Boeing's plan for Mars

kbd512 · 2015-02-01 12:44:47

Terraformer wrote:

Wut? If I have a budget of $2000 to spend, and something comes up that will cost me $500, I don't care if someone else spent $2000 on getting it to that point that it costs me $500; I'm only interested in whether it fits in my budget. If something else comes up that will cost me $2000 for the same capability, then I'm not going to choose that just because it's $2k vs. $2.5k; I'm interested in what it costs *me*.

If the government actually operated in that manner, then this notion of "what it costs me today" would carry water. If we take any technology and only look at "what it cost us today", we'll find that it didn't just cost the $500 we're spending today. We didn't magically get to "today" without the money spent in the "past". It's a false basis for comparison for what something actually costs.

If we spent $10B in the previous five years on a technology and only spend $1 every year thereafter to use a technology, then the technology doesn't magically cost $1 to use unless we also magically get our $10B back.

Terraformer wrote:

Sure, I'd like to see a nuclear rocket developed, but at the moment and for the foreseeable future it's politically infeasible. The government won't develop it, the public won't support it, and private companies wouldn't be allowed to develop it even if they want to. So any plan relying on nuclear rockets to work is doomed to failure.

Development of nuclear technology is infeasible because people have convinced themselves it's infeasible. To a person, every single one that complains about what it costs will cheerfully ignore what all other technologies cost to develop and then proclaim it's too expensive. To a person, every single one brings up the specter of death from nuclear radiation, ignores the lethal nuclear radiation that our own star emits, and proclaim that it's too dangerous.

I attribute this behavior to a complete lack of understanding of radiation and an inability to cope with potential dangers like a rational adult. Nuclear technology is one of the favorite, and fanciful, boogeymen that environmentalists like to use to inhibit progress towards their stated goal of "green" energy, whatever that is, and reduction of our carbon footprint.

The e-tards whine about how burning coal destroys the environment, but when we already have a technology that doesn't dump billions of tonnes of CO2 into the environment every year, they completely ignore it and propose construction of solar and wind power plants that only operate in certain conditions, require heavy industry to manufacture components for that also dumps many more tonnes of CO2 into the environment, and naturally the plants costs more money per kW/h than competing technologies. Burning coal dumps more radiation into the environment than nuclear power plants in normal operations.

kbd512 · 2015-02-01 12:57:16

SpaceNut wrote:

kbd512 and Impaler it looks like to me that the disagree to agree comes back to the engine for Nuclear vs Solar if power levels and mass are comperable for each source but not of funding or maturity of readiness.
That said can we get back to the Beoing plan details as to what does not make the grade....please.
From first post:
So whats wrong here?

Certainly:

- These vehicles require a SLS launch of their own because they're so massive and those launches cost more than a STS launch
- Burns that reduce the trip time to 6 months dramatically lower the Isp of the supposedly more efficient electric thrusters
- There is no comparison whatsoever between what a kilo of enriched Uranium yields in energy output and a solar panel that operates at theoretical maximum efficiency; no amount of efficiency improvement is going to make solar technology more efficient than fission or fusion
- The drag produced by these enormous solar panel arrays would bring a SEP tug down in days if we do assembly in LEO or require burning propellant to maintain orbit
- Massive increases in surface area increase the risk of the vehicle being struck by space debris, both in LEO and in transit
- No alternative means we're stuck with a technology that doesn't operate efficiently in places beyond Venus or Mars

kbd512 · 2015-02-01 13:57:11

Let's add to that list:

- No artificial gravity can be provided for the crew. 18 months worth of transit time with no artificial gravity if the higher efficiency, lower thrust burns are used. Is this a deal breaker? No.
- The actual tug that Boeing proposes masses 130t. SLS won't throw 130t into LEO without the addition of advanced boosters and a 5th SSME (if the Dynetics liquid boosters that won't fit on the MLS aren't utilized), requiring a complete redesign of the SLS launch vehicle. This is a deal breaker. You either design something that uses 1 SLS launch at it's actual maximum payload capacity that can provide propulsion to Mars and back or don't bother designing it at all.
- The quoted solar panel efficiency is at 1AU. Mars is not 1AU from the sun, thus the massive transfer vehicle.
- Uses Orion, which requires an additional SLS for a gumdrop that can't land anywhere but a terrestrial ocean.

As I've stated before, I have no problem with this technology being utilized for non-human cargo. It only matters that it gets there and if it doesn't, nobody died because we'll have contingency planning in effect to deal with the loss of cargo.

Side Show Bob is quite correct. We're going to try any number of rope tricks because they're conceivably possible, but we're going to ignore the most obvious way of getting from LEO to LMO, which would be direct from LEO to LMO.

RobertDyck · 2015-02-01 14:41:27

SpaceNut wrote:

So whats wrong here?

