule if the SDs are not doing their job.

If the abort takes place from the pad or at low altitude, that may be true. But at high speed--maxQ for example, the capsule itself would not not aerodynamically stable nose forward. Its centre of mass is so positioned that it would tend to tumble to blunt end forward when released into the air stream.  You don't want that if you're trying to get away from a speeding LV.

No. On max-Q abort, the stability comes from nailing the capsule to the shock wave ahead of the capsule, and the software can adjust the throttle's of each engine to not only stabilize the craft but moderate turbulence of flow / flow separation issues.

Now if the Dracos and SD's are powerful and can react fast enough to overcome these aerodynamic forces, no problem. However, my take is that SpaceX have modeled this and have almost certainly done wind tunnel tests and have decided that aerodynamic stabilization is required.

I actually think that rather than being Fins, they are "pre-deployed, launch-proof" solar cells/radiators - basically they are shaped like fins so that they can survive launch and still give added area on orbit.  They don't really act as stabilizers.

If they don't act as stabilizers they don't need four. Only two carry solar cells. If that was their only purpose two could be omitted. I don't buy the radiator argument. There is a large area on the antisolar side of the trunk for radiators.

Let's not overthink this. I suggest that the fins are exactly what they appear to be: aerodynamic stabilizers.

Yes they need four - because if there were two, the absence of the others would amplify buffeting/turbulence on ascent.

The fins increase surface area. Defacto radiators no matter what.

My take on why they are there - the asymmetrical X pattern of thruster housings in the vertical airstream amplify (as above) on ascent. It throws off the precision of the guidance system and creates feedback terms for the software that aren't easy to cope with. Easier to buy back stability passively. E.g. a "quick fix"

Perhaps long term they change the mold line and the fins vanish, More payload to orbit. Don't sweat it.

[ChrisWilson68]

The fins confuse me.

During the first part of the abort, there's so much input from the SDs that that fins can't passively stabilize the capsule if the SDs are not doing their job.

If the abort takes place from the pad or at low altitude, that may be true. But at high speed--maxQ for example, the capsule itself would not not aerodynamically stable nose forward. Its centre of mass is so positioned that it would tend to tumble to blunt end forward when released into the air stream.  You don't want that if you're trying to get away from a speeding LV.

No. On max-Q abort, the stability comes from nailing the capsule to the shock wave ahead of the capsule, and the software can adjust the throttle's of each engine to not only stabilize the craft but moderate turbulence of flow / flow separation issues.

I don't buy that.  I think the fins buy you passive stability in an abort.  The software can just open the throttle up all the way on all engines on abort and it will be stable.  There's less that can go wrong with that approach than with an active-stability approach where the computer has to do fine throttle adjustments.

There's no plausible reason for the trunk to stay attached in an abort other than for stability.  If the trunk is there for stability, it's not much of a stretch to see that the fins might be too.

Edit: But on further reflection, this probably isn't the ideal thread for debating the reasons for fins.  Perhaps we can take further discussion to a more appropriate thread?

[Space Ghost 1962]

No. On max-Q abort, the stability comes from nailing the capsule to the shock wave ahead of the capsule, and the software can adjust the throttle's of each engine to not only stabilize the craft but moderate turbulence of flow / flow separation issues.

I don't buy that.  I think the fins buy you passive stability in an abort.  The software can just open the throttle up all the way on all engines on abort and it will be stable.  There's less that can go wrong with that approach than with an active-stability approach where the computer has to do fine throttle adjustments.

There's no plausible reason for the trunk to stay attached in an abort other than for stability.  If the trunk is there for stability, it's not much of a stretch to see that the fins might be too.

On abort the fins are BEHIND you on a SEPARATE VEHICLE. Not coupled.

Furthermore, you have a HUGE stagnation that will occur once the Dragon sans trunk exposes the trunk to the high Mach shockwave. Will be like hitting a brick wall.

During separation, thrust smacks Dragon against a max-Q wall and the bending deviations below dragon are inconsequential until stream separation - nothing can outrun the incident shock wave, which acts as a barrier as the trunk breaks up.

There is nothing in the plane of separation that interferes with Dragon at the separation instant and beyond.

So how does it matter, how does it help?

[sublimemarsupial]

On abort the fins are BEHIND you on a SEPARATE VEHICLE. Not coupled.

As per the pad abort test plan, the trunk (and its fins) stays attached to Dragon during the abort, and is only separated after a safe distance from the vehicle is achieved and the drogue parachutes are deployed.

[douglas100]

...Edit: But on further reflection, this probably isn't the ideal thread for debating the reasons for fins.  Perhaps we can take further discussion to a more appropriate thread?

Since I brought up the question of the fins I'm partly responsible for take this off course. Agree.

[TrevorMonty]

Here is my costing estimates for lunar flyby.
$135m. ELV FH
$10m. Use of reusable Dragon
$20m. Expendable BEAM
$45m. Profit and extras

Say $210m. If mission can handle 4 ie 1 pilot + 3 passengers. That is $70m each. NB with 4 one row of seats can be removed, freeing up a lot of space.

If boosters are recoverable we maybe able to save $60m making it $50M a seat.

At these prices there maybe a market for one or two flights a year.

[Space Ghost 1962]

On abort the fins are BEHIND you on a SEPARATE VEHICLE. Not coupled.

As per the pad abort test plan, the trunk (and its fins) stays attached to Dragon during the abort, and is only separated after a safe distance from the vehicle is achieved and the drogue parachutes are deployed.

Yup, right there in the plan. Mea culpa. In that way they'd work as tail fins. And the trunk would buffer the Dragon above the separation plane.

Which is not what I remembered from an earlier presentation.  I guess the first stage destruction has more energetic debris pattern than thought before, and the hypersonic stability of the SD's in stream is much more in doubt. Originally there wasn't even going to be a trunk on crewed Dragon.

End of discussion of "fins".
Keeping the trunk attached also creates a negative pressure zone behind the Dragon. Perhaps that helps by being able to gain distance before the flow separation. A kind of hypersonic shadow.

[llanitedave]

What's the thrust to weight ratio of the Super Dracos carrying the Dragon plus trunk as opposed to the Dragon alone?

[Space Ghost 1962]

What's the maximum manifested weight of trunk contents? Or do you mean trunk weight only?

[docmordrid]

The DragonFly EIS quotes a vehicle mass of 7 tonnes with an integrated trunk. Pick your thrust number and have at it.

[moralec]

Let's try to see this from a more sustainable perspective. If you want to have tourists going to the moon and back on a regular basis, while maximizing safety and minimizing costs, it doesn't make sense to think about a single Apollo-like system around the Drago capsule, handling both the transportation from earth to the moon and the landings. Carrying a Dragon capsule with a heat shield all the way to the moon for example, is unnecessary. You could have instead several specialized pieces of infrastructure (one of them being the Dragon spacecraft), each handling a different part of the trip. For example :

- the reusable dragon v2 could be used to take costumers from the earth to LOE, and back. This spacecraft was designed and its optimized for this. It does not need to be larger as it currently is, as this would be a shirt trip.
- A new large permanent vessel (a space cruise), with several modules, would be the ideal way of taking the tourists from LOE to moon orbit. It would make sense to build this in LEO. Spacex could preform several FH launches to take all the necessary parts. The use of light materials seems attractive, but is important to take into account that materials to minimize radiation exposure are required. A ship like this  could be powered with ion thrusters, or with a liquid fuel burner.  You could use unmanned dragon ships to supply it with food, water and other consumables while it is on LEO. A permanent life support like the one on the IIS could be included here, as this vessel should be used on a permanent basis.
- A lunar lander could be included in the setup in order to do the lunar excursions. Landing a large ship in the moon is unnecessary. A smaller one like the one used on the Apollo program is a better choice. It could be even left on lunar orbit. Is a waste of resources to bring it back and forth.

This modular system seems more appropriate for the idea of moon turism. Additionally it could be expanded with LEO, lunar orbit and lunar surface stations acting like hotels. All required supplies should be handled with pure cargo vessels as many elements do not require pressurization.

Comments?

[aero]

2001: A Space Odyssey - without the monoliths.

[groundbound]

I think we need to be awfully careful about excluding mars from the discussion.

SpaceX is a company that has mars as its central ambition. That is unlikely to change. So the success of any plans to do anything else will depend on how well it dovetails with mars-focused hardware and plans. In many cases, suboptimal schemes that more highly leverage pre-existing (and reusable) hardware and expertise.

Make lunar plans mars-agnostic, and you likely talking about some company other than SpaceX.

[AncientU]

Let's try to see this from a more sustainable perspective. If you want to have tourists going to the moon and back on a regular basis, while maximizing safety and minimizing costs, it doesn't make sense to think about a single Apollo-like system around the Drago capsule, handling both the transportation from earth to the moon and the landings. Carrying a Dragon capsule with a heat shield all the way to the moon for example, is unnecessary. You could have instead several specialized pieces of infrastructure (one of them being the Dragon spacecraft), each handling a different part of the trip. For example :

- the reusable dragon v2 could be used to take costumers from the earth to LOE, and back. This spacecraft was designed and its optimized for this. It does not need to be larger as it currently is, as this would be a shirt trip.
- A new large permanent vessel (a space cruise), with several modules, would be the ideal way of taking the tourists from LOE to moon orbit. It would make sense to build this in LEO. Spacex could preform several FH launches to take all the necessary parts. The use of light materials seems attractive, but is important to take into account that materials to minimize radiation exposure are required. A ship like this  could be powered with ion thrusters, or with a liquid fuel burner.  You could use unmanned dragon ships to supply it with food, water and other consumables while it is on LEO. A permanent life support like the one on the IIS could be included here, as this vessel should be used on a permanent basis.
- A lunar lander could be included in the setup in order to do the lunar excursions. Landing a large ship in the moon is unnecessary. A smaller one like the one used on the Apollo program is a better choice. It could be even left on lunar orbit. Is a waste of resources to bring it back and forth.

This modular system seems more appropriate for the idea of moon turism. Additionally it could be expanded with LEO, lunar orbit and lunar surface stations acting like hotels. All required supplies should be handled with pure cargo vessels as many elements do not require pressurization.

Comments?

Sustainable... infrastructure... reusable.
Sounds like what we've been missing.
Just add fuel -- in LEO for the cruise ship, and Lunar orbit for the lander.  Perhaps Meth/LOX???
Great practice for Mars!

