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Aerospace Galactic Navigation System (GNS)

  1. Jun 7, 2012 #1
    We've all seen them in sci fi movies and video games like Mass Effect.

    Assuming you had built a spaceship, you would need some sort of Navigation system.
    A Starmap if you will, detailing such bodies as stars, exoplanets, gas planets, moons, asteroid fields, comets, etc. Also including their trajectories, orbits and orbital periods, rotation speed(or spin). Detailing all information within the Milky Way, would be a considerable easier challenge than trying to count the stars of the universe.

    Also, you would need to be capable of detecting all objects in your path, currently we have the ability through NASA to pick up on objects about as small as a basketball, but a particle of dust at high speeds could cause failure in a spaceship. Not that we could reach those speeds in the next hundred years anyways. Suffice to say though, a complex navigation system comprising of scanning technology, speedometer, starmap information, and a new theoretical technology, holographic technology so that you can view the starmap like Tony Stark in his garage with his computer, would be the basis for my Navigation systems in my theoretical spaceship. Now with the exception of Stark-like holographic tech, all of this is possible today. Of course over the next few years all current techs will improve, and within the next 20 I foresee them figuring out the holographic situation.

    With that explanation out of the way.

    I intend to build my own ship. Yes, I'm crazy, dumb, it can't be done, etc, etc, etc... Now that all the haters have left.

    What am I missing with this Navigation system? What properties would it need to be a viable Navigation system for a spaceship reaching .113 the speed of light?

    I hope to have meaningful discussion here, as well as the fact that I may or may not be looking for some help in building this.

    I can make the ship, it's easy.
    The propulsion system will be my main issue.

    I have no intention of pursuing electrical engineering and computer science. I build sh!t, not write. So I need a teammate, that is willing to work on a theoretical navigation system, for a theoretical spaceship that may or may not ever exist, for free. Simply because I am a ME student, pursuing AE, with a focus on astronautics. and because of that, I cannot pay for help, but rather would be looking into a sort of partnership of sorts.

    I understand that 10% lightspeed is an unrealistic lifes work, but I'm sure reaching Alpha Centauri within 15-30 years is well within our technological grasp as it stands TODAY, so what will another 15 years bring to the space table?

    I understand I will most likely have to find a space-oriented partner through school, or the industry when I complete my education, but I lack the patience to wait that long to meet people of like mind and goal.

    So let the discussion begin, and I hope to meet you all in good time.

    Btw, I'm Matt, new to the forum, hey guys. :)
  2. jcsd
  3. Jun 7, 2012 #2


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    It's pretty well agreed that we could not do it today.

    1] We absolutely cannot build any craft that could do it in that short a timeline. Our fastest craft to-date has taken 30 years just to get to the front stoop of our solar system.
    2] We certainly can't do it and carry the life support for passengers to keep them alive for many, many decades on the trip there and back again.
  4. Jun 7, 2012 #3
    With Ion drives, as the technology stands today, we could reach alpha centauri in just over 40 years. Utilizing fusion energy, we could increase the amount of thrust they produce, although the overall weight of the craft would be increased, to hold the extra fuel to make up for your ion drive. I would prefer a meaningful discussion instead of you coming in here telling me how it will not work, quit being negative, and contribute something positive.

    and btw, voyager is not our fastest craft. being that it is the only one that has reach the outer limits of our solar system I assume you could not mean any other craft.
    as far as life-support is concerned, you make an excellent point, however, your negativity overshadows your creativity and productivity.

    Did I come to the wrong forum?
  5. Jun 7, 2012 #4

    D H

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    No, we couldn't. And certainly not with people on board. The ideal rocket equation gets in your way.

    A mission that comes to rest at Alpha Centauri will require a lot more fuel. A whole lot more fuel. So let's make it a flyby mission. The vehicle will accelerate until it runs out of fuel and just coast the rest of the way to and through the Centauri system. A life support system adds an incredible amount of mass, and besides, the passengers won't like the idea of being stuck on the spaceship forever. So let's make it a robotic mission.