- too many launches
- transit too slow: 7 or 8 months, instead of 6
- living space on Mars too small
- constructing a station at Earth-Moon-L2
- Deimos and/or Phobos precursor missions
- does not use ISPP
- propulsive capture, not aerocapture

Mars Direct requires 2 launches per mission. The first mission includes the ERV for the second mission, then each mission is a hab plus the ERV for the next one. Since the following ERV can be used as backup, the last mission would require an ERV as well. So to be blunt, Mars Direct requires 3 SLS launches for the first mission, plus 2 for each mission thereafter.

The video said 5 or 6 SLS launches, but the PowerPoint lists 5. That is 2 SLS Block 2 for a cargo lander, then 2 more SLS Block 2 for the crew vehicle, then one SLS Block 1 for Orion. That's a lot more launches.

Transit from Earth to Mars and back will have TransHab, but while on the surface they only have a cab about the size of the Apollo Lunar Module. About twice the size to accomodate 4 crew, but space per crew member is the same. This is the same cab that Boeing came up with for an Asteroid mission.

The "Gateway" will be a new station built at Earth-Moon-L2 (EML2). That will not be in perpetual shaddow; Earth-Sun-L2 is, but Earth-Moon-L2 is always on the opposite side of the Earth than the Moon. We don't need another space station, we already have ISS. Building another is just a waste of money. And EML2 is so high that only SLS could reach it. Although I believe Dragon launched on Falcon Heavy could also reach it. From Boeing's perspective, this reduces competition. Not good for NASA/Congress/Taxpayers. But perhaps the biggest problem is EML2 is outside the magnetosphere. That means 3 to 4 times the radiation that ISS gets. Interplanetary radiation was measured by Mars Odyssey and Curiosity; Odyssey at solar minimum, Curiosity at solar maximum.

Deimos and Phobos do not have an atmosphere for radiation shielding, or micrometeoroid shielding. And gravity is so slight that the human body will still have full microgravity effects. And Mars atmosphere can be used for Entry/Descent/Landing. Deimos and Phobos require fully propulsive landing. And no CO2 atmosphere for ISPP. So they're harder than Mars.

This mission does not use ISPP at all, so maximum propellant from Earth for maximum expense. They try to mitigate that with solar/electric, but not good enough. And they use propulsive orbital capture, not aerocapture. This is why it requires 5 launches instead of 2.

SpaceNut · 2015-02-01 18:26:01

So with the pork spelled out then can we look at how we could change the pieces... first gateway is a distraction and has not value for mars.

Boeings Mission profile is 254 days out with a 454 day stay on surface with a return to home of 204 days giving the entire mission 936 which means there is a 28 day window built in....

Here is the Tradable parameters:

• Crew size (3,4,5,6)
• Cost of the mission
• Cost to repeat the mission
• International participation
• Timing of the mission
• Mode of transportation
• Propulsion technology
• Aerobraking technology
• Duration of surface stay
• Surface landing site
• Surface mobility
• Quantity and quality of science
• Quantity of sample returns
• In-situ propellant production
• Radiation protection

Crew size does effect ship mass but increases risk to crew in some situation.

Repeat cost is only reduced by mission element removal or reusability.

Internation cooperation does not garrantee success or cost control...

Mode of transportation I guess is pending orbital assembly and cargo seperation from crew as well as different vehicles for crw travel in both legs of the mission via different vehicle.

Surface landing site does change insitu useage but thats only when designed into the profile.

Surface mobility is a cargo mass as its not part of survival of crew and it is part of sample quality as a provision to greater exploration.

Radiation protection on the cheap or not at all is bad for publicity of the after effects to the crew as it would stop all progress towards colonization.

Here are a few items that I would look at to start.

One thing is to look at changes needed in Dragon V2 and CST-100 for terrestrial ocean return as this gives a big change to price and mass to start.

Also do we feel that the transhab or bigelow inflateable is worth the reduction in mass versus a real transport home for both legs of the journey due to time duration that we might be struck by micrometeor impact...especially with ion drive times.

As noted no insitu use for refuel of return from surface vehicle (mav) makes for a very heavy descent vehicle which is already problematic if doubling as the surface habitat even when we do use the refuelling on the surface from an InSitu refueling plant.

kbd512 · 2015-02-01 22:49:08

The problem is not the reliability of our launch vehicles or our ability to assemble mission components in orbit. The crushing cost of Orion and SLS does not leave budget for anything else. If NASA is actually serious about going to Mars, something has to go. I would kill the Orion program and focus funding on Dragon.

The breaks:

- With ATK's Dark Knight boosters SLS will peak between 110t and 120t, absent enormously expensive or impractical design changes, that's the maximum capability that we obtain from a 4-SSME/2-5SSRM SLS configuration with evolutionary hardware development

Q: What is the timeline for Dark Knight dev and restart of RS-25D production?

- A SEP tug that comes in at 110t or less has to push an equally heavy cargo to Mars

Q: How much would a SEP tug weigh that just takes the cargo to Mars?

- Orion can't land anywhere but an ocean on Earth

Q: Is there any way to kill this program gracefully that retains the teams and refocuses their work on Dragon development?

