DBowman Posted June 3, 2020 Share Posted June 3, 2020 Re the Dynetics lander: This seems to say FHCore and F9e put the upper stage at 2.5 km/s horizontal (ignore vertical and payload for now). I guess the max velocity is reuse reentry limited. Anyway it's about 11.5 km/s from there to lunar surface or 8,930 to Gateway. Ignore that the to LEO burn will be lossy for now. (5.3 to LEO, 3.2 to TLI, either( 430 to Gateway or ( 1.1 for LOI, 1.9 to surface))) A 111,500 kg methalox stage would land 5 ton of dry mass, or send 10 ton to Gateway. Could one eliminate the upper stage altogether by having Dynetics lander components be the upper stage engines and add some more drop tanks for the circularization and TLI. (ignore geometry for now). Have one F9e + engine quad fly the can and structure and another fly prop to Gateway and assemble it there. Upper stage makes sense for Sats, but the lander is supposed to do sizable dV with reusable engines of reasonable thrust (though it may well not have enough to circularize...) why waste 4 ton dry mass holding lower isp prop? Quote Link to comment Share on other sites More sharing options...
StrandedonEarth Posted June 8, 2020 Share Posted June 8, 2020 Quote Link to comment Share on other sites More sharing options...
cubinator Posted June 8, 2020 Share Posted June 8, 2020 44 minutes ago, StrandedonEarth said: Oh, I am totally sending my bugs there! Quote Link to comment Share on other sites More sharing options...
Nightside Posted June 8, 2020 Author Share Posted June 8, 2020 49 minutes ago, StrandedonEarth said: Where on the moon are those astronauts? North pole? Quote Link to comment Share on other sites More sharing options...
cubinator Posted June 8, 2020 Share Posted June 8, 2020 (edited) 1 minute ago, Nightside said: Where on the moon are those astronauts? North pole? South pole. NASA wants to use water ice that's been found there. Edited June 8, 2020 by cubinator Quote Link to comment Share on other sites More sharing options...
Nightside Posted June 8, 2020 Author Share Posted June 8, 2020 7 minutes ago, cubinator said: South pole. NASA wants to use water ice that's been found there. Ok, I can't see enough definition on the earth to see which way it is oriented. Is it really that sunny there? Quote Link to comment Share on other sites More sharing options...
RCgothic Posted June 8, 2020 Share Posted June 8, 2020 I love being able to post Elon in the Artemis thread. Also SpaceX will kill it with cost per kg. Quote Link to comment Share on other sites More sharing options...
cubinator Posted June 8, 2020 Share Posted June 8, 2020 27 minutes ago, Nightside said: Ok, I can't see enough definition on the earth to see which way it is oriented. Is it really that sunny there? Probably not! Looong shadows... Quote Link to comment Share on other sites More sharing options...
tater Posted June 8, 2020 Share Posted June 8, 2020 1 hour ago, Nightside said: Is it really that sunny there? That's actually a feature of the desired landing locations. They are crater rims that are illuminated almost 100% of the time. The crater bottoms are in perpetual shadow (hence water ice), the rims are in near perpetual sunlight. https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20170007365.pdf http://lroc.sese.asu.edu/posts/271 Quote Link to comment Share on other sites More sharing options...
cubinator Posted June 8, 2020 Share Posted June 8, 2020 Oh wow, I didn't know it was going to be right on the south pole. I hope no astronauts accidentally step on the spike there! Quote Link to comment Share on other sites More sharing options...
mikegarrison Posted June 8, 2020 Share Posted June 8, 2020 54 minutes ago, cubinator said: Oh wow, I didn't know it was going to be right on the south pole. I hope no astronauts accidentally step on the spike there! They expect there is water there because it can be permanently shaded. But it has to be right on the pole to have a chance of that. Quote Link to comment Share on other sites More sharing options...
tater Posted June 9, 2020 Share Posted June 9, 2020 1 hour ago, mikegarrison said: They expect there is water there because it can be permanently shaded. But it has to be right on the pole to have a chance of that. It's a function of distance to the pole and crater depth (and surrounding mountain height, I guess). The water areas are non-trivial to reach, too, so they land on the edge, then... maybe send a robot down? Rappel? (that would be fun on the Moon) Quote Link to comment Share on other sites More sharing options...