    Let's say that the total mass of the spacecraft structure, the sensors, the comm system, thrusters, and fuel tanks is 1,000 kg. That's ridiculously small (while we can minimize sensors nowadays, we can't do so with the comm system, nor with the thrusters, and certainly not the fuel tanks (this project need some BIG fuel tanks)), but's let's just pretend.

    Let's assume a 30,000 second specific impulse, and ignore that ion thrusters with that high of an Isp attain this at the cost of near zero force. Let's ignore relativity (it will only make matters worse). Let's ignore the acceleration time: Pretend the vehicle gets up to your 0.113 c almost immediately.

    This amount of fuel we need to load into this vehicle to achieve this goal is 1053 kg. That's about the mass of 1010 Milky Way galaxies.
  6. Jun 7, 2012 #5


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    I'm sorry if you thought I was being negative. I figured you were looking for some facts so that you could make at least a reasonably plausible construct.

    You did make a claim that you thought it could be done with our current technology. I put that claim in perspective.

    I would call that the very essence of meaningful discussion.
    Again, didn't impart any negativity on it.

    This forum will most certainly give you the facts, and realistic scenarios. If you're looking for creativity, you should have this post moved to General Discussion and be explicit about what you want.
  7. Jun 8, 2012 #6


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    Welcome to the forums. I wouldn't necessarily call you crazy (Elon Musk has taken some small but positive steps towards his goal of a Martian retirement) nor necessarily dumb but it would definitely be advantagous for you to carefully learn from the feedback you are going to get. Aerospace is utterly non-trivial. It takes billions of dollars to fund a space agency and even if you just took off-the-shelf designs millions of dollars to build a rocket and get to orbit.

    Aerospace is only just entering the realm of privitisation and there's no way to know how that is going to go. There's no reason to think that amateur aerospace will ever be a reality (or at least be one any time soon).
    What's wrong with a database of stars and their relative positions and speeds?
    Minor quibble (compared to the rest of the feedback you are going to get) but as far as I am aware holographic technology as seen on TV is impossible. You can't just project light into the air and get it to form 3d, flourescent shapes. You can simulate the effect with 3D screens and motion capture technology and that will probably get a lot better over the next few years.
    I'm pretty sure it wont be. Construction of a rocket just capable of delivering a payload to orbit takes a highly technical industry with thousands of skilled workers, millions of dollars and a sophisticated design to follow. Interplanetary manned travel (that we have never done) will take far more and interstellar far more than that.

    Off the top of my head an interstellar craft will need a highly sophisticated propulsion system, produce planetary scales of energy*, contain a totally self-sufficient productive and sustainable ecosystem (capable of keeping a crew skilled and large enough to maintain the vehicle alive) and have very good protection from radiation. That's something I doubt an intercontinental collaboration could pull off anytime soon, let alone one person with (presumably) everyday resources.

    *Following D H's example with a 1,000kg craft the absolute minimum energy needed to accelerate it to 0.113c would take ~575PJ of energy. That's enough to power the entire of human civilisation for nearly half a day. And as D H points out our technology is nowhere near that efficient.
    If you have most of a design for a viable interstellar craft that can be built by just a couple of people with everyday resources then you are already a rich man.
    I don't doubt you at all but could you show your working for those of us unfamiliar with the math? :smile: I'd quite like to learn more about these sorts of things.
  8. Jun 8, 2012 #7