[sanman]

Let's try to see this from a more sustainable perspective. If you want to have tourists going to the moon and back on a regular basis, while maximizing safety and minimizing costs, it doesn't make sense to think about a single Apollo-like system around the Drago capsule, handling both the transportation from earth to the moon and the landings. Carrying a Dragon capsule with a heat shield all the way to the moon for example, is unnecessary. You could have instead several specialized pieces of infrastructure (one of them being the Dragon spacecraft), each handling a different part of the trip. For example :

- the reusable dragon v2 could be used to take costumers from the earth to LOE, and back. This spacecraft was designed and its optimized for this. It does not need to be larger as it currently is, as this would be a shirt trip.
- A new large permanent vessel (a space cruise), with several modules, would be the ideal way of taking the tourists from LOE to moon orbit. It would make sense to build this in LEO. Spacex could preform several FH launches to take all the necessary parts. The use of light materials seems attractive, but is important to take into account that materials to minimize radiation exposure are required. A ship like this  could be powered with ion thrusters, or with a liquid fuel burner.  You could use unmanned dragon ships to supply it with food, water and other consumables while it is on LEO. A permanent life support like the one on the IIS could be included here, as this vessel should be used on a permanent basis.
- A lunar lander could be included in the setup in order to do the lunar excursions. Landing a large ship in the moon is unnecessary. A smaller one like the one used on the Apollo program is a better choice. It could be even left on lunar orbit. Is a waste of resources to bring it back and forth.

This modular system seems more appropriate for the idea of moon turism. Additionally it could be expanded with LEO, lunar orbit and lunar surface stations acting like hotels. All required supplies should be handled with pure cargo vessels as many elements do not require pressurization.

Comments?

Well, if you can have a Red Dragon, then you could also have a Silver Dragon. The Silver Dragon would be a custom-designed variant meant to travel back and forth between the Moon's surface and LEO/ISS. It would not have a heat shield, and could have a larger form factor comparable to Dragon+Trunk, carrying extra propellant and possibly additional cargo/crew space. It would also be equipped with the solar panels that are on the trunk of DragonV2. It would be capable of docking with ISS.

[Manabu]

To sidestep all this concern about the escape system with extra weight, what about doing this in two launches: one FH to put the BEAM and vehicle in orbit, and another F9R carrying just the Dragon with the tourist. Both dock in orbit and then proceed for the Moon.

The weight savings on FH could be directed at a bigger living module, or in making the boosters reusable, thus paying for the extra F9R launch that should be relatively cheap if all goes right with SpaceX reusability plans.

[CuddlyRocket]

SpaceX is a company that has mars as its central ambition. That is unlikely to change. So the success of any plans to do anything else will depend on how well it dovetails with mars-focused hardware and plans. In many cases, suboptimal schemes that more highly leverage pre-existing (and reusable) hardware and expertise.

Make lunar plans mars-agnostic, and you likely talking about some company other than SpaceX.

Another point to make is that SpaceX is a commercial company; it's not going to go to the Moon or set up a Lunar transportation infrastructure unless someone else is paying for it; and if that someone is also a commercial entity they're going to want to minimise capital at risk and maximise return. That suggests they're going to use either pre-existing equipment or reasonably straightforward modifications thereof; expenditure on additional equipment will have to wait until a profitable business model is established.

There's also the matter of the crew. I should imagine that the FAA or equivalent will insist on two qualified astro-pilots, and it's not common for employees to pay for their own ticket! That means there'll be even stronger pressure to maximise the number of people carried at one time. One possibility is that passengers who are qualified astro-pilots could get a discount for acting as the co-pilot. That would probably mean them paying for their own training - which could be a nice sideline for someone - and be a common career path for civilian astronauts.

As for the problem with toilet functions and lack of privacy, they might manage this in the early days by running all-male and all-female flights (though there could be a legal problem if there's a substantial imbalance and therefore employment opportunities for one gender).

[Dave G]

I should imagine that the FAA or equivalent will insist on two qualified astro-pilots...

Why?

As I understand it, the FAA is not really concerned with astronauts dying in space.  The FAA is concerned with potential accidents affecting people/property on the ground. 

In general, if you want to risk your life doing something, the government usually doesn't get in your way, they just want to be sure you don't cause any damage to others in the process.

Astronauts travel at their own risk.

[Dave G]

Carrying a Dragon capsule with a heat shield all the way to the moon for example, is unnecessary. You could have instead several specialized pieces of infrastructure (one of them being the Dragon spacecraft), each handling a different part of the trip. For example :

- the reusable dragon v2 could be used to take costumers from the earth to LEO, and back. This spacecraft was designed and its optimized for this. It does not need to be larger as it currently is, as this would be a shirt trip.

- A new large permanent vessel (a space cruise), with several modules, would be the ideal way of taking the tourists from LEO to moon orbit.

...

The same approach could be used to go to Mars.

However, the main issues are:
1) decelerating the large transfer vehicle into a Lunar or Mars orbit.
2) decelerating the large transfer vehicle back into low Earth orbit.

Aerobraking could be used for Earth and Mars orbits, but this would require some amount of heat shielding.  For the moon there's no atmosphere, so you would need to use a lot of propellant, which would add significant mass. Perhaps a nuclear thermal rocket would solve this issue.

As an alternative, an expendable hab module is relatively cheap, and a free return trajectory would not require decelerating to any orbit.  Note that the Dragon heat shield is designed for planetary return speeds.

Also, it may be possible to use the FH second stage LOX tank as a hab module.  Remember that the second stage powers TLI, so it's already on the trip to the moon.  All you would need is a hatch and some thrusters on the second stage for docking.

[AncientU]

Carrying a Dragon capsule with a heat shield all the way to the moon for example, is unnecessary. You could have instead several specialized pieces of infrastructure (one of them being the Dragon spacecraft), each handling a different part of the trip. For example :

- the reusable dragon v2 could be used to take costumers from the earth to LEO, and back. This spacecraft was designed and its optimized for this. It does not need to be larger as it currently is, as this would be a shirt trip.

- A new large permanent vessel (a space cruise), with several modules, would be the ideal way of taking the tourists from LEO to moon orbit.

...

The same approach could be used to go to Mars.

However, the main issues are:
1) decelerating the large transfer vehicle into a Lunar or Mars orbit.
2) decelerating the large transfer vehicle back into low Earth orbit.

Aerobraking could be used for Earth and Mars orbits, but this would require some amount of heat shielding.  For the moon there's no atmosphere, so you would need to use a lot of propellant, which would add significant mass. Perhaps a nuclear thermal rocket would solve this issue.

As an alternative, an expendable hab module is relatively cheap, and a free return trajectory would not require decelerating to any orbit.  Note that the Dragon heat shield is designed for planetary return speeds.

Also, it may be possible to use the FH second stage LOX tank as a hab module.  Remember that the second stage powers TLI, so it's already on the trip to the moon.  All you would need is a hatch and some thrusters on the second stage for docking.

Multiple choice(chose one):
A. Cis-lunar Space Tourism
B. Expendable

[InfraNut2]

Multiple choice(chose one):
A. Cis-lunar Space Tourism
B. Expendable

An important point presented in a fun way. I like it!   

It deserves to be repeated, and I'll do it in a less over-simplified and less fun way:

    Reuse is the key to make cis-lunar space tourism widespread instead of rare

[ChrisWilson68]

Well, if you can have a Red Dragon, then you could also have a Silver Dragon. The Silver Dragon would be a custom-designed variant meant to travel back and forth between the Moon's surface and LEO/ISS. It would not have a heat shield, and could have a larger form factor comparable to Dragon+Trunk, carrying extra propellant and possibly additional cargo/crew space. It would also be equipped with the solar panels that are on the trunk of DragonV2. It would be capable of docking with ISS.

You're missing the whole point of Red Dragon, which is that it makes only minor modification to the existing Dragon.

Your Silver Dragon is so vastly different from Dragon that you get virtually no benefit from starting with Dragon at all.  You might as well start from scratch and design a Moon lander.

[ChrisWilson68]

There's also the matter of the crew. I should imagine that the FAA or equivalent will insist on two qualified astro-pilots

I've flown as a passenger on two different commercial flights in the United States that included only one crew member, the pilot.  One was a small airline flight from Puerto Rico to the U.S. Virgin Islands and the other was a helicopter tour in Hawaii.  The FAA has no problem with only a single pilot when the number of passengers is small.

[A_M_Swallow]

{snip}
Also, it may be possible to use the FH second stage LOX tank as a hab module.  Remember that the second stage powers TLI, so it's already on the trip to the moon.  All you would need is a hatch and some thrusters on the second stage for docking.

LOX tanks are empty boxes.  You would also have to add things like a galley, toilet, air conditioning, cabinets and lights before you could live in it.  Such modifications can only be done on the Earth's surface.

[cryptoanarchy]

As for the problem with toilet functions and lack of privacy, they might manage this in the early days by running all-male and all-female flights (though there could be a legal problem if there's a substantial imbalance and therefore employment opportunities for one gender).

Or they could use a curtain.

[CuddlyRocket]

I should imagine that the FAA or equivalent will insist on two qualified astro-pilots...

Why?

As I understand it, the FAA is not really concerned with astronauts dying in space.  The FAA is concerned with potential accidents affecting people/property on the ground. 

In general, if you want to risk your life doing something, the government usually doesn't get in your way, they just want to be sure you don't cause any damage to others in the process.

Astronauts travel at their own risk.

There's a difference between employees and passengers. Also between adventurers and tourists. And between screened and trained people and anyone with the money for the ticket. There's already political pushback against the laxer safety regime envisaged for commercial crewed flights; can you imagine the press and political furore when (and it will be when) there's the first fatality? Careers have been blighted, even ended, for less and any politician and especially bureaucrat will want to ensure they have their umbrella in place when blame rains down from on high (a common simile used every week by British civil servants).

They could say 'at your own risk' for flying; but they don't.

I've flown as a passenger on two different commercial flights in the United States that included only one crew member, the pilot.  One was a small airline flight from Puerto Rico to the U.S. Virgin Islands and the other was a helicopter tour in Hawaii.  The FAA has no problem with only a single pilot when the number of passengers is small.

That's a hangover from the fact that passenger flights with single pilots were already the mainstay of the industry before it started to be regulated. In the US regulation started in 1926. Aeromarine Airways had gone out of business before that having made more than 2,000 scheduled flights and carried nearly 10,000 passengers (i.e. <5 passengers a flight on average), and that's one airline. (They were brought down by a crash with passenger fatalities.) Passenger spaceflight won't have that luxury, especially as we're constantly being told that spaceflight is much, much more dangerous than aviation.

As for the problem with toilet functions and lack of privacy, they might manage this in the early days by running all-male and all-female flights (though there could be a legal problem if there's a substantial imbalance and therefore employment opportunities for one gender).

Or they could use a curtain.

Which would stop neither sound nor smells nor the inescapable fact that everyone will know what you're doing. People can be very squeamish about such things, especially in mixed-gender company.

[docmordrid]

Which would stop neither sound nor smells nor the inescapable fact that everyone will know what you're doing. People can be very squeamish about such things, especially in mixed-gender company.

One of my late 1960's college dorms was an early co-ed with a shared bathroom in each hall, each having several shower and toilet stalls. Quite interesting when someone joined the group on a weekend when it was empty, only to have  someone of the opposite gender pass the soap over the wall on Monday.

You get over it.

