Is this egg-shaped nose cone a good, aerodynamic design?

Question

So Jeff Bezos has recently travelled to space aboard an Amazon-funded rocket, which has an unusual, egg-shaped nose.

However, just about every other rocket I've seen has more of a cone-shaped nose, coming to more of a point. Here's an example, the Saturn V rocket:

I'd always assumed that the more straight-edged cone-shaped nose had been found to have the most favourable aerodynamics for a rocket to take flight.

Has this assumption now been proven wrong and an egg-shape offers less air resistance? or is there some other reason for this choice of design?

Are your examples meant to show that most rockets have cone shaped tips? The falcon rocket picture looks egg shaped at the top. The orbiter part of the space shuttle doesn't have a tip which comes to a sharp point. The solid boosters appear to have spherical nose tip. The examples, IMO, show the variety in the tips. — AJN, Jul 21 '21 at 11:58
@user40799 According to Jeff Bezos, yes. https://www.independent.co.uk/life-style/gadgets-and-tech/jeff-bezos-amazon-workers-space-flight-b1887468.html — AJFaraday, Jul 21 '21 at 13:59
@user40799 This is getting off-topic, but what part of Bezo's statement "I also want to thank every Amazon employee and every Amazon customer because you guys paid for all of this" did you not understand? — David Hammen, Jul 21 '21 at 14:26
@DavidHammen - Bezos taking his assets based on founding Amazon and using them for his space company is different from Amazon paying directly. ] — Jon Custer, Jul 21 '21 at 14:34
related answer & question : Why/when is the blunt nose better? — user721108, Jul 21 '21 at 15:42
FWIW: A conical surface has zero Gaussian curvature. That makes it easy to fabricate cone shapes from flat material such as sheet aluminum. Curved surfaces like the dome-shaped nose of the New Shepard capsule are more expensive. I don't know what the New Shepard is made of, but the relative cost of curved vs. flat surfaces is much less with modern composite materials than it used to be with classic, metal "skin and stringer" airframe designs. — Solomon Slow, Jul 21 '21 at 17:46
I was just about to ask the same question. The modern capsules of Falcon and (especially) New Shepard are noticeably rounder than the cone-shaped 1960's capsules. — dan04, Jul 22 '21 at 02:04

CuteKItty_pleaseStopBArking · Answer 1 · 2021-07-25T05:20:21.247

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Rocket noses come in all sorts and sizes. The driving factor is more likely to be functional than purely aerodynamic.
For example, the shown Saturn V has a pointy nose, because that nose is wearing a pointy Launch Escape System.
The Falcon 9 fairing nose is a blunted cone. (no escape system)
The Falcon 9 hoisting a crew Dragon2 has a mostly-cone with a rounded nose. (escape system mounted on the sides, which is part of why it's not a smooth cone shape)
The Soyuz nose is pointy, because like the Saturn V it has a very pointy launch escape system.
In the case of BO's New Shepard, it has a launch escape system, but the motor is affixed to the capsule bottom, between it and the rocket body. Thus it does not affect the shape of the nose.
If you are asking what shape is most aerodynamic, it would be a very sharp cone with a pointy tip. This shape is ok at subsonic speeds, and very superior at super->hypersonic speeds. Superior for drag, that is. It also heat up much more, and thus requires really fancy materials at the sort of speed rockets reach while still in real atmosphere.
However, for a rocket mass is more important. The very small aerodynamic advantage a pointy tip confers is outweighed by the mass saving benefit of a blunted cone. That shape has much smaller surface area and is a naturally stronger shape, thus can be built using lighter materials.

Yes, BO's New Shepard's nose is quite sufficiently aerodynamic. It is also a very good shape to facilitate reentry, house the parachutes, and give the passengers a decent window view. As with most engineering designs, it is the balance of all the requirements that leads to a suitable compromise solution. Remember also that the New Shepard does not get to go very fast, it's top speed on the way up is only about 1000m/s, or mach 2.9-ish. Actual orbital rockets reach three times that speed in atmosphere on the way up, and 8 times that speed coming down.

