CEV may be UNNECESSARY for moon missions!

[gaetanomarano]

<br />true... a lagrange point is "efficient" only for a static station (but I'm not sure it will be completely safe)<br /><br />also, a space station in a lagrange point is an incredibly little target to hit and the probability to fail this essential stop may be very high<br /><br />too risky for to-day's technology<br />

 

[mlorrey]

On the contrary, a lagrange point is a whole region that stations tend to orbit around the center of. The advange to the traveller going there is that they don't need delta v to fly by the moon and depend on the moon to capture you. Instead, you launch in a Hohman transfer trajectory to peak out at apogee in the Lagrange region, and then proceed on thrusters or other small burns to the station. Even more efficiently, you can take several orbits from LEO, using several short burns at perigee to progressively increase your apogee until your apogee is at the lagrange region.<br /><br />The advantage of these methods is that it uses three body orbital mechanics rather than the standard two body mechanics of ordinary spacecraft navigation.

 

[gaetanomarano]

<br />from the first day (20+ years ago) I've read of a possible (little or giant) lagrange station, my doubt was (and is) the lagrange point by itself<br /><br />we have not an experimental notion of lagrange point... then, we don't know if an object may be REALLY stable and safe<br /><br />gravity forces of earth and moon are very powerfull... How we can be sure to find the RIGHT point?<br /><br />which kind of high res laser align it will need?<br /><br />do we have a similar technology now?<br /><br />and if we fails the right point?<br /><br />how we can brake a giant station falling toward earth or moon?<br /><br />how we can (and how many vehicles will need) to rescue a 100+ lagrange station's crew in time?<br /><br />how they can survive if the station falls to moon?<br /><br />and, if it will crash on a future moon base?<br /><br />no, it's too dangerous for to-day's technology and it need many real experiments to do<br />

 

[bwhite]

My understanding of some of the advantages of EML-1 are:<br /><br />Considerable stability compared with low lunar orbit. Not perfectly stable (the other L points are said to be better, just not as convenient) yet vastly superior to LLO with respect to stuff staying where you leave it.<br /><br />Rendezvous from the lunar surface is not constrained by launch windows. If a CEV (or a Shenzou) is in low lunar orbit, an LSAM faces limited launch windows to be able to successfully meet the on orbit vessel. The EML-1 launch window is open 24/7. <br /><br />An EML-1 station can support lunar landings pole to pole.<br />

 

[nacnud]

There are currently space craft at SEL1 (the Sun Earth Lagrange point 1) and have been for years, look up SOHO.

 

[ve7rkt]

Gateano, here's what you do. You figure out where the station is. Maybe you use something not entirely unlike GPS. Maybe you bounce laser rangefinders off the Moon. Maybe you just do the same navigational stuff they've been doing since Apollo, only better now that a star tracker the size of a PC mouse has many times the accuracy of an Apollo-era star tracker the size of an office chair. Maybe you have an instrument mount with two opposed cameras, one pointed at the Moon and one pointed at the Earth, and you're in the right place when the Moon and Earth are exactly centered in each camera and each is the right size in the field of view (for correct distance).<br /><br />And you watch for the moment that you drift more than a few meters out of position. And you will. Even the best placed satellites in geosynchronous orbit drift. Some drift as little as 0.001 degrees per year [edit: by my math, that's 736 meters], but they drift.<br /><br />And when you drift, you take one of those little maneuvering thrusters on your hull, and here's what you do, this is the really great trick: you turn one on for a tiny fraction of a second. And it pushes you back into place.<br /><br />How can we evacuate a 100+ person crew from a Lagrange station? Well, by not putting 100 people on it. People are talking about a gas station, not a trade and convention centre. NASA's plan for an L1 gateway station was far smaller than the ISS. Here is a picture of their concept with something that looks like an LSAM, an early idea for a crew transfer ship, and an astronaut on EVA for scale.

 

[gaetanomarano]

<br />I don't know so much of SOHO but a "sun lagrange" point may be similar to a "sun geostationary orbit" or an "earth parallel little planet" (I will better know it), also, the sun-earth distance is very long... and SOHO is not a manned station<br /><br />the earth-moon distance is apparently safe, but, in case of problem may become very short!<br /><br />and the time to save the station's crew will be of only a few days<br /><br />+/- 1000 miles out of the "right point" may be sufficient to start a disaster<br /><br />too dangerous... however, practical experimenting may give exact info about right points, object stability, gravity fluctuations, etc.<br /><br />my opinion is that lagrange point is interesting under scientific aspect, but not so much usefull for space travels... probably for a telescope...