[TrevorMonty]

I found this article on cis lunar space craft after listening to Space Show about it.
Definitely not a near term thing but interesting concept.

http://denecs.usc.edu/hosted/ASTE/527_20111/03%20-%20The%20US%20Department%20of%20Space%20-%202011/J.1%20AIAA%20Space%202012.pdf

[ChrisWilson68]

It's kind of hard for me to see someone saying, "Well, I'd really like to go to the Moon.  I'm even willing to pay $20 million to do it.  I'm willing to risk my life.  I'm willing to be in an uncomfortably small space for days.  I'm willing to throw up repeatedly from space sickness.  I'm willing to use zero-g toilets.  But have to put up with someone of the opposite sex using the toilet on the other side of curtain?  No, I won't put up with that.  Cancel the trip."

[Dave G]

There's a difference between employees and passengers. Also between adventurers and tourists.

I respectfully disagree.  Human space travel is an inherently risky proposition, and will be for a long time.  This is well understood.

Its like TT racing on the Isle of Man, where people die every year.  Same with hang gliding.  As long as the risks are well understood by participants, nobody blames politicians. 

But if a TT motorcycle crashed into a group of spectators, that would be a major issue, since spectators didn't sign up for that type of risk.

So that's the type of approach the FAA is taking for space tourism.  They're not focused on tourist safety.  They're focused on preventing any collateral damage.

[sanman]

You're missing the whole point of Red Dragon, which is that it makes only minor modification to the existing Dragon.

Your Silver Dragon is so vastly different from Dragon that you get virtually no benefit from starting with Dragon at all.  You might as well start from scratch and design a Moon lander.

Alright, then call it a forerunner of MCT. Maybe it would be an antecedent of MCT before the heat shield and aerobraking are added on.

[Burninate]

{snip}
Also, it may be possible to use the FH second stage LOX tank as a hab module.  Remember that the second stage powers TLI, so it's already on the trip to the moon.  All you would need is a hatch and some thrusters on the second stage for docking.

LOX tanks are empty boxes.  You would also have to add things like a galley, toilet, air conditioning, cabinets and lights before it could live in it.  Such modifications can only be done on the Earth's surface.

I went most of my life not understanding what the hell 'reuse an upper stage as a habitat' actually meant, because it's presented as some kind of miracle innovation, with the implication that astronauts are going to literally climb into a spent stage and make it home.  What it means is just re-using the *earthside tooling* currently being used for making 5-10m diameter pressure vessels that hold propellant, and building a habitat of that size on Earth.  The only actual savings is not having to build an entirely new factory in order to pump out one habitat.

[darkenfast]

I'm going to be a pessimist here.  I don't think that there will be a market for cis-lunar trips once it's been done one or maybe two times.  We know that fairly well-off people will pay the 1/4 million dollars to go sub-orbital.  We know that there are a group of millionaires who will spend $30 million to spend a few days on a space station.  I think that there are some fairly wealthy individuals who would spend a big chunk of their fortune to walk on the Moon (and they won't give a hoot about the toilet arrangements, any more than any forum member here would).

What I don't think is that there is a market for more than a couple of record-setters to pay a multiple of what it costs to go to orbit in order to fly near the moon without landing. 

[TrevorMonty]

IMHO lunar flybys are going to be about it with FH in near future. To make lunar landings viable they need fuel in Lunar orbit to supply landers, the possible options I see for this are ISRU from Asteriod or lunar ice both of which will require large infrastructure and years to develop.

The other near term option is SpaceX's BFR, if this can deliver around 50t to lunar orbit as a fully reusable LV then tourism to lunar surface may drop to tens instead of hundreds of millions per seat.

[Celebrimbor]

I'm going to be a pessimist here.  I don't think that there will be a market for cis-lunar trips once it's been done one or maybe two times.  We know that fairly well-off people will pay the 1/4 million dollars to go sub-orbital.  We know that there are a group of millionaires who will spend $30 million to spend a few days on a space station.  I think that there are some fairly wealthy individuals who would spend a big chunk of their fortune to walk on the Moon (and they won't give a hoot about the toilet arrangements, any more than any forum member here would).

What I don't think is that there is a market for more than a couple of record-setters to pay a multiple of what it costs to go to orbit in order to fly near the moon without landing. 

I don't know.  For me - it would be qualitatively cooler than orbiting the Earth to leave Earth behind, fly around the moon, look at the far side up close, for real, and return (at extreme speed!) into the Earth atmosphere and land softly.  Definitely worth pay more than twice (if I could afford it).

[rst]

I went most of my life not understanding what the hell 'reuse an upper stage as a habitat' actually meant, because it's presented as some kind of miracle innovation, with the implication that astronauts are going to literally climb into a spent stage and make it home.  What it means is just re-using the *earthside tooling* currently being used for making 5-10m diameter pressure vessels that hold propellant, and building a habitat of that size on Earth.  The only actual savings is not having to build an entirely new factory in order to pump out one habitat.

Actually, there have been proposals to refit spent stages in orbit; Wernher von Braun himself was pushing the idea, during the design discussions that ultimately led to Skylab.

http://en.wikipedia.org/wiki/Wet_workshop

[moralec]

I found this article on cis lunar space craft after listening to Space Show about it.
Definitely not a near term thing but interesting concept.

http://denecs.usc.edu/hosted/ASTE/527_20111/03%20-%20The%20US%20Department%20of%20Space%20-%202011/J.1%20AIAA%20Space%202012.pdf

Amazing find! This is very similar to what I had in mind. A vessel designed specifically to stay (and travel) in space is the logical way to go. I never thought about the possibility of assembling it on the ISS, but is not a crazy idea. Spare progress ships could in fact be used for extra space at a cheap price, although they may increase the amount of fuel required for the journey.

I insist that having large modules in this extraterrestrial vessel is important: in order to make the trip attractive for tourists, it is important to provide a comfortable accommodation (at least decent bathrooms). Larger ships also generate redundancy: in case of an emergency you could disassemble a damaged section of the ship, bringing tourists safely to the rendezvous point. Furthermore, the larger the crowd the better as you split fixed costs with more people.

The concept could be expanded with a lunar lander. I'm thinking in the Morpheus here (very similar to the Apollo Lander but completely automated). It could preform various excursions while the vessel is on lunar orbit, taking tourists from the vessel to surface and back. And it could stay parked on the moon while the vessel goes back to LEO.

While on LEO the vessel could be obtain supplies from dragon 1 unmanned capsules, and the dragon 2 could function like a taxi  taking and returning tourists. Neither of these ships are needed to make the entire lunar transfer trip. They just need to go back and forth with people, supplies and trash.

[ChrisWilson68]

You're missing the whole point of Red Dragon, which is that it makes only minor modification to the existing Dragon.

Your Silver Dragon is so vastly different from Dragon that you get virtually no benefit from starting with Dragon at all.  You might as well start from scratch and design a Moon lander.

Alright, then call it a forerunner of MCT. Maybe it would be an antecedent of MCT before the heat shield and aerobraking are added on.

There has been a lot of discussion of this on other threads -- the requirements of a lunar lander/ascent vehicle are so vastly different from the requirements of a Mars lander/ascent vehicle that its counterproductive to try to combine them or use one to develop the other.

It's like trying to develop a combination screwdriver and hammer, or trying to develop a screwdriver that will lead to a hammer.  If you need to pound in a nail, develop a hammer.  If you need to drive a screw, develop a screwdriver.  They may both be things that help you fasten objects together, but they're not similar enough to share a development path.

[guckyfan]

There has been a lot of discussion of this on other threads -- the requirements of a lunar lander/ascent vehicle are so vastly different from the requirements of a Mars lander/ascent vehicle that its counterproductive to try to combine them or use one to develop the other.

It's like trying to develop a combination screwdriver and hammer, or trying to develop a screwdriver that will lead to a hammer.  If you need to pound in a nail, develop a hammer.  If you need to drive a screw, develop a screwdriver.  They may both be things that help you fasten objects together, but they're not similar enough to share a development path.

MCT will be designed for one purpose only, that is landing on Mars and returning from there, no compromise.

However landing on Mars and developing a capsule design for LEO crew transport are even more different tasks. Yet there is the Red Dragon concept.

I would be very surprised if MCT will not turn out to be able to do a moon landing and return as well as landing on Mars and return.

[docmordrid]

ISTM Mars and Moon landers share enough features that an omnivorous device is possible - especially if we shade towards using a Mars lander on the Moon.

It'll carry mass it doesn't need (TPS) and require deep throttling (and/or multiple engines with some shut down) but as a proof of capability test (as Musk put it) before taking the big leap, why not?

[guckyfan]

It'll carry mass it doesn't need (TPS) and require deep throttling (and/or multiple engines with some shut down) but as a proof of capability test (as Musk put it) before taking the big leap, why not?

It does need the TPS because it will reenter earth atmosphere. Deep throttle may be the biggest problem. Also without refuelling on the moon it would suffer a very severe payload drop. I thought of sending two vehicles. One tanker fully refuelled in LEO and the MCT. The tanker can refuel MCT after earth departure and return on a free or almost free return trajectory while a well fuelled MCT lands on the moon.

BTW it took me a few seconds to get your picture.

[docmordrid]

I was actually thinking of a stripped down TPS-less vehicle as an adapted  lunar lander, but yeah.

As for the hammer-driver, that's not the only kind. I was actually surprised at how many there are.

[AncientU]

IMHO lunar flybys are going to be about it with FH in near future. To make lunar landings viable they need fuel in Lunar orbit to supply landers, the possible options I see for this are ISRU from Asteriod or lunar ice both of which will require large infrastructure and years to develop.

Why is it that so many think you need ISRU to have fuel in orbit?  Load it on a reusable launcher (tanker upper stage) and stand back... presto, fuel in orbit.  And that didn't take "large infrastructure and years to develop."

Depots if and only if ISRU is logical and technical fallacy.

[Elmar Moelzer]

Why is it that so many think you need ISRU to have fuel in orbit?  Load it on a reusable launcher (tanker upper stage) and stand back... presto, fuel in orbit.  And that didn't take "large infrastructure and years to develop."
Depots if and only if ISRU is logical and technical fallacy.

Agreed, there are several studies featuring that concept.

[moralec]

I was actually thinking of a stripped down TPS-less vehicle as an adapted  lunar lander, but yeah.

As for the hammer-driver, that's not the only kind. I was actually surprised at how many there are.

I think it all comes down to cost. What is cheaper? to develop a new lander (huge cost in terms of development, but probably cheaper in operation) ? or to use a stripped down version of the existing capsule (the other way around)...

If the plan is to use it on an ongoing basis (like for turism), I think the idea of a new lander is better. However, if it just for a few times (preparing for mars) maybe is just better to use the existing capsule. 

[TrevorMonty]

IMHO lunar flybys are going to be about it with FH in near future. To make lunar landings viable they need fuel in Lunar orbit to supply landers, the possible options I see for this are ISRU from Asteriod or lunar ice both of which will require large infrastructure and years to develop.

Why is it that so many think you need ISRU to have fuel in orbit?  Load it on a reusable launcher (tanker upper stage) and stand back... presto, fuel in orbit.  And that didn't take "large infrastructure and years to develop."

Depots if and only if ISRU is logical and technical fallacy.

AncientU: If you are going to quote somebody's statement, make sure you include all the relative parts of the statement. Here is the 2nd paragraph of my statement which you forgot include. 

