NASA teams evaluating ISS-built Exploration Platform roadmap

[JohnFornaro]

There isn't likely to be an "R-Bar" approach, for example.

With my new, in the last week or so, beginning understanding of R-Bar, would this mean just flying in?

I couldn't quite figure out what you meant.

[clongton]

EP's problem in respect to mars or anywhere is that the low thrust bites when attempting to get into and out of orbit. In the case of mars SEP could keep thrusting all the way to mars building up tremendous velocity but if you try to go into Orbit then the low thrust and the time it could take to get into Orbit makes the Chemical rocket either faster for the trip or even. SEP also cannot use the same trajectories as a Chemical Rocket and this it's Delta V's can be higher (but still very manageable).

Precisely why I tend to lean towards Dr. von Braun’s move toward NEP rather than SEP. The NEP engine has the capability to be designed as a hybrid engine by having thrusters built into the system as a whole, which could be turned on or off at will. The thrusters would be switched on to run in NTR mode (high thrust/moderate ISP) to break out of orbit, switched off to run in NEP mode (low thrust/high ISP) for the majority of the trip in cruise mode and then switched on again to run in NTR mode to decelerate as the spacecraft approaches the planet, allowing capture to orbit. Returning home would be done the same way. Dr. von Braun’s plans actually called for the NEP to eventually be a dual mode engine in this way.

[RocketmanUS]

EP's problem in respect to mars or anywhere is that the low thrust bites when attempting to get into and out of orbit. In the case of mars SEP could keep thrusting all the way to mars building up tremendous velocity but if you try to go into Orbit then the low thrust and the time it could take to get into Orbit makes the Chemical rocket either faster for the trip or even. SEP also cannot use the same trajectories as a Chemical Rocket and this it's Delta V's can be higher (but still very manageable).

Precisely why I tend to lean towards Dr. von Braun’s move toward NEP rather than SEP. The NEP engine has the capability to be designed as a hybrid engine by having thrusters built into the system as a whole, which could be turned on or off at will. The thrusters would be switched on to run in NTR mode (high thrust/moderate ISP) to break out of orbit, switched off to run in NEP mode (low thrust/high ISP) for the majority of the trip in cruise mode and then switched on again to run in NTR mode to decelerate as the spacecraft approaches the planet, allowing capture to orbit. Returning home would be done the same way. Dr. von Braun’s plans actually called for the NEP to eventually be a dual mode engine in this way.

Any link(s) to specs and drawings on such a hybrid NTR/NEP?

[clongton]

EP's problem in respect to mars or anywhere is that the low thrust bites when attempting to get into and out of orbit. In the case of mars SEP could keep thrusting all the way to mars building up tremendous velocity but if you try to go into Orbit then the low thrust and the time it could take to get into Orbit makes the Chemical rocket either faster for the trip or even. SEP also cannot use the same trajectories as a Chemical Rocket and this it's Delta V's can be higher (but still very manageable).

Precisely why I tend to lean towards Dr. von Braun’s move toward NEP rather than SEP. The NEP engine has the capability to be designed as a hybrid engine by having thrusters built into the system as a whole, which could be turned on or off at will. The thrusters would be switched on to run in NTR mode (high thrust/moderate ISP) to break out of orbit, switched off to run in NEP mode (low thrust/high ISP) for the majority of the trip in cruise mode and then switched on again to run in NTR mode to decelerate as the spacecraft approaches the planet, allowing capture to orbit. Returning home would be done the same way. Dr. von Braun’s plans actually called for the NEP to eventually be a dual mode engine in this way.

Any link(s) to specs and drawings on such a hybrid NTR/NEP?

Sorry no. I'm speaking from memory only. It was a long time ago. I remember reading everything about it I could get my hands on but that was slide rule days - pre-computer. BTW I still have (and occasionally still use) my K&E slide rule.

[alexw]

Precisely why I tend to lean towards Dr. von Braun’s move toward NEP rather than SEP. The NEP engine has the capability to be designed as a hybrid engine by having thrusters built into the system as a whole, which could be turned on or off at will. The thrusters would be switched on to run in NTR mode (high thrust/moderate ISP) to break out of orbit, switched off to run in NEP mode (low thrust/high ISP) for the majority of the trip in cruise mode and then switched on again to run in NTR mode to decelerate as the spacecraft approaches the planet, allowing capture to orbit. Returning home would be done the same way. Dr. von Braun’s plans actually called for the NEP to eventually be a dual mode engine in this way.

Any link(s) to specs and drawings on such a hybrid NTR/NEP?

Sorry no. I'm speaking from memory only. It was a long time ago. I remember reading everything about it I could get my hands on but that was slide rule days - pre-computer. BTW I still have (and occasionally still use) my K&E slide rule.

