What are the consequences of literal interstellar travel?

In the background for my book, I'm looking for an alternative way for space travel. What I'm currently considering: A starship travels to the center of a star by using the natural downwards flows that occur naturally in some stars, then uses the extreme gravity down there to create a wormhole and appear inside another star. Then, the ship gets out again and goes to wherever it needs to go through more traditional methods (Orion drive, lightsail, Em-drive, whatever).

1. How would you protect yourself against the extreme gravity and heat inside a star? And how much energy would this take?
2. Would creating a wormhole inside a star have any unintended side effects?
3. Would the properties of certain stars mean you cannot enter or leave them in this way?

To explain more about the concept: gravity distorts spacetime. This happens in a different universe with slightly different laws of physics, and the idea is that the most distorted spacetime spots (i.e. stars and black holes) are actually distorted so much that the ones in the same galaxy have their spacetime distortions almost meet, but not quite. Because of this, it's actually much easier to create wormholes inside a star than it is to create starlike conditions that allow you to create a wormhole anywhere.

• how do you prevent the two stars to interact through the wormhole? – Erik vanDoren Mar 7 '16 at 13:47
• I can't even begin to imagine the issues with surviving or navigating in the core of a star. Your best bet is an improbabilty drive. At high enough improbability, all of the steps will happen successfully, bringing you to your destination unharmed. Second best is to have your ship converted to dark energy, so the universe itself keeps expanding around you fast enough to not get crushed. – Cyrus Mar 7 '16 at 14:22
• There was a similar plot point in the Niven/Pournelle novel The Mote in God's Eye. Technology allows FTL travel between a network of special points in space ("Alderson points"), and an alien civilization is isolated from the rest of the galaxy because the only Alderson point in their system leads to a point inside the nearest star beyond their own. Humans are able to enter the star and use the Alderson point because they have shielding technology. – Michael Seifert Mar 7 '16 at 15:54
• Gravity isn't the issue (the surface of the Sun has, roughly, the same gravitational acceleration as Jupiter). It is the densities, pressures, and temperatures involved. The Sun's core is denser than any terrestrial solid. At ~340 billion times ($3.4 \cdot 10^{11} \times$) the pressure of Earth's atmosphere, the core will have pressed electrons almost into the nucleus of each atom. At $10 \cdot 10^6$ Kelvin, atoms colliding with each other hit with so much energy that they fuse into a single nucleus - this is what releases energy at our Sun's core. – Jim2B Mar 7 '16 at 16:25
• Your civilization can create wormholes inside stars but you worry about the plausibility of getting inside said star? If you want scientific plausibility at all, you may want to look at current theories on how to create wormholes, I think you're better off sticking to those instead. – Hackworth Mar 7 '16 at 18:43

You are going to have some very interesting problems, and may have to resort to some form of unobtanium to bypass them.

1. While inside a star, you have to worry about maybe 3 things to have a starship: heat, pressure, and radiation. Gravity isn't a problem in the star: as you get close to the center, you become weightless. Pressure is possibly the hardest to deal with. The submarines that we make to go down to the bottom of the ocean are built to deal with around 1000 atm. Diamond anvils can get above 3 000 000 atm. But the core of the sun is close to 300 000 000 000 atm. We don't have materials that get near that pressure. The temperature is a similar problem: 15 000 000 K. Diamond boils at around 5 000. If you want to move inside the sun, you can't use normal materials. Perhaps you could generate a magnetic field to keep the stellar plasma off of the surface of the ship, and maybe have the magnetic field generators (which, by newton's third law, needs to be taking the pressure from the field) compress a fusion reactor in the ship. You could just pick up bits of the star to fuel it. That just leaves you with the radiation: most of which could probably be mitigated with the field and lead.

A brief aside: the pressure near the core means that the density is very large: around 150x that of water. This means that most ships will be VERY buoyant. Gravity will go down to mitigate this, but the ship will need to fire engines (or otherwise propel itself) to get to the centre. You have a lot of options here, from conventional fuel to magnetic interaction, to an actual propeller (or other engines used in normal aircraft). My personal favourite would be a fusion-ramjet style engine: you just need to throw the ship at the star fast enough, then the structure takes care of the rest.

2. If you linked two stars with a wormhole, you would have an interesting effect where the star with higher pressure had mass flow into the star with low pressure. Essentially, for two stars, they would change size until they are the same. This could be potentially disastrous to the orbits of the planets in the system, but might happen slowly enough if the wormhole is small that it doesn't matter: note that all stars already constantly loses mass from solar wind and radiation.