"The other near term option is SpaceX's BFR, if this can deliver around 50t to lunar orbit as a fully reusable LV then tourism to lunar surface may drop to tens instead of hundreds of millions per seat."

[ncb1397]

You're missing the whole point of Red Dragon, which is that it makes only minor modification to the existing Dragon.

Your Silver Dragon is so vastly different from Dragon that you get virtually no benefit from starting with Dragon at all.  You might as well start from scratch and design a Moon lander.

Alright, then call it a forerunner of MCT. Maybe it would be an antecedent of MCT before the heat shield and aerobraking are added on.

There has been a lot of discussion of this on other threads -- the requirements of a lunar lander/ascent vehicle are so vastly different from the requirements of a Mars lander/ascent vehicle that its counterproductive to try to combine them or use one to develop the other.

It's like trying to develop a combination screwdriver and hammer, or trying to develop a screwdriver that will lead to a hammer.  If you need to pound in a nail, develop a hammer.  If you need to drive a screw, develop a screwdriver.  They may both be things that help you fasten objects together, but they're not similar enough to share a development path.

Actually, this is not completely true. A Mars lander capable of launching from the surface again would have all the capability needed to land on and launch from the moon. Delta-V for Mars launch is 4.1 km/s. Delta v for moon landing + launch is 3.75 km/s. You only run into a problem if the Mars ascent engines don't throttle in aggregate low enough to safely land at lower lunar gravity. Mars would require refueling on the surface. Moon would require no such refueling. There is only significant deviation between a mars lander and a moon lander if there is no mars ascent capability. That being said, a moon lander wouldn't necessarily be good at landing on mars except perhaps high altitude locations, if it has extremely good delta-v to slow walk to the surface and reduce aerodynamic affects or if the moon lander happens to be strong enough to take the loads regardless. Of course, the heat shield would be dead weight and possibly the aerodynamic form as well, but you don't take off your breaks on your car to improve fuel economy if the trip is only uphill.

In venn-diagram form....



This is basically what Elon was alluding to when he said he could land MCT on the moon just to prove a point. This is also why all HSF development should be focused on Mars while Moon and asteroid capability is icing on the cake with no new spacecraft/launchers required. You build the mars hardware, and then you use asteroid and moon as proving grounds...the stepping stones.

[Nydoc]

Bonus: Detaching the hab in high-elliptical lunar orbit saves you a little dV.

Actually it saves a lot ov delta-V compared to LLO. Maybe enough to do it with a stock Dragon?

Never going to LLO saves a lot of delta V.  Getting to the Moon, inserting in a small burn, then sticking to a high elliptical orbit that lasts about four weeks, then transferring back to Earth in a small burn at just the right orbital phase (as you're going at close to escape velocity at periapsis, in the direction you would want to go to transfer, already), is what makes it delta V efficient.  BEAM itself is a pretty small/light hab - only 1.5 tons for 16 m^3 is what Bigelow is claiming.  Add another ton for a 4-way docking nexus and a small ion thruster or two for stationkeeping, , and you're up to 2.5 tons on top of the Dragon.  That's not a lot, compared to the mass of the Earth descent module (Dragon) and service module (trunk), because the Lunar periapsis burn to transfer back to Earth is in theory a small one.  What it would buy you if you left the hab in high lunar orbit is, if you run this mission again a year later, you can insert into the same trajectory, rendezvous, and get to use the same hab again, as part of a 2-BEAM station, and the next year, a 3-BEAM station.  If BEAM's mass is manageable but the volume is unfortunately low, using a bunch of them should quickly allow for a fairly comfortable station, relative to the alternative;  It doesn't require advanced aerocapture tech to be developed, it doesn't require a larger more comfortable, expensive inflatable to burn up every cruise, and it doesn't limit the cruise to a level of privacy and claustrophobia that most billionaires won't tolerate.

Concept, I dub thee 'Earthrise Lunar Cruise' and 'Earthrise Lunar Station'.

Here's a thought: put your 'Earthrise Lunar Station' in a Lunar Cycler Orbit so that it does a flyby of the Earth every 9 or 14 days. How much delta V would you need to dock with the station?

[QuantumG]

Here's a thought: put your 'Earthrise Lunar Station' in a Lunar Cycler Orbit so that it does a flyby of the Earth every 9 or 14 days. How much delta V would you need to dock with the station? Could crew launch be done with a F9?

Translunar injection is still required. Plus you now need rendezvous and docking delta-v. Plus you no longer can choose your launch window to control the lighting conditions at the lunar end. Plus... there's a lot of other trade-offs.

The advantage of a lunar cycler is that you get to build up a lot of mass which remains in that cycling orbit (and if you do it right, requires very little fuel to do so), but it's not free.

[Nydoc]

The advantage of a lunar cycler is that you get to build up a lot of mass which remains in that cycling orbit (and if you do it right, requires very little fuel to do so), but it's not free.

It seems like it would be an interesting orbit in which to put a Bigelow station. You could eventually add shielding and perhaps electric propulsion for station keeping. Might such a station have a longer life expectancy than ISS due to having less thermal cycling?

[Lar]

I found this article on cis lunar space craft after listening to Space Show about it.
Definitely not a near term thing but interesting concept.

http://denecs.usc.edu/hosted/ASTE/527_20111/03%20-%20The%20US%20Department%20of%20Space%20-%202011/J.1%20AIAA%20Space%202012.pdf

Love that idea. It seems plausible, but some attention to making the module interconnects more easily changeable would be needed. A different approach than MCT, for sure. I could see if it worked, that the ISS hosting a constrution project for one at all times so that as one finishes, another one would be started. Eventually ISS would itself have to be rebuilt but by then perhaps the module production lines were such that it could be done salvaging the truss?

But that is a bit off topic.

[hkultala]

IMHO lunar flybys are going to be about it with FH in near future. To make lunar landings viable they need fuel in Lunar orbit to supply landers, the possible options I see for this are ISRU from Asteriod or lunar ice both of which will require large infrastructure and years to develop.

Why is it that so many think you need ISRU to have fuel in orbit?  Load it on a reusable launcher (tanker upper stage) and stand back... presto, fuel in orbit.  And that didn't take "large infrastructure and years to develop."

Depots if and only if ISRU is logical and technical fallacy.

what fuel? what reusable upper stage?

I don't know any reusable tanker upstages exist. spacex is going to develop a reusable upper stage, but that's with much smaller tanks, the "payload part" is not reusable.

what fuel? if kerolox/methalox, how you keep the lliquid oxygen cool?

what about station keeping and orbits? the destination orbit may be quite different than the "easy orbit" for the tanker/depot, wasting a lot of delta-v.

I dont' see the point of complex in-space refuelling procedure when you could just use bigger launcher and have all the fuel on the spacecraft since the beginning of the operation.

[ChrisWilson68]

IMHO lunar flybys are going to be about it with FH in near future. To make lunar landings viable they need fuel in Lunar orbit to supply landers, the possible options I see for this are ISRU from Asteriod or lunar ice both of which will require large infrastructure and years to develop.

Why is it that so many think you need ISRU to have fuel in orbit?  Load it on a reusable launcher (tanker upper stage) and stand back... presto, fuel in orbit.  And that didn't take "large infrastructure and years to develop."

Depots if and only if ISRU is logical and technical fallacy.

what fuel? what reusable upper stage?

I don't know any reusable tanker upstages exist. spacex is going to develop a reusable upper stage, but that's with much smaller tanks, the "payload part" is not reusable.

The post you are replying to was in reply to a post advocating ISRU.  Obviously, we don't have depots and reusable stages today, but we don't have ISRU either.  The post was saying that compared to developing ISRU we could develop depots and reusable stages.

what fuel? if kerolox/methalox, how you keep the lliquid oxygen cool?

There are many studies on that, and many threads on this site discussing it too.

Have a look at the Wikipedia page for a basic introduction that discusses these points.

http://en.wikipedia.org/wiki/Propellant_depot

what about station keeping and orbits? the destination orbit may be quite different than the "easy orbit" for the tanker/depot, wasting a lot of delta-v.

I dont' see the point of complex in-space refuelling procedure when you could just use bigger launcher and have all the fuel on the spacecraft since the beginning of the operation.

The point is that depots have the potential to make it all much cheaper.  There are several reasons for that, including the fact that if you can refuel in space you can launch your in-space vehicle once and then leave it there and keep using it over and over, just bringing up new propellant.  It also sets the stage for eventual ISRU as a source of propellant.

[TrevorMonty]

Here's a thought: put your 'Earthrise Lunar Station' in a Lunar Cycler Orbit so that it does a flyby of the Earth every 9 or 14 days. How much delta V would you need to dock with the station?

Thanks for the info.
 I've never heard of Lunar Cycler Orbit before, interesting concept.

[TrevorMonty]

I've found some papers on web regarding Lunar Cyclers but still need some questions answered if anybody can help it would be appreciated.

Would it be possible to park the Cycler in HLO while doing a lunar mission. Once the mission is complete inject it back into a lunar cycler orbit. What would be the DV required?

[RanulfC]

Which would stop neither sound nor smells nor the inescapable fact that everyone will know what you're doing. People can be very squeamish about such things, especially in mixed-gender company.

One of my late 1960's college dorms was an early co-ed with a shared bathroom in each hall, each having several shower and toilet stalls. Quite interesting when someone joined the group on a weekend when it was empty, only to have  someone of the opposite gender pass the soap over the wall on Monday.

You get over it.

Just an FYI but YOU got over it, (I did too when faced with similar situations in the military ) "adventure" tourists would probably not have that much of an "issue" with it but the "tourists" in the money-class that seems to be the main "market" are  a bit different. Unless the "person" on the other side of that curtain is a close family member or friend the "etiquette" standards get different real quick.

How much of a "differance" it will make will greatly be effected by the "market's" point-of-view.

It's kind of hard for me to see someone saying, "Well, I'd really like to go to the Moon.  I'm even willing to pay $20 million to do it.  I'm willing to risk my life.  I'm willing to be in an uncomfortably small space for days.  I'm willing to throw up repeatedly from space sickness.  I'm willing to use zero-g toilets.  But have to put up with someone of the opposite sex using the toilet on the other side of curtain?  No, I won't put up with that. Cancel the trip."

You would be surprised actually. For the most part the "risk-of-life" issue is theoretical to the passenger at best. Usually they won't or don't believe it can "happen" to them at all. "Comfort" is another thing that comes down to the "user" and the situation. Specifically they may not feel "comfortable" about some stranger seeing them sick or having accidents in their diapers. (Which to be honest is a LOT more likely to be the "toilet" than an actual zero-g toilet for most uses) Your first half dozen "tourists" might not care and probably won't but you can't COUNT on that staying the standard because as you move deeping into your "market" the actual attitudes WILL change.

People will WANT more and wish to PAY less as time goes on. That means they will put up with fewer "difficulties" and demand higher and better "services" and it helps greatly to plan for that inevitable change BEFORE than to try and make major adaptions later

RAndy

[RanulfC]

Actually, this is not completely true.

