Quote from: MATTBLAK on 05/01/2017 07:08 amThe traditional Mars Direct by Robert Zubrin and David Baker had Direct vehicles of about 45 tons being sent on Trans-Mars Injection. This is about what the SLS Block II with 'Dark Knights' solid boosters could achieve with an Exploration Upper Stage. If the corestage was redesigned for 5x RS-25E and the EUS had slightly higher thrust engines, this could raise the Direct Vehicle's masses to about 50 tons.We probably need to have a new thread about Mars Direct redesigned for alternate launch vehicles such as New Glenn, Vulcan/ACES and Falcon Heavy
The traditional Mars Direct by Robert Zubrin and David Baker had Direct vehicles of about 45 tons being sent on Trans-Mars Injection. This is about what the SLS Block II with 'Dark Knights' solid boosters could achieve with an Exploration Upper Stage. If the corestage was redesigned for 5x RS-25E and the EUS had slightly higher thrust engines, this could raise the Direct Vehicle's masses to about 50 tons.We probably need to have a new thread about Mars Direct redesigned for alternate launch vehicles such as New Glenn, Vulcan/ACES and Falcon Heavy
around the 3 minute mark, he says that if you can refuel a vehicle in orbit it's a very valuable thing to do.
This is where I take exception with the commonly held concept that cargo and humans have to be landed together in one big ship and thus also where I take exception with Elon.If you've got a very heavy vehicle then yes, Mars atmosphere is a pita and a fully propulsive landing is very expensive fuel wise. And that's precisely where you're at if you insist on landing people on the same vehicle as cargo.However, if you separate cargo from people then the numbers work out a lot differently. You can land cargo exactly how Elon proposes. In fact without people on board there are optimisations you can perform because you have the freedom to pull even higher gs. Likewise, people don't weigh much and its not that costly to land them fully propulsively. Another point worth repeating is that you'd like a fast transit to Mars. That means more fuel. And if you're taking cargo on the same flight then that's even more fuel that you didn't need to use, which could be used to better advantage in other ways.Again, where people go wrong is the almost universally held notion that it all has to come down to Mars surface in a single vehicle.
Quote from: Russel on 10/06/2017 09:43 amThis is where I take exception with the commonly held concept that cargo and humans have to be landed together in one big ship and thus also where I take exception with Elon.If you've got a very heavy vehicle then yes, Mars atmosphere is a pita and a fully propulsive landing is very expensive fuel wise. And that's precisely where you're at if you insist on landing people on the same vehicle as cargo.However, if you separate cargo from people then the numbers work out a lot differently. You can land cargo exactly how Elon proposes. In fact without people on board there are optimisations you can perform because you have the freedom to pull even higher gs. Likewise, people don't weigh much and its not that costly to land them fully propulsively. Another point worth repeating is that you'd like a fast transit to Mars. That means more fuel. And if you're taking cargo on the same flight then that's even more fuel that you didn't need to use, which could be used to better advantage in other ways.Again, where people go wrong is the almost universally held notion that it all has to come down to Mars surface in a single vehicle.There is no way to land on Mars (or the Moon) besides than propulsive landing. You can get rid of hypersonic retropropulsion, but you can't get rid of propulsive landing.
This is where I take exception with the commonly held concept that cargo and humans have to be landed together in one big ship and thus also where I take exception with Elon.
Quote from: Russel on 10/06/2017 09:43 amThis is where I take exception with the commonly held concept that cargo and humans have to be landed together in one big ship and thus also where I take exception with Elon.Who says cargo will have to be landed together with people? I am sure there will be an unmanned, cargo only BFR spaceship variant as well as a manned one. But there is no point in designing entirely different vehicles for cargo and for crew, that would be a waste of resources, IMHO. In the end humans are just an especially fragile type of cargo anyway..
There is one thing you cannot escape with Elon's architecture4 to 6 gs on Mars entry for passengers.
Quote from: Russel on 10/06/2017 10:13 pmThere is one thing you cannot escape with Elon's architecture4 to 6 gs on Mars entry for passengers.What way of landing do you propose that would have reduced G forces that differ significantly from that?
