Hacker News Reader

Comment by mikeash | Hacker News Reader

Shipping is less of a concern for a fully reusable system. Instead of shipping a giant rocket for every launch, you ship it once and use it for dozens or hundreds of launches.

View on HN

You still need to inspect it after each launch and perhaps repair? I'd imagine there would be some overlap with manufacturing if only for the expertise.

Currently with the Falcon 9 they do the manufacturing in Hawthorne, initial testing in McGregor Texas, and then in Florida they have facilities for integration and inspection. They are leasing/building more facilities in Florida at Port Canaveral to handle inspection and refurbishment of landed boosters.

Eventually it might make sense to move final assembly closer to the launch site for BFR, but I would expect a lot of the component assembly (like engines) to remain in Hawthorne.

At first, but I believe the plan would be multiple flights per day with regular maintenance/inspection/rebuild intervals similar to how aircraft are maintained.

From [1]

>In addition, the lease would accommodate recovery operations undertaken by Space Exploration Technologies to bring to shore vehicles returning from space that are retrieved by an autonomous drone ship offshore.

So they would have the option of doing that at the new manufacturing facility (even though we can speculate that that would not be the norm).

1: https://www.reddit.com/r/spacex/comments/85i6rd/bfr_producti...

Launch it from LA and land it in Florida for the test flight?

If the rocket can be used without limit this almost makes perfect sense.

If you launch to the west this might be viable. The government wouldn't be particular thrilled about test flights over land (or any flight over land), but for a test flight you would want something longer than a jump across the continent anyway.

Rockets rarely launch at a retrograde (western) orbit because you have to overcome the earth’s rotation to reach orbital velocity, rather than the speed boost you get from launching with the earth’s rotation. IIRC, satellites launching from Vandenberg AFB in California take a polar orbit.

OTOH if they're just trying to get from California to Florida they don't need full orbital velocity.

Even if they went all the way up to the ISS's orbit (which would be useless both because it's a test flight and because they would be going the wrong direction), the difference between going in a western or eastern orbit is a ~10% difference in delta-v requirements. Normally that's an enormous difference, but if you can just decrease the size of the test payload at will it shouldn't matter much beyond spending a few thousand dollars more on fuel.

It's not the height that counts, it's the sideways speed. Getting to 250 miles above sea level is relatively easy. Getting to 5 miles a second it far harder.

But if you're not aiming for orbital velocity the earth's rotational speed doesn't make any difference -- the relative speed of start and end points are the same. It doesn't take more fuel to travel west than east because of the rotation of the earth (jet stream sure, but if rockets are affected by the jet stream there's something seriously wrong)

Disclaimer: my entire picture of orbital dynamics comes from KSP

Check your orbital velocity at the surface. It's not 0. The direction you head does matter.

I don't think anybody is allowed to launch rockets from the United States where any part of the boost phase is over land.

Traditionally, rockets dropped their boosters. If they are no longer dropping large explosive things, such a requirement could go away.

Even if the intent is not to drop boosters, as long as there's some reasonable chance boosters will be dropped (accidentally), I can see that requirement sticking around.

> If they are no longer dropping large explosive things

If you were a rocket engineer, would you stake your life on it? Every single launch?

Are you afraid of jumbo jet engines falling out of the sky near airports?

Exactly, that's the end goal.

The energy output of a jumbo jet is four orders of magnitude less then that of a rocket. A jet engine is equivalent to a controlled fire. A rocket is equivalent to a controlled nuclear explosion.

There's almost as much energy stored in a BFR as there is in the nuclear bomb dropped on Hiroshima. This energy is released over 3 minutes.

Considering their long term plan involves building pads out in the ocean and doing suborbital hops between cities:

https://www.youtube.com/watch?v=zqE-ultsWt0

maybe

Reply on news.ycombinator.com