No but it's one of those that for the most part is "close-enough" to use as a baseline assumption. Where it gets "fuzzy" is when your vehicle is directly designed to service one OR the other which is often the case

A Mars lander capable of launching from the surface again would have all the capability needed to land on and launch from the moon. Delta-V for Mars launch is 4.1 km/s. Delta v for moon landing + launch is 3.75 km/s. You only run into a problem if the Mars ascent engines don't throttle in aggregate low enough to safely land at lower lunar gravity.

Don't know if you noticed but you "changed" vehicles in mid-justification there A "Mars-lander" that is capable of launching from the surface of Mars such as suggested either is a "dedicated" Mars Ascent Vehicle or its a SINGLE-stage to the surface and back. Where you run into problems is NOT the engines but what gear and systems were used to land on Mars? If there was aerobraking and parachutes then those systems have to be replaced by propellant for the Moon. If NOT then you're going to have a lot of "spare" propellant on-board that is going to be "wasted" on a Moon mission. (Normally anyway, I'm sure we can all figure "uses" for the stuff once its there

If it is a "single-stage" all-up lander/ascent vehicle (as has been suggested for the MCT) then "changes" to accomodate a lunar mission are going to require some extensive work. (Or a lot of "wasted" capacity you don't need for the Moon)

If its "just" the ascent stage of the Mars lander then you need to design, build and test a seperate "Lunar" mission descent and lander stage or at least a Lunar lander "kit" to fit to the Mars ascent stage. Not impossible by any stretch but its going to cost and its going to be "different" than the Mars stage.

This is basically what Elon was alluding to when he said he could land MCT on the moon just to prove a point. This is also why all HSF development should be focused on Mars while Moon and asteroid capability is icing on the cake with no new spacecraft/launchers required. You build the mars hardware, and then you use asteroid and moon as proving grounds...the stepping stones.

That's not what I got from EM's statements. More that it "could" just to prove it could but it would not be well suited for doing so. Nor have I seen or heard anything that makes me think he's changed his position on Mars being THE goal (and only worthwhile one at that) and everything will be designed towards THAT end. I can hope I'm wrong but so far I haven't really seen anything...

The problem with making "Mars" the driver behind design for HSF is that a "dedicated" Mars vehicle and transport system (such as being discussed here for the MCT) has very little utility or ability to do transportation missions to other destinations such as the Moon or an asteroid without serious redesign or large "wasted" capacity per flight. So while MCT COULD land on the Moon to "prove-a-point" it won't be as capable of efficent as a vehicle DESIGNED to do so.

I would be happily surprised if the neccessary design comprimises are included in the design of the MCT to allow at least "semi" efficent use in either the Lunar or Mars transport roales but it WILL be a surprise given EM's statements so far if that is the case.

Randy

[docmordrid]

One of my late 1960's college dorms was an early co-ed with a shared bathroom in each hall, each having several shower and toilet stalls. Quite interesting when someone joined the group on a weekend when it was empty, only to have  someone of the opposite gender pass the soap over the wall on Monday.

You get over it.

Just an FYI but YOU got over it, (I did too when faced with similar situations in the military )

I meant "you" in the inclusive context, as in people can get used to it. Not "you" in the personal sense meaning, well, you.

[Burninate]

"doublequote"
"doublequote"
"doublequote"
"doublequote"

[RanulfC]

One of my late 1960's college dorms was an early co-ed with a shared bathroom in each hall, each having several shower and toilet stalls. Quite interesting when someone joined the group on a weekend when it was empty, only to have  someone of the opposite gender pass the soap over the wall on Monday.

You get over it.

Just an FYI but YOU got over it, (I did too when faced with similar situations in the military )

I meant "you" in the inclusive context, as in people can get used to it. Not "you" in the personal sense meaning, well, you.

Understood But I was making the point that some people do NOT "get-over-it" either because they don't want to or they don't feel they NEED to

"Those" people tend not to choose communal collage facilities or government service, but they DO tend to be some of the "higher" income folks whom such services as we're discussing would be aimed at

Randy

[RanulfC]

"doublequote"
"doublequote"
"doublequote"
"doublequote"

I never said it was "inconceivable" but that there were going to be "issues"

(BTW: in·con·ceiv·a·ble, adjective, 1. impossible to think about or imagine, 2. difficult to believe. so unlikely that it is difficult to believe.. )

Randy

[moralec]

Here's a thought: put your 'Earthrise Lunar Station' in a Lunar Cycler Orbit so that it does a flyby of the Earth every 9 or 14 days. How much delta V would you need to dock with the station?

Thanks for the info.
 I've never heard of Lunar Cycler Orbit before, interesting concept.

These type of orbits are super interesting. Actually, Buzz Aldrin in his book "Mission To Mars" talks about a vessel that stays permanently in space making a similar orbit that connects the earth to the moon. It also has clear advantages in the case of lunar transit, like the possibility of including a complex life support system (Sabatier reactor, anyone?) 

[JasonAW3]

The DragonFly EIS quotes a vehicle mass of 7 tonnes with an integrated trunk. Pick your thrust number and have at it.

Hmmm... Seems to me they may be trying to develope the MCT now.

[CuddlyRocket]

The problem with making "Mars" the driver behind design for HSF is that a "dedicated" Mars vehicle and transport system (such as being discussed here for the MCT) has very little utility or ability to do transportation missions to other destinations such as the Moon or an asteroid without serious redesign or large "wasted" capacity per flight. So while MCT COULD land on the Moon to "prove-a-point" it won't be as capable of efficent as a vehicle DESIGNED to do so.

Who cares? As long as it's not more expensive than any alternative (if there is one) and it can do the mission what's it matter if there's spare capacity or it's not optimally designed for that mission scenario?

SpaceX optimises for cost, not performance. A Mars-optimised vehicle and transport system that can also work for the Moon may well be cheaper doing so than a separate Moon-optimised one through economies of scale.

[RanulfC]

The problem with making "Mars" the driver behind design for HSF is that a "dedicated" Mars vehicle and transport system (such as being discussed here for the MCT) has very little utility or ability to do transportation missions to other destinations such as the Moon or an asteroid without serious redesign or large "wasted" capacity per flight. So while MCT COULD land on the Moon to "prove-a-point" it won't be as capable of efficent as a vehicle DESIGNED to do so.

Who cares? As long as it's not more expensive than any alternative (if there is one) and it can do the mission what's it matter if there's spare capacity or it's not optimally designed for that mission scenario?

"Who cares" is a good question actually If the MCT is designed as is being discussed in that specific thread then landing it on the Moon, while possible to "prove-a-point" (funny but no one has commented on how ominus that sounds rather than reassuring ) would only be a "stunt" and prove that it would NEVER be "less expensive" than an alternate. If it has to carry all the "gear" for the entire trip that it would normally carry and USE on Mars but has no use on the Lunar mission, there is going to have to be extra propellant carried to deal with a fully propulsive mission profile.

SpaceX optimises for cost, not performance. A Mars-optimised vehicle and transport system that can also work for the Moon may well be cheaper doing so than a separate Moon-optimised one through economies of scale.

Now of course there are ways to help make such an architecture work at least "well" for both (or more) destinations, but you are going to run into "costs" if the vehicle is heavily "optimized" for delivery costs to any specific destination. If one only "cares" for Mars as a destination and optimizes "costs" for that particualr destination then the "cost" of going anywhere else is going to be that much higher.

People have been "assuming" that MCT will be highly optimized towards Mars which would make it far less optimum for Lunar operations, in many cases to the point where it would not be cost effective to use to transport people/cargo anywhere BUT Mars

"I" care because I'd really like to see SpaceX (and EM) avoid the "obvious" conclusion that being a "mutli-planet" species means "Earth-and-Mars" when it could mean so much more so easily

Randy

[guckyfan]

Now of course there are ways to help make such an architecture work at least "well" for both (or more) destinations, but you are going to run into "costs" if the vehicle is heavily "optimized" for delivery costs to any specific destination. If one only "cares" for Mars as a destination and optimizes "costs" for that particualr destination then the "cost" of going anywhere else is going to be that much higher.

People have been "assuming" that MCT will be highly optimized towards Mars which would make it far less optimum for Lunar operations, in many cases to the point where it would not be cost effective to use to transport people/cargo anywhere BUT Mars

"I" care because I'd really like to see SpaceX (and EM) avoid the "obvious" conclusion that being a "mutli-planet" species means "Earth-and-Mars" when it could mean so much more so easily

Randy

It will be optimized for Mars. But again, who cares? Until the day at least when someone comes with a solution that is more cost effective for the moon. I don't see that happen any time soon.

Yes, propellant is a problem assuming ISRU on Mars and no ISRU on the moon. One way around that is launch two vehicles on a moon trajectory. One being a tanker. Transfer fuel from the tanker after TLI and let the tanker return on a free or nearly free return trajectory. More expensive than Mars maybe, but maybe not because the MCT will be back much sooner for reuse. But try to beat the per ton price to the moon with any other archictecture.

[RanulfC]

It will be optimized for Mars. But again, who cares? Until the day at least when someone comes with a solution that is more cost effective for the moon. I don't see that happen any time soon.

"Technically" it's already "happened" in that more efficent and effective Lunar transport systems have already been considered and designed Like just about every OTHER transport system destination in "space" the main issue has been and remains actually "proving" a market. I've also been pointing out that even "optimized" for Mars doesn't mean it can't be "effective" for the Moon as long as THAT is a consideration during the design process. As an "after-thought" its a serious liability...

I'll repeat what I've said before though; Nothing I've seen has made me think that EM is seriously considering Lunar or even Cis-Lunar "tourism" as part of SpaceX's business. He mentioned having an MCT land on the Moon to "prove-a-point" but that seems to be aimed at achieving a "stunt" not a precident for a business plan. I will admit that EM is giving the appearance of opening consideration for more in depth "infrastructure" but he's been pretty careful to avoid saying that SpaceX will specifically develop any of it.

At this point EM seems to have SpaceX set on course for providing for a "high-traffic" business model for LEO as the "near-term" goal. Following this he plans on moving to the methane powered Raptor engines and designs derived from that which will culminate in a BFR and/or MCT design built for going directly to Mars. Everything points to him leaving "development" of Cis-Lunar space to someone else, and if no one does then he will not care since it is not a factor in his planning.

Yes, propellant is a problem assuming ISRU on Mars and no ISRU on the moon. One way around that is launch two vehicles on a moon trajectory. One being a tanker. Transfer fuel from the tanker after TLI and let the tanker return on a free or nearly free return trajectory. More expensive than Mars maybe, but maybe not because the MCT will be back much sooner for reuse. But try to beat the per ton price to the moon with any other archictecture.

I got "dissed" in the MCT thread for suggesting the use of tankers as you recall I'd say rather than launching them together the Tanker will be launched and landed on the Moon first and refueling will take place there. Everything is much simpler that way. But in any case I don't see the MCT being "effective" in a Lunar mission role, not if it's "optimized" as much as has been discussed for Mars. I'm still hoping to be pleasntly surprised when actual details emerge

Randy

[sheltonjr]

I have developed a notional MCT to go to Mars that has the following characteristics that can be launched with  2 250 MT Fully reusable SpaceX BFRs. The first one is the MCT and the second one tops off the fuel.

