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John Doe

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  1. John Doe
    OK. Got it, and successfully pulled it off. I was just ending up with the moon right in the line of my initial escape trajectory towards it, so that my Pe to the moon was zero, with either the option of travelling the other direction, OR the option of smashing into the moon at a relatively high velocity.
  2. John Doe
    But for the fact that the STS payload (the orbiter ) was ALOT heavier than the Apollo CSM / lM payload. YET the STS stack was quite a bit smaller than the Saturn V stack. If the Saturn V had to be big due to the Payload, one would think the STS stack would have had to have been more around the size of the current SLS / Orion, given the fact that the orbiter itself was much larger. (the Apollo craft weighed at around 37,000 lbs, where as the STS orbiter (without the two SRBs and External Fuel Tank) weighed in at around 151,419. IF more weight should necessarily mean a bigger stack, then it stands by reason that the STS stack should have been somewhere around twice as big as the Saturn V. ( This also accounts for the fact that the STS External tank, was roughly the same diameter, though considerably shorter than the Sat V stack,) However, the external tank, when the stack was pad-ready, was the largest and heaviest component of the stack, (66,000 Lbs Empty and 1,667,667 Lbs in launch-ready state) with most of the space / weight being nothing but fuel, as opposed to the Saturn V's weight being influenced a bit more hardware-dependent. This would tend to suggest that the size of a stack is dictated by the ratio of how much mass within the stack is actual fuel Vs. payload and hardware, which may not necessarily require an increase the size of the stack itself.
  3. John Doe
    So then from what I'm reading here, is that upon reaching the Pa node of the tranfer orbit, near the moon, the moon should then, by operation of it's field of gravity, start causing a descent in line with it, since the moon's gravitational field should have more influence than kerbin's ? and what I'm seeing on the lunar insertion burn is that I end up changing directions after about 30 into the burn..
  4. John Doe
    Ok to clarify things a bit, when I said prograde, I meant the retrograde marker, which is a prograde burn in orientation to the the moon. (i.e. firing in the opposite direction of velocity, in order to resist and slow the velocity.) Second, by parabolic orbit, i mean an quite elliptical orbit with around a LEO Pe to Kerbin (around 228,000 m or so ) and a really high Ap (around 3K m or so) which extends slightly beyond the moon, while keeping the moon inside the orbital path at the time I'm at or arround Ap, to where essentially I'm on the backside of the moon. (this seems to be, from what I've read in the NASA archives, what Apollo 11 did, when they did most of the dirty work of insertion into lunar orbit and the LM decent on the back side of the moon.) What I was also finding was that, within the training tutorial, that the retrograde burn was causing me to essentially change directions and end up on what the map calls an escape path back toward Kerbin.
  5. John Doe
    The thing is that I'm trying to learn as much of the basic theory as I can, as to prepare myself for the lunar mission. I've figured out how to establish a nice, fairly ciruclar orbit. The thing is that my instinct is to then establish a parabolic orbit that places the moon on the inside of the orbit, as the transfer orbit, and then to do a burn from there to do a decent stage toward the moon, and finally to to counter my decent at a certain point by firing on the prograde, in order to establish a lunar orbit. Problem is that when trying to do this, my initial burn is a good 13 second burn, and I establish the parbolic orbit as planned. The second one usually ends up on a kerbin escape path, and I end up at an astronomical altitude (like 3K to 4K) orbiting the sun, by which point my rocket says no more, and I have to drop it, leaving poor Mr. Kerman in orbit around the sun forever.
  6. John Doe
    Great so that explains WHY accelerating to a velocity of around 800 m/sec. or better (which my intuition told me was a good idea, in the sense of faster as early as possible would seem to afford one the best chance of orbit.) was just NOT working... lol. I was getting a velocity of around 900 m/sec. by 1 minute to 1:30 minutes into the mission. The question then becomes, just so I'm getting the concept right, why then, NASA's Saturn V rocket was so BIG. ( at around a little less than a 100m stack), If the idea that faster- sooner is a bad thing for establishing orbit. I mean, even with throttle control, the bottom of the Saturn V was a MONSTER as compared to the Redstone or Atlas rockets. and I would therefore at least think, that the velocity between the two (even given the differences between the weight of the payload) would be as such that the velocity encountered with the saturn V, but for the roll and turn which was standard in the Apollo launch sequence, would result in an escape path.
  7. John Doe
    Got it- so the elipical shape of the orbit is really only elpitical by such small fractions that its not observable by looking at the geometric shape....(i.e. the shape is so marginally eliptical that it still appears to be circular. I was making the assumption that hyperbolic was synonymous with elliptic. I was also understanding the orbit to be an complete escape of gravity combined with the effect of inertia.