     I'm finding that difficult to visualize, having multiple thermal-plasma "thrusters". Perhaps you are thinking of the opposite role for the thrusters; that is, having a single main NTR built with a large electrical generation tap-off capability, and using that to power a set of very high ISP electrical thrusters for the cruise phase, while running in pure NTR core for high-thrust maneuvers?
       -Alex

[Archibald]

What about this maybe ? "Study of a NERVA-Electric Manned Mars Vehicle" by Stuhlinger, circa 1966.
http://www.wired.com/wiredscience/2012/04/ernsts-ions-week-concludes-nerva-ion-mars-mission-1966/

(reading this article I realized that electric propulsion, be it SEP or NEP, may be easier in Mars orbit, since there's no Van Allen belts there to fry the solar arrays and the crew; plus, Mars is smaller, so the gravity is weaker, so Delta-V to orbit and escape are also smaller. How about that ?!)

[a_langwich]

I agree with alexw's analysis (and Robotbeat as well).

NEP and NP are still in the realm of flying cars, despite pushes every decade since the 60s.  Von Braun's public visions were very optimistic, but as an engineering manager he was much more pragmatic.  The technology is very promising, but there are dozens of websites (Science Today, PhysOrg) with an endless parade of very promising ideas.

I think human missions to Jupiter and beyond are many decades out. 

And I think chemical rockets and EP will continue to be the practical choices.  If you need more ISP and solar poops out, couple fuel cells or IVF's ICE to a big hydrogen tank (ACES) and use that to drive ion/hall thrusters.  The IVF concept also included an attitude control thruster, which could make a hybrid CP/CEP concept.  It seems to me likely that the ability to launch large objects like that will come before NP or NEP.

[RocketmanUS]

I agree with alexw's analysis (and Robotbeat as well).

NEP and NP are still in the realm of flying cars, despite pushes every decade since the 60s.  Von Braun's public visions were very optimistic, but as an engineering manager he was much more pragmatic.  The technology is very promising, but there are dozens of websites (Science Today, PhysOrg) with an endless parade of very promising ideas.

I think human missions to Jupiter and beyond are many decades out. 

And I think chemical rockets and EP will continue to be the practical choices.  If you need more ISP and solar poops out, couple fuel cells or IVF's ICE to a big hydrogen tank (ACES) and use that to drive ion/hall thrusters.  The IVF concept also included an attitude control thruster, which could make a hybrid CP/CEP concept.  It seems to me likely that the ability to launch large objects like that will come before NP or NEP.

SEP will be good for LEO to GEO and for cargo to EML-1/2.
Small SEP would work for space tugs for cargo but not crew.
For Mars and NEA that could be a strong possibility.
For crew and cargo between LEO and EML1/2 or LLO fusion NEP would be the better system if and when we can develop it.

For NEP to Mars for the near term that might not be a good choose, however for Jupiter it would be needed. Jupiter missions I don't seen starting until the 2030's. So NEP development can wait until the 2020's so we have funding for our near term missions. Let domestic needs fund better nuclear power for now ( fusion or better fission ).

First there needs to be a reason for all this hardware. Using what has been developed and learned from the ISS for the gateways and DSH we will still need to first blaze a trail.  There has to be something already there for the business case. Once people started to come to the America's then there was a need for faster transportation, lower cost and more of it. Orion can open the door and the OTV could follow as the more routine and lower cost between LEO and EML1/2. The goal has to be a more long term one , not just Mars and some NEA missions. A Mars base and or colony with further exploration out to Jupiter and beyond. Lunar is more of a place for possible propellents and Morpheus can at a lower development and running cost open that door (  blaze the trail ). From there landers would be needed for Mars for ISRU for the short and long term needs.

So the ISS-built Exploration Platform with Orion ( or like ) would be or first steps and with the Morpheus Lunar ISRU to follow by larger landers and tankers to LLO and EML1/2. Would still give robotic exploration of the moon with the option for crew.

We can have a flex path forward to Mars with side options Lunar and NEA  especially with partners, both commercial and other governments. Let someone other than NASA develop the larger landers for Lunar. From another thread and PDF they could use the SEV as the crew cabin for a reusable lander.

[mmeijeri]

Small SEP would work for space tugs for cargo but not crew.

Especially for propellant, which would make up the bulk of the mission mass. That can be done with mature technology.

[RanulfC]

Precisely why I tend to lean towards Dr. von Braun’s move toward NEP rather than SEP. The NEP engine has the capability to be designed as a hybrid engine by having thrusters built into the system as a whole, which could be turned on or off at will. The thrusters would be switched on to run in NTR mode (high thrust/moderate ISP) to break out of orbit, switched off to run in NEP mode (low thrust/high ISP) for the majority of the trip in cruise mode and then switched on again to run in NTR mode to decelerate as the spacecraft approaches the planet, allowing capture to orbit. Returning home would be done the same way. Dr. von Braun’s plans actually called for the NEP to eventually be a dual mode engine in this way.

Any link(s) to specs and drawings on such a hybrid NTR/NEP?

Sorry no. I'm speaking from memory only. It was a long time ago. I remember reading everything about it I could get my hands on but that was slide rule days - pre-computer. BTW I still have (and occasionally still use) my K&E slide rule.

