I don't know why parents these days even bother with requests like that.
My parents were all like "Oh you don't like triangles? Look who's obviously not hungry."
Then I had two options: start eating triangular shaped sandwiches at once, or not eating sandwiches at all.
To break orbit the kid would need to accelerate at 11 kilometers per second. That’s about 27983.4 kgf kgf thrust you’d have to apply to a 55lb kid. However- unless you could apply this thrust externally (which presently for all intents you could not-) the weight of the thrusters, fuel, and support structures would need to be applied to the mass we want to break orbit- increasing the force required. Now- if we do this- we will not likely “fling him into the sun” as the force applied directly to him would kill him most likely, and the heat would leave nothing or almost nothing of him. We need to add a launch vehicle, support systems, and likely computer controls unless the kid is spec’s out to fly a space craft and willing to fly themselves into the sun.
Once we break orbit it just becomes a question of “when” we want him to reach the sun and if he has to be alive when he does. The TOTAL force required “door to door” goes down greatly if we go to minimum corrective thrust and drift once we clear orbit, then reduce as gravity allows, and let the suns gravity take care of the last part of the trip. If “force required” refers to how much force we must apply- we don’t count gravity or other “free” force like acceleration from a sling shot maneuver- we are referring to thrust we must supply.
If “force required” is asking how much force is NEEDED to get from point A to point B as an absolute- you have to supply the specifics. For instance, the “force required” to open a stuck door doesn’t change, but the force YOU require can change if you use a lever or other tool. If you ask for total force required to open the door and reach the other side that depends. It will take more total force in the equation to open the door in leather gear than naked, in steel toe boots than shower flip flops. If you want to do it faster that’s more force, how wide you want to door opened etc etc.
But to calculate the theoretical force needed to achieve the goal here is simple. If you want to use the MINIMUM force necessary that becomes more complex- and the answer changes based on wether you are asking for force as a measure of what you must apply or force as a measure of total forces needed to be applied.
If you don’t use the suns gravity to pull the mass in to the sun, the TOTAL force goes down, as does if you don’t sling shot earth’s orbit on the way to the sun. However- to keep the same speed you’ll need far more fuel and propulsion- so the supplied force has to go up.
But- rough numbers, with some assumptions such as: the child must actually reach the sun relatively completely, intact, and living at least until out of orbit; and that NO magic or crazy solution to apply thrust beyond what is presently available is an option, AND that we aren’t concerned with MINIMUM force or maximum speed- 1 55lb child, a launch vehicle to keep them in tact and alive for at least most of their journey, earth sea level optimal launch site and weather, to the sun... rough round numbers- 3-4 million kilograms of thrust should get the job done.
You're forgetting the solar wind. You're going to have to slingshot it. There's no other way you can reach the speed necessary to overcome the solar wind in any practical sense without it... dude would just get bounced out into oblivion and freeze to death.
You are correct! I did not mention solar wind. Comprehensive isn’t comprehensive when you miss out. But that’s why I estimated 4 at the high end. A light launch vehicle (it doesn’t need to re enter and dude is dead long before the corona unless we build a theoretical and nonexistent monstrosity), so it isn’t specified he has to reach the sun alive- but we can infer he at least needs to be in relatively complete shape. So light launch vehicle, sling shot, corrective thrust here and there- 4 million kg of thrust total is back of the envelope. But.... you’re right that still might not cut the mustard. It all depends on specifics as coronal discharge and other factors can increase or decrease the intensity of solar wind encountered.
My parents were all like "Oh you don't like triangles? Look who's obviously not hungry."
Then I had two options: start eating triangular shaped sandwiches at once, or not eating sandwiches at all.
TLDR: It'd take a lot of force.