- Orion's service module design was so compromised by mass reduction that it's useless for the purpose for which it was originally intended

Q: Can ESA have their team create a methalox descent/ascent engine for Red Dragon, or is this beyond their capability?

- Every single one of these goofy development programs is a total hack job from start to finish and there's no reason to believe that the design of the service module will be completed on time, that SLS will fly with Orion on schedule, or that there will be funding for a manned Orion joy ride around the moon

Q: If there's no money to actually do ARM, can we stop funding it now?

- We need heavy lift to go to Mars, but we don't need an expensive and heavy capsule that can't land on Mars

Things to figure out:

Will NASA connect the dots and determine that it can't simultaneously pay for SLS, Orion, multiple commercial crew providers and still have money left for manned space exploration?

What is the state of development of Red Dragon?

What's the best way to accelerate Red Dragon by directing funding towards development of a methalox engine for propulsive descent/ascent?

Can Boeing kill CST-100 and direct funding towards SEP tugs without massive layoffs?

Can Boeing and Lockheed collaborate on Orion development to keep both Orion and SLS and retain the Boeing people who work on development of manned spacecraft to supply crew/cargo for government/military?

RobertDyck · 2015-02-01 23:56:54

kbd512 wrote:

- With ATK's Dark Knight boosters SLS will peak between 110t and 120t, absent enormously expensive or impractical design changes, that's the maximum capability that we obtain from a 4-SSME/2-5SSRM SLS configuration with evolutionary hardware development

True, the version that can lift 130t was to have 5 SSME, and a pair of "advanced boosters", and a full size upper stage with 2 J-2X engines and same tank diameter as the core module. Isn't that "Dark Knight"? What would be the lift capacity be for 5-SSME/2-5SSRM/2-J2X?

kbd512 wrote:

Can Boeing kill CST-100 and direct funding towards SEP tugs without massive layoffs?

Orion is not the same as CST-100. Orion has 16.5 feet diameter capsule, CST-100 is 15.0 feet. Orion can carry 6 crew to ISS, CST-100 can carry 7 (ironic). Orion has total launch mass including LAS, ATV-based SM, and fairing of 28.0 metric tonnes; CST-100 is 10t. Orion uses a launch abort rocket like Apollo, CST-100 uses its SM main engines for abort. Orion has an exhaust shield around the capsule to protect from LAS exhaust, CST-100 doesn't need it. Orion SM has a fairing, CST-100 doesn't.

Could we "throw a bone" to Boeing by letting them keep CST-100 for crew transport to ISS, but kill Orion?

kbd512 wrote:

Can Boeing and Lockheed collaborate on Orion development to keep both Orion and SLS and retain the Boeing people who work on development of manned spacecraft to supply crew/cargo for government/military?

They already do. United Launch Alliance (ULA) is a 50:50 joint venture of those two. ULA now owns the former Boeing launch vehicle Delta IV, and the former Lockheed-Martin launch vehicle Atlas V. Boeing has the primary contract for Orion, but Lockheed-Martin is collaborating.

Impaler · 2015-02-02 00:28:03

kbd512 wrote:

- These vehicles require a SLS launch of their own because they're so massive and those launches cost more than a STS launch
- Burns that reduce the trip time to 6 months dramatically lower the Isp of the supposedly more efficient electric thrusters
- There is no comparison whatsoever between what a kilo of enriched Uranium yields in energy output and a solar panel that operates at theoretical maximum efficiency; no amount of efficiency improvement is going to make solar technology more efficient than fission or fusion
- The drag produced by these enormous solar panel arrays would bring a SEP tug down in days if we do assembly in LEO or require burning propellant to maintain orbit
- Massive increases in surface area increase the risk of the vehicle being struck by space debris, both in LEO and in transit
- No alternative means we're stuck with a technology that doesn't operate efficiently in places beyond Venus or Mars

- When SpaceX produces their Raptor based Rocket it will certainly supplant the SLS, if SpaceX doesn't produce this rocket we are not going to Mars so their is no point in fixating on the launch vehicle other then to specify that it is in a particular size class.

- Again you speak out of an appalling ignorance of SEP, in a variable specific impulse system you can trade off between thrust and ISP, but you can also just add more electric power to get more absolute thrust which keeping your trip times up. 'Low gear' aka high thrust and low ISP for current thrusters is still in the 3000s range which is bloody fantastic compared to NERVA and as good as your pixie-dust coated fantasy of GassCore NTR.

- Actually their is a comparison, the fuel pellet in a nuclear reactor have a heat output 20,000 - 30,000 W/kg Thermal, only 8-15x the theoretical maximum of thin-film-solar. But of course by the time you actually contain them within cladding rods and coolant flows and the like your looking at substantially lower density for the whole thing and these parasitic masses for Nuclear are vastly high then the parasitic mass on solar which is basically a rod or mast to hold the film. What matters is the system level performance, not machismo chest thumping about power density in some tiny portion of the whole system. If you want to look at life-time energy output then Solar is likely to come out ahead because nuclear fuels last less then a year before needing reprocessing while solar systems can operate for decades thus yielding more total energy as they are COLLECTORS rather then fuels and are not limited by their own mass. A NTR is actually even worse then a nuclear power plant because as a high thrust system it operates for only a few MINUTES before it's out of propellent and has to be shutdown with control rods, thus it ultimately imparts LESS energy into it's propellent and wouldn't you know it, LOWER ISP results from lower energy (who would have imagined!!!). When you actually do the math nuclear is pathetic.