Initially I began a thread in the SpaceX department inquiring about applying the ITS booster toward the original Mars Direct effect vehicles. MATTBLAK quoted: QuoteQuote from: MATTBLAK on 05/01/2017 07:08 amThe traditional Mars Direct by Robert Zubrin and David Baker had Direct vehicles of about 45 tons being sent on Trans-Mars Injection. This is about what the SLS Block II with 'Dark Knights' solid boosters could achieve with an Exploration Upper Stage. If the corestage was redesigned for 5x RS-25E and the EUS had slightly higher thrust engines, this could raise the Direct Vehicle's masses to about 50 tons.We probably need to have a new thread about Mars Direct redesigned for alternate launch vehicles such as New Glenn, Vulcan/ACES and Falcon HeavyWhen Baker and Zubrin conceived Mars Direct back in the 1990s there was only the space shuttle and, at best, the Titan rockets available with no signs of commercial rocketry beyond the ULA monopoly or perpetually-stalled-pie-in-the-sky plans within NASA. 20 years later now, we miraculously have a new world opening up despite the end of the space shuttle. There may quickly be a huge range of options Mars Direct launchers to utilize for a plan created when there essentially were none.The thread rules are the following:1) Assume we wish to land 20+ metric ton vehicles onto the Martian surface with as minimal an architecture as possible - i.e. at least 2 but not more than 4 vehicles and launchers per expedition to Mars2) Debate any launch vehicle from any company so long as it has the ability to throw over 20 metric tons to Mars3) Focus discussion on launch vehicles that are active as of 2010 onward; we are trying to update Mars Direct's options4) Discuss the ITS booster as a launcher but NOT the ITS spaceship as one; the spaceship isn't a launch vehicle by itself applicable to Mars
I wonder could an ACES or F9 upper stage lift both a Dragon V2 and a BA-330 or DOS module for use as the ERV habitat off the surface of Mars?As this would be within the landed payload of a cargo BFS.It just needs to reach Mars orbit as a departure stage can have been left in LMO ahead of time.
If you're leaving a return stage in LMO, why not leave the ERV hab there also? I don't think there's any way to keep a ACES full of LH2 fueled long enough for a Mars return. Boiloff is going to catch up with it eventually.
Quote from: envy887 on 10/19/2017 02:53 amIf you're leaving a return stage in LMO, why not leave the ERV hab there also? I don't think there's any way to keep a ACES full of LH2 fueled long enough for a Mars return. Boiloff is going to catch up with it eventually.Yah the hab could be left in LMO if it's not being used on Mars such as a separate BFS being used for the surface hab I was mostly thinking about getting everything on one BFR.I'm also not sure if ACES would have enough thrust to weight it depends on the version and what engine is used but hydrogen boil off was one reason I figure the F9 US might be a better choice for an ascent stage.The kerosene probably can sit inside it for the entire mission and lox can come from residual propellants in BFS or the Merlin can be switched to a derated Raptor or a cluster of Chase-10s and all the propellants can come for BFS.If the BFS solar arrays could be removed and deployed on the ground they might be able to power enough ISRU for a small MAV just enough to lift a Dragon into LMO.
I believe that the reailities of (very) large scale fuel manufacture on Mars means that any kind of direct return from Mars will come after earlier missions that don't depend on industrial scale mining. But its still worth contemplating.So have you guys considered a scaled version of Elon's vehicles? Perhaps with the ability to land methane but with indigenous oxygen?
One of the things that grates on me about Musk's vision (apart from the absurdity of the whole idea of a colony) is the idea of sending civilians into space for several months of zero g and then subjecting them to 4 to 6 gs on Mars entry. I think we can and should do better than that.
I can't comment on the absurdity of a colony because its off topic. But I can say that 5 tonnes per colonist is hopelessly unrealistic.What I will say that is on topic is that 6gs is a lot of force on a civilian plucked at random. What makes it worse is months of bone loss in zero g.Its not a case of grinning and bearing. Its a case of being stretchered out.
Years ago when I was a lot younger and fitter I pulled 6.5 g in a jet fighter for about 20 seconds. Not being a dedicated pilot, I was wrecked for a good 24 hours afterwards. A barely trained person enduring those g's for 5+ minutes during EDL is going to suffer for days.
What makes it worse is months of bone loss in zero g.Its not a case of grinning and bearing. Its a case of being stretchered out.
