We are NASA Glenn engineers who work on Ion Propulsion. Ask Us Anything!

No question, I just wish you guys would get more funding.

Send cash or check made out to NASA! :) (DH)

Just going to put it out there: if NASA accepted small donations from the public in an official capacity, I would donate everything I could as regularly as I could. I would rather scientific research be in the name of science, not death and destruction. I love you guys.

Edit: Hey look what I (and nikkorizz) found http://spaceindustrynews.com/how-to-donate-to-nasa/

NASA can accept donations from the public, but they are not allowed to ask for them or advertise in any way. If you send a check to the correct place, they will absolutely use it. I believe they are only allowed to accept money from American citizens as well, because taking foreign donations would create some interesting conflict of interests.

EDIT: Thanks for the link /u/nikkorizz. It looks like the money can come from anyone, but it cannot have any "strings" attached.

But, hypothetically, nothing could stop an influential person from advertising for them?

There was an indiegogo campaign to show a version of our "We are the Explorers video in theaters before showings of "Star Trek Into Darkness". - SMT

I'll write you a $20 billion check. Good luck to BoA collecting on that overdraft!

"Just take my money!"

Seriously though, they should get more funding.

If there was a war in space, NASA would be swimming in cash.

Edit: Holy Space Batman, highest post ever!

We are a peaceful people. We are working on collaboration over competition. (DH)

Thanks! - DM

What are they key problems to solve today with ion thrusters? Or another way, if you could wave a magic wand and make one obstacle in your field go away, what would it be?

For electric propulsion thrusters, to get the big payoff of such a high fuel efficiency propulsion system you need to operate them for a long period of time (measured in years). The key problem we face is designing a device to last as long as we need it and to prove that it has this life with margin. You can imagine that running a device for multiple years can be costly and delay implementation. If I could wave a magic wand I would make them last forever and be able to prove that it meets the life requirement with few resources. I might be biased though since I ran an 8 year thruster life test for 5 of those years! (DH)

Do the standard methods of accelerated life testing not apply to ion thrusters?

To date we have been unsuccessful in accelerated life testing. Those tests uncovered failure mechanisms that were not observed in standard wear testing. (DH)

This sounds really interesting. Hate to be a bother, but do you think you could point us to any published work on this topic?

There are loads of AIAA papers published on ion thruster life testing, modeling and validation. Reporting on both the NSTAR and NEXT thruster covers a lot of this. -SB

Have you thought about calling yourselves Glenngineers?

Awesome, I will now! - DM

How well do your experiments work when tested in the best simulator, Kerbal Space Program?

Considering how highly everyone is talking about KSP (I've never played it), I might actually have a shot of convincing my boss it's critical software for my job :)

A lot of the work we do at Glenn is experimental, as opposed to simulation. I don't know too much about the software we use for orbital simulations, but developing codes to simulate the physics of the thrusters themselves is a big part of research. Experimental testing (and life testing) can get expensive, so an accurate simulation would save a lot of time and money. - RS

Howdy! Rohit answered a similar question here. None of us have too much experience with it, but with all the recommendations, I'm sure one of us will look into it! - SMT

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Ion propulsion technologies are low thrust compared to the chemical propulsion systems. This is the main reason why chemical propulsion systems are used to launch things (thrust to mass ratio is greater than 1). Ion propulsion is used only for access through space (once you get into orbit). The current technologies that are flying and are being invested in by NASA are at thrust levels a fraction of a pound or a few grams. Working in metric units, thrust levels range from hundreds of mN to a few N. This low thrust is applied for long periods of time to continually accelerate the vehicle. Power levels for thrusters doubles every 10 - 15 years so thrust levels should be double in about 10 years. Maybe 3 - 5 X in 50 years. (DH)

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I've seen them as small as a few cm in diameter. They typically have lower efficiency (higher wall losses due to the lower ratio of volume to surface area). The longevity issue is the same. (DH)

Sorry, maybe a dumb question: Are you saying that thruster technology in general doubles every 10-15 years or that any one specific thruster increases thrust (some crazy long warm up period or something?).

As I would guess it's the first scenario, are there any new technological jumps on the horizon that might increase thrust much faster? Something like when ICs took over for discrete components for computer processors back in the day?