3. This also has the secondary effect that two very different stars may behave poorly when linked. If you link a white dwarf or neutron star to a normal star (like the sun), then as the mass flows from the neutron star to the sun, two very destructive things can happen: first of all, when the sun reaches a certain amount of mass, it will supernova. This is a type 1a supernova, and normally only occurs in binary systems because they need to be close to transfer mass. The other thing that can happen is that the neutron star can have its mass move to less than is required to maintain the size, so it would really rapidly expand at some point - turning into a white dwarf, or a white dwarf would turn into a brown dwarf.

I answered what I could. I'm not sure if this is exactly what you want, but at least these are some things to think about.

• I get the impression that magnetic shielding won't work. You're depending upon a magnetic dipole for connected magnetic field lines. My understanding is that the Sun is full of all sorts of extremely powerful magnetic field lines. Those will connect to your field lines and eliminate any shielding your magnetic fields provided. Honestly, the Sun would quickly dismantle any of the planets (even Jupiter). I don't see any plausible method of traveling safely to the Sun's core :( – Jim2B Mar 7 '16 at 17:23
• @Jim2B Honestly, I don't either. But this doesn't have the hard sci-fi tag, so I think that doing something with magnets is one of the best ways to go. In terms of field lines, if they were coming out of the sides of the craft then it would do a decent amount to protect it, because the craft is moving. – Lacklub Mar 7 '16 at 18:18
• Two problems with the magnetic shield powered by a fusion engine. One, the magentic field in a star is already quite strong. Two, fusion power must be a heat engine. That means you would need to bring a cold heat sink to produce a thermal gradient - the difference in temperature is what provides the potential energy. Unless you have an unobtanium negative heat fusion that "makes cold", getting a meaningful temperature gradient in the core of a star will be impossible. – wedstrom Mar 7 '16 at 18:36
• @wedstrom First of all, fusion releases gamma rays that can be captured to generate energy without something like a heat engine. Second of all, conventional fusion reactors can operate at closer to 1 billion K, which IS a meaningful temperature gradient. You end up with >50% efficiency, easily. – Lacklub Mar 7 '16 at 18:46
• @Lacklub now that you mention it, 1 billion K from the reactor and 15 million K outside, it does generate temperature gradients. Then how would the cargo to withstand the temperature between the two? You still need cold heat sink for the cargo, not only for the machine. What kind of matter could withstand temperature that high? – Hendrik Lie Mar 11 '16 at 14:39

You have some problems:

1. The circulation in a star is NOT fast. While plasma is more fluid than rock, you still can't travel through it at space like speeds. And with our sun, you have 400,000 miles of it to reach the center. To do that in 100 hours (4+ days)requires a speed of 4000 mph.

2. The core of the sun, according to wikipedia has a density of ~150 g/cubic cm. https://en.wikipedia.org/wiki/Sun There are going to be substantial bouyancy forces on your ship.

3. And you have to insulate that 15 million K temperature. At those temps radiation is the dominant form of heat transfer: You need a layer that reflects all radiation perfectly.

4. In this seething mess of hot gas, how do you navigate?

5. The gravitational field gradient at the center of the sun (or center of any spherical body) is zero. You are at minimum gravitational potential energy for the local region however.

Any civilisation capable of creating wormholes in the centre of a star to be able to accomplish a hyperspatial shortcut to another star should be able to perform the technological operation necessary for surviving the journey to the centre of the star and getting back out again.

Spacecraft undergo a conversion from normal matter into what is called either shadow matter or mirror matter. Further details can be found here

Mirror matter, if it exists, would need to interact weakly with ordinary matter. This is because the forces between mirror particles are mediated by mirror bosons. With the exception of the graviton, none of the known bosons can be identical to their mirror partners. The only way mirror matter can interact with ordinary matter via forces other than gravity is via kinetic mixing of mirror bosons with ordinary bosons or via the exchange of Holdom particles.[10] These interactions can only be very weak.

A spacecraft will accelerate towards its local primary star until it reaches a velcoity either equal to or greater than the star's escape velocity. It converts its matter into mirror matter and plunges into the star. None of the star's plasma, radiation, pressure due to density, neutrons or whatever will affect the spacecraft. Gravity inside the star won't be a problem. Effectively it will be like being inside a hollow sphere where the gravity cancels itself out. On reaching the centre the wormhole generator is activated and the ship passes through to the centre of the destination star. The wormhole only needs to open for as long as it takes the vessel to pass through. This will minimise any affects due to the exchange of matter between the two stars. Its velocity will carry out of the other star and into its planetary system. Once the ship is well and truly clear of that star it reconverts itself back into normal matter again.

It can then go on its way but the one thing we can guarantee is that won't use primitive propulsion systems such as these crude technologies (Orion drive, lightsail, Em-drive, whatever) it will soar on its super-advanced drive-systems. What else if they already possess technologies from converting ordinary matter into shadow matter and back again as well as wormhole generators.