    D H

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    Any vehicle that operates by expelling momentum in a direction so as to accelerate in the opposite, aka a rocket, is limited by the ideal rocket equation. Suppose you find it takes Δm reaction mass (e.g., fuel) to change the velocity of a vehicle of mass m by some amount Δv. Now suppose you want to go twice as fast. You can't just another quantity Δm of reaction mass to the rocket. You instead need to that much plus a lot more because now the payload has a mass of m+Δm. Going ever faster requires an exponential increase in reaction mass. This is the subject of the ideal rocket equation,
    [tex]\Delta v = v_e \ln\left(\frac{m_p+\Delta m}{m_p}\right)[/tex]
    Here, [itex]v_e[/itex] is the velocity of the exhaust relative to the rocket, [itex]m_p[/itex] is the mass of the payload, and [itex]\Delta m[/itex] is the mass of the reaction mass, all of which is eventually ejected by the time the rocket has changed its velocity by [itex]\Delta v[/itex]. Another way to express this is
    [tex]\Delta m = m_p\left(e^{\Delta v/v_e} - 1\right)[/tex]
    A rocket can be made to go faster than the exhaust velocity, but only at the cost of an exponential growth in reaction mass. In this case, we have a specific impulse of 30,000 seconds (which is very, very good), or an exhaust velocity of 294 km/s. That's less than 1/1000 the speed of light. To achieve a velocity of 0.113 c, the ratio [itex]\Delta v/v_e[/itex] is 115. [itex]e^{115}[/itex] is a very, very big number.

    Another problem with rockets, one that I completely ignored, is that adding a lot more fuel requires increasing the size of the fuel tanks. Those big fuel tanks are dead mass; they're payload. (I ignored this because a fuel tank that could contain the mass equivalent of 1010 Milky Way would weigh a bit more than 1000 kg.) One way around this problem is to use a multi-stage rocket. Now those big fuel tanks needed to get the first stage going are not a problem at the end.

    It is possible to use ion propulsion to reach Alpha Centauri. Just not in 30 years. Reaching it in a 1000 years (in a flyby mission) is quite doable with a rocket with a specific impulse of 30,000 seconds.
  9. Jun 8, 2012 #8


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    Excellent! Thank you very much D H. I've stored that in an excel spreadsheet to play around with later.

    EDIT: If you have the time is there a way to modify this to take into account a deceleration leg of a journey and continuous thrust?

    EDIT2: Would I be right in saying that to calculate the required fuel for a decelleration one just has to add the reaction mass and payload and put that number into the equation again as just payload?
    Last edited: Jun 8, 2012
  10. Jun 8, 2012 #9
    So I'm p!ssed, I wrote out a whole reply to you guys, and this dang website logged me out so I couldn't reply, now I have to type everything all over again. It was quite lengthy as well.

    Anyways, out of frustration and impatience I'll try to shorten it.

    I'm sorry for being mean.(and I'm sorry for typing like a child, this site censors language.)
    I was full of ego, and having a bad day, but it's not like you care for excuses anyways.

    Moving on.

    I don't have the info in front of me, it was weeks ago that I read into the Ion drive last, and I remember them saying under optimal conditions it could reach the speed of light, I thought that claim to be quite asinine, and that 10%LS would be a more approachable goal. Truth be told, we probably won't be able to achieve even 1%LS in my lifetime, so I need to put my childish fantasies in a box and lock it, cause that's mainly what I was going off of. I know I asked you for Navigation system info, but by commenting on the initial idea for an interstellar craft you helped me to see the error in my ways and have saved me a lot of time and heartache. I realize now that the cost of such a craft is outside my budget, so I give up.

    Also, the math you included in this thread, I have no idea what it means, it's gibberish to me. Clearly I am an uneducated fool in need of a real education instead of putting bits and pieces together. Time to grow up and get my head out of the clouds.

    As I said previously I had not thought about the life-support systems, and I don't believe cryo to be a realistic proposal, so some other form of cryo(I'll use the term "stasis") will need to be looked into, which I will not be focusing my career on, so it's a mute point in trying to create an interstellar craft at this point in time, and probably for the next 2 centuries, although man will try, all attempts will most likely, even with exponential technological growth, be laughable at best.