The power that spacecraft produce has been growing at the rate mentioned. The higher power allows higher power thrusters all though you can just gang up several lower power thrusters too - DM

How can someone get started in your field from a high school level?

Doing well in math and science is helpful. NASA offers high school and college internships at all the centers and that might interest you. Learn more at https://intern.nasa.gov

I think we all have different paths that we followed to get here. I started by studying engineering in college - DM

First question: Given that ion propulsion has such a high specific impulse and low fuel mass requirement but also a very high electrical energy requirement, do you ever see nuclear electric spacecraft becoming a realistic option for deep space travel? How might this be done?

It seems to me that even very large solar arrays won't do the job for large, complex (read: manned) missions to the asteroids and beyond.

Second question: are any of you involved in getting VASIMR on the ISS?

Nuclear power sources would be awesome, but we there doesn't seem to be support for that. In the past the public has been afraid because sometimes launch vehicles fail and there is a concern regarding radioactive material Solar arrays can be used for relatively high powers. A spacecraft with solar arrays equal in size to the ISS, using current photovoltaic cells would have hundreds of kilowatts of electric power. We have been involved with VASIMR on ISS in the past, but there is nothing I am working on right now - DM

do you think it may one day be feasible to acquire the nuclear fuel only once in orbit, probably by way of some kind of asteroid mining operation. the fuel was never on the ground.

is that possible, or am i crazy to think we'd be doing uranium enrichment in space, or whatever it might take

I think we will have to use material from space to make it affordable. We call in "in-situ resource utilization" or ISRU. I'm not sure about the uranium part, but I agree that if we want to have a greater human presence in space we will need to mine asteroids - DM

Seeing as this is one of the most efficient sources of travel in space, where do you guys plan on this going in the near future? Where do you guys want to see it go personally?

While it is very efficient, it generally produces low level of thrust, which makes it most well suited for certain applications (and not good for others). Around small bodies for example. Personally I would like to see ion propulsion used for transportation for just about anything from low Earth orbit - DM

How would adding more engines affect the ISP of the craft? Is there a spot where the ISP goes asymptotic, while adding more engines increases the thrust?

In general, clustering of engines together won't affect the Isp and the total thrust is just the summation of individual thrust levels. With certain devices, however, clustering together thrusters actually causes interactions which can affect performance, which is an active area of research. - RS

What are some applications it is best suited for?

Any application where propellant mass is at a premium and trip time not so much. (DH)

Anything requiring a large velocity change in deep space. Asteroid and comet rendezvous. Sending large spacecraft to the outer planets. Getting small observatories outside of the zodiacal dust cloud. Moving an external occulter for a exoplanet observatory like New Worlds Observer. - SB

Can electric ion propulsion ever become a feasible propulsion method for human flight? Or is it just too slow?

One day I think it could be, it depends on how much power is available. For ion propulsion power = thrust and thrust equal trip time. At lower powers the thrust is just to low to move around human spacecraft - DM

What is the most redeeming quality of your job? In other words, what about your job do you find most satisfying?

Working for NASA is great. The fact that it is never the same thing is what I like the most - DM

Personally I enjoy performing experiments to better understand the physics behind these devices. This information leads to improvements in efficiency, lifetime etc. Also, working on these devices that can really be mission-enabling (especially for science missions) is just really cool in my mind. - RS

Can you elaborate on some of the experiments you've done?

I typically use what's called electrostatic probes - in general I apply voltages to probes and measure how much current is being drawn from the plasma. This can give us a lot of information on the thruster, such as how fast the ions are coming out. I've also used probes imbedded in surfaces to determine the properties of the ions reaching them and how this affects erosion. - RS

Hi team, and thanks for the AMA! For starters, from a complete layman, some basic questions:

*More specifically than harnessing solar energy, how do ion engines work?

*What are the biggest differences between ion and chemical drives, and the advantages and disadvantages of each?

*More generally, do ion drives allow for major differences in the scope of missions? Are ion drives what will take us to Mars in a week instead of six months?

*When can we expect to be flying one of these?