13m diameter base, 15 Degree side walls, 20m tall (Big Dragon shaped capsule)
30 MT MCT Empty weight, 70 MT Cargo, 228 MT of Fuel (CH4/LOX), 700 m3 of cargo/crew/systems volume
It has 5.325 km/s delta velocity capability to Mars and 7.173 km/s back to Earth.

As a thought experiment for this thread I wondered if it would be capable for a Moon mission. The resulting capability was:

Reduce MCT empty weight to 28 MT (Which is just a wild guess anyway, Smaller Launch Engines)
14 MT Cargo to the Moon, and 2 MT returning to Earth.
1-? MT of the Cargo may be batteries/Fuel cell to survive the Lunar night if the mission is more than two weeks. These would stay on the Moon to reduce return mass.
It has 6.1 km/s delta velocity capability to the Moon and 2.8 km/s back to Earth.


Summary:
* Big loss of cargo capability due to no aerocapture and refueling capability on the Moon.
* Added battery/fuel cell system to last the Lunar night would be required.
* MCT Main engine would have to be reduced to a Super Draco equivalent. MCT Mars Launch engine would be too much thrust.

* Still, 14 MT to the Moon and 2 MT returning would be much better than anything done previously.
* 2/3 MCT and 1/3 cargo is not very efficient, but if everything is reusable it only cost fuel and reprocessing.
* 700 m3 of space for 14 MT of cargo. Lots of room for crew, supplies, scientific equipment and rovers.

* I think it would be worth the minor mods.

Apollo Lunar Module Stats:
6.7 m3 volume
4.2 MT Mass Dry, 14.7 MT Wet

Edit: formatting, clarity and added summary items.

[CuddlyRocket]

The problem with making "Mars" the driver behind design for HSF is that a "dedicated" Mars vehicle and transport system (such as being discussed here for the MCT) has very little utility or ability to do transportation missions to other destinations such as the Moon or an asteroid without serious redesign or large "wasted" capacity per flight. So while MCT COULD land on the Moon to "prove-a-point" it won't be as capable of efficent as a vehicle DESIGNED to do so.

Who cares? As long as it's not more expensive than any alternative (if there is one) and it can do the mission what's it matter if there's spare capacity or it's not optimally designed for that mission scenario?

"Who cares" is a good question actually If the MCT is designed as is being discussed in that specific thread then landing it on the Moon, while possible to "prove-a-point" (funny but no one has commented on how ominus that sounds rather than reassuring ) would only be a "stunt" and prove that it would NEVER be "less expensive" than an alternate. If it has to carry all the "gear" for the entire trip that it would normally carry and USE on Mars but has no use on the Lunar mission, there is going to have to be extra propellant carried to deal with a fully propulsive mission profile.

But propellant is dirt cheap (relatively speaking, in this context). It's less than $250,000 for a F9. You can get an awful lot of 'extra-propellant' missions for the costs of developing an entirely separate lunar vehicle and transport system.

SpaceX optimises for cost, not performance. A Mars-optimised vehicle and transport system that can also work for the Moon may well be cheaper doing so than a separate Moon-optimised one through economies of scale.

Now of course there are ways to help make such an architecture work at least "well" for both (or more) destinations, but you are going to run into "costs" if the vehicle is heavily "optimized" for delivery costs to any specific destination. If one only "cares" for Mars as a destination and optimizes "costs" for that particualr destination then the "cost" of going anywhere else is going to be that much higher.

People have been "assuming" that MCT will be highly optimized towards Mars which would make it far less optimum for Lunar operations, in many cases to the point where it would not be cost effective to use to transport people/cargo anywhere BUT Mars

Not necessarily. There are costs incurred (and savings foregone) in having two separate vehicles and transport systems. These may well outweigh the additional costs due to a sub-optimal design for a lunar mission; especially if your reusable MCT is sat around doing nothing in the 15-20 months between its return to Earth and the next Mars launch window!

The question as to whether it is more economical to have multiple vehicle types optimised for various routes or a single one that is therefore sub-optimal for some routes is well understood in the airline industry; and the conclusion is that it is often the latter that is more profitable. And the difference usually comes down to the amortisation of fixed costs. In fact, it could well be more profitable overall for SpaceX to use the MCT to run lunar missions at a loss!

"I" care because I'd really like to see SpaceX (and EM) avoid the "obvious" conclusion that being a "mutli-planet" species means "Earth-and-Mars" when it could mean so much more so easily

Randy

I don't think SpaceX or Elon have drawn that conclusion. But they may well have drawn the conclusion that a Mars-optimised transport system is overall the most cost efficient way to go!

[JohnFornaro]

Mars is dry, but the Moon is drier, and that matters.  Mars has little atmosphere, but the Moon has far less, and that matters.  Methane can be produced fairly easily on Mars.  Try that on the Moon.  Mars also has more gravity.  We don't really know the long-term health effects of either Mars' or the Moon's gravity, but Mars gravity is closer to Earth's, so it may well be that Mars is significantly better for your health.  Mars has a day-night cycle similar to Earth's.  The Moon doesn't, and it is hard to bake in the direct sun for two weeks, then shiver through a two-week night.

I don't think any of those issues matter in the near term, since proximity rules. 

From the department of clinical interest, while you point out that Mars' gravity is twice that of the Moon's, remember that many Mars first advocates argue that landing in the Moon's gravity well is a major showstopper.  Go figger.

In the near term, lunar flybys sound like quite the adventure for well heeled tourists.  Still, they're not going to want to orbit the Moon for four weeks; spend a couple of days up there, conceive, and then come home.

The moon is closer from a travel time, and communication perspective but it's not that much closer from a deltaV perspective, as upthread analysis shows.

The deltav argument fails because it is not the pertinant human statistic; time is.

Going to the moon and back is harder delta-v wise if there is fuel ISRU on Mars and not on Luna.

That difference cannot be granted until the lunar ice craters have been assayed and lunar prop ISRU disproven. 

If there is sufficient water ice on Luna, then the prop factory cannot be unilaterally granted to Mars, but not Luna.

... the requirements of a lunar lander/ascent vehicle are so vastly different from the requirements of a Mars lander/ascent vehicle that its counterproductive to try to combine them or use one to develop the other.

It's like trying to develop a combination screwdriver and hammer, or trying to develop a screwdriver that will lead to a hammer. ...

The two landers are different.  But your analogy fails, in that a lunar lander is more like a VW bug, and the martian lander more like a Tesla.  There is a conceptual path evolving from the more primitive one to the more advanced one.

Possibly another analogy would be a quarter inch drill compared with a one inch magnetic drill.

[guckyfan]

Going to the moon and back is harder delta-v wise if there is fuel ISRU on Mars and not on Luna.

That difference cannot be granted until the lunar ice craters have been assayed and lunar prop ISRU disproven. 

If there is sufficient water ice on Luna, then the prop factory cannot be unilaterally granted to Mars, but not Luna.

I disagree. Assuming there is water on the moon is a fair assumption. But getting it from those cold traps is hard and requires very advanced technology. Then processing it to fuel and get it where it would be needed for launch is not easy again. Two weeks sun and then two weeks night is very harsh on a station or settlement also.

On Mars water is at the places we would want to go anyway.

So the proof is on those who want to go to the moon.

[RanulfC]

But propellant is dirt cheap (relatively speaking, in this context). It's less than $250,000 for a F9. You can get an awful lot of 'extra-propellant' missions for the costs of developing an entirely separate lunar vehicle and transport system.

"Depends" really because we don't KNOW what MCT is going to be like, it's mission mode, design, etc. Propellant is "realtivly" cheap, but not if it ends up "costing" you somewhere else.

Not necessarily. There are costs incurred (and savings foregone) in having two separate vehicles and transport systems. These may well outweigh the additional costs due to a sub-optimal design for a lunar mission; especially if your reusable MCT is sat around doing nothing in the 15-20 months between its return to Earth and the next Mars launch window!

True, but then again WHY is your MCT sitting around in the first place "Down-time" is the bane of any transportation system and I'm sorry if I've given the impression that I somehow don't SEE the logic of using a "sub-optimal" system IF you've got it, but MY point was and remains that "supposing" using MCT for Lunar missions somehow assumes MCT's facing "sitting-around" somewhere instead of doing their "job" which is flying to Mars. Couple it with the fact that any "optimized" transport system is going to eat the lunch of a sub-optimum system and I really don't see MCT managing a Lunar role UNLESS, (key point since the begining) its not soley dedicated to Mars as has been discussed

The question as to whether it is more economical to have multiple vehicle types optimised for various routes or a single one that is therefore sub-optimal for some routes is well understood in the airline industry; and the conclusion is that it is often the latter that is more profitable. And the difference usually comes down to the amortisation of fixed costs. In fact, it could well be more profitable overall for SpaceX to use the MCT to run lunar missions at a loss!

I hope you weren't expecting me to disagree here I fully understand the line of reasoning, however, (to continue the analogy hopefully not far enough to shatter ) the main reason why airlines don't run 747s on "feeder" air-routes is far to much "capacity" than is needed. By the same token though airlines have been really wanting to increase the range and avialability of smaller airliners to longer routes but have never found the "incentive" to take that as far as specialty built aircraft or "non-standard" operations. (Till I looked at the subject I never really KNEW just how far the airlines had taken the idea of adapting air-to-air refueling but they have actually spent serious time and money into checking the feasabilty of making it a 'routine' airline operation

If SpaceX has MCT's "sitting-around" for months on end then, yes it would make sense to use them for things like Lunar runs. So far I've not seen anything like that much "time" between runs mentioned, in which case taking an MCT out of service to run to Luna doesn't make enough sense to justify

"I" care because I'd really like to see SpaceX (and EM) avoid the "obvious" conclusion that being a "mutli-planet" species means "Earth-and-Mars" when it could mean so much more so easily

I don't think SpaceX or Elon have drawn that conclusion. But they may well have drawn the conclusion that a Mars-optimised transport system is overall the most cost efficient way to go!

I don't think they have either, (but you can't tell that from the "speculation" thread and I don't DISAGREE that a "Mars" optimised system might be the way to go for a general "Interplanetary" transport system. But I also know that it is very often easier to "tweek" a general system for an optimum solution than to try and tweek an optimum solution to a general situation.

Randy

[oldAtlas_Eguy]

Going to the moon and back is harder delta-v wise if there is fuel ISRU on Mars and not on Luna.

That difference cannot be granted until the lunar ice craters have been assayed and lunar prop ISRU disproven. 

If there is sufficient water ice on Luna, then the prop factory cannot be unilaterally granted to Mars, but not Luna.

I disagree. Assuming there is water on the moon is a fair assumption. But getting it from those cold traps is hard and requires very advanced technology. Then processing it to fuel and get it where it would be needed for launch is not easy again. Two weeks sun and then two weeks night is very harsh on a station or settlement also.

On Mars water is at the places we would want to go anyway.

