Author Topic: Why separate the New Shepard capsule from the booster?  (Read 3553 times)

Offline msat

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Is there a good reason to separate the two for a suborbital system (other than emergency abort?), especially considering that the booster will propulsively land? Even though turnaround time likely isn't going to be of the essence, it still seems like post-landing inspection, prepping, and mating of the capsule to the booster is a bit unnecessary. Maybe it just seems more "rocket ship like".

Offline SoTOP

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Re: Why separate the New Shepard capsule from the booster?
« Reply #1 on: 10/08/2016 08:39 AM »
There is very good reason to do that - booster engine malfunction while landing.
« Last Edit: 10/08/2016 08:39 AM by SoTOP »

Offline rpapo

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Re: Why separate the New Shepard capsule from the booster?
« Reply #2 on: 10/08/2016 09:06 AM »
In the current setup, where the first stage and the capsule follow pretty much the same flight path, you have good reason to wonder.

It seems to me that they intend to eventually use the capsule in a two-stage (i.e. orbital) configuration.  In that case, you want the capsule to be able to come back on its own.  And when you do that, and want to recover the first stage, you want that first stage to behave on its way down too.  As it is, the combination of the single stage booster and the relatively heavy (compared to a nearly empty first stage) capsule is off balance, aerodynamically.  The center of gravity is way too high.  To bring the two of them back together would require a different design.
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Online Dante80

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Re: Why separate the New Shepard capsule from the booster?
« Reply #3 on: 10/08/2016 02:05 PM »
Is there a good reason to separate the two for a suborbital system (other than emergency abort?), especially considering that the booster will propulsively land? Even though turnaround time likely isn't going to be of the essence, it still seems like post-landing inspection, prepping, and mating of the capsule to the booster is a bit unnecessary. Maybe it just seems more "rocket ship like".

I don't see any benefit to tell you the truth.

1. Since you need the LAS, you still have to treat NS as a two stage rocket.
2. If the propulsion unit malfunctions during the landing burn, you may not have the margins needed to abort and land on parachutes (remember, this thing is coming down fast).
3. I don't know what the current design loads are for the capsule and the booster, I think though that propulsive landing (the way Blue does it now) might be too extreme for them.
« Last Edit: 10/08/2016 02:06 PM by Dante80 »

Offline TrevorMonty

We may see propulsive landing on separated capsule in future versions.


Offline RonM

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Re: Why separate the New Shepard capsule from the booster?
« Reply #5 on: 10/08/2016 03:36 PM »
Safety and performance. It's safer to separate and land with parachutes. With the additional drag of the booster, the stack probably would not reach the desired altitude.

No LAS is perfect and hoping it will always work at the last moments prior to landing is wishful thinking. Note that the vehicle is heading towards the ground and a last minute abort would require more thrust than an ascent abort.

As technology and reliability improves maybe the next version can land as a unit.

Online Prettz

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Re: Why separate the New Shepard capsule from the booster?
« Reply #6 on: 10/08/2016 06:10 PM »
The more-gentle capsule descent also increases the length of the experience for the passengers, which can't be bad. The booster has landed before the capsule's even deployed its chutes.

Offline TrevorMonty

The more-gentle capsule descent also increases the length of the experience for the passengers, which can't be bad. The booster has landed before the capsule's even deployed its chutes.
A good point, floating down under parachute is additional experience.

Offline ZachS09

How about activating the capsule LAS just after MECO? We've seen the booster survive an abort.

I ask that because then the capsule can reach a higher apogee.
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Offline Graham

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Re: Why separate the New Shepard capsule from the booster?
« Reply #9 on: 10/08/2016 06:36 PM »
How about activating the capsule LAS just after MECO? We've seen the booster survive an abort.

I ask that because then the capsule can reach a higher apogee.

An abort is high G, and not exactly the calmest event. It's not exactly something you'd want to do in a situation where it wasn't necessary
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How about activating the capsule LAS just after MECO? We've seen the booster survive an abort.