- Again your pathetic concern troll falls flat, if we are assembling a SEP vehicle we won't deploy the panels until were going to depart, or we will simply rotate the panels edge on the atmospheric drag and largely eliminate it. Only when we go to thrust do we need to orient the panel to the sun and incur drag when that angle happens to be broadside to the atmosphere. We can easily calculate the drag force at altitude and know how high we must be to escape the drag, it works out to about 300 km for most SEP system, they would have over a month before orbital decay at that altitude with panels deployed.

- Solar panels on EVERY single object in LEO are struck by debris all the time, including the huge panels on ISS and it has not destroyed it. With modern thin-film solar the damage from such impacts are likely to be even less severe as they just poke clean holes right through it. Their is also no risk of being hit 'in transit' as in actually flying between Earth and Mars, space that hasn't been polluted by humans is in fact mind blowing EMPTY, being hit by meteorites in space is a science-fiction plot device not something that has any statistical likelihood of happening regardless of the size of the vehicle, even in LEO where all that space junk resides it is still fantastically empty. The core vehicle obviously has the same risk of being hit as any other vehicle and is a wash.

- SEP is good at least to Jupiter before solar power becomes too weak. But even then we either use Nuclear powered electric propulsion or do something like plunge inward toward the sun and burn our propellent rapidly in a Oberth maneuver to slingshot ourselves into the outer solar system and use a ballistic capture at our destination planet (getting back might be tough though). In any case your argument that we need to develop NOW a propulsion system that only going to be used for a trip to Saturn is laughable, Mars is the most aggressive destination currently under consideration for 'next' and it is unquestionably the limit of our technological reach for all the non-propulsive aspects of a mission and or settlement and may even be beyond it. Your simply grasping at straws here to try to come up with something to slander SEP with, you might as well say we should put ALL our money into anti-matter drive so we won't be 'limited' to destinations within the solar-system.

kbd512 · 2015-02-02 02:57:05

Impaler wrote:

- When SpaceX produces their Raptor based Rocket it will certainly supplant the SLS, if SpaceX doesn't produce this rocket we are not going to Mars so their is no point in fixating on the launch vehicle other then to specify that it is in a particular size class.

The booster fixation has to do with having a launch vehicle, any launch vehicle, that can actually launch something with the mass that Boeing is proposing.

SpaceX has stated that Raptor and BFR are low on the priorities list. Will it be available 10 years from now? I certainly hope so.

Impaler wrote:

- Again you speak out of an appalling ignorance of SEP, in a variable specific impulse system you can trade off between thrust and ISP, but you can also just add more electric power to get more absolute thrust which keeping your trip times up. 'Low gear' aka high thrust and low ISP for current thrusters is still in the 3000s range which is bloody fantastic compared to NERVA and as good as your pixie-dust coated fantasy of GassCore NTR.

Boeing says that the Isp is in the 2600s range for the type of thrust needed to make the transit in 6 months. They must be appallingly ignorant of SEP capabilities, too.

I'm seeing a pattern here. Everyone who doesn't agree with Impaler is a stupid/ignorant space cadet.

Impaler wrote:

- Actually their is a comparison, the fuel pellet in a nuclear reactor have a heat output 20,000 - 30,000 W/kg Thermal, only 8-15x the theoretical maximum of thin-film-solar. But of course by the time you actually contain them within cladding rods and coolant flows and the like your looking at substantially lower density for the whole thing and these parasitic masses for Nuclear are vastly high then the parasitic mass on solar which is basically a rod or mast to hold the film. What matters is the system level performance, not machismo chest thumping about power density in some tiny portion of the whole system. If you want to look at life-time energy output then Solar is likely to come out ahead because nuclear fuels last less then a year before needing reprocessing while solar systems can operate for decades thus yielding more total energy as they are COLLECTORS rather then fuels and are not limited by their own mass. A NTR is actually even worse then a nuclear power plant because as a high thrust system it operates for only a few MINUTES before it's out of propellent and has to be shutdown with control rods, thus it ultimately imparts LESS energy into it's propellent and wouldn't you know it, LOWER ISP results from lower energy (who would have imagined!!!). When you actually do the math nuclear is pathetic.

If you're going to rant about something, could you at least rant about something that I actually proposed using? I did not, I am not now, nor will I ever advocate using a solid core reactor. Make an argument with applicability to what I advocated using. Gas core reactors don't have fuel cladding, unless you consider the coolant/propellant to be cladding.

A NTR doesn't have to provide thrust all the way to Mars and back. It will still get the crew there in six months or less.