kerbiloid Posted June 9, 2020 Share Posted June 9, 2020 Spoiler 7 hours ago, cubinator said: Oh wow, I didn't know it was going to be right on the south pole. I hope no astronauts accidentally step on the spike there! There also can be a Moonhole. 10 hours ago, cubinator said: NASA wants to use water ice that's been found there. Because they need ice for cola. 10 hours ago, Nightside said: Is it really that sunny there? Only on the top, where they'll put deck chairs. And the ice is in the pit with walls. Cooling the bottles of Polar-Cola. They prefer South pole because they know that North is cold, while South is hot. So, they need just sunglasses instead of furcoats. *** Main cupola. Quote Link to comment Share on other sites More sharing options...
RealKerbal3x Posted June 9, 2020 Share Posted June 9, 2020 8 hours ago, cubinator said: Oh wow, I didn't know it was going to be right on the south pole. I hope no astronauts accidentally step on the spike there! It could also be a really deep hole... Quote Link to comment Share on other sites More sharing options...
tater Posted June 10, 2020 Share Posted June 10, 2020 Quote Link to comment Share on other sites More sharing options...
tater Posted June 11, 2020 Share Posted June 11, 2020 Quote Link to comment Share on other sites More sharing options...
tater Posted June 12, 2020 Share Posted June 12, 2020 Quote Link to comment Share on other sites More sharing options...
RCgothic Posted June 22, 2020 Share Posted June 22, 2020 Hah Quote Link to comment Share on other sites More sharing options...
kerbiloid Posted June 23, 2020 Share Posted June 23, 2020 The key word is "to". Spoiler Quote Link to comment Share on other sites More sharing options...
sevenperforce Posted June 23, 2020 Share Posted June 23, 2020 10 hours ago, kerbiloid said: The key word is "to". Hide contents I would like to see the numbers on getting Dragon 2 + a hypergolic service module to LLO and back. I have a feeling it is either at or beyond the limits of FH. Quote Link to comment Share on other sites More sharing options...
wumpus Posted June 23, 2020 Share Posted June 23, 2020 2 hours ago, sevenperforce said: I would like to see the numbers on getting Dragon 2 + a hypergolic service module to LLO and back. I have a feeling it is either at or beyond the limits of FH. Pretty sure Falcon Heavy + Dragon 2 can make it around the Moon (not stopping to orbit) and back. Dragon has ~400 m/s delta-v and the minimum for a lunar lander is >3000m/s (I'm pretty sure Dragon 2 doesn't have that). I don't think there's much a service module can provide, except perhaps enough delta-v for lunar orbit (>1200m/s). Granted, once you orbit the Moon, docking with other gear you'll need to land becomes possible (FH's flyby mode doesn't help at all). Anybody have RSS/RO loaded and a good falcon heavy model? Jiggle the parts around and what adding another stage will do... Quote Link to comment Share on other sites More sharing options...
RCgothic Posted June 23, 2020 Share Posted June 23, 2020 With a large proportion of its payload given over to extended hypergolic tanks in the trunk Dragon can push over 1200m/s with its Draco thrusters. Quote Link to comment Share on other sites More sharing options...
