It's the familiar opening--the space family Robinson is preparing for a mission to another planet.  The story is slightly changed--they are to create a hyperspace gate at the other end, so that colonists can follow them more quickly.  Doctor Smith (I don't know that they ever give the familiar name "Zachary"), who is the pre-flight doctor, is a mole for the enemy, taking large bribes to sabotage the mission.  After he programs the robot to do the necessary damage, his paymasters renege on the deal, trapping him on the doomed spaceship.  We'll try to cut the story short here, as it has little to do with the time travel aspects of the film.  During the robot's rampage, the Robinsons are revived, and manage to shut it down.  With the ship badly damaged and off course heading into the sun, Professor John Robinson and Major Don West agree on a desperate plan--activate the hyperdrive, and come out at some random point in the universe.

They are now lost.  The computer is unable to match their position with its star charts.  But almost immediately, they stumble on a hole in space.  The precocious Will Robinson says that it's very like the time bubbles which he predicts would be a side effect of the time machine concept on which he's working, but Dad doesn't have time for the boy's daydreams.  They pass through the bubble, and find, of all things, another earth ship:  The Proteus.

Strange thing about the Proteus--it's all familiar but wrong.  All the evidence suggests that the ship is old; at the same time, everything on it is well advanced from that which was on the Jupiter 2.  Tapping the captain's logs, we learn that it was under the command of a pilot who served with Major West, but who now is much older--and that it was sent on a rescue mission to search for the lost Jupiter 2.  But no one is on it--except the space spiders who are soon attacking them.  Will Robinson saves them by using the robot, which he has reprogrammed to a remote control unit; the robot is lost in the process.  They flee, although Dr. Smith takes a flesh wound from a spider attack, and Major West blows up the Proteus; but, caught in the blast, they are forced into a less than textbook landing on a barely habitable planet.  To make it worse, their power systems are damaged, and they won't be able to achieve orbit--and the planet is becoming unstable, undergoing geologic upheavals which (although they seemed rather mild to me) are expected to result in the breakup of the planet.

The scanners pick up evidence of a radiation source which could be adequate to provide the needed additional fuel; but it seems to come from inside another bubble.  Professor Robinson and Major West are going to attempt to retrieve it, while Dr. Smith is kept locked up and the Robinson women make the necessary hull repairs.  Will is busily rebuilding the robot.  Professor Robinson gives Will the dog tags which his father always gave him before going on a mission, as a promise that he would return.

The men enter the bubble, and are captured--by the robot.  They are taken to what is apparently a temporal duplicate of the Jupiter 2, considerably damaged by the ravages of time.  Meanwhile, Dr. Smith cons Will into going to save his father, and taking him along.  They, too, enter the bubble; and Dr. Smith finds the graves and personal effects of the women--but he doesn't tell Will.

Soon enough, they arrive at the Jupiter 2, where by now we've learned that Will Robinson has survived for 20 years, and built a time/space machine by which he intends to return to earth to abort the mission and save the family.  If you've followed these pages, you know that if successful that would create an infinity loop, destroying the timeline itself.  However, it is not.  He also has told his father that the professor never returned that day; and that the others were killed by spiders who escaped the destruction and found their way to the planet (although this proves not to be true).

Once Dr. Smith arrives, he takes control of the situation--and the robot--and announces that he will be the one to return to earth.  But he has missed one thing:  an older version of him has survived, horribly mutated from the injury inflicted by the spider.  He surprises and disables his younger self, and now he takes control of the situation.

The younger Will Robinson manages again to save them, by reminding the robot of the lessons of friendship which he taught it when he was building it (just a while ago, for Will).  Will, Robot, West, and a somewhat incapacitated Smith make it back to the Jupiter 2, while Professor Robinson tries to reach the time machine.  The power core which they need to achieve escape velocity is being used to power the time machine; if he can get it, he will try to bring it back to the ship, so they can use that material.

The mutant Smith then reveals that he, not Will, will be going back to earth--and neither to stop the mission nor to collect his reward, but to carry back the spiders who have sprung up within him to conquer the planet.  It is he, now very much spider himself, who killed the women.  Will is incapacitated, but Professor Robinson arrives in time and kills the mutant Smith.  He saves Will--but the time bubble collapses, and he can no longer cross the time barrier to get to the other Jupiter 2.  Yet somehow he sees it take off, and be destroyed by a piece of debris from the now fragmenting planet.