I ask that because then the capsule can reach a higher apogee.

An abort is high G, and not exactly the calmest event. It's not exactly something you'd want to do in a situation where it wasn't necessary

Also, the LAS is a solid rocket, so no "gas and go". This would increase the ticket price somewhat.

If Blue wants to increase the apogee then they'll build a more capable booster.

edit: spelling
« Last Edit: 10/09/2016 02:58 AM by pstephens »

Offline msat

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Re: Why separate the New Shepard capsule from the booster?
« Reply #11 on: 10/08/2016 11:43 PM »
Good point about the LAS possibly lacking the margins to avoid buying the farm considering the velocity of the booster immediately prior to powered landing.

"The booster has landed before the capsule's even deployed its chutes."

How can this be? Significantly more lift (or rather, drag to mass ratio) for the capsule than the booster?


" As it is, the combination of the single stage booster and the relatively heavy (compared to a nearly empty first stage) capsule is off balance, aerodynamically.  The center of gravity is way too high.  To bring the two of them back together would require a different design."

Hmm. Presumably they could have sized the airbraking system at the top of the booster more appropriately then?

Offline TrevorMonty

At this stage Blue trying to make safest reusable suborbital system they can. It may not be perfect system but it is a good working system and just about ready to carry passengers which is more than can be said for competition.

As saying goes "The Perfect Is the Enemy of the Good".

Offline savuporo

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Re: Why separate the New Shepard capsule from the booster?
« Reply #13 on: 10/09/2016 12:49 PM »
At this stage Blue trying to make safest reusable suborbital system they can. It may not be perfect system but it is a good working system and just about ready to carry passengers which is more than can be said for competition.

As saying goes "The Perfect Is the Enemy of the Good".
Exactly. Get about 10 000 flights on it, and there is going to be enough data for a better operational system design, whatever better may mean at that point.
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Offline whitelancer64

Also, the top of the New Shepard booster is a ring fin. Keeping the capsule on it would reduce the stability of the rocket during descent.

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Online rayleighscatter

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Re: Why separate the New Shepard capsule from the booster?
« Reply #15 on: 10/11/2016 06:13 PM »
It's an ambitious first step out of the capsule when it's still on top of the booster.
« Last Edit: 10/11/2016 06:13 PM by rayleighscatter »

Offline Ludus

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Re: Why separate the New Shepard capsule from the booster?
« Reply #16 on: 10/11/2016 08:52 PM »
It's an ambitious first step out of the capsule when it's still on top of the booster.

Plus a lot of new safety issues with people siting for a long while on top of a landed booster waiting for somebody to get them down. The engine is hot, there's still some propellant in the tanks. The booster would have to go through a safing process before you got the passengers out.

As opposed to the current process where they could just climb out themselves into the desert as soon as they land.

Offline msat

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Re: Why separate the New Shepard capsule from the booster?
« Reply #17 on: 10/12/2016 06:49 AM »
Also, the top of the New Shepard booster is a ring fin. Keeping the capsule on it would reduce the stability of the rocket during descent.

http://www.damngeeky.com/wp-content/uploads/2015/11/Chaotic-moon-Biometric-Tattoo_2.png

This had crossed my mind, but I figured this could have been accounted for in the design from the start if it was a requirement.

It's an ambitious first step out of the capsule when it's still on top of the booster.

It's an ambitious first step out of the capsule when it's still on top of the booster.

Plus a lot of new safety issues with people siting for a long while on top of a landed booster waiting for somebody to get them down. The engine is hot, there's still some propellant in the tanks. The booster would have to go through a safing process before you got the passengers out.

As opposed to the current process where they could just climb out themselves into the desert as soon as they land.


Good points which I haven't at all considered! While the booster isn't huge thus leaving the capsule accessible by a nearby boom lift (since they know where it's going to land), other safety considerations show that it would be quite dangerous. This is the most compelling explanation.

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