What is not so aerodynamic is that ridge/ledge under the tip, where it joins the shaft. But this is required for the separation of the booster, and subsequent return of both pieces.

Supplemental info, specially added for jamesqf

THIS is a symmetrical aerofoil shape. Also known as "streamlined body"
(Airflow from the right to left. )
It is very aerodynamic. CD as low as 0.04

THIS is the shape of a raindrop.
It is very non-aerodynamic, CD from 0.5 (very small droplets, almost spherical, image B below) up to 1.45. Yes, you read that right. One point four five, for a large raindrop about to break up under its own aero drag, image E below.
(Airflow from bottom to top)

And the aerodynamic shape of the New Shepard is roughly a match for the rightmost of these shape, called the "bullet", which is basically a hemisphere on top of a long cylinder.
It is a pretty good but not perfect aerodynamic shape,
with a subsonic coefficient of drag of about 0.3 (due to the discontinuity leading to the rocket body)

(Airflow from left to right in this image)

edited Jul 25 '21 at 05:20

answered Jul 21 '21 at 14:27

CuteKItty_pleaseStopBArking

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Re #2, a pointy cone with a sharp tip is quite un-aerodynamic at subsonic speeds. In fact, it would be more aerodynamic if you turned it around :-) A raindrop is most aerodynamic, if you don't consider the effects of all that expanding gas coming out of the tail. And with rockets like the Saturn V, the taper is because of the different size of the stages, not aerodynamic considerations. (That is, there's a height/diameter ratio that minimizes weight, which is why soda cans are the shape they are.) Bezos' rocket appears to have only a single stage. – jamesqf Jul 22 '21 at 05:43
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@jamesqf "A raindrop is most aerodynamic" is false. A raindrop is an incredibly high drag object. Are you maybe forgetting that a falling raindrop looks like a beanbag that uncle albert is sitting on? – CuteKItty_pleaseStopBArking Jul 22 '21 at 06:12
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Actual shape of raindrops: https://www.scienceabc.com/pure-sciences/shape-falling-raindrop-pressure-sphere-surface-tension-hydrostatics-aerodynamics-gravity-myth.html or for image only https://www.scienceabc.com/wp-content/uploads/2016/06/2000px-Raindrops_sizes.svg_.jpg – CuteKItty_pleaseStopBArking Jul 22 '21 at 06:19
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@jamesqf additionally, "a pointy cone with a sharp tip is quite un-aerodynamic at subsonic speeds. In fact, it would be more aerodynamic if you turned it around" is very false. Flat-based pointy cone with nose into the wind has CD of 0.34, same cone turned around has CD of 1.14 – CuteKItty_pleaseStopBArking Jul 22 '21 at 06:23
The trailing side does not follow traditional aerodynamics because of the rocket exhaust. – jpa Jul 22 '21 at 14:24
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You're all really missing the point here, which is that aerodynamics on launch is fr from the primary consideration for shape. If you take for instance the Saturn V, the tip is pointy because that's the way they built the launch escape system. Then the Apollo CM is the size and shape it is because it had to hold three astronauts and have a re-entry heat shield. The SM/LM package fits nicely behind it. Then you have three stages that are basically soda can shapes, because that's how you minimize structure weight while maximizing propellant load. – jamesqf Jul 22 '21 at 16:15
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@jamesqf Isn't that exactly what my answer says in the first place? Which point you tied to muddy by making multiple false statements in comments? – CuteKItty_pleaseStopBArking Jul 22 '21 at 16:25
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@PcMan: No, that is not what your answer says, though it might be what you meant it to say. And I made no false statements, though some might (and have!)quibble about details. But let me say it again: as a design factor, aerodynamics is well behind quite a number of other considerations. – jamesqf Jul 23 '21 at 17:27
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@jamesqf FALSE STATEMENT THE FIRST "A raindrop is most aerodynamic". FALSE STATEMENT THE SECOND "a pointy cone with a sharp tip is quite un-aerodynamic at subsonic speeds. In fact, it would be more aerodynamic if you turned it around". – CuteKItty_pleaseStopBArking Jul 23 '21 at 17:31
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@PcMan: The classic raindrop shape IS the most aerodynamic, at subsonic speeds. If you don't believe me, ask NASA: https://www.grc.nasa.gov/www/k-12/airplane/shaped.html Or look at the shape of anything that is designed to minimize drag. – jamesqf Jul 24 '21 at 17:08
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I've strongly criticized RonJohn's answer because it was overly reliant on imagery and because that user did not replace the enter image description here with something more meaningful. It would help your answer if you replaced that default with something more meaningful. – David Hammen Jul 25 '21 at 00:05
The raindrop image and a discussion of it might make for a good answer to What are typical ranges of rainfall drop sizes, speeds, and areal or volume densities? in Earth Science SE. – uhoh Jul 30 '21 at 12:37

David Hammen · Answer 2 · 2021-07-21T14:15:16.047

I'd always assumed that the more straight-edged cone-shaped nose had been found to have the most favourable aerodynamics for a rocket to take flight.

There's a key problem with sharp-nosed tips: They have a tendency to melt at high speeds. The Concorde only flew at Mach 2, and it's tip heated to 127 °C. This heating is a huge problem for hypersonic aircraft. This heating around sharp edges was part of why the Space Shuttle Columbia experienced its disastrous failure.

Modern launch vehicles don't have the pointy tips that the Saturn V and other early launch vehicles had. The pointy tip doesn't buy much with regard to aerodynamic efficiency, and it adds lots of risk.

Björn · Answer 3 · 2022-10-29T11:35:39.273

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In Joe Rogan's podcast #1609, talking with Elon Musk, Elon mentioned it makes no difference when it comes to rockets. It is arguable worse to be pointy.

As Antzi mentions, this is because of the speeds involved, and the issues with hypersonic flows.

edited Oct 29 '22 at 11:35

answered Jul 22 '21 at 17:15

Björn

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In subsonic flows, the pointiness serves to move the air around. In hypersonic flows this can’t happen so it doesn’t matter much. You are right – Antzi Jul 22 '21 at 19:13
I feel like the answer quite clearly answers the asked question, with references. And also adds the more indepth pointer to Antzi's post. Most answers were elaborate, which is in some cases wanted, but not always. – Björn Oct 29 '22 at 11:38

RonJohn · Answer 4 · 2021-07-24T23:36:30.910

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Boeing and SpaceX also use blunt nose cones (as demonstrated in these images), and not just for human capsules. Thus, unless all these engineers are incompetent, blunt cones must be a good idea.

edited Jul 24 '21 at 23:36

answered Jul 23 '21 at 14:39

RonJohn

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A good idea, yes, but is it good because of aerodynamics, or other considerations? – jamesqf Jul 23 '21 at 17:31
@jamesqf aerodynamic means "of or having a shape which reduces the drag from air moving past", and a smooth, rounded surface certainly helps the air flow by. The Space Shuttle has a rounded nose, Boeing airliners have rounded noses, and the leading edges of most wings are rounded, so that "roundness" must be a good, all-purpose aerodynamic shape; otherwise it wouldn't be used so much. (At some point, the amount of anecdotes piles up so high that "argument from anecdote" morphs into "evidence of truth".) – RonJohn Jul 23 '21 at 18:05
The tip of the ascent stack for shuttle was extremely pointy. https://space.stackexchange.com/q/39183/6944 – Organic Marble Jul 24 '21 at 01:38
@OrganicMarble very interesting. However, I was referring to the Space Shuttle itself. https://inteng-storage.s3.amazonaws.com/images/uploads/sizes/space-shuttle-1_resize_md.jpg – RonJohn Jul 24 '21 at 01:45
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Downvoted for an utter lack of accessibility. – David Hammen Jul 24 '21 at 07:46
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@DavidHammen what does "lack of accessibility" mean in this context? – RonJohn Jul 24 '21 at 11:59
@RonJohn The answer excessively relies on imagery, and you have not placed any description of those images as alt text. – David Hammen Jul 24 '21 at 14:28
@DavidHammen why is alt-text so vital? – RonJohn Jul 24 '21 at 20:54
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@RonJohn Alt text can make an image-based answer comprehensible to those who are visually impaired. As is, this answer is useless to those who are visually impaired. Keep in mind the phrase "a good picture is worth 1000 words". This is not the case for the visually impaired. A nice description is essential. It doesn't have to be 1000 words long, but it is essential. – David Hammen Jul 24 '21 at 22:04
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I'm picking on you because this answer is one of the least accessible answers I've seen. You are not the only one who I've picked on for lack of accessibility. Accessibility is a touchy issue for me. I was exposed to the problem because I've had the privilege of working on multiple projects with a brilliant NASA mathematician who is totally blind. He's employed because he's brilliant. More than half of the visually impaired are not employed, and the problem is getting worse because of a growing over-reliance on imagery on the internet. – David Hammen Jul 24 '21 at 22:11
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@DavidHammen I hovered my mouse over every other image in teh question, and all the other answers, but saw no alt text. – RonJohn Jul 24 '21 at 22:11
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@RonJohn Why should I enter image description? A halfway decent screen reader will access the image description. – David Hammen Jul 24 '21 at 22:36
@DavidHammen have you down-voted the question, and all the other answers for not having alt-text? If not, you're a hypocrite. – RonJohn Jul 24 '21 at 22:43
@RonJohn Though it's primarily about text, you can check the discussions, answers and comment at Shall we make it explicit site policy that screenshots of text ≠ readable text? Though it wasn't pointed out very diplomatically, we really do try to make sure that whenever possible, and to the extent possible, our posts contain all the key information as text so that they retain their value, utility and readability both to folks using screen readers and to search engines for indexing and findability for future readers. – uhoh Jul 24 '21 at 23:33
Is it possible to add a bit more text explaining what it is that the images show and what it is about them that constitutes an answer? Thanks! – uhoh Jul 24 '21 at 23:33
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@uhoh I wait for you also to make these same "images must have alt text" comments in the other answers. – RonJohn Jul 24 '21 at 23:35
@RonJohn I have tried to do just that. Every single one? That's not possible. I still have a job. But I do try to hit the worst ones that I do see. – David Hammen Jul 24 '21 at 23:38
@DavidHammen every single answer in this question (and the question itself) would show that you're not a hypocrite. – RonJohn Jul 24 '21 at 23:40
@RonJohn I've made almost 18,000 comments on this site, and I'm 100% certain that I've left many, many similar comments over the past 5+ years. You're not being singled-out for criticism. Instead I think your answer has value and folks are simply encouraging you to improve it and not rely on pictures to speak for themselves. – uhoh Jul 24 '21 at 23:40
@RonJohn This is one of the most inaccessible answers I've come across. It might well be the most inaccessible answer I've ever come across. Answers are supposed to be of higher quality than are questions, so I am more judgmental with regard to answers. The question was asked by a newbie, so I gave that newbie a break. – David Hammen Jul 24 '21 at 23:41
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@DavidHammen tell me honestly what's so inaccessible about "Boeing and SpaceX also use blunt nose cones (as demonstrated in these images), and not just for human capsules. Thus, unless all these engineers are incompetent, blunt cones must be a good idea." I can live with you thinking it's a poor answer, but to call it inaccessible is nonsense. – RonJohn Jul 24 '21 at 23:48
All that you have to do for me to reverse my downvote is to replace the default enter image description here with descriptions of the imagery. It's not that hard. Anyhow, I'm done. – David Hammen Jul 24 '21 at 23:49
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Accessibility aside, "Thus, unless all these engineers are incompetent, blunt cones must be a good idea." is a terrible answer. You should explain why blunt cones are ok. Some rockets have sharp nosecones, and presumably their engineers are equally competent. – Organic Marble Jul 25 '21 at 00:16

Is this egg-shaped nose cone a good, aerodynamic design?

4 Answers4