Wikipedia:Reference desk/Archives/Science/2021 October 14

Welcome to the Wikipedia Science Reference Desk Archives
The page you are currently viewing is a transcluded archive page. While you can leave answers for any questions shown below, please ask new questions on one of the current reference desk pages.

October 14

New Shepard flight profile

This article from CNN (https://www.cnn.com/2021/10/13/tech/william-shatner-space-blue-origin-everything-you-need-to-know-scn/index.html) states:

New Shepard's suborbital fights hit about three times the speed of sound — roughly 2,300 miles per hour — and fly directly upward until the rocket expends most of its fuel. The crew capsule then separated from the rocket at the top of the trajectory and briefly continued upward before the capsule almost hovered at the top of its flight path, giving the passengers a few minutes of weightlessness. It works sort of like an extended version of the weightlessness you experience when you reach the peak of a roller coaster hill, just before gravity brings your cart — or, in this case, your space capsule — screaming back down toward the ground.

Am I to understand that they only experience weightlessness at the very top of the flight trajectory, or is that simply a limitation of the rollercoaster metaphor, since on a rollercoaster the occupants are strapped in and can't experience weightlessness while the cart is moving downward? I would have thought that the occupants of New Shepard experience weightlessness as long as they are in free fall, since they and the capsule are accelerating toward the ground at the same rate. Is that incorrect? --Puzzledvegetable^{Is it teatime already?} 00:25, 14 October 2021 (UTC)

The article Free fall gives a pretty good explanation and points out that free fall occurs whenever gravity is the only force acting on something. Hence the rollercoaster analogy is a poor one because, as you say, the occupants are subject to forces from the straps. Mike Turnbull (talk) 08:59, 14 October 2021 (UTC)

​Is it correct that the occupants only experience weightless at the very top of their trajectory, because the flight is so low that the atmosphere gets thick enough to provide a noticeable normal force very shortly after they start falling? In other words, when they experience weightlessness, is approximately half of it felt while moving upwards after turning the engine off and the other half felt when falling back down to approximately the altitude that they turned the engine off at, or is most of the free fall spent moving downwards toward the Earth, with the only the very beginning occurring while still moving upwards?

Do you know where I can find technical information like this about the flight? --Puzzledvegetable^{Is it teatime already?} 11:50, 14 October 2021 (UTC)

At the height when the manned capsule detaches from the rocket and starts "free fall" (although it still ascending for a time), atmospheric drag is minimal, so weightlessness is experienced. There were in total about three minutes of weightlessness in a flight lasting ~ten minutes, so you might think (and I would agree) that it is all a rather expensive publicity stunt. The free fall ended roughly when the parachutes were deployed which of course is only sensible when the atmosphere is dense enough that its drag can act on them. Mike Turnbull (talk) 14:37, 14 October 2021 (UTC)

​Do they experience weightlessness up until the moment the parachutes deploy, or does the atmosphere get thick enough to provide a normal force before it gets strong enough to fill the parachutes? --Puzzledvegetable^{Is it teatime already?} 16:34, 14 October 2021 (UTC)

Weightlessness should end when the spacecraft experiences significant air resistance. With Mercury spacecraft reentering, something was set to happen when it got to 0.05g, which was well before the parachutes were deployed. Bubba73 ^{You talkin' to me?} 06:17, 15 October 2021 (UTC)

These flights are just more expensive versions of the vomit comet flights that use parabolic flights in conventional aircraft to induce feelings of weightlessness. The only differences are 1) they use ballistic rockets rather than conventional aircraft to become airborne. 2) They cross the Kármán line, an arbitrary line that defines the "legal" outer edge of the earth's atmosphere for defining where "space" starts (there is no practical physical definition where one clearly leaves the earth's atmosphere and enters space). The two factors make for a more intense ride than the vomit comet, with longer periods of freefall, but it's a difference of degree and not nature in terms of the type of experience and the kind of flights these are. These are super expensive amusement rides, and not "space flights" in the normal understanding of the term. --Jayron32 14:56, 14 October 2021 (UTC)