Recent Posts

Pages: 1 ... 8 9 [10]
It will be hard to make BFS fly 10,000,000 times straight without having a fatal accident.  (Airplanes do that).

Airplanes do that because even though they malfunction all the time, it takes a lot of malfunctions to bring down an airplane.

However, even if BFS flies 10 times a day for a year, that's only 3000 flights.  BFS doesn't have to be as safe as airplanes.  It has to be safe enough for its intended use.

Adding a LAS (LAS, remember LAS? This is a thread about LAS) will not improve the safety aspect of BFS by much, since it's only effective during initial lift-off.  During late ascent, BFS can already escape, and during landing, a LAS can't do much.

The good news is that once re-entry is figured out, there's none of the "order of magnitude higher" energy anymore.  At that point, it's not much more demanding than airplanes landing in cross winds, as is performed 1000 of times a day around the globe.

Spaceflight Entertainment and Hobbies / First Man Premiere
« Last post by Star One on Today at 06:23 AM »
It debuted third at the box office behind Venom & A Star is Born.
But a passenger airplane moving at nearly the speed of sound is safer per mile than trains and cars moving an order of magnitude slower. And those, in turn, are safer per mile than walking/running which is an order of magnitude slower again.
Spaceflight Entertainment and Hobbies / Re: First Man Premiere
« Last post by Eric Hedman on Today at 06:00 AM »
I haven't seen the movie yet.  I will soon.  But for all the comments about how sad and dour he was supposed to be I always remember one thing funny Neil Armstrong said when they were first entering the LM after opening the hatch.  He and Buzz had gone in during a TV broadcast.  Charlie Duke the Capcom at the moment asks if they're going to let Michael Collins come in.  The lines from the mission transcript:

056:37:44 Duke: Rog. Must be some experience. Is Collins going to go in and look around? [Pause.]

056:37:56 Armstrong: We're - we're willing to let him go but he hasn't come up with the price of the ticket yet.

He doesn't sound like a sad humorless individual to me.
Correct. Decrewing ISS for a single crew launch cycle would not pose any danger to the ISS.
This is clearly not accurate. There are well known failure modes which are recoverable by crew, but likely to result in loss of vehicle if crew were not present (i.e. the Big 14). The odds may be low enough to not be a big deal as woods170 put it, but they are clearly not zero and it's something that NASA has gone to significant effort to avoid in the past.

This of course does not mean harebrained schemes to rush other vehicles into service would be a better idea.

 Corrected unintentional 20% undervaluation of woods170 :-[

Out of curiosity, what are the 'Big 14'?
Energy levels aren't that different. Energy required on very long distance flights (in the form of fuel) is about the same as orbit, or nearly so.

Chemical or non-chemical rocketry could indeed be just as safe as flying in an airliner. It just depends on flight count.

The fuel load isn't published for the 2017 BFR booster, but I think between the upper and lower stage, you are looking at well over 800,000 kg of fuel. The 2018 version is even bigger. For comparison, a 787 carries a maximum of 102,000 kg of fuel. A380 is ~250,000 kg. So, you are probably looking at a fuel load for the 2018 version of ~4x the largest commercial airliner. Jet fuel energy density is about 45 MJ/kg. Methane is 56 MJ/kg. Factoring in energy density bumps it up to 5x.
BFR is not the limit of chemical rocket efficiency. You can probably improve on it by a factor of 2 at least by using careful adjustment of mixture ratios, running stoichiometric hydrolox for the upper stage, and operating deeply oxygen-rich for the first stage.

It's pretty close, same order of magnitude. Not "as much as 3 orders of magnitude higher."

I believe he is talking about the kinectic energy of a fixed mass which is proportional to the square of the velocity. So, comparing an Apollo capsule at 40,000 kilometers per hour and sub sonic jet liner at 1050 kph yields a kinectic energy of 1 kg of 1450x or 3 orders of magnitude. Burning off the energy of an airliner is not very stressful and very easy. Burning off the energy of an Apollo capsule? Not so much.

He is essentially describing the danger of increased speed. A train moving at 5 miles per hour isn't really a danger to its passengers no matter what happens. It can derail and it wouldn't be suprising if everyone lives. Now compare that to a train moving at 300 miles per hour derailing. The forces on the human body and the train itself then go way way up.
Here is another version of the above:

Soyuz MS-10 Failure extended (stabilization, zoom 2x, slow motion 25% with frame interpolation)

Published on Oct 14, 2018

Edit by Riccardo Rossi (ISAA) - Attribution-NonCommercial-ShareAlike 4.0 International License -

Original footage courtesy of Roscosmos

My question is, is the rocket moving sideways at this point? 

Here is a better video of the sideways motion of the second stage after the incident.  Several swings are indicated.

Soyuz MS-10 in-flight abort (close-up)

Published on Oct 14, 2018

A Soyuz-FG rocket launched the Soyuz MS-10 spacecraft from the Baikonur Cosmodrome in Kazakhstan, on 11 October 2018, at 08:40 UTC (14:40 local time). Shortly after launch, an in-flight abort was triggered by an issue with the booster. The spacecraft separated and the capsule returned in a ballistic decent mode. International Space Station Expedition 57-58 crew members, NASA astronaut Nick Hague and Roscosmos cosmonaut Alexey Ovchinin were safely recovered.

Pages: 1 ... 8 9 [10]