Blue Origins capsule for New Shepard.

RGClark · 2017-03-30 08:32:14

Blue Origin released some interior images of the capsule they intend to use for the New Shepard suborbital tourism rocket:

Take a Peek Inside Blue Origin’s New Shepard Crew Capsule.
Published: 29 Mar , 2017
by Nancy Atkinson
17458383_1518234718221709_2632460151475955651_n.jpg?oh=e1d91a04b72e90cde9edbbb0e2f46547&oe=594C61EE
http://www.universetoday.com/134783/tak … w-capsule/

I don't like the solid rocket escape motor being placed in the center of the passenger cabin. From discussion on other forums I understand this is a center of gravity issue. They need the heavy mass of the solid rocket motor to be placed forward for stability reasons.

Still, I get a very visceral negative reaction to this arrangement. Anyone else get that reaction?

Bob Clark

Last edited by RGClark (2017-03-30 08:33:25)

Oldfart1939 · 2017-03-30 08:59:08

It's a not-so-subtle reminder that things could go wrong. I like the Dragon Manned capsule design better.

GW Johnson · 2017-03-30 17:37:40

That thing in the middle is a solid rocket motor, or the end of one?

The rest of it looks pretty nice.

GW

SpaceNut · 2017-03-30 20:28:18

Its got that new car smell, just overlook where the engine is and its fine to have the ride as its only sub orbital...
When they get the next rocket built for launches to orbit then we will know that they have caught up to space x and could pass them on there was to the moonn and mars quite possibly.

RGClark · 2017-03-31 03:06:16

GW Johnson wrote:

That thing in the middle is a solid rocket motor, or the end of one?
The rest of it looks pretty nice.
GW

Well, it's the propellant chamber. But for solid rockets the propellant chamber is the combustion chamber when ignited.

Bob Clark

Last edited by RGClark (2017-03-31 03:06:48)

louis · 2017-03-31 03:49:33

I get a visceral negative reaction to sub-orbital tourism...I think things are moving so fast that anyone with the bucks or dosh as we say in the UK to indulge in space tourism is going to wait until they can do something that will really impress their friends: orbit the Earth or take a trip to lunar orbit or spend time on the moon.

Remember, Space X is planning lunar orbit tourism from 2018 ie next year! Even if they are delayed a couple of years, if you were a multi-millionaire, why wouldn't you wait until such trips were on offer?

RGClark wrote:

I don't like the solid rocket escape motor being placed in the center of the passenger cabin. From discussion on other forums I understand this is a center of gravity issue. They need the heavy mass of the solid rocket motor to be placed forward for stability reasons.
Still, I get a very visceral negative reaction to this arrangement. Anyone else get that reaction?
Bob Clark

RobertDyck · 2017-03-31 04:04:40

Apollo LM, museum display. You realize the grey cylinder on the floor of the back part is the cover for the ascent engine.

Still. This is for space tourism. The New Shepard abort engine is "in your face".

Last edited by RobertDyck (2017-03-31 04:06:32)

Terraformer · 2017-03-31 04:14:52

Louis, it's going to be a very long while before the prices for suborbital flights and orbital ones are similar. Even if orbital flights cost the same that suborbital ones are meant to cost at the moment ($100-200k), it's to be expected that the cost of suborbital flights would come down significantly as well, to the point where non-millionaires could easily afford them (i.e. comparable to a cruise).

RGClark · 2017-03-31 10:40:12

RobertDyck wrote:

Apollo LM, museum display. You realize the grey cylinder on the floor of the back part is the cover for the ascent engine.
https://www.hq.nasa.gov/alsj/LMSimulator.jpg http://farm3.static.flickr.com/2643/408 … d84685.jpg http://www.hq.nasa.gov/pao/History/SP-350/i4-4a.jpg
Still. This is for space tourism. The New Shepard abort engine is "in your face".

Thanks for that. I wonder what that must have sounded and felt like with that engine firing right under your rump.

Bob Clark

GW Johnson · 2017-03-31 13:51:50

From what I heard and read, it was noisy and it really shook.

Solids are more noisy and vibration-inducing than liquids. I used to build them.

GW

louis · 2017-03-31 16:02:23

You get a glorified funfair ride for a lot of bucks with sub-orbital - just a few minutes of weightlessness. Sub-orbital is sub-optimal in my view. Once orbital tourism becomes available at not much more, then people will simply not be interested in my view.

Terraformer wrote:

Louis, it's going to be a very long while before the prices for suborbital flights and orbital ones are similar. Even if orbital flights cost the same that suborbital ones are meant to cost at the moment ($100-200k), it's to be expected that the cost of suborbital flights would come down significantly as well, to the point where non-millionaires could easily afford them (i.e. comparable to a cruise).

