SpaceX and cis-lunar Space Tourism

[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.