Let's look at some charts to show just how pathetic the energy density of Uranium is:

http://www.cleanenergyinsight.org/inter … omparison/

I'm starting to see what you mean.

http://thebreakthrough.org/index.php/pr … footprints

Yep, it's official, the energy density of those nuclear fuels is absolutely pitiful.

Impaler wrote:

- Again your pathetic concern troll falls flat, if we are assembling a SEP vehicle we won't deploy the panels until were going to depart, or we will simply rotate the panels edge on the atmospheric drag and largely eliminate it. Only when we go to thrust do we need to orient the panel to the sun and incur drag when that angle happens to be broadside to the atmosphere. We can easily calculate the drag force at altitude and know how high we must be to escape the drag, it works out to about 300 km for most SEP system, they would have over a month before orbital decay at that altitude with panels deployed.

You ever think there might have been more than one reason why Boeing wanted to do assembly at a Lagrange point?

Impaler wrote:

- Solar panels on EVERY single object in LEO are struck by debris all the time, including the huge panels on ISS and it has not destroyed it. With modern thin-film solar the damage from such impacts are likely to be even less severe as they just poke clean holes right through it. Their is also no risk of being hit 'in transit' as in actually flying between Earth and Mars, space that hasn't been polluted by humans is in fact mind blowing EMPTY, being hit by meteorites in space is a science-fiction plot device not something that has any statistical likelihood of happening regardless of the size of the vehicle, even in LEO where all that space junk resides it is still fantastically empty. The core vehicle obviously has the same risk of being hit as any other vehicle and is a wash.

Great. Has it degraded the power output of those panels appreciably? Being hit by meteorites is so much science fiction that NASA considers it in the design of their spacecraft and space suits? I guess their just "stupider" than you, as you would put it.

Impaler wrote:

- SEP is good at least to Jupiter before solar power becomes too weak. But even then we either use Nuclear powered electric propulsion or do something like plunge inward toward the sun and burn our propellent rapidly in a Oberth maneuver to slingshot ourselves into the outer solar system and use a ballistic capture at our destination planet (getting back might be tough though). In any case your argument that we need to develop NOW a propulsion system that only going to be used for a trip to Saturn is laughable, Mars is the most aggressive destination currently under consideration for 'next' and it is unquestionably the limit of our technological reach for all the non-propulsive aspects of a mission and or settlement and may even be beyond it. Your simply grasping at straws here to try to come up with something to slander SEP with, you might as well say we should put ALL our money into anti-matter drive so we won't be 'limited' to destinations within the solar-system.

Good for what? For powering small satellites or space tugs that have more mass than Skylab? How am I slandering your favorite technology?

Childish insults aren't arguments for whether or not something will or won't work.

kbd512 · 2015-02-02 03:40:46

RobertDyck wrote:

True, the version that can lift 130t was to have 5 SSME, and a pair of "advanced boosters", and a full size upper stage with 2 J-2X engines and same tank diameter as the core module. Isn't that "Dark Knight"? What would be the lift capacity be for 5-SSME/2-5SSRM/2-J2X?

Dark Knight is ATK's proposed advanced SRM. Even with better SRM's, SLS won't quite hit the 130t target without 5 RS-25's and ATK is quoted as stating this. However, it gets to between 110t and 120t with the advanced boosters. That's about as good as we're reasonably going to get from SLS.

RobertDyck wrote:

Orion is not the same as CST-100. Orion has 16.5 feet diameter capsule, CST-100 is 15.0 feet. Orion can carry 6 crew to ISS, CST-100 can carry 7 (ironic). Orion has total launch mass including LAS, ATV-based SM, and fairing of 28.0 metric tonnes; CST-100 is 10t. Orion uses a launch abort rocket like Apollo, CST-100 uses its SM main engines for abort. Orion has an exhaust shield around the capsule to protect from LAS exhaust, CST-100 doesn't need it. Orion SM has a fairing, CST-100 doesn't.

CST-100 is, in certain ways, more capable than our advanced space exploration capsule.

The wheel reinvention thing that NASA likes so much is something that reputable aerospace companies typically avoid if it isn't mandated by nutty government contract requirements.

RobertDyck wrote:

Could we "throw a bone" to Boeing by letting them keep CST-100 for crew transport to ISS, but kill Orion?

I'd much rather kill Orion than CST-100, but money has to come from somewhere to fund SEP tugs and SLS launches. Honestly, I think both systems need to be killed to free up money for Boeing to develop SEP tugs and produce SLS hardware.

The only way I see one of these capsule systems living a useful life is if the Air Force finds utility in manned space flight capability and assists with funding. NASA is out of money and they're not going to be given more.

RobertDyck wrote:

They already do. United Launch Alliance (ULA) is a 50:50 joint venture of those two. ULA now owns the former Boeing launch vehicle Delta IV, and the former Lockheed-Martin launch vehicle Atlas V. Boeing has the primary contract for Orion, but Lockheed-Martin is collaborating.

This would be collaboration to produce a real service module for Orion and to produce a cargo variant of Orion for contingency operations. Some of this is related to national insecurity. The government wants NASA to retain manned space flight and cargo delivery capability for military operations independent of any commercial vehicles and launch systems, even though it won't give the agency money to actually use it.