Generally ion engines work by making ions and using an electric field to then accelerate those ions For chemical thrusters the energy is in the propellant, for ion propulsion the energy comes from the sun (via a solar array) Ion propulsion can do the same types of missions as chemical propulsion but it requires less propellant, potentially making missions cheaper There are over 200 spacecraft flying electric propulsion today - DM

There are over 200 spacecraft flying electric propulsion today

I have decided this means that NASA have developed the TIE fighter and are currently amassing a fleet, and have so far made 200 of them. This probably means NASA's next shuttle will look like this.

You got us, thats it! Good for you - DM

Would an ION propulsion drive be viable for getting a robotic orbiter to either Uranus or Neptune?

Yes indeed!! The technology we're currently working on, NEXT ion propulsion, was designed for outer planet orbiters. We would use the ion system in the inner solar system to get the spacecraft on a fast transfer to Uranus or Neptune, then eject the ion propulsion stage (at somehwere around 3 AU). The proposed Titan/Saturn System mission employed this approach. SB

In what areas do you think the technology is lacking and in what ways do you think it has potential to improve?

The main barrier to the more widespread uses for ion propulsion is power sources. Right no we are working on better/lower cost solar arrays that will be a step in the right direction - DM

Have you guys ever played Kerbal Space Program? (I know people at NASA love it.) How realistic is the ion propulsion in that game versus real life?

Personally I've never played it, but I have friends that do. I didn't even know that ion propulsion was in the game! Now I gotta check it out... - RS

What's the cost of the typical ion engine?

The actual thrusters are themselves are fairly cheap. The entire propulsion system for ion propulsion includes the solar arrays (or other power source), the power electronics, the feed system, and the thruster. The various technologies all have different costs, but the entire ion propulsion system (less arrays) typically start in the few $M range. For larger missions that use multiple thrusters, the cost can grow to the 10's of $M. (DH)

any recommended books about the topic?

Most seem to be textbooks. Rocket Propulsion Elements has introductory material. SB

could NASA hire some writers and start writing more friendly readers books about their future missions, that way the public could understand it better and maybe invest more in it?

When NASA awards a mission to one of it's centers or other team members, a certain percentage of the award is allocated to education and public outreach. My experience is that is usually used for web content, student projects and the like. I understand and appreciate your recommendation! - SB

Thanks for the AMA guys!

What kind of propulsion will power the next NASA human landing on the Moon, or even better, Mars?

I think missions to Moon or Mars could use ion propulsion, but not for landing or taking off for the surface. The thrust is too low. Chemical propulsion is the best choice for that - DM

What are the prospects of using ion engines for deep space missions (Pioneer, Voyager, etc)?

Ion propulsion is currently being used on a number of spacecraft ranging from GEO CommSats (over 200 currently fly electric propulsion). Ion engines (a specific technology within electric propulsion) have been used on both GEO Commsats and NASA science missions: Deep Space 1 and Dawn (dawn.jpl.nasa.gov/). Electric propulsion is becoming more and more widespread and will continue to enable deep space missions that are more ambitious. I suspect if we wanted to do a Pioneer or Voyager today it would have utilized electric propulsion. (DH)

What are some of the most mind-blowing projects that could result from ion propulsion? Are we talking colony ships, here?

I don't know if any of the projects I work on are mind-blowing, but I think using ion propulsion to help humans go further than they have ever gone before is pretty exciting. Right now we are trying to understand the best way to send people to Mars. Ion propulsion is one of the options being considered- DM

How do you think Ion Propulsion will affect future space missions?

Also, do space vehicles that employ Ion Propulsion technology have to rely on current methods of transportation (solid rocket fuel or the like) to reach orbit?

Thanks!

Ion propulsion is very useful for deep space propulsion. We will still use conventional launch methods to put the spacecraft into orbit. We optimize the launch vehicle with the electric propulsion system together. SB

I have two unrelated questions.

1. How did you end up getting a job working for NASA? (As someone looking for work right now, I feel compelled to ask.)
2. Do any of you play Kerbal Space Program? And if so, do you make heavy use of the ion engine in the game too?

1. For me, NASA was looking to fill a position around the time I was ready to finish grad school, so it was good timing (and a perfect fit). There should be job postings on the USAjobs.gov website.