So the proof is on those who want to go to the moon.

Right next to these cold traps on the moon are continuous sunlight peaks for 24/365 operations support.

[RanulfC]

Going to the moon and back is harder delta-v wise if there is fuel ISRU on Mars and not on Luna.

That difference cannot be granted until the lunar ice craters have been assayed and lunar prop ISRU disproven. 

If there is sufficient water ice on Luna, then the prop factory cannot be unilaterally granted to Mars, but not Luna.

As John says and I'll point out the fact that LUNAR ISRU was proposed and studied long before Mars ISRU so there's no way to make a case of one having and the other not having local resources!

I disagree. Assuming there is water on the moon is a fair assumption. But getting it from those cold traps is hard and requires very advanced technology. Then processing it to fuel and get it where it would be needed for launch is not easy again. Two weeks sun and then two weeks night is very harsh on a station or settlement also.

On Mars water is at the places we would want to go anyway.

So the proof is on those who want to go to the moon.

Far, oh so far from the case I'm afraid. You can "disagree" all you want but you should keep in mind that "water" isn't the only possible source of ISRU and never has been. The "fact" that water on Mars is probably more prevelant doesn't negate the fact that the Moon has had extensive and indepth study done on how to and what local resources are available.

Mars, despite the best efforts of some does not get any "freebies" as a destination simply because some "wish" it were so. It has advantages, yes, so does the Moon and the biggest remains proximity which despite all the rhetoric to the contrary is STILL a major factor.

Even more so since this thread is "SpaceX and CIS-LUNAR Space Tourism" lets back off the versus fight and get back on track shall we?

Randy

[JohnFornaro]

Going to the moon and back is harder delta-v wise if there is fuel ISRU on Mars and not on Luna.

That difference cannot be granted until the lunar ice craters have been assayed and lunar prop ISRU disproven. 

If there is sufficient water ice on Luna, then the prop factory cannot be unilaterally granted to Mars, but not Luna.

I disagree. Assuming there is water on the moon is a fair assumption. But getting it from those cold traps is hard and requires very advanced technology. Then processing it to fuel and get it where it would be needed for launch is not easy again. Two weeks sun and then two weeks night is very harsh on a station or settlement also.

On Mars water is at the places we would want to go anyway.

So the proof is on those who want to go to the moon.

That the "proof is on those who want to go to the Moon", is certainly true, if your several assumptions are correct:

Assuming there is water on Mars is a fair assumption. Getting that water is easy and does not require very advanced technology. Then processing it to fuel and get it where it would be needed for launch is very easy again. Twelve hours of weak sun and then twelve hours of a very cold night is not at all harsh on a station or settlement.

Are your assumptions as easy as you must be asserting?

[guckyfan]

That the "proof is on those who want to go to the Moon", is certainly true, if your several assumptions are correct:

Assuming there is water on Mars is a fair assumption. Getting that water is easy and does not require very advanced technology. Then processing it to fuel and get it where it would be needed for launch is very easy again. Twelve hours of weak sun and then twelve hours of a very cold night is not at all harsh on a station or settlement.

Are your assumptions as easy as you must be asserting?

Yes certainly.

That weak sunlight near the equator is about as much as Germany gets on average, probably more because of long time of clouds. When a Mars rover can find visible amounts of ice by scratching the surface it cannot be too hard to collect. The methods of transforming water and CO2 to methane and LOX  are very easy, basic chemistry. The amount of energy needed is a lot in total but not that much assuming a two year window for production.

Actually I see one major problem in getting the fuel from the production site a few hundred meters or a km to the launch vehicle while on the moon the distance would be a lot larger, hundreds of km if not more. I don't see a station right beside those cold spots. But that last assumption may be wrong.

[RanulfC]

That the "proof is on those who want to go to the Moon", is certainly true, if your several assumptions are correct:

Assuming there is water on Mars is a fair assumption. Getting that water is easy and does not require very advanced technology. Then processing it to fuel and get it where it would be needed for launch is very easy again. Twelve hours of weak sun and then twelve hours of a very cold night is not at all harsh on a station or settlement.

Are your assumptions as easy as you must be asserting?

Yes certainly.

That weak sunlight near the equator is about as much as Germany gets on average, probably more because of long time of clouds. When a Mars rover can find visible amounts of ice by scratching the surface it cannot be too hard to collect. The methods of transforming water and CO2 to methane and LOX  are very easy, basic chemistry. The amount of energy needed is a lot in total but not that much assuming a two year window for production.

Actually I see one major problem in getting the fuel from the production site a few hundred meters or a km to the launch vehicle while on the moon the distance would be a lot larger, hundreds of km if not more. I don't see a station right beside those cold spots. But that last assumption may be wrong.

Getting into OT-ISRU issues here but...
JF:"Are your assumptions as easy as you must be asserting?
GF:"Yes certainly."

No, certainly Again, your "assuming" from a false basis that "water" is the key to any ISRU... Energy is actually the key and by "giving" yourself a two-year production "window" on Mars your ignoring the fact that much more can be done with a two-WEEK production window on the Moon. The "cold-traps" at the Lunar poles are a "nice-to-have" but they were never the basis of Lunar ISRU planning or study and you're ignoring past work in order to concentrate on a singular NEW Lunar development rather than the full situation.

Don't make assumptions you can't support to support your point

Randy

[guckyfan]

Getting into OT-ISRU issues here but...
JF:"Are your assumptions as easy as you must be asserting?
GF:"Yes certainly."

No, certainly Again, your "assuming" from a false basis that "water" is the key to any ISRU... Energy is actually the key and by "giving" yourself a two-year production "window" on Mars your ignoring the fact that much more can be done with a two-WEEK production window on the Moon. The "cold-traps" at the Lunar poles are a "nice-to-have" but they were never the basis of Lunar ISRU planning or study and you're ignoring past work in order to concentrate on a singular NEW Lunar development rather than the full situation.

Don't make assumptions you can't support to support your point

Randy

So you assume extracting water from regolith? That's really going into exotic engineering. I am not following you there. And as you are right this is OT on this thread so let us stop.

[RanulfC]

That the "proof is on those who want to go to the Moon", is certainly true...

Just an FYI John but this isn't true and never has been, the "burden-of-proof" has always been on the one making the assertion of "truth" not only to provide proof of the statement but also to provide and/or discuss the basis for assumptions involved

As I pointed out to GF, the "assumption" that Lunar ISRU is predicated on water being available is a RECENT development and as never the actual basis for Lunar ISRU research. Nice-to-have, but not the basis so by using that as the "base" assumption for a "Mars-vs-Moon" argument its up to GF, not the Lunar advocates to provide "proof" of his argument. First he has to rule out all the previous work done on non-water based Lunar ISRU which I believe would be difficult for him to say the least to do

ISRU has always been about using "local" resources to most extent possible and just because Zubrin happened to have an "epiphany" to apply it to Mars doesn't mean much OTHER than how it was applied to Mars. The Moon was planned ISRU territory long before Bob got ahold of the idea and no matter how he and others try to spin it, his "success" at getting folks to listen to the IDEA of Mars ISRU is directly based on peopl pushing LUNAR ISRU for years prior to him rather than it being a "brillant" idea in and of itself

Randy

[RanulfC]

So you assume extracting water from regolith? That's really going into exotic engineering. I am not following you there. And as you are right this is OT on this thread so let us stop.

You're going to throw THAT argument out and then call for stopping??!!??

Let me say it this way: Why do you "assume" that water is REQUIRED for ISRU of ANY type? Lunar propellant ISRU dates from the mid-70s and ASSUMED that no significant water was available from the regolith to work with. Depending on what propellant you wanted to make (start off by NOT assuming that Meth/LOx or LH2/LOX are a "requirement" no matter what RZ says determines your level of engineering needed. None of the studies saw a need for "exotic" engineering though some were a lot more difficult that others.
(Getting actual "water" from normal lunar regolith is actually EASY you just have to process a lot of it to get amounts equal to ice-mining. Water and Oxygen were always outputs of regolith processing)

If, as we're assuming given its a SpaceX thread, that the transport system will use Meth/LOX propulsion then the ISRU issue becomes less about producing ISRU Methane than producing ISRU LOX which was always a Lunar ISRU "staple" for production. Methane is brought in with the transport as part of the payload and ISRU LOX loaded on. Any traffic model has in-place storage building up rapidly from the start, especially if some seed-stock is brought in early and local energy and resources used to jump start production. (The same situaton as proposed on Mars actually)

The main point everyone needs to understand is that there is NO place in space where ISRU is "impossible" to do. Everyplace HAS resources that CAN be used it's just that not all places have the EXACT same resources in the same concentrations so ISRU has to be "adjusted" to fit each place. Different resources may take different methods to extract and it may take more or less of a process TO extract but it can be done.

Randy

[guckyfan]

So you assume extracting water from regolith? That's really going into exotic engineering. I am not following you there. And as you are right this is OT on this thread so let us stop.

You're going to throw THAT argument out and then call for stopping??!!??

Let us look for a proper thread. Not here.

Edt: Actually no. I responded too early. I am not willig to argue on the basis of your assumptions.

[MP99]

I have developed a notional MCT to go to Mars that has the following characteristics that can be launched with  2 250 MT Fully reusable SpaceX BFRs. The first one is the MCT and the second one tops off the fuel.

13m diameter base, 15 Degree side walls, 20m tall (Big Dragon shaped capsule)
30 MT MCT Empty weight, 70 MT Cargo, 228 MT of Fuel (CH4/LOX), 700 m3 of cargo/crew/systems volume
It has 5.325 km/s delta velocity capability to Mars and 7.173 km/s back to Earth.

As a thought experiment for this thread I wondered if it would be capable for a Moon mission.

After fuelling in LEO, MCT with 70 mT cargo can get itself to EML-2 (<4 km/s?), with substantial residuals .

IIRC, the round-trip EML2-surface-EML2, is in the ballpark of your 5.3 km/s capability, so after refuelling MCT can land its 70 mT on the surface then lift something close to that back to EML2 without refuelling on the surface. I'd suggest landing at beginning of Lunar night, and taking off not much after dawn in order not to boiloff the propellants.

* MCT Main engine would have to be reduced to a Super Draco equivalent. MCT Mars Launch engine would be too much thrust.

MCT landing on the Moon is heavier than MCT landing on Mars (also carries ascent prop), so you can use the same propulsion without T:W issues.

More interestingly, the EML2-surface-TEI dV isn't much more than EML2-surface-EML2, so substantial payload could go back to Earth's surface if you assume no propulsion required for Earth reentry.

Methalox is storable at EML2 - basically same boiloff control technology that will be required for a Mars mission, given quite similar thermal environments. Also, given that trip times for the prop to EML don't matter much (it's the same methalox-is-storable environment), this can get from LEO to EML via a slow-boat trajectory for ~3.2 km/s plus a three-month transit time.



This trades multiple MCT launches (prop delivery to EML) against Mars needing an ISRU plant to enable return, so it could be available sooner without waiting for that tech development. While it's capable of the same 70 mT "biggest smallest" chunks that you have for building the Mars infrastructure, you can trade lower cost by taking on less prop at EML (less tanker flights).