SpaceX and Orbital have begrudgingly been given a seat at the table, but Boeing and Lockheed-Martin are the government's go-to contractors for national security.

I have serious doubts about whether or not ESA will develop the Orion SM in a timely manner.

RobertDyck · 2015-02-02 04:39:49

kbd512 and Impaler: SpaceNut asked you to simply agree to disagree. Your constant bickering is annoying. Neither of you will convince the other. But I do have to take exception to one point:

Impaler wrote:

in a variable specific impulse system you can trade off between thrust and ISP, but you can also just add more electric power to get more absolute thrust which keeping your trip times up. 'Low gear' aka high thrust and low ISP for current thrusters is still in the 3000s range which is bloody fantastic compared to NERVA and as good as your pixie-dust coated fantasy of GassCore NTR.

The only engine capable of variable specific impulse is VASIMR. That's an electric engine, it doesn't matter if electricity is generated by solar or nuclear reactor. But the important point is this is "pixie-dust coated fantasy". VASIMR has never demonstrated the ability to do this. VASIMR is about as "ready" as gas core NTR. To be fair, VASIMR has demonstrated one single Isp using Argon gas and 5000 second Isp. They claim "First stage operation with krypton was also demonstrated in 2012." However, their paper does not quote Isp for that propellant. There is no work at all with LH2.
http://www.adastrarocket.com/AndrewIEPC13-336-Paper.pdf

RobertDyck · 2015-02-02 04:48:04

kbd512 wrote:

money has to come from somewhere to fund SEP tugs

why?

kbd512 · 2015-02-02 08:47:25

RobertDyck wrote:

why?

Why does funding have to be available for SEP tugs or why do we have to kill other programs to fund SEP tugs?

RobertDyck · 2015-02-02 09:16:56

We can go to Mars without SEP. That's "nice to have", but not necessary. We need:
- aerocapture
- ISPP
- life support

In fact, ISPP generally produces methane. SEP doesn't use methane as propellant. So SEP is not required for a human mission to Mars. For the architecture I came up with, a reusable spacecraft travels from ISS to Mars orbit and back. Aerocapture at both ends. Propulsion stage for both ends is initially expendable, but can be replaced by a reusable stage later once technology is available. Whether that is nuclear thermal, nuclear electric, solar electric, or other, is left undefined. However, reusable means we need to harvest propellant from Mars or one of its moons, and deliver that propellant to the reusable stage. That means infrastructure on Mars. That's why no reusable stage for the first mission. Initially, the Mars Ascent Vehicle acts as the TEI stage, so no propellant transfer is required. And return to Earth is entirely ISPP. This required methane/LOX engines.

kbd512 · 2015-02-02 17:27:14

RobertDyck wrote:

We can go to Mars without SEP. That's "nice to have", but not necessary. We need:
- aerocapture
- ISPP
- life support
In fact, ISPP generally produces methane. SEP doesn't use methane as propellant. So SEP is not required for a human mission to Mars. For the architecture I came up with, a reusable spacecraft travels from ISS to Mars orbit and back. Aerocapture at both ends. Propulsion stage for both ends is initially expendable, but can be replaced by a reusable stage later once technology is available. Whether that is nuclear thermal, nuclear electric, solar electric, or other, is left undefined. However, reusable means we need to harvest propellant from Mars or one of its moons, and deliver that propellant to the reusable stage. That means infrastructure on Mars. That's why no reusable stage for the first mission. Initially, the Mars Ascent Vehicle acts as the TEI stage, so no propellant transfer is required. And return to Earth is entirely ISPP. This required methane/LOX engines.

I've stated before that advanced composite technology would make it possible to have a habitat module that the crew could launch with, transit to/from Mars, and make entry on the outbound/inbound legs. Instead of requiring a piece of tech for this/that/the other, we'd have one PE fabric composite habitat module with carbon foam overwrap (the PE minimizes secondary effects from received radiation, keeps weight comparable to 2219, and the overwrap can withstand a thermal flux equivalent to HRSI), we could use aerocapture combined with propulsive landing, ISRU to refuel for the trip home, and not require a complicated support infrastructure.

This would require two SLS rockets and utilize existing chemical tech. Our explorers don't have the same exploration options available to them that they get with the expedition class missions, but it's far more economical than other plans.

SpaceNut · 2015-02-02 18:57:18

ISPP and Life support sort of go hand in hand on the early missions and we need dependability, to which is not there yet as seen with the unit onboard the ISS.

While searching for Sabatier reator diagrams I came across these links....

Nancy's LSS document

http://www.marspapers.org/papers/Zubrin_1994.pdf

Concept of Small Power Autonomous Molten-Salt Reactor with Micro-Particle Fuel

SpaceNut · 2015-02-02 20:46:54

From CO2 to H2O SwRI compressor technology helps NASA produce water in space

Sabatier Reactor System Integration with Microwave Plasma Methane Pyrolysis Post-Processor for Closed-Loop Hydrogen Recovery

International Space Station Water Balance Operations

RobertDyck · 2015-02-03 05:10:31

Microwave plasma methane pyrolysis. Brilliant!