 

[gaetanomarano]

<br />if the station will unmanned the risk don't exist (but it costs, so it need some practical experiments)<br /><br />my refer is to an old idea to put giant city on lagrange point (I've not a link now but certainly you know it)<br /><br />accepting that a lagrange station will be stable... the problem posted by Nibb31 exist... too much fuel to brake and restart... probably much more of the advantage to have a lagrange fuel station... also, why put a fuel station in a lagrange point if we can put it in lunar orbit? all will be easier!<br />

 

[bwhite]

Low lunar orbit is quite unstable compared with EML-1. You will need to keep that fuel depot from hitting the lunar surface.<br /><br />Also, if you place your fuel depot in LLO, what orbital inclination do you choose? EML-1 can be reached from anywhere on the Moon, at any time. And vice versa.<br /><br />My proposed Gateway is indeed small. <br /><br />1 FGB-2 module<br />1 Bigelow style TransHab<br />1 docking module (but with multiple air locks)<br />Racks for a tank farm<br /><br />Tanks of methane and water provide radiation shielding. One major disadvantage for any station beyong LEO is being bathed in hard radiation. But that is equally true for LLO and EML-1.<br /><br />A dozen people when its really really busy changing trains.

 

[strandedonearth]

" for redundancy and crews' safety..."<br /><br />Space is like the Wild West in the 1800's, or settling the New World in the first place: It's not for cowards. You keep yapping about doing things on the cheap then throw money away by having 3 spare LSAM's way up there. People that open up frontiers accept that they may only come back in a bag/box/urn, if at all.<br /><br />I'd happily go to the Moon or Mars knowing I might not make it back. It beats being stuck on this miserable mudball. At least the first person buried on the Moon will have a spot in the record books, and won't have to worry about being worm food.<br /><br />Sure, you want to try to make it safe, but there comes a point of diminishing returns. Like 3 backup LSAM's? Why, you might be able develop the nose cone of a a spaceplane with that money.<br />

 

[mlorrey]

It should also take less delta v to get to EML-1 than to get into lunar orbit from the lunar surface. Why? Because to get to EML-1, you only need delta v for a straight up suborbital trajectory that peaks out at L-1. Getting into orbit requires going much faster.

 

[mlorrey]

It should also take less delta v to get to EML-1 than to get into lunar orbit from the lunar surface. Why? Because to get to EML-1, you only need delta v for a straight up suborbital trajectory that peaks out at L-1. Getting into orbit requires going much faster.

 

[bwhite]

<i>It should also take less delta v to get to EML-1 than to get into lunar orbit from the lunar surface. Why? Because to get to EML-1, you only need delta v for a straight up suborbital trajectory that peaks out at L-1. Getting into orbit requires going much faster</i><br /><br />Cool! <i>peak's out</i> means zeroes out, same as a baseball or golf ball at the top of its trajectory before it starts coming down, right?<br /><br />Like catching a can of corn tossed up to a 2nd floor balcony, at apogee and for an instant, its stationary? Right?<br /><br />Yup, that is cool! With zero velocity at apogee, it would return to the Moon except for Earth's gravity which balances it out. <br /><br />Any suggested links to illustrate the point? <br /><br />= = =<br /><br />Edit to add this link for EML-1 information:<br /><br />http://www.space-frontier.org/cgi-bin/BBS/MoonBase/read/8505

 

[gaetanomarano]

<br />if a low lunar orbit is unstable they can use an higher orbit<br /><br />but lagrange point or lunar orbit refuel may be completely unnecessary of LSAM will be refuelable<br /><br />after lunar landing half tanks' volume is 2/3 empty, then, it may simply refueled on lunar surface (that is clearly stable...)<br /><br />I think that lagrange use need long experiments with "dumb" objects<br />

 

[gaetanomarano]

<br />it's not a problem of brave or coward astronauts<br /><br />we can send only very brave guys, but this don't open space to real scientific research and business use<br /><br />for that purpose we must develop safer vehicles and procedures<br /><br />the early years of airplanes and spacecrafts was only for brave, hard guys (due to technological limits and lack of experience), but, now, astronauts and space-scientists don't need to play a russian roulette at every launch<br /><br />now we don't fly on Wright's planes or DC3 driven by Red Baron... we use safer airlane for common peoples<br /><br />the three LSAM I suggest to send on the moon are not "spare" but USED in turn and (if possible) repaired on the moon changing defective hardware or electronics... like with jets and military fighters!<br /><br />it's safe and reliable<br /><br />also, don't forget that each Shuttle accident have grounded it for years!<br /><br />a lunar accident may delay much more all lunar missions for a complete (and safer) re-design or a possible end of the entire plan! (think at this when you suggest "risky" and "low redundancy" space flights for "non cowards peoples" only!!!)<br /><br />about money... 4 "REUSABLE" LSAMs instead of 12 "EXPENDABLE" LSAMs mean OVER $20 billions saved (for 8 LSAMs, 8 SDHLVs, etc.) that NASA can use for TWICE moon mission of TWICE duration!!!<br /><br />again... my question is (also for you)... do you (really) want MORE moon missions and MORE "science" or only MORE expendable vehicles... then... MORE BUSINESS???<br />