     I'm finding that difficult to visualize, having multiple thermal-plasma "thrusters". Perhaps you are thinking of the opposite role for the thrusters; that is, having a single main NTR built with a large electrical generation tap-off capability, and using that to power a set of very high ISP electrical thrusters for the cruise phase, while running in pure NTR core for high-thrust maneuvers?
       -Alex

Thats the way I understood it from the get-go... Then again I suspect I might have read the same books clongton did

At any rate what you want to look up is "Bi-Modal" or "Multi-Mode" Nuclear Thermal Rocket or take a look at the Trition NTR P&W designed:
http://www.pwrengineering.com/dataresources/AIAA-2004-3863.pdf

Randy

[Robotbeat]

I agree with alexw's analysis (and Robotbeat as well).
...

Thank you.

And I think chemical rockets and EP will continue to be the practical choices.  If you need more ISP and solar poops out, couple fuel cells or IVF's ICE to a big hydrogen tank (ACES) and use that to drive ion/hall thrusters. ...

*facepalm*

[a_langwich]

I agree with alexw's analysis (and Robotbeat as well).
...

Thank you.

And I think chemical rockets and EP will continue to be the practical choices.  If you need more ISP and solar poops out, couple fuel cells or IVF's ICE to a big hydrogen tank (ACES) and use that to drive ion/hall thrusters. ...

*facepalm*

what's your alternative?

[93143]

Just use a chemical rocket.

It can be shown that given a store of any energy-containing material (hydrazine, hydrogen/oxygen, enriched uranium, helium-3, protium/boron-11...), maximum total impulse is obtained by throwing the material out the back with its internal energy converted as efficiently as possible to kinetic energy.  Let's call the corresponding exhaust velocity the intrinsic exhaust velocity (IEV) of the propellant.

The reason for this is that kinetic power is proportional to the square of the exhaust velocity while thrust is only linear with it, resulting in total impulse being inversely proportional to exhaust velocity, at least above the IEV.  Sure, the impulse from the mass you shoot backwards is greater than it would be at the IEV, but you use energy-containing material faster than you can shoot it backwards, and you have to dump the rest uselessly.  If your exhaust velocity drops below the IEV, impulse becomes linear with exhaust velocity unless you can figure out some way to use more reaction mass than you brought with you (jet engines do this very well.  It's harder in space).

In the case of nuclear fission, this ideal gives you a fission fragment rocket.  For fusion, you get a directed fusion product drive.  For chemical propellants, you get chemical rockets.

[hectorlamadrid]

Hello everyone,

It is is an honor for me to  post in this forum. I think this is not being discussed yet. It seems like there is not going to be much support for this idea after all...


http://www.space.com/18750-nasa-moon-missions-obama-administration.html

[Robotbeat]

Hello everyone,

It is is an honor for me to  post in this forum. I think this is not being discussed yet. It seems like there is not going to be much support for this idea after all...


http://www.space.com/18750-nasa-moon-missions-obama-administration.html

Title should be changed to reflect what the article says. "Despite speculation to the contrary, NASA's ambitious plans for a manned space station beyond the moon have not yet been cleared by the White House, a senior administration official told SPACE.com." (my emphasis)

Still, it's hard to see anything that looks exciting will be announced while the austerity bomb talks are on-going. Exciting looks expensive.

[Ben the Space Brit]

A dark, cynical part of me suspects that any goal for NASA other than the clearly-stated and non-specific "inspire to learn" runs counter to the wishes of the current administration.  Because of that, approving a mission would be unlikely.

Well! If confirmed, that's the end of any hope for SLS doing anything except spend money!

[Warren Platts]

NASA can't afford to pay for 2 ISS's, especially if one of them is hundreds of thousands of miles away. Meanwhile, ISS is slated to run at least until 2020, and most likely be extended to at least 2028. And why throw it away then? B-52's last 50 years or more. Why can't the ISS?

[rdale]

And why throw it away then? B-52's last 50 years or more. Why can't the ISS?

A simple search would help explain why... There is no comparison between a B52 and the ISS. It cannot last 50 years, let alone more.

[IRobot]

NASA can't afford to pay for 2 ISS's, especially if one of them is hundreds of thousands of miles away. Meanwhile, ISS is slated to run at least until 2020, and most likely be extended to at least 2028. And why throw it away then? B-52's last 50 years or more. Why can't the ISS?

EML-2 outpost is much smaller than the ISS, does not have scientific payloads and the idea is to be inhabited for long periods, meaning lots of robotic operations. It is not (should not!) be on the same cost category as the ISS.

[Khadgars]

NASA can't afford to pay for 2 ISS's, especially if one of them is hundreds of thousands of miles away. Meanwhile, ISS is slated to run at least until 2020, and most likely be extended to at least 2028. And why throw it away then? B-52's last 50 years or more. Why can't the ISS?

EML-2 outpost is much smaller than the ISS, does not have scientific payloads and the idea is to be inhabited for long periods, meaning lots of robotic operations. It is not (should not!) be on the same cost category as the ISS.

Indeed.  Isn't the EML-2 outpost more or less a DSH with a few more add-ons?

Though I kinda agree, it would be hard to have both the ISS and EML-2 outpost running at the same time.