Impaler · 2015-02-03 17:12:45

RobertDyck wrote:

kbd512 and Impaler: SpaceNut asked you to simply agree to disagree. Your constant bickering is annoying. Neither of you will convince the other. But I do have to take exception to one point:
Impaler wrote:
in a variable specific impulse system you can trade off between thrust and ISP, but you can also just add more electric power to get more absolute thrust which keeping your trip times up. 'Low gear' aka high thrust and low ISP for current thrusters is still in the 3000s range which is bloody fantastic compared to NERVA and as good as your pixie-dust coated fantasy of GassCore NTR.
The only engine capable of variable specific impulse is VASIMR. That's an electric engine, it doesn't matter if electricity is generated by solar or nuclear reactor. But the important point is this is "pixie-dust coated fantasy". VASIMR has never demonstrated the ability to do this. VASIMR is about as "ready" as gas core NTR. To be fair, VASIMR has demonstrated one single Isp using Argon gas and 5000 second Isp. They claim "First stage operation with krypton was also demonstrated in 2012." However, their paper does not quote Isp for that propellant. There is no work at all with LH2.
http://www.adastrarocket.com/AndrewIEPC13-336-Paper.pdf

Wrong, latest Hall thrusters are able to varying Impulse as well, the range is not as large as VASIMIR which is specifically designed to maximize that aspect but it exists and it not something fundamentally limited to the VASIMIR concept. Also your caracterization of VASIMIR as equal TRL to Gass-Core is absurd, they have working VASIMR units being tested in vacuum chambers, it only needs to be validated in space to be TRL 9, while GCNTR is a TRL 1 concept with no idea how it would even be built with materials that don't even exist yet. Your giving kb a race for greatest intellectual dishonesty here.

Last edited by Impaler (2015-02-03 17:28:19)

Impaler · 2015-02-03 17:18:26

kbd512 wrote:

RobertDyck wrote:
why?
Why does funding have to be available for SEP tugs or why do we have to kill other programs to fund SEP tugs?

You do realize the SEP is already funded and in development, no other program had to DIE for it because it's costing a pittance compared to what your proposing. The fact that you need to kill SLS and Orion and take it's WHOLE budget to get your Nuclear fantasy off the ground just shows have utterly unrealistic it is. That SLS/Orion money is unfortunately lost to any useful purpose due to congress (not NASA stop harping on them for having their hand forced). But if by some miracle that money were available to redirect to other uses it would better go to the aerocapture, ISPP, life support trinity that was just mentioned as KEY must have technologies.

Last edited by Impaler (2015-02-03 17:23:36)

RobertDyck · 2015-02-03 21:31:31

Impaler wrote:

The fact that you need to kill SLS and Orion and take it's WHOLE budget to get your Nuclear fantasy off the ground just shows have utterly unrealistic it is. ... But if by some miracle that money were available to redirect to other uses it would better go to the aerocapture, ISPP, life support trinity that was just mentioned as KEY must have technologies.

I did not argue for nuclear. I said nuclear is nice to have, but not key. And I didn't say kill SLS, rather I said SLS is necessary. My mission plan uses SLS. What I said is kill Orion, keep SLS, and redirect Orion money to a human mission to Mars. Since my mission plan requires aerocapture, ISPP, and life support, if you want to characterize that as redirecting money to that trinity, then fine.

I based my plan on Mars Direct, with elements taken from NASA's DRM. Since Mars Direct uses nuclear to power ISPP, I said continue to use that. But, I said specifically to use the SAFE-400 nuclear reactor. Development for that was complete in 2007. I'm not sure, but I think it's TRL 6.

Last edited by RobertDyck (2015-02-03 21:32:27)

kbd512 · 2015-02-03 21:55:00

Impaler wrote:

kbd512 wrote:
RobertDyck wrote:
why?
Why does funding have to be available for SEP tugs or why do we have to kill other programs to fund SEP tugs?
You do realize the SEP is already funded and in development, no other program had to DIE for it because it's costing a pittance compared to what your proposing. The fact that you need to kill SLS and Orion and take it's WHOLE budget to get your Nuclear fantasy off the ground just shows have utterly unrealistic it is. That SLS/Orion money is unfortunately lost to any useful purpose due to congress (not NASA stop harping on them for having their hand forced). But if by some miracle that money were available to redirect to other uses it would better go to the aerocapture, ISPP, life support trinity that was just mentioned as KEY must have technologies.

You keep throwing out this TRL9 term to describe technologies that don't seem to quite measure up to NASA's standard for TRL9 technology.

This is what TRL9 means to NASA:

TRL 9 Actual system "mission proven" through successful mission operations (ground or space): Fully integrated with operational hardware/software systems. Actual system has been thoroughly demonstrated and tested in its operational environment. All documentation completed. Successful operational experience. Sustaining engineering support in place.