Recovering those tanker stages could be fun, though!

cheers, Martin

[guckyfan]

After fuelling in LEO, MCT with 70 mT cargo can get itself to EML-2 (<4 km/s?), with substantial residuals .

IIRC, the round-trip EML2-surface-EML2, is in the ballpark of your 5.3 km/s capability, so after refuelling MCT can land its 70 mT on the surface then lift something close to that back to EML2 without refuelling on the surface. I'd suggest landing at beginning of Lunar night, and taking off not much after dawn in order not to boiloff the propellants.

..............

MCT landing on the Moon is heavier than MCT landing on Mars (also carries ascent prop), so you can use the same propulsion without T:W issues.

................

Recovering those tanker stages could be fun, though!

cheers, Martin

EML-2 might be an interesting staging point for reusable moonlanders flying between lunar surface and EML-2.

MCT goes back to earth. No point in going through EML-2. My idea about refuelling is send one MCT and one tanker through TLI, refuel MCT in flight and let the tanker RTLS after looping around the moon with very little or no delta-v after TLI except for the landing burn, which is very small.

[sheltonjr]

After fuelling in LEO, MCT with 70 mT cargo can get itself to EML-2 (<4 km/s?), with substantial residuals .

IIRC, the round-trip EML2-surface-EML2, is in the ballpark of your 5.3 km/s capability, so after refuelling MCT can land its 70 mT on the surface then lift something close to that back to EML2 without refuelling on the surface. I'd suggest landing at beginning of Lunar night, and taking off not much after dawn in order not to boiloff the propellants.

..............

MCT landing on the Moon is heavier than MCT landing on Mars (also carries ascent prop), so you can use the same propulsion without T:W issues.

................

Recovering those tanker stages could be fun, though!

cheers, Martin

EML-2 might be an interesting staging point for reusable moonlanders flying between lunar surface and EML-2.

MCT goes back to earth. No point in going through EML-2. My idea about refuelling is send one MCT and one tanker through TLI, refuel MCT in flight and let the tanker RTLS after looping around the moon with very little or no delta-v after TLI except for the landing burn, which is very small.

Yeah, A lot of interesting permutation are possible. I think what I showed was the simplest possible worst case option with refueling only in LEO.  (Actually a High Eccentric Earth orbit).

Analyzing this further is fruitless in my opinion being a largely fictitious though theoretically feasible vehicle if I have the MCT empty mass anywhere close. 

Thanks for reading and responding to my post.

[RanulfC]

Let us look for a proper thread. Not here.

Not sure there CAN be one really, what we're essentially argueing is the question of ISRU viability

Edt: Actually no. I responded too early. I am not willing to argue on the basis of your assumptions.

Saw that coming actually, then again "I" am not willing to let the idea that Mars is the only possible place to do ISRU go un-challenged

Randy

[meekGee]

I say this as the one who started the thread, and who is on the "Mars side" of the ISRU argument.

The words in the title add up to a description of what this thread is about.  There is no "Mars" in "SpaceX and cis-lunar Space Tourism"

Randy - see you on the Mars HSF thread, we can slug it out there.

[TrevorMonty]

There is some demand out there for a lunar flyby mission. Space Adventures Soyuz mission is all go.

 http://spaceflightnow.com/news/n1406/15lunarsoyuz/#.U59XkGf7Jgg

[Vultur]

There is some demand out there for a lunar flyby mission. Space Adventures Soyuz mission is all go.

 http://spaceflightnow.com/news/n1406/15lunarsoyuz/#.U59XkGf7Jgg

Wow. If that really happens it would be incredible.

[meekGee]

There is some demand out there for a lunar flyby mission. Space Adventures Soyuz mission is all go.

 http://spaceflightnow.com/news/n1406/15lunarsoyuz/#.U59XkGf7Jgg

In terms of value-per-$, I think that's the ultimate deal.

Much rather have a destination-based trip, with all sorts of views of Earth and moon, then spend a week in "Space Hotel".  Adventure all the way.

[RanulfC]

I say this as the one who started the thread, and who is on the "Mars side" of the ISRU argument.

The words in the title add up to a description of what this thread is about.  There is no "Mars" in "SpaceX and cis-lunar Space Tourism"

Randy - see you on the Mars HSF thread, we can slug it out there.

Trust me I TRIED to avoid this but... Well the MCT was mentioned and of course part of the "name" there is "Mars," so while not in the title it WAS part of the "subject"

Running now... very fast...

Randy

[MP99]

After fuelling in LEO, MCT with 70 mT cargo can get itself to EML-2 (<4 km/s?), with substantial residuals .

IIRC, the round-trip EML2-surface-EML2, is in the ballpark of your 5.3 km/s capability, so after refuelling MCT can land its 70 mT on the surface then lift something close to that back to EML2 without refuelling on the surface. I'd suggest landing at beginning of Lunar night, and taking off not much after dawn in order not to boiloff the propellants.

..............

MCT landing on the Moon is heavier than MCT landing on Mars (also carries ascent prop), so you can use the same propulsion without T:W issues.

................

Recovering those tanker stages could be fun, though!

cheers, Martin

EML-2 might be an interesting staging point for reusable moonlanders flying between lunar surface and EML-2.

MCT goes back to earth. No point in going through EML-2. My idea about refuelling is send one MCT and one tanker through TLI, refuel MCT in flight and let the tanker RTLS after looping around the moon with very little or no delta-v after TLI except for the landing burn, which is very small.

I note that you left out my comment:-

More interestingly, the EML2-surface-TEI dV isn't much more than EML2-surface-EML2, so substantial payload could go back to Earth's surface if you assume no propulsion required for Earth reentry.

...so I came to same conclusion as you re the return journey. (The direct return makes this much easier than having to make plane changes to rendezvous with an orbiting return capsule in LLO.)

However, I don't think it's as easy to dismiss the detour via EML-2 on the outbound journey.

Your architecture requires two launches - lander & tanker.

The slow-boat trajectory can get an almost identical tanker prop payload to EML-2 as your TLI, as long as you can wait three months for delivery. But if the lander is carrying a smaller payload, it may only need to take on part of the tanker's prop load, so you may need less tanker flights, overall.

And, IIRC, the dV penalty to land is much smaller once you target non-equatorial landing sites.

Also, MCT would have daily launch opportunities to EML-2, and no time constraints on the EML-2 to landing site leg, vs monthly launch windows if going direct to LLO.



Also, I believe EML-2 is a good accumulation point for tankers in support of a convoy of MCTs bound for Mars. They can be launched in the quiet times between conjunction / opposition windows and loiter at EML until ready, fuelling either Moon or Mars missions as needed.

cheers, Martin

[AncientU]

Also, MCT would have daily launch opportunities to EML-2, and no time constraints on the EML-2 to landing site leg, vs monthly launch windows if going direct to LLO.

Also, I believe EML-2 is a good accumulation point for tankers in support of a convoy of MCTs bound for Mars. They can be launched in the quiet times between conjunction / opposition windows and loiter at EML until ready, fuelling either Moon or Mars missions as needed.

cheers, Martin

Q.E.D. ==> Gateway!

Edit: added quote for clarity

[TrevorMonty]

If SpaceX have any hope of a tourist business,  their launches need to be a lot more reliable. How many scrubs as space tourist would you put up with?

[QuantumG]

If SpaceX have any hope of a tourist business,

They don't. This thread has nothing to do with SpaceX's hopes.

[Dave G]

How many scrubs as space tourist would you put up with?

Many.

I think the word "tourist" may not be fitting.  Think of the people who pay $100,000 to climb Mount Everest.  They know the journey will be arduous.  They know they may die.   That's part of the lure.

Space "tourists" may not experience as much difficulty as climbing Everest, but I think there is a general  expectation of thorough training, cramped quarters, very limited amenities, and possible death.

When space tourism becomes easy, safe, and routine, then much of the excitement will be gone.  It will be like a commercial airline.  But that's a long way off.

[meekGee]

How many scrubs as space tourist would you put up with?

Many.

I think the word "tourist" may not be fitting.  Think of the people who pay $100,000 to climb Mount Everest.  They know the journey will be arduous.  They know they may die.   That's part of the lure.

Space "tourists" may not experience as much difficulty as climbing Everest, but I think there is a general  expectation of thorough training, cramped quarters, very limited amenities, and possible death.

When space tourism becomes easy, safe, and routine, then much of the excitement will be gone.  It will be like a commercial airline.  But that's a long way off.

Obligatory mandatory late evening quote:

[TrevorMonty]

Just watched documentary on moon landings. All astronauts said how fragile earth looked from space and how they never it for granted now.

 This had me thinking how important space tourism could be in affecting terrestrial affairs. Any body who can afford a space flight especially orbital will have a lot money and most likely political  influence. It would be interesting to see what they do with that money and power after going to space.

[oldAtlas_Eguy]

How many scrubs as space tourist would you put up with?

Many.

I think the word "tourist" may not be fitting.  Think of the people who pay $100,000 to climb Mount Everest.  They know the journey will be arduous.  They know they may die.   That's part of the lure.

Space "tourists" may not experience as much difficulty as climbing Everest, but I think there is a general  expectation of thorough training, cramped quarters, very limited amenities, and possible death.

When space tourism becomes easy, safe, and routine, then much of the excitement will be gone.  It will be like a commercial airline.  But that's a long way off.

At first the ride up and back is part of the experience of Space "Travel".  Eventually when it becomes routine, like intercontenental air travel, the ride up and down will just be a method of getting there and the focus of the "tourist" will be what they will do at the destination.  Like space walks, zero g sports/activities, and walking on the moon.

[Oli]

If SpaceX have any hope of a tourist business,

They don't. This thread has nothing to do with SpaceX's hopes.

Without tourists they won't be able to fly Dragon v2 "thousand of times".

How many scrubs as space tourist would you put up with?

Many.

I think the word "tourist" may not be fitting.  Think of the people who pay $100,000 to climb Mount Everest.  They know the journey will be arduous.  They know they may die.   That's part of the lure.

Actually the word tourist is very fitting, Everest has become a tourist destination, with very little risk involved (if you pay).

[wannamoonbase]

How many scrubs as space tourist would you put up with?

Many.

I think the word "tourist" may not be fitting.  Think of the people who pay $100,000 to climb Mount Everest.  They know the journey will be arduous.  They know they may die.   That's part of the lure.

Space "tourists" may not experience as much difficulty as climbing Everest, but I think there is a general  expectation of thorough training, cramped quarters, very limited amenities, and possible death.

When space tourism becomes easy, safe, and routine, then much of the excitement will be gone.  It will be like a commercial airline.  But that's a long way off.

If I was shelling out $100,000,000 to go to the moon I'd want more of an experience than being treated like a piece of cargo.  Like going to a great restaurant or flying first class it's an experience, not just a meal or flight.  i think the service side with the training, handling, education, access to unusual places and scenes is important.

I think it's much more likely to come from a US provider than any other country.  But I hope to see Lunar flyby tourism in the 5-10 year window.