The older Will decides not to carry out his plan, but instead to allow his father to go back and save the Jupiter 2 from the collision; the logic of this escapes me--after all, if Will can abort the mission, the collision never happens either--but it has a certain emotional impact at that moment.  The professor succeeds; they save themselves the problem of bringing back the duplicate Will Robinson by maintaining that the machine only has enough power for one person, one trip.  And the movie ends with them heading off in the direction they think (based on star charts downloaded from the Proteus) might be home.

If you think the time problems here are enormous, you've underestimated them.  Let's try to unravel them.

The problem which should be immediately obvious is that the time bubbles exist in the past because the time machine exists in the future, but the time machine only exists in the future because they cause the accident which results from the Jupiter passing through the time bubble.  This kind of paradox is usually created by writers who want either to tell us that time lines are immutably written without sequential causal rules, or to suggest that time travel must be impossible since it leads to such absurd results.  In this case, it seems rather to be a poorly considered backdrop for a moral lesson about family being more important than work.  But we'll try to find some solutions for it.

What if someone else was experimenting with time travel, and created time bubbles?  This is not so unlikely as you might think.  After all, the planet on which they crashed might have supported life at some time in the past or future, and there might be other planets in the area which support life.  And since it's a time bubble which displaces itself in time, it could appear anywhen.  It might even move temporally, which means it would exist at every point in time, creating a gate to another point in time a fixed temporal distance from it.  Thus, we have time bubbles occurring which are independent of the time machine which appears later in the film--but that we shall discuss in a moment.

This suggests that there is an original history in which there is no time bubble.  Although the time bubble could have been generated in the past, it is more likely to have been generated in the future.  In fact, the only way in which this is soluble is if the time bubbles are created by a time machine created in the future, probably on the planet on which the Jupiter 2 will crash.  In this original history, the Jupiter 2 is lost, never finds the Proteus, and probably is not found for at least decades.  Perhaps at some time in the future, the crew of the ship or its descendants settle on a less than hospitable planet which does support some carbon-based life already; and perhaps one of them eventually tinkers with Will Robinson's theories and creates a time machine; perhaps Will Robinson himself does it as he grows up.  Perhaps not--perhaps another intelligent life form arises on the planet on which the Jupiter 2 is about to crash, and they develop the time machine while the humans continue to wander in space.

Of these the theory which I find most feasible is that it is Will Robinson who develops the machine.  Not having the added impetus of losing his family, he does it later in his life--but he still does it at about the same point in the timeline (remember, once the time bubbles are created, the Jupiter 2 jumps forward at least a couple of decades before crashing.)  This seems the best possibility, since it is most likely to create similar bubbles.

The events which would follow are not so unpredictable.  The Jupiter 2 goes through the bubble into the future, and so becomes the lost ship for which the Proteus is seeking.  It finds the Proteus, which has been attacked by the space spiders, and the action proceeds from there.  Were the ship to crash on that planet, it is likely that Professor Robinson and Major West would leave for some reason related to repairing it.  Once they've left, Dr. Smith would certainly try to take over the situation, and would have to kill at least the older two of the women; but he can't escape the planet in that ship, and he's not aware of the spreading infection from the spiders within his system.  Eventually, he would also kill Penny--but he would keep Will alive, and encourage him to develop the time machine on the pretext that Will can prevent the accident, but for the purpose of returning to earth himself (originally perhaps to collect his reward or get his revenge, but eventually to carry the spiders to earth).  Thus the time machine is built for a different reason, but the bubbles are still created, remarkably close enough in time and space to the other time line that the Jupiter 2 encounters the same bubble in the same place in space.

I know this is getting confusing; but at the moment, we're trying to identify the problems and determine whether there is any solution for them  This most obvious problem is soluble; but it is not the only problem.