    So I will focus my efforts on my original dream, a lifelong career where I do not work an 80 hour week making video games,(I am an artist, not a gamer) so that I can have time to make and have a family, as well as eventually create my own shuttle to go play in space, whether to see the moon, or even mars, or any other planet in our system. With this in mind. (fantasy alert)How would I reach Pluto in less time than it takes to drive from new york to LA, I understand this is a lofty goal, and impossible today, but the private industry is opening up, and I believe we will see a lot more in the coming decades. I am interested in theories here. and I must apologize again because I came here unprepared, I have not reviewed any of Einsteins work, so relativity is just a word to me, I have no knowledge about any of it. All I know is energy is equal to mass, or something like that, and you cannot get more out of something than you put into it.

    So, to summarize, I am sorry for being mean, and dreams of interstellar space travel on a timescale that I will actually get to see my destination are unattainable, I am however under the firm conviction that we need options, we need to get man off this planet and spread amongst the galaxy. That is perhaps another thread all together, but I am open to ideas.

    Having read over this reply, it seems childish and dumb to me, but I hope despite my lack of communication skills, I was able to relay the general message to you guys.
  11. Jun 8, 2012 #10

    D H

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    Now that's a better attitude.

    One thing to keep in mind: Sci fi is just that, fiction. Usually mediocre fiction and very badly done science. Real human space exploration is not what you see in the movies or on TV, Apollo 13 excepted.

    If you don't understand the math, you can learn. Some people can't, but that's OK. There are plenty of key places in the space industry for people who aren't "rocket scientists". (And rocket scientists can be really dumb in those other key places.) Besides the obvious, which I'll get to in a second, we need
    • Life scientists (e.g., biologists and doctors). We're sending people into a very hostile environment. The next breath of fresh air is 100 km away even in low Earth orbit. NASA has an entire directorate at the Johnson Space Center whose main goal is making things easier/better/safer for astronauts in space.
    • Policy wonks. That's primarily what NASA Headquarters is populated with. The question of whether we will or will not perform space exploration is ultimately decided by politicians. Someone needs to communicate NASA's goals and aspirations to those politicians, and those someones typically are not engineers. They're policy wonks who have been infected with the space exploration virus. Policy wonks are also needed in NewSpace to convince potential investors that some private venture is the right way to invest their billions. This obviously is not the typical salesperson. The term policy wonk is still apropos here.
    • Bean counters (accountants). Whether its public or private, getting into space requires lots and lots and lots of beans. It's not cheap. Engineers, doctors, and policy wonks are all very bad at counting beans.
    • MBAs. Engineers, doctors, and policy wonks are also pretty bad with regard to managing people and projects. One of my co-workers on one of the projects I work on is currently getting his MBA, financed by his employer. When he get's it, I'll drink him a toast and say goodbye. He'll be moving on to a more influential (and better paid) position.

    Now for the obvious. The space industry needs:
    • Aerospace engineers. Somebody needs to understand all that stupid math. Those somebodies are aerospace engineers. Guidance, navigation, control: Aerospace engineers do that.
    • Mechanical engineers. Spacecraft are structures. Structural engineering is a sub-branch of mechanical engineering. Spacecraft for astronauts need life support. That's also a sub-branch of mechanical engineering, with a good dose of biology tossed in.
    • Electrical engineers. Modern spacecraft contain lots and lots of wire. Wire for power, wire for carrying signals from sensors, wire for carrying signals to effectors. Some of that heavy wire is being replaced with radio, and that's also the domain of EEs.
    • Computer programmers / computer scientists / software engineers. Aerospace engineers, mechEs, and EEs all design algorithms. For the most part, they are absolutely atrocious programmers. Really, really bad programmers. Processing all of those signals, safely encoding all of those algorithms, making everything in the spacecraft fly-by-wire takes good computer programmers, computer scientists, and software engineers.

    There are lots of choices. The above lists are not complete. The key thing is to get educated in something. You wouldn't believe how many silly resumes the company for which I work receives. "My degree is in art, but I've watched all of the Star Wars movies and I really want to work on going to the stars."
  12. Jun 8, 2012 #11
    I've done construction and art my whole life, I like to build things, but also the artist in me would like to not only put this piece here, but design the pieces as well. I believe it to be something unique that I bring to the table, I had thought of being a propulsion engineer, and wondered what would be required of me?