2. I've never played it before, and until now I didn't even know ion propulsion was in it. Gotta check it out! - RS

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I started working at NASA in 80's, so I don't have first-hand info, but the main differences are related to budget and the amount of risk we are willing to take. Remember, back then the "space race" with the USSR was politically motivated, and those goals encouraged us to take risks I don't think we would accept today - DM

Voyager has been one of the most impressive probe projects ever undertaken - they're still transmitting to us, and we're still learning from them decades later! What are your thoughts on building a new Voyager-like probe based on ion propulsion? What other interesting missions are in the works based on ion propulsion?

Thanks for the AMA!

Ion propulsion needs electrical power. If that power is from a solar array, that loses effectiveness as the distance from the sun increases. If the electricity was from a nuclear power source ion propulsion could be used for leaving the solar system - DM

Hello fellow Clevelanders!

• How do you test this stuff in real life?
• Are there many prototypes for the larger variety of engine (for pushing humans towards other planets) as of yet? Or still mostly simulation/calculations?
• What kinds of materials are you using to keep the weight down for initial lift?
• Any and all other nerdy details would be appreciated.

EDIT: for clarity on second question

Howdy!! We have a number of large vacuum chambers at Glenn that provide a very good simulation for ion propulsion testing. Basically, you are most concerned about simulating the space vacuum. There have been some laboratory thrusters built that could be useful for human-class missions, but much of that work is still to come. We don't have to get too exotic in keeping mass down; the benefit of electric propulsion is a huge decrease in propellant mass, so efficiency is sometimes as important as mass. SB

Does the iss use ion engines for altitude holding or boosting?

The ISS uses chemical propulsion for drag makeup - DM

Also, NASA has done studies of using electric propulsion for reboost, but it is difficult to implement after the ISS configuration was set.

Do you guys think there is any chance of the space elevator happening this century? I imagine that would make Ion propulsion infinitely more attractive by removing the need for chemical propulsion to get them started.

It certainly would! The reduced cost of the Falcon 9 launch vehicle can also be enabling for more widespread use of the technology similarly. I'm no expert on space elevators, but I wouldn't want to be on it when some kid presses all the buttons on the way to the top! (DH)

How badly did the government shutdown affect your research?

Well we had originally planned this forum in October so the shutdown delayed it. The biggest impact was on ongoing programs and tests. The uncertainty is the biggest impediment to making steady progress. Personally, we also had to scramble to "safe" hardware that had been under test for 8 years! It would have been a shame to damage that equipment because of political gridlock. In the end we avoided that catastrophe. (DH)

With propulsion being one of the most important technologies in Space exploration, do you all believe that we are doing enough research into this sector?

How long do you think it will be before Ion Propulsion is used on Space missions?

Do you feel that we are entering a new Space Age with more nations participating and private enterprise? How do you all feel this will affect the future of NASA research?

Ion propulsion flying today - mostly used for station-keeping of communication satellites. As far as space being a private enterprise activity, I think that doesn't happen without the possibility for profit. There are start-ups looking at it, but for now space exploration seems to be a government endeavor - DM

Hi there, I just wanted to know just how useful ion propulsion is. Is it a way forward in interplanetary travel? How useful is this technology compared to conventional space-flight propulsion methods. Thanks.

Ion propulsion is great when you don't need to reach your destination very quickly and would like the benefits of reduced propellant mass (smaller cheaper launch vehicle, larger payload). Most of the time this corresponds to science missions or station-keeping in Earth orbit. I would still consider it a traditional-type propulsion (it accelerates gas), and the thrust levels are really low the trip times can be long. Interplanetary travel can require a lot of propellant, so ion propulsion would be a great way to reduce that, but you would be waiting a long time to reach your destination (so it wouldn't be so good for a human mission). - RS

How much fuel would it take for a current or on-the-drawing-board Ion-propelled probe to journey from the solar system to Alpha Centauri, assuming constant acceleration to the halfway point and constant deceleration from the halfway point? Assume a probe of negligible mass (compared to the fuel) and whatever departure conditions are reasonable (gravity sling around Jupiter or other outer planet(s) for a "free" boost).

