That begs the question of why it would be either big budget, or done by
NASA. :-)
On 2/28/21 10:00 PM, Henry Spencer wrote:
On Sat, 27 Feb 2021, Robert Steinke wrote:
imparting about... 15km/s if the back of my envelope is
correct. That's a whole lot for a chemical rocket...
That close to the sun it should be easier to do high thrust solar thermal.
Wikipedia says Isp up to 1000 seconds so the mass ratio would need to be
~4.5. Use a drop tank for boiloff so the burn starts out with a full tank.
Unfortunately, that Isp requires LH2, and after circa a decade in space (out to Jupiter and back), almost certainly it will all be gone.
There are ways of storing LH2 for years, in principle, e.g. active refrigeration, but it's beyond today's state of the art, and I believe Bill is hoping for a relatively low-cost mission.
(A big-budget planetary mission isn't going anywhere unless you can convince a Decadal Review to make it their first priority, which isn't going to happen for this. Smaller efforts can sometimes do end runs around the traditional process, but ill-defined costs and risks from techological pioneering are just what you don't want if you're trying to convince people to stick their necks out in support.)
Henry