To my eye, Elon's first couple of flights to Mars look very much like Mars Direct. Zubrin's ideas did not have a hope to be funded. It is not clear how Elon's Mars ambitions will be fully funded, but he does have both enormous financial and technical clout. It is plausable to think that either private investors, philanthropists, and/or the government will step up and contribute the rest of money to make a Mars effort a reality.
https://en.wikipedia.org/wiki/High-G_trainingThe human body is considerably more able to survive g-forces that are perpendicular to the spine....Early experiments showed that untrained humans were able to tolerate 17 g eyeballs-in (compared to 12 g eyeballs-out) for several minutes without loss of consciousness or apparent long-term harm.
Quote from: MickQ on 11/30/2017 11:40 pmYears ago when I was a lot younger and fitter I pulled 6.5 g in a jet fighter for about 20 seconds. Not being a dedicated pilot, I was wrecked for a good 24 hours afterwards. A barely trained person enduring those g's for 5+ minutes during EDL is going to suffer for days.What actually were the issues. Was it all the blood forced into your legs? Lack of blood to the brain?If someone was flat in a properly supporting bed, wouldn't it be pretty similar to the pressure of being under 6 feet of water?https://en.wikipedia.org/wiki/High-G_trainingVertical quote: This seems to be talking about vertical acceleration, as you would experience in a roller coaster or jet doing a turn:The g thresholds at which these effects occur depend on the training, age and fitness of the individual. An untrained individual not used to the g-straining maneuver can black out between 4 and 6 g, particularly if this is pulled suddenly. Roller coasters typically do not expose the occupants to much more than about 3 gHorizontal quote: This seems to be talking about flat on your back.The human body is considerably more able to survive g-forces that are perpendicular to the spine....Early experiments showed that untrained humans were able to tolerate 17 g eyeballs-in (compared to 12 g eyeballs-out) for several minutes without loss of consciousness or apparent long-term harm.[3]
Quote from: Russel on 11/30/2017 02:32 amI can't comment on the absurdity of a colony because its off topic. But I can say that 5 tonnes per colonist is hopelessly unrealistic.What I will say that is on topic is that 6gs is a lot of force on a civilian plucked at random. What makes it worse is months of bone loss in zero g.Its not a case of grinning and bearing. Its a case of being stretchered out.Years ago when I was a lot younger and fitter I pulled 6.5 g in a jet fighter for about 20 seconds. Not being a dedicated pilot, I was wrecked for a good 24 hours afterwards. A barely trained person enduring those g's for 5+ minutes during EDL is going to suffer for days.
Kelvin that's still for healthy people who haven't lost bone density in zero g.
Quote from: Russel on 12/04/2017 02:40 pmKelvin that's still for healthy people who haven't lost bone density in zero g.My understanding is that for colonists, the trip time has to be only 3 months in order to reuse the BFS each synod.We have a lot of experience with that timeframe, including reentry afterwards. A lot of medical science has been done to model the effects, and predict the effects of exercise (or lack of)It also isn't happening tomorrow. There will be experience with small crews to Mars. Probably there will be experience with moon bases. Maybe colonists will need some sort of regimen. Personally I think anyone choosing to go to mars should first spend a year in a simulated Mars base on earth. It is not something to do on a whim like buying an airline ticket. This could also help prevent disease outbreaks in flight, and help with developing mars base technology.The big unknown at the moment seems to be long term bone health in moon and mars gravity. Maybe even a single synod in Mars gravity will be debilitating. As far as I know, that could still be a show stopper. Im not claiming to be an expert though. Perhaps science can already make a very good guess. We will know before it progresses to 100 colonist trips though.
I believe we already know a full year in uG on the ISS is not a showstopper. I have no reason to think the 1/3rd G of Mars would be. Potentially worthwhile sending up a well chained chimp and returning them first.Or a volunteer.
Quote from: tdperk on 12/05/2017 12:43 amI believe we already know a full year in uG on the ISS is not a showstopper. I have no reason to think the 1/3rd G of Mars would be. Potentially worthwhile sending up a well chained chimp and returning them first.Or a volunteer.I think there is time to work it out too. Supposing Mars does turn out to be a failure, eaten by space goat or something, we could just choose another direction like asteroid colonies and space habitats with full 1g spin gravity. I personally expect significant LEO space tourism before mars, if Elon really achieves the "747 of space" that the plan hinges on. BFS carrying 100 colonists probably doesn't happen until at least 3 or 4 synods and a lot of experience in cislunar space could happen before that, if this thing is flying regularly.