 

[rubicondsrv]

many DC3s are still in use. <div class="Discussion_UserSignature"> </div>

 

[gunsandrockets]

"Considerable stability compared with low lunar orbit. Not perfectly stable (the other L points are said to be better, just not as convenient) yet vastly superior to LLO with respect to stuff staying where you leave it."<br /><br />I doubt this is a practical advantage for EML-1 over LLO. It's not as if a spacecraft in LLO has to cope with atmospheric drag degrading it's orbit.<br /><br />"Rendezvous from the lunar surface is not constrained by launch windows. If a CEV (or a Shenzou) is in low lunar orbit, an LSAM faces limited launch windows to be able to successfully meet the on orbit vessel. The EML-1 launch window is open 24/7." <br /><br />"An EML-1 station can support lunar landings pole to pole."<br /><br />Exactly right. I think these are the real advantages of EML-1. <br /> <br />

 

[gunsandrockets]

"It should also take less delta v to get to EML-1 than to get into lunar orbit from the lunar surface. Why? Because to get to EML-1, you only need delta v for a straight up suborbital trajectory that peaks out at L-1. Getting into orbit requires going much faster."<br /><br />That does not sound right. Look at it this way, is it easier for a spacecraft from the Earth to reach EML-1 than LEO? I think you are confusing escape velocity with orbital velocity. Reaching EML-1 should take less delta vee than escape velocity, but more than orbital velocity.<br /><br />As for the efficiency (or lack) of reaching EML-1 compared to more conventional flight architectures, I believe I remember a comment by NASA administrator Griffin. When asked about EML-1 he replied that it took a little more delta vee to rendevous at EML-1 than at LLO. The disadvantage was tiny though, and I bet EML-1 takes less delta vee than LLO rendezvous when visiting high latitudes of the moon.

 

[gaetanomarano]

<br />do you use it to fly for business or holidays with your family?<br />

 

[ace5]

I simply cant see how the best pílot-cosmonaut could dock the second Soyuz or Shenzhou besides the first one. No space for manouver. Too close to each other.

 

[gaetanomarano]

<br />docking ports can be inclined or with more distance or on LSAM sides<br />

 

[mlorrey]

velcro, of course, with magnets.... <img src="/images/icons/wink.gif" />

 

[mlorrey]

<blockquote><font class="small">In reply to:</font><hr /><p>"It should also take less delta v to get to EML-1 than to get into lunar orbit from the lunar surface. Why? Because to get to EML-1, you only need delta v for a straight up suborbital trajectory that peaks out at L-1. Getting into orbit requires going much faster." <br /><br />That does not sound right. Look at it this way, is it easier for a spacecraft from the Earth to reach EML-1 than LEO? I think you are confusing escape velocity with orbital velocity. Reaching EML-1 should take less delta vee than escape velocity, but more than orbital velocity. <br /><p><hr /></p></p></blockquote><br />That isn't the right way to look at it. Earth is far deeper in the gravity well than the Moon is, so reaching EML-1 from earth is certainly more difficult than LEO.<br /><br />Moon's orbital velocity about the Earth ~1 km/sec<br />Lunar Orbital Velocity: 3400 mph, or about 1.5 km/sec<br />Lunar Escape Velocity: 2.4 km/sec<br /><br />Apollo passed through the L1 region at over 2,000 mph. That is delta v in excess of that needed to just peak out at L1. No extra delta v needed to retrofire into lunar orbit (Apollo had to slow from 7000 mph down to 3400 mph).<br /><br />It is clear that Griffin is full of it. Going to EML-1 is clearly cheaper. Like the whole overguesstimation of weight on the CEV, they are trying to BS extra delta v into the project.

 

[bwhite]

This link (see page 2) asserts that the delta V from the lunar surface to LL1 is about 2500 m/s<br /><br />http://www.mars-lunar.net/Arch.Elements/fueling.around.pdf<br /><br />= = =<br /><br />More details - see page 5 at this link:<br /><br />http://www.mars-lunar.net/Arch.Elements/3.delta.v.Lunar.pdf

 

[mlorrey]

That has to be wrong. L1 deltav cannot be greater than the escape velocity of 2.4 km/sec, which 2500 m/s is...