I think we will have to check with Neil Degrasse Tyson on this one! Needless to say it would take a very long time. Being over 4 light years away and the limitation that our current ion propulsion technologies accelerate particles to 10's of km/s (four magnitudes lower than the speed of light) it would take a long, long time. (DH)

Seeing as how ion propulsion is the key to the outer solar system, how does the ion engine scale? Are we looking at having only satellites use the technology? Or will we see space stations use the technology to move around in orbit?

Ion propulsion technologies (a.k.a electric propulsion) are devices designed for a range of current densities. To scale to higher power and higher thrust you need to increase the physical exit area of the device. There are a range of devices with different current density ranges at which they perform the best. So there are ion propulsion technologies that range from a few W up to MW. Over 200 spacecraft currently are flying electric propulsion (ion propulsion). Currently they are mostly communications satellites, but at higher power levels the technology can be used move around larger (heavier) things such as a space station or elements of a human exploration architecture beyond the orbit of the space station. Ion propulsion works great for moving cargo and logistics support of human exploration! (DH)

Mechanical/aerospace engineering student here, graduating in a few months. How does NEXT impact systems integration? (Unique challenges, significant simplifications). Would also really appreciate any advice for a young guy just getting started.

Thanks so much for this awesome AMA!

Edit: I can't spell

NEXT or any other electric propulsion system poses the challenge of integrating a large solar array (if not already on the spacecraft, which it is for GEO Commsats) and multiple electric propulsion thrusters. The thrusters produce high energy ions and plasma that can erode spacecraft surfaces if they are put in the plume (not advised!) and interact with the spacecraft. So there are some challenges to make sure the ion propulsion system doesn't cause damage to the spacecraft.

Advice: Keep taking math and science courses. Get to know your professors and attend office hours! Also consider an internship, co-op, or fellowship. https://intern.nasa.gov/ossi/web/public/main/

(DH)

Hi! I'm an Engineering student at Embry-Riddle, currently in my statics class...

I want to know, what's your favourite thing about what you do as in, what makes you the most excited about what you do? What's it like working at NASA and what stands out for a student to land an internship or, maybe someday, a career at NASA?

Thanks! :)

What really drives me is envisioning propulsion system I worked on being used for a mission like Voyager, Cassini, and others. We don't all get that opportunity though. SB

I don't really have a favorite thing, but I get most excited about working on new mission concepts - DM

What is the current method of propulsion used by spacecraft? And how does ion propulsion differ from this current tech?

Thanks

there are 2 main kinds of propulsion: chemical and electric. Ion propulsion is electric propulsion. Chemical propulsion uses the energy from a chemical reaction to generate thrust. Electric propulsion adds electrical energy to a propellant - the result is much higher fuel economy - DM

Ion propulsion is used on over 200 spacecraft! For traveling through space (after launch), spacecraft use either chemical propellants like a rocket or some alternate advanced propulsion system such as ion propulsion. Chemical propulsion (think rockets) uses a fuel and oxidizer and ignites them producing a hot exhaust gas that provides high thrust to the vehicle. Maximum exhaust velocity limited to the chemical bonds. Ion propulsion uses electric energy to ionize and accelerate a gas to much higher exhaust velocities. This is more fuel efficient, but lower thrust. (DH)

Do you guys think that it's more realistic for ion thrusters to be a secondary form of position adjustment, rather than main thrusters on a theoretical future ship, or do you think that you can ramp up the technology to provide a proper amount of speed?

Various forms of electric propulsion have been considered for attitude control. For example, the Earth Observer 1 mission used a pulsed plasma thruster, in a technology demonstration, to control spacecraft attitude. Large interferometric observatories could use electric propulsion for fine control of position. Exoplanet observatories, such as New Worlds Observer, would use ion propulsion to move the occulter spacecraft around to the observatory-target line of sight. SB

Ion thrusters are already used for station keeping. It is already being used for exciting missions like Dawn. For very large spacecraft, ion propulsion can't be used without a large power source - DM

On a scale of 1-1000 how good are you at Kerbal Space Program?

1, never played. But from how often it is being referenced, I'll have to check it out! (DH)

Is the cost of your research a major limitation? Is more funding necessary for quality research like this to continue at NASA?

Research can be expensive, but space missions can really be expensive. I think the need for ion propulsion technology to conduct important missions is what drives our funding - DM

Why does NASA refuse to hire anyone that has graduated college?