    SpaceX has a position open(Ya, I know) for a propulsion engineer, with a requirement of a bachelors in mechanical engineering. I seriously doubt school is gonna prepare me for advanced propulsion engineering, so where would I expect to start. such as responsibilities and duties with only a meager BA?

    I hope I'm asking the right person, I don't mean to assume you have all the answers, you just seem quite knowledgeable of the industry overall, rather than a one specific area.
  13. Jun 9, 2012 #12


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    Sorry about that, if you don't click "remember me" it will auto log you out after 5 minutes. Often I find myself copying what I write into a word processor or just onto the clip board just in case.
    No worries :smile: we all have bad days. And I'm very impressed by your attitude, most people simple close their ears to criticism and get nowhere. Well done for recognising where you need to learn more and embracing that. Try not to get disheartened, we all have grand ideas when we're first starting out.
    Don't be so hard on yourself. Honestly recognising areas you need education in is a great skill and a positive asset :)
    Be careful here, there is a pervasive narrative myth that technology in all sectors is "exponentially developing" and that this will always continue. The truth is there is no evidence that this is the case, outside of Moore's law most technologies and fields develop at various rates but even more important to remember is that for many fields there is no good way to determine a metric by which to measure improvement by.
    Best of luck :smile: sounds like a good goal, though you may want to lay off the hours when you're perusing the family.
    I'm afraid most of the objections raised apply to this as well. NASA's space shuttle cost billions and required a high tech industry of tens of thousands of workers to build and maintain and it only went to LEO. IMO the best the average young person can hope for is that at some point in their lifetime space tourism will become affordable for a quick jaunt to orbit, perhaps even in a space hotel.

    The biggest problem with these things isn't the technology though (obviously better technology that brings down the cost is important) but the economics. Even if a small private space station could be built for a few billion and tickets there sold for tens-hundreds of thousands per person how much of a market will you actually have? It's a bit of arguing over angels dancing on heads of pins because we wont really know how the market for space tourism will work until it is tried properly.
    A bit of googling tells me that NY-LA by car takes about two days. Using this resource it seems that to travel the 7.5 billion kilometres to Pluto in that time would take a continuous thrust of 100gs (more than enough to kill a human). I've probably used my new ideal rocket equation excel incorrectly but it seems that the fuel required is far in excess of the mass of the universe for a 1 tonne craft...
    There's a lot to learn obviously but just to start you on something interesting:
    I disagree that we need to do this, IMO most of the arguments for the need to colonise space defeat themselves because the technology required to achieve them removes the threat they were proposed to deal with. E.g. Colonise space in case the ecosystem collapses, but to do that we'll need to know how to construct and maintain self-sufficient, productive ecosystems so it's A) incredibly unlikely that a civilisation with this science would let their ecosystem collapse and B) if it did start to it would be more economical to fix it where they are.

    Best of luck in your education :smile:
  14. Jun 9, 2012 #13
    Thank you.
    Yeah, I figured it would take about a week to get to LA from NYC, it takes me 2 days to get from where I'm at to LA driving through the night. In Idaho. Still though I meant simply as an example. for instance travel to pluto could be completed in 2 months, still unrealistic but I just wanted to clarify what I was saying previously.

    True, it would probably take millions to create even a mediocre craft and even then with what's swirling around in my head, NASA could get to the moon faster, lol.
    I must also say that I may have been unintentionally misleading, the craft that the Danish made for $100k doesn't actually reach space, just the end of our atmostphere.

    Thank you for the links, I have a lot to learn and I feel that me coming here was the best thing that's ever happened.

    I have my answers. Mods if no one else wishes to contribute a final note, feel free to close this thread.

    You have made an excellent impression upon me, and I will see you around :)
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