VASIMR isn't fully integrated with anything, has never been demonstrated in its operational environment, and there have been no spacecraft propelled with VASIMR technology, successful or otherwise.

SpaceNut · 2015-02-03 22:43:05

This paper http://scholar.lib.vt.edu/theses/availa … tation.pdf has some graphs on pages 63-65 for transfer times with various types of low-thrust propulsion, including SEP.

Impaler · 2015-02-04 21:07:14

kbd512 wrote:

You keep throwing out this TRL9 term to describe technologies that don't seem to quite measure up to NASA's standard for TRL9 technology.
This is what TRL9 means to NASA:
TRL 9 Actual system "mission proven" through successful mission operations (ground or space): Fully integrated with operational hardware/software systems. Actual system has been thoroughly demonstrated and tested in its operational environment. All documentation completed. Successful operational experience. Sustaining engineering support in place.
VASIMR isn't fully integrated with anything, has never been demonstrated in its operational environment, and there have been no spacecraft propelled with VASIMR technology, successful or otherwise.

Your attempt to nitpick is as tiresome as always. Hall and Gridded Ion are TRL 9 which is what I am referring to when I say SEP, aka CONVENTIONAL SEP, If I am talking about something unconventional like VASIMIR I will call it out specifically and never said VASIMIR was TRL 9. As the words 'Solar Electric Propulsion' can be satisfied by any combination of any solar power and any electric propulsion system and their are NUMEROUS concepts for both solar collectors and electric propulsion out their at a variety of TRL's so any twat can come up with a combination of thouse two with any arbitrarily low TRL like concentrated solar-steam engines running a Mach-effect reaction-less drive (a piece of complete nonsense that violates conservation of momentum, TRL 0), thus what I say SEP is TRL X, the only sensible interpretation is "the current highest TRL of techs under the SEP umbrella is TRL X". VASIMIR is TRL 8, it just needs the in flight test as the system has gone full ground testing. And again Solid-core NTR is 5-6 (generous) and Gas-core is 1, simply no contest.

I do not even think the VASIMIR concept is going to prove decisive or perhaps even viable in the marketplace as it is getting left behind by improvements in conventional SEP and it's features set of variable impulse and variable propellents are just not particularly unique given whats happened with HALL thrusters lately, someday VASIMIR might be picked up when we start to max out the capability of HALL but that will be a while.

GW Johnson · 2015-02-06 12:45:16

Arguing about this vs that is not a good thing, as vitriolic as this conversation became. All those propulsion ideas deserve serious attention in a balanced program. Some are readier-to-use than others, in some cases by enormous margins.

I rather like electric propulsion for unmanned cargo, in spite of the flight times. Spiraling is a real problem there, that and the gravity-loss penalties. But cargo doesn't care. Doesn't get radiation-sick, doesn't go psycho from confined boredom, doesn't eat or breathe.

You simply can't leave Earth that way with men, because you spend weeks in the Van Allen belts, when days will kill you.

To utilize the advantages of electric with men, you need to put both electrics and conventional engines on the craft, and use both. You simply have to do impulsive dV's at Earth departure and arrival to limit radiation exposure times crossing the belts. At Mars, you could spiral in and out, iff you can afford the extra flight time. ("iff" = "if and only if")

The real advantage using electric with men is faster transit times between parking orbits. You can build up speed efficiently to midpoint, and then efficiently slow yourself back down. That cuts transit time very significantly. 1 month's thrusting at 0.001 gee adds up to around 25 km/s. Whether that's realistic at all for a mission I do not know. But numbers anywhere near that class are very impressive.

Immature things like gas core ought to be worked on, with an eye to making them mature. Those need not be huge money-pit projects, either. Wise outfits always invest in longer-term R&D as well as the short-term stuff. Only the foolish outfits insist on funding only near-term-payoff R&D. Too bad the fools outnumber the wise by such huge margins, in and out of government.

I don't know if VASIMR will ever pay off. No one does. But you have to try to find out. That's just life. VASIMR is no further along than it is because of poor funding, like so many other things. I agree completely that there are at least two other electric schemes that are readier-to-apply. And it sounds like the solar power thing to power them is just about ready, too. That's a good thing, and I'd like to see it used ASAP.

Beyond the asteroid belt, we're going to need nuke electricity for our electric propulsion schemes. Today those are still kinda heavy for the power. Sounds like some R&D needed there.

If nuke propulsion is objectionable to test here on Earth, then do it on the moon. Good reason to go back: build a testing base. There's solid core NTR, gas core NTR, and explosion propulsion, that I know of. Explosion is probably the closest-to-ready, followed by a decent solid core scheme. All need work to make them ready for when we do need them. And eventually we will.

We need to do some more supersonic-hypersonic retro-propulsion work, too. What Spacex has done so far (Dragon and Falcon 1st stages) is marvelous, but there is more to do before we fully understand how to really do this reliably. We're going to need it for practical Mars landing boats.

GW

Last edited by GW Johnson (2015-02-06 12:49:33)

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