sevenperforce Posted June 23, 2020 Share Posted June 23, 2020 29 minutes ago, wumpus said: Pretty sure Falcon Heavy + Dragon 2 can make it around the Moon (not stopping to orbit) and back. Dragon has ~400 m/s delta-v and the minimum for a lunar lander is >3000m/s (I'm pretty sure Dragon 2 doesn't have that). I don't think there's much a service module can provide, except perhaps enough delta-v for lunar orbit (>1200m/s). Granted, once you orbit the Moon, docking with other gear you'll need to land becomes possible (FH's flyby mode doesn't help at all). Anybody have RSS/RO loaded and a good falcon heavy model? Jiggle the parts around and what adding another stage will do... Falcon Heavy can send Dragon 2 on a circumlunar free-return with side core recovery, no problem. Expended, Falcon Heavy can push around 21-22 tonnes onto TLI. Dragon 2 is 9-10 tonnes with a full prop load and carries up to 6 tonnes of payload, but that must include the crew and whatever they are bringing along. 5 minutes ago, RCgothic said: With a large proportion of its payload given over to extended hypergolic tanks in the trunk Dragon can push over 1200m/s with its Draco thrusters. The Dracos aren't plumbed to pull from tanks in the trunk. SpaceX would need to build a drop-in service module which fits inside the trunk and has its own thrusters. With a six-tonne drop-in service module in the trunk, in addition to about 3 tonnes of crew and supplies, the total TLI throw would come to 19 tonnes, well within FHe's limitations. You need 900 m/s to get into low lunar orbit from TLI and 900 m/s more to get back to Earth. Let's say that Dragon 2's onboard propellant reserves are going to be utilized for pointing, docking, rendezvous, and the like. With the Dracos coming in at 300 s of specific impulse, you'd need nine tonnes of propellant to do that, which is a non-starter. If you can cut internal mass to 2 tonnes and you zero out the internal propellant then you cut internal propellant consumption to 7 tonnes, which is still not going to work. If you can jettison the service module after using it (somewhere around halfway through the Earth return burn, which is really a bad idea), and your service module has a propellant fraction of 10:1 (which is probably overly generous), then you get 1049 m/s out of the service module and you have 365 m/s left internally, which only gets you to 1400 m/s -- not enough to get home. Finally, if you say that FHe can push a full 22 tonnes to TLI, and you forget about the structural limitations of Dragon 2's trunk, and you say that the service module has a propellant fraction of 12:1, then you end up with a 10-tonne service module which has 1585 m/s of dV, which combined with internals is just barely enough for the round trip, but without sufficient margins for rendezvous, docking, and so forth. So yeah, Zubrin is full of it. Quote Link to comment Share on other sites More sharing options...
RCgothic Posted June 23, 2020 Share Posted June 23, 2020 (edited) Falcon Heavy isn't crew rated, which means Moon!Dragon is going up on Falcon9, limiting it to 15.8te max (reusable, although 15.8te is the heaviest monolithic payload we've ever seen F9 launch). The article suggested four SpaceX launches total, so let's see if we can make that work. Falcon Heavy semi-expendable can put 90% of 63.8te in LEO. That's 57.4te (of which 4.5t is F9US, conservatively counted as payload to LEO). Plus 15.8te Moon!Dragon is 73.2te. To push that through TLI takes about 50t of propellant which leaves 7.5te payload on the FH launch. (27.5te to TLI) The Falcon Heavy launch payload is a drop tank with an APAS adaptor to mate to Moon!Dragon. 6.5te propellant with 0.3te APAS and 90% propellant fraction. 23.3wet, 16.8drop tank exhaustion, 960m/s enough for LOI and lunar manoeuvres. Meanwhile Moon!Dragon's drop in service module needs 3t of propellant in addition to Dragon's onboard supply. That leaves 3t for crew, extended life support, comms, and rear APAS. 15.8te wet, 11.5te dry, 935m/s. This could be limited by how much load a F9US can support, which is unknown. Edited June 23, 2020 by RCgothic Quote Link to comment Share on other sites More sharing options...
wumpus Posted June 23, 2020 Share Posted June 23, 2020 1 hour ago, RCgothic said: Falcon Heavy isn't crew rated, which means Moon!Dragon is going up on Falcon9, limiting it to 15.8te max (reusable, although 15.8te is the heaviest monolithic payload we've ever seen F9 launch). Pretty sure they sold Yusaku Maezawa a ticket on the Falcon Heavy before dropping the crew paperwork. So presumably it is possible, although it would probably put a dent in the schedule (unless you still need SLS. Starship should be ready before SLS). Apollo LEM was ~18tons, meaning that it probably can't be fitted with something to circularize once it makes it to LTI (assuming fired from FH). Also I doubt anyone is going to achieve modern safety levels in 18 tons or less, every gram was sweated there. Quote Link to comment Share on other sites More sharing options...
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