Terraformer · 2017-04-01 10:20:11

louis, as I pointed out (in a post you quoted but clearly did not read), *suborbital tourism will not be similar in cost to orbital tourism*. It's not a choice between paying $200k for a suborbital ride and $300k for an orbital ride, but between $200k for a suborbital ride and $20M for an orbital ride. If orbital rides do come down to the point where they cost $200k, then suborbital rides will still be very cheap, maybe $2k or less.

RGClark · 2017-04-01 13:17:49

GW Johnson wrote:

From what I heard and read, it was noisy and it really shook.
Solids are more noisy and vibration-inducing than liquids. I used to build them.
GW

It's likely the solid abort motor has to be placed forward into the passenger compartment for reasons of positioning the center of gravity in relation to the center of pressure.

So perhaps it could be placed further to the rear if it were a smaller mass. We might also be able to give the capsule a trunk like SpaceX's Dragon to move rearward the center of pressure.

In regards to getting a smaller solid motor I found this remarkable example, called the Super Roadrunner. It's used on the last two stages of the rocket sled at the Holloman Air Force test track:

January 15th, 2006 at 8:30 pm
The Fastest Rocket Sled On Earth.

The final two stages each use single Super Roadrunner, or SRR, rocket motors. Designed specifically for the HHSTT, they weigh in at a mere 1100 pounds apiece. Yet, during burns of just 1.4 seconds, each produces a total of 228,000 pounds of thrust.

http://www.impactlab.net/2006/01/15/the … -on-earth/

Being able to develop 228,000 pounds of thrust to fully expend ca. 1,000 pounds of propellant in only 1.4 seconds amounts to an extraordinary burn rate. But 228,000 pounds is more than what we need for the abort motor. So perhaps we can get an even smaller mass by reducing the thrust on a small scale version of this motor.

The SpaceX Dragon abort system get's about 8 g's. Let's say the Blue Origin capsule weighs in the range of 10,000 pounds. Then for a 8 g acceleration we would want the thrust to be 80,000 pounds, a third that of the Super Roadrunner.

We also need the solid rocket motor to be smaller because based on the images it would be too long to fit under the capsule. So the question is can we scale down a solid rocket motor by just reducing the size?

Also, the 1.4 second burn is actually too short for our purpose. While we do want the high thrust to pull the capsule away from the launcher rapidly in an emergency, we need a longer burn time to get sufficient distance away. For the SpaceX Dragon abort test, the SuperDracos had a 6 second burn time. So how can we get a longer burn time for the miniature Super Roadrunner solid motors?

Bob Clark

GW Johnson · 2017-04-01 22:51:45

Solids don't scale, they have to be designed. Otherwise, somebody's expensive thrust stand is going to get blown up, and maybe somebody killed.

What I read just above says you want 80,000 lb thrust for 6 sec. The total impulse of that is 480,000 lb-sec. If the specific impulse is in the vicinity of 245 sec (a realistic goal to be exceeded, if possible), then the propellant mass required is about 1959 lbm.

That is a big motor. The as-cast volume of the propellant would be about 31,100 cu.in, if the propellant density is 0.063 lbm/cu.in. That desity and Isp goes with an AP-HTPB-Aluminum propellant. .2 to .7 in/sec is an achievable burn rate at 1000-1500 psia with that material.

If I was to attempt a keyhole slot at L/D ~ 4, cross sectional loading could be 80%. The insulated inside volume of the case could be about 39,000 cu.in. That would be around a 23 inch dia case ID, and about 93 inches long inside. Web fraction might be as high as 75%, for a propellant web of 8.66 inch. That must burn in 6 seconds, for a burn rate of 1.44 in/sec. Very few propellants are practical with burn rates that high.

What that means is I need a longer L and a smaller ID with that keyhole. Try L/D = 6. Get ID = 20 inch. Web = 7.5 inch. Burn rate = 1.25 in/sec, still too high. Longer L/D is impractical with the keyhole, as it gets too progressive.

We could try a finocyl type design, with which I had less experience. To get around 0.5 in/sec burn rate, we'll need a web of about 3 inches. We'll need lower web fraction ~.67 and average cross sectional loading ~.65 for this type of design. We will need about a 9-inch ID motor that is somewhere around 940 inches long, which is not practical. Too much void space and too small a web needed.

I would have to think about this. The really long multi-motor they used for the rocket sled may not be so ridiculous. Perhaps I could go back to a high volume-packing L/D = 5 keyhole if I was to cluster multiple motors together. Dunno yet.

GW

Last edited by GW Johnson (2017-04-01 22:53:57)

RGClark · 2017-04-02 06:14:25

GW Johnson wrote:

Solids don't scale, they have to be designed. Otherwise, somebody's expensive thrust stand is going to get blown up, and maybe somebody killed.
What I read just above says you want 80