  8. John Doe
    So, then basically what your saying is that it's pretty much impossible to raise Ap And Pe at the same rate? ( you actually have me confused. trying to really get the hang of orbits as there was this point in the basic demo about establishing a lunar orbit, wherein I am at the stage of being on a collision course with the moon, in which the only hint was "remember what you learned about orbits in the previous tutorial" which was basically nothing more than how to raise /lower Ap / Pe. So My instinct was to fire Prograde to slow down my velocity to avoid impact, and perhaps establish a Pe. (not a good idea) So basically Yeah, I'm trying to learn all the crap that the tutorial isn't saying. Also bear in mind that I'm used to flying STS missions in orbiter, which always involve the pretty much SAME type of orbit, and the orbiter is doing practically ALL of the hard parts- the burns are automatic once you program the computer to tell it what you want to accomplish. So really, outside of really basic concepts, I have no idea of how newtonian physics might somehow apply differently than what would be plainly obvious.
  9. John Doe
    I'm using the old 0 series demo. So all I have are the three stock liquid engines, two sizes of fuel tanks, and the small SRB to work with. and none of the basic tutorials mentioned the concept of TWR. Basically what I'm after is a twist on the Saturn V design.( i.e. a massive tri-coupled lower stage with a moderate middle stage, and a smaller final stage, to where what we get is more or less something like a Saturn II-B sitting on top of a massive bottom stage, which is is quite large because of all the weight sitting on top of it.
  10. John Doe
    Which makes the shape of the orbit an offset CIRCLE, NOT an Ellipse, by defintion. An perfect ellipse is twice as long as it is wide, with Ap and Pe at, or near, the length of the ellipse. Think about it like this. Take a coffee cup and turn it upside down. the perimeter of the cup represents a perfect circular orbit. Now, place a bottle cap in the middle. This represents the object orbited, such as Kerbin. Now, if we move the bottle cap, we see that we modify the Ap and Pe nodes, WITHOUT modifying the shape. (i.e The coffee cup DIDN'T change it's shape and turn into an ellipse just because we moved the bottle cap.) So long as we keep the Pe node high enough, (i.e. we don't place the bottle cap closer than x to the perimiter of the coffee cup, where x is the maximum Pe allowed that will allow a re-entry ) the laws of physics do not allow re-entry, and because we haven't accelerated towards an escape node, (which changes the shape and path of the orbit) we will not rise higher than Ap. Thus, we cannot travel outside the path of the orbit, and we cannot re-enter unless we drop the Pe enough. There's nothing I've been able to locate within newton's laws on gravity that state this theory to be incorrect, assuming that our velocity never changes. (which can be accomplished with a burn in the right direction at the right time.) I've seen nothing in newtonian physics that states that this cannot happen, though it is extremely difficult to make it happen.
  11. John Doe
    What seemed to do the job was throttling down to about 75 percent or so after reaching a velocity of around 150 m/sec or so, before 10,000 m, executing the 45 turn , and Then opening up the throttle and burning all out, which in turn, caused my suborbital path to broaden out quite a bit. I have two possible schools of thought on this- The first one, the obvious one, is by keeping my velocity relatively low before the 10,000 m mark slowed down the overall max velocity proportionately. The second is that it saved the fuel until a point in the flight with significantly lower gravity / drag effects, and thus burning the engines at the same rate does more work, thus increasing velocity that you might not get otherwise.
  12. John Doe
    only seems to hold true to a certain extent- What then, do you suppose happens if we offset a circular orbit, but not enough to lower the Pe below the threshold for re-entry? We haven't changed the shape, we have just lowered Pe and raised Ap.
  13. John Doe
    Not necessarily- If I take a perfect circle and off-set it- its geometrical shape doesn't change, but relative to the object in the center, the Ap and Pe WILL change, Ap=Pe ONLY if we have a perfect circle AND zero off-set in relation to the object being orbited. The same can hold true for a perfect ellipse- Ap = Pe IF the shape is geometrically perfect AND there is zero offset of the body being orbited. (i.e. the object is perfectly centered within the geometric structure of the orbit.)
  14. John Doe
    If your trying to be funny, don't quit your day job :-P
  15. John Doe
    I figured out what happened. I was accelerating with about 8 times too much velocity during the initial phases of the launch, causing me to accelerate to Ap so fast that I ended up doing my burn too late, and thus have to fight both my fall toward the suborbital Pe AND at the same time fight to Raise the Ap, so in, effect I was doing two manuevers at once, in a single really LONG burn.
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