Looked up how close could we get to the sun; The Space shuttle reinforced carbon-carbon heat shield is designed to withstand temperatures of up to 4,700°, if the shield wrapped the entire shuttle, it could fly within 1.3 million miles of the sun. Venus is 107 million miles from the Sun. Surely getting 82 times closer would change this calculation; based on surface area enclosed at 1.3M miles and 107M miles, hydrogen concentration should be ~942 thousand x greater at 1.3M. Assuming it can be transported, instead of 3/4 million years, you'd be looking at about 10 months, not 750,000 years.
And that is with existing materials, used on the Space Shuttle. If you take some minor liberties with future shielding technology, you could probably get the Ram jets much closer to the Sun.