NASA has a large contractor community which hires people fresh out of college too. Those jobs are advertised regularly and civil servant positions are listed on http://usajobs.gov .

What is the time frame for an ion engine to get to relative speeds post separation from its launch vehicle? Like how long does it take to get to 100000 kph, or any other specific speed?
Actually The best way to answer this would probably be, what is one of, or the (idk how all of your equations work) equation that models your speed for engines on satellites, launched or scheduled?

Lastly how awesome is it when something you have worked on or built actually gets launched? Like do you all have a big party? or is it just another day at the office?

Sorry for the large number of questions, I'm actually in an astronomy class going over star life cycles now and some of my friends asked me to write them. FOR SCIENCE! - DrPineappleButts

For many of our planetary missions, we thrust for years to get to our destination. The fundamental equation for deep space is The Rocket Equation, which tells you how much velocity change you get for a given thruster (specific impulse), spacecraft mass and propellant mass. Then you need to know the propellant flow rates to convert the prop mass to time. That however, over-simplifies things. With low thrust trajectories, the propulsion system usage is significantly affected by position in the solar orbit. It is an incredible feeling to have worked on something that flies. We have big parties! Unfortunately, not everyone at NASA gets that experience. - SB

What are your academic backgrounds?

I have 2 degrees in Chemical engineering (BS & MS) and 1 degree in Mechanical engineering (PhD) - DM

I am so fascinated yet so confused. Can you explain what you do like I'm 5? After all, this is the internet... I could actually be 5... But seriously, can you?

I can, because it too, think like I'm 5 (at least some of the time). What we do is work on making space propulsion cheaper and easier. The way we do it is by adding electricity. Its kind of like adding solar panels to an electric car, instead of just relying on the battery power you left home with. The good thing is the sun is always shining in space - DM

Do you think the future of space exploration is with robots or humans? What does landing a human on a planet/space object mean now vs the 1960's?

I think in the future we will continue to rely on both robotic and crewed missions. I think sending crew to planet/space object now is just exciting as in the as in the 60's, but in the information age all of our accomplishments are competing with many more things making it generally harder to capture the public's attention - DM

Kind of like TIE Fighters? Seriously, how has science fiction influenced your desire to do what you guys do?

The dream of making tech for the Galactic Empire is what gets me up in the morning :) Seriously though, science fiction can be a great inspirational tool to push the technology. A lot of science fiction 100+ years ago is now science reality, so it's exciting to think where we'll be in another 100 years. On a separate note my officemate constantly draws spaceships in his spare time, so I'm sure it affects him. - RS

What do you guys think about the whole Mars one mission?

I think its exciting. I am amazed at the willingness of people to risk their life for exploration - DM

Are you able to harness enough solar energy to use multiple ion engines at a time?

Is that even a feasible thing?

Also, if solar cell tech was drastically advanced would that make a difference in the thrust you could achieve?

Yes, but it is all relative. The technology we're working on, NEXT ion propulsion, requires 7 kW per thruster. JPL did a design for a robotic mission to Saturn/Titan that used a 17 kW array (at Earth orbit distance) to power 2 operating NEXT engines in the inner solar system. Solar cell tech improvements would allow you to get more power to the ion propulsion system, thereby increasing the thrust (or to reduce the solar array size and cost and get to a cheaper solution) - SB

I'm currently sitting in an engineering conference, and you guys make me feel stupid. Can you "explain like I'm 5" ion propulsion? Love your work, I hope you get more funding!

My daughter is 3 and she asks me all the time about my job so I'll give it a shot. You take a particle and ionize it so it has a positive charge. Then you try to accelerate the particle somehow. We use electric and magnetic fields to do that. If you put 2 oppositely polarized magnets together they repel each other. We basically do the same thing between the spacecraft and that tiny charged particle. The spacecraft pushes the charge particle and it pushes a little on the spacecraft. Just like if you were on a chair with wheels and were shooting a paintball gun. Every shot would push the chair in the opposite direction a little bit. Take millions of shots and you get going! As you can guess my daughter's follow-up is typically, "huh?" Hope this helps! (DH)

Here's an /r/ExplainLikeimFive post about ion thrusters that might be helpful! - SMT