You might have missed this one.  After the Jupiter 2 crashes, they have a fuel problem.  But they detect a radiation source which could solve that problem.  However, that radiation source is the crashed Jupiter 2 of the future; it can't be there on the first timeline on which it crashes.  So what did they find?  The answer is not significantly altered.  They will still find the power supply for the time machine.  The ship had not crashed in the A-B segment, so the ship from the future in this segment can't be the crashed version.  It's the version which settled here.  But Will Robinson--or whoever created this time machine--has no reason to imagine that his father might be coming.  The security arrangements could be fatal to the two intruders, and their identities might never be determined.

You probably did catch this one:  at the end of the movie, there is a robot on board the Jupiter 2 which will never be built.  Therefore, you might say, it can't be there.  But it's not really so much of a problem.  In Back to the Future 1, a Marty McFly is running around who has not been born, and who never will be born (remember--it is a different Marty McFly who will be born).  The existence of the robot is predicated on its creation in the other time line; it was removed from that timeline, and introduced into this one, so it can exist in this timeline.  The only question is whether it will exist in the next timeline--and that answer is predicated on more complex matters than merely whether Will Robinson completes what he began.

So let's try to reconstruct the timelines as well as we can.

The time bubble has the same effect as a trip back in time.  Time must advance to the moment at which the bubbles are created before they can affect events in the past.  Thus we have point A, the point at which the time bubble will appear but doesn't.  The J2 is lost, wanders for an uncertain period of time, and ultimately lands on a reasonably habitable planet, perhaps for supplies, perhaps to build a future for the Robinson family.  Will Robinson continues his researches, and eventually builds his time machine.  Activating it throws time bubbles back, changing the past, and intrinsically ending the history which led to this moment.  Thus we have created point B, the activation of the time machine, and point C, the moment at which the bubble does appear.  We've ended the AB time line, and begun the CD timeline.

Moments after point C, the J2 passes through the bubble, disappearing into its own future.  This has no new effect on the timeline; but it does cause the awkward situation that the J2 has been completely missing for decades, yet no one on board has aged a day.  (Let me clarify this:  the moment Will Robinson creates a time bubble, he alters history, creating a new CD timeline.  When the J2 goes through the time bubble, that's part of the altered time line, but it is not a new timeline itself--just a significant event in the already established CD timeline which distinguishes it from the AB timeline.)  This time, the crew fights with the spiders, Dr. Smith becomes infected, and in their escape they crash on that same somewhat habitable planet.  There is another time bubble there--generated at the same instant as the first, so events surrounding one cannot prevent the creation of the other.  (Note that were it generated at a different time, it would create a distinct anomaly, and both timelines would have to be traced as nested or overlapping loops.  It is unlikely that the future could be preserved if the bubbles are created in separate events.)  Within that time bubble there is the power source of the time machine, so the J2 will detect the radioactive material, and send a team to recover it.  That team will almost certainly be Professor Robinson and Major West--chauvinism survives into the next millennium, at least for husbands and fathers.

They enter the time bubble; this bubble carries them to a very short time before the activation of the time machine.  However, the content of the bubble is the future--not the future of the AB timeline, but the future of the CD timeline.  Thus, the world of Will Robinson's time machine built after the crew landed on this planet for repairs is gone.  It is replaced by the world in which the J2 crashed after a battle with spiders, and Professor Robinson and Major West went in search of the power source.

But there are some inconsistencies between this timeline and what we are given in the film; we shall have to unravel these.  First, did Will and Dr. Smith follow them into the time bubble, and if so, what happened?  Second, did Major West make it back to the J2, and if so, why did it not take off--but if it did take off, how was it neither destroyed nor stranded on the planet?  Third, if Professor Robinson never made it back to the J2, then who used the time machine to go when and where?  And fourth, where is the robot?

One thing which will help is a distinction of events.  It must be supposed that the time bubbles are created by an event which preceeds the use of the time machine for travel--that is, perhaps at the moment the machine is first activated the time bubbles occur.  This is necessary--if it is the use of the time machine which creates the bubbles, then it is likely that whoever used the time machine at the end of this timeline will have interfered with the launch of the J2 from earth initially, preventing it from being at the first bubble (even in the CD timeline).  By contrast, if the bubbles are created at the moment the machine is activated, the end of the CD time segment (and the AB segment) comes at that moment, before Professor Robinson reaches his grown son and the older Jupiter 2.  Based on that determination, the CD time segment will cause itself--all of the events leading up to the moment the time machine is activated can be repeated based on the activation of the time machine, given only the necessary coincidence that this time machine causes the same bubbles as were caused by that time machine built at the end of the AB segment.  Time moves on from this N-jump (illustrated on the home page of this site and in the Primer on Time) into the future.

Similarly, it should be recognized that although the bubbles are all caused from a point in the future, from the perspective of the past each time someone crosses the time barrier it is a separate event.  Thus during the CD time segment, Professor Robinson and Major West leap forward in time in one event, and Will Robinson and Dr. Smith do so in another.  (As I did with Star Trek:  First Contact, I am assuming that this is one event, although it could be dissected into three distinct events.  Were it not so, we would have to observe that when Will tells Dr. Smith about passing through the bubble, that is a communication into the past from the future which alters the past, establishing a new timeline; determining what would have happened in the timeline in which Will entered the future and Smith did not follow would be far too complex a matter even for guesses.)  But when West, Smith, Will, and the Robot return to the past, this creates a new timeline.

By this reckoning, Dr. Smith and Will Robinson should enter the bubble; and although the Will Robinsons of the AB segment of the first anomaly never see their selves, it is far more complex for the Will Robinsons of the CD segment.  For when Will Robinson steps through the barrier into the future, all is undone.  The time machine is not here, because he did not grow up to build it.

At this moment, as it was with Back to the Future 2, the movie must end.  Since Will Robinson will not grow up to build the time machine, it is not there, and it has not created the bubble, and Will Robinson cannot step into the future undoing his own life; this throws us back to the beginning of the first N-jump, the original AB history in which the ship lands on the planet to make repairs, and so he will grow up to build the time machine, but if so he will create the time bubbles, and perpetuate the cycle.  We have an infinity loop built within an N-jump.  Time ends.

But, as I did before, I will consider what would happen were we to take the movie on its face.  It is suggested that Will Robinson returned to the past, but that his father did not; Dr. Smith also returned to the past--yet Professor Robinson did not.  But perhaps there is an easier solution, albeit an improbable one.  In this reckoning, Will Robinson did not enter the bubble at all, did not step out of the time line, did not see himself or what he would do, nor what Dr. Smith would become; did not bring back the robot.  It is this history which results in the future which is encountered by Professor Robinson and Major West; and without the young Will Robinson to save them from the robot, they remain prisoners until the end of this timeline, the moment at which the time machine is activated and someone will go somewhen in the past.

This does not undo the problem alluded to a moment ago; but it does delay it, and is the only history I perceive which will.  I say it is improbable.  Will is working on the robot, Dr. Smith will attract his attention with his Morse code, the arguments which occur to Smith which convince the boy will be the same, and they will take the same route.  There is no reason which can be imagined why they should not enter the bubble.  But there is one thing which might be different which might save the timeline, at least this time:  the time bubble here is not created by the time machine we see in the future, but by the time machine we did not see, the one built by the Will Robinson whose family merely landed here to make repairs.  If that bubble were different, it might collapse before Will can reach it and enter it.  He will return to the ship without ever having entered the future, and so grow up without his father.  Then, as the spider DNA within Dr. Smith causes him to mutate and produce arachnid offspring within himself, he kills the women--I'd wager he killed Judy first, as she was the physician who might have ferreted out the condition; then he killed Maureen, who remained in command of the situation.  Much later he would have killed pretty Penny--although he has a soft spot for her, her rebellious spirit would eventually be trouble.  Will he keeps around.  The boy, in addition to finishing the robot, is building a time machine, and that is Smith's hope of escape from this forsaken planet, and the spiders' chance to move on to green pastures.  The machine will be built, as it was, from the wreck of the J2.  Eventually Professor Robinson and Major West, stepping through the bubble, arrive in the time of the grown Will Robinson, and are taken prisoner by the robot, held captive by his son, the mutant, and the robot.

But it does not save us.  If the bubble is different, then there is a difference in the past caused by a change in the future, and we now must repeat history with the EF segment, in which the bubbles are those created by the time machine built by the Will Robinson we met, whose ship crashed and whose family was killed.  This Will Robinson will pass through the bubble, destroying the time line.  So much for saving the time line; the movie's over.

O.K., let's assume that somehow the CD timeline is different, that Will and Dr. Smith don't enter the bubble (which makes no sense, but must be so to continue).  It thus is reasonable to suppose that if they never entered the time bubble for whatever reason, that Professor Robinson and Major West will be captured and held prisoner--or perhaps killed--by the older Will Robinson and the mutant Dr. Smith.  Thus, they never return to the J2.  All that we come to know as the history of that older Will Robinson comes to pass, and a bleak future comes into being.

But this future is leading to the moment at which Will expects to go back in time and save his family by aborting the mission (the prototypical infinity loop scenario, to be sure--exactly as with Terminator, they are attempting to change the past based on knowledge of the future).  Given what we've reconstructed, we have every reason to suppose that the time machine will be activated, and the mutant Dr. Smith will go back through it to earth, shortly before the launch.  The spiders will swarm from him into the world.  We can only wonder at this point what will happen--either the J2 will launch before any of this is known, or the presence of the spiders will cause the J2 mission to abort.  If the J2 mission is aborted, we have an infinity loop--in short, Dr. Smith will not be infected, and Will Robinson will not build a time/space machine on another world through which he can return.  However, if the J2 mission is not aborted, we are forced to wonder whether the infinity loop will occur anyway.  I'm inclined to suspect that humanity will have more serious problems than merely the location of the Jupiter 2; unless they discover a wonderfully effective way to destroy the spiders very quickly, they will never send the Proteus to look for the J2--and if they do discover such a weapon, the crew of the Proteus will recognize the spider threat immediately, and use that weapon to destroy it, so the J2 will not find the derelict Proteus or the spiders.  We're creating a new timeline the nature of which we can barely guess; but let's not spend time guessing.

It seems that we cannot get to the point to which the movie takes us.  The problem is that you cannot leave the past to enter a future and find yourself in it.  But, you may say, Will Robinson leaves the past because the older version of himself creates the machine which brings him forward.  Is this a limit on my time travel theories--is it not possible to bring your younger self forward to the future?  Not quite.  You can bring your younger self forward; but you will undo yourself in the process.  Look at it this way.  In the AB timeline, you create a time machine (or otherwise become involved in the creation thereof).  At point B, you operate your machine to change the past by removing yourself from the past and pulling yourself forward to point B.  But the instant you are removed from the timeline, an alternate history is created in which you are not involved in the creation of a time machine, and in which you are not there to reach back in time to pull yourself forward.  Thus the younger you arrives at point D, but this history cannot continue because you were not there to move yourself forward, and time must return to point A (or possibly, if someone else for some reason chooses to pull the younger you forward, to point E), you never having seen yourself.  (Note that the older you could go back in time to meet the younger you; it just can't work the other way around, because until the younger you returns to the past, the older you can't exist in the future.)

It also seems that we can't get to the point to which the movie takes us for another reason.  We've carefully constructed a timeline which carries us to the moment that Professor Robinson and his grown son meet; but now there doesn't seem to be any way to alter this timeline to allow Will Robinson to enter the time bubble in the CD segment.  But it's worse than that:  either the J2 never leaves earth, or the Proteus never leaves earth, or the spiders never defeat the crew of the Proteus.  Any way you slice it, there cannot be a future in this timeline in which a Dr. Smith infected by the spiders exists in the future.  We're trapped in an infinity loop, because the cause in the future is prevented by the effect in the past.

Try to get around this--but how?  We could assume that Will Robinson, not Dr. Smith, leaps through the time machine to reach earth of the past.  If he thwarts the launch of the J2, he undoes--well, everything--and cannot return to the past to prevent the launch, so we have the infinity loop.  If he doesn't stop the launch, he becomes a wildcard.  Will he be taken for a madman and ignored completely?  In that case, the ultimate time trip at the end of the film becomes an N-jump, as the same course of events will lead the same Will Robinson to build the same time machine and make the same trip with the same consequences.  But perhaps in time he will be able to convince someone--not soon enough to stop the mission, but soon enough to have some impact on the search.  He would certainly tell of the spiders, and the crew of the Proteus (especially the Proteus--he knows which ship they found) would be prepared for that encounter.  The ramifications of Will Robinson going back in time are tremendous.  He will almost certainly undo the future at some critical moment which prevents his ability to return to the past.  His best hope is that he fails to convince anyone of who he is, and time will continue into the future with Dr. Smith and his spiders stranded alone on the distant planet--an N-jump.

But this is not the story given us in the movie.  Let's once again leap past our impossibilities.  We come to a new point.  Before the bubble collapses, Will and Dr. Smith and Major West are going to go back through it into the past, taking the robot with them.  This obviously changes the past.  Up to now, we've had a ship and three women who were stranded on this planet until they died, or who attempted to launch without the missing men and were forced to return to the ground (if the expert pilot West was unable to achieve escape velocity, how will the biologist Maureen Robinson do so?).  There is no Dr. Smith to kill them, and no Will Robinson to grow up and build the time machine.  But now three of the four men return, and there is a new history being written.  (Since this is a new temporal event, this is also a CD segment; the AB segment covers the time unseen during which the women were on the planet without the men.)  We still can't get to the future shown in the film, because once Will and Major West return they will launch the ship and be destroyed--and again, if Will is killed when young, he cannot grow to build the time machine, and it vanishes.  Oops--another dead end, another infinity loop.

I pause to consider this.  A moment ago, it was not possible in the AB segment for Will Robinson to find himself in the future.  But now we've created a CD segment by a reverse time trip, and in this segment Will Robinson could grow up to build a time machine; and once he's grown up, a younger Will Robinson leaps forward from the past into this segment and does find his older self there--in the CD segment, it is an older self who did not find himself in the future when he leapt forward.  Were this able to continue, it would create an EF segment, as the Will Robinson who did meet his older self would meet his younger self.  But there are several reasons why this can't happen in this film.  First, because the older Will is the cause of the trip made by the younger Will (as we have already seen), once the younger Will makes that trip, the trip and its return become impossible--an infinity loop.  Second, this suggests a version of events inconsistent with any we've been able to extrapolate, in which Will and Dr. Smith return without Major West--yet there seems no logical course for events to follow which will lead to this; Major West and the Robot both return with Will and Dr. Smith.  (And lest you think you can split the reverse trip into two separate events, I must observe that the Robot was with Will, and Major West was practically carrying Dr. Smith--you'll get the wrong two people any way you slice the trips.)  Once Major West returns, launch is inevitable.  Third, even were you to suppose that Will and Dr. Smith made it back, but Major West and the Robot did not, this Will and this Dr. Smith have glimpsed pieces of the future which will change their perception of the present.  Do you imagine that Dr. Smith would not immediately seek Dr. Robinson's attention to his infected wound? that Will would not warn his mother and sisters of the danger of a spider attack? that his encounter in the future would not alter his perception of his father?  No, the future is still not possible.

But "I always believe seven impossible things before breakfast", so let's make yet another jump, and again pretend that we can have what the movie shows us.  The major takes the others back to the ship while the professor goes for the fuel.  The ship takes off and crashes with all hands, but it doesn't change the future (this is so bad, maybe I should try TimeCop).  The mutant Smith prepares to go back to the past, but Professor Robinson (in a tactic which might just save this movie for gamers interested in game ideas) stops him and revives Will.  The bubble collapses, and it is now too late to take the temporally duplicated core materials back to the J2.  They watch helplessly as the ship which is one man's past and the other man's future is destroyed, and in an emotional decision the older Will decides that it is more important for his father to go back a few minutes before that accident and save the family lost in space than for him to go back to earth and undo the whole thing in the first place.  Professor John Robinson makes the last time trip of the film, returning to the deck of the Jupiter 2 as it prepares to fail to escape the planet.  He gives instructions in an effort to avoid the disaster, and the ship flies through the center of the planet as it breaks up.  It should be noted that the cause of this breakup proves to be the disturbances created by the time machine itself; thus the planet is destroyed in the past by the time machine in the future.

This horribly dissatisfying ending creates two infinity loops from separate causes.  The first, to which we've just alluded, is that the activation of the time machine in the future has caused the destruction of the planet in the past--the very planet on which the time machine must be built in the future.  Thus the planet is destroyed, and the time machine is not built, and the time distortion does not occur, and the planet is not destroyed, and the time machine is built, and the distortions occur, and the planet is destroyed--the classic infinity loop based on the temporal trip which makes itself impossible.  The second cause relates to the more direct effect of the trip.  Will and Professor Robinson have agreed that Professor Robinson should go back to prevent the destruction of the ship--which destruction they have just witnessed.  But in undoing the destruction of the ship, they have undone their ability to have witnessed it, and so they will have no strong emotional reason to have the professor go back "to save the ship" instead of having his son go back "to save the family".  And even if Professor Robinson is chosen to go back, in the altered history he does not see the ship fail and be destroyed--he saw it dive into the debris of an exploding planet and vanish.  He must be wondering why it did that, and he doesn't know that it's because he directed it to do that.  No, whether or not Professor Robinson returns to the deck of the J2, it will crash into the meteor and be destroyed; and given that the ship is not destroyed in the CD segment but is destroyed in the AB segment (or in the EF segment, if Professor Robinson returns from D to E).  This is the classic infinity loop based on the temporal trip which erases the reason for itself.

O.K., it's a warm fuzzy movie about family values.  There are plenty of other "little" problems.  Will Robinson is the one who noticed that the spiders eat their wounded--but his father was quite a distance from him and occupied by other things when he made that comment, so when did he learn it?  The spiders are analyzed as silicon-based life forms--so how can they consume or convert carbon-based DNA?  Exobiology is not my field, but from what I can tell, there is no vital biological chemistry in common between silicon and carbon based life forms.  Consider it from the other end--if the creatures are made of silicon and other mineral elements, not of carbon-based proteins and hydrocarbons, what nutrition would we derive from consuming them?  It's a bit like eating sand--either it passes somewhat awkwardly through your system, or it poisons you.  Going down into a planet which appears to be breaking up is extremely unlikely.  Unless there is a tremendous explosive force emanating from the inside toward which you are plummeting which has insufficient vents to escape to the surface (in which case, there is unlikely to be a passage through the middle), the attraction of masses (gravity) will draw the material together, filling gaps and causing the planet to reform as a solid mass--again with no passage through the inside.  I'll admit that not all planets have molten interiors; but enough of them do that betting on a clear path through a solid interior of an earth-like planet with 1G gravity is a bad bet.  They might get lucky--but it's crazy to try it, even given what they knew.  Better to try to rise above the debris--or even to remain on a solid piece of ground which might come off intact--and ride the shockwave out if it explodes.  You might take too much damage from the debris and the blast to continue, but your odds are better.

Besides, I'm getting tired of the slingshot approach to acceleration.  Yes, as you plummet toward the sun--or to the center of the planet--you gain a tremendous boost to your acceleration from the gravity pulling you down; but as you slingshot past the sun, you face the force of an equal amount of gravity slowing you down an equal amount.  If the objective is to achieve a high velocity in some direction for a brief time, it's a good idea; but if it's intended to throw you out of the area, you'll lose all that you gain by the time you reach the same distance.  And the problem is compounded if you go into the heart of a planet.  It is an abstraction to think of the center of a planet as "down".  "Down" is toward the bulk of the mass of the planet.  Because of this, as you enter the planet you reduce the amount of force pulling you toward the center.  Much of the mass is surrounding you laterally, and more and more of it is behind you.  At the moment you reach the center of mass, all gravitic forces are balanced, and you are weightless.  Your momentum will carry you past that point, but now as you come up through the other side the amount of mass behind you continues to increase as that which is ahead of you decreases, and so the amount of gravity behind you starts to pull you back.  By the time you break the surface on the other side, all of the force which has pulled you in has been countered by equal force pulling you back as you come out.  You've built up some momentum, but all of it has been from the acceleration of continuous engine thrust.  (And coming up through the ocean is a neat effect, but I find myself wondering if between the fact that they started on top of a mountain of rock and burst through the other side fighting the water resistance as it rushed into the deep cavities of the earth in what would be a low-density location--by now they have used a great deal of fuel, lost most of their momentum, and are farther from orbital altitude with less time to get there than they were in the first place.)  If they can't escape by going up, they don't have a better chance by going down.

Hey, I enjoyed the movie.  I've seen a lot of worse efforts in sci-fi.  But if you're looking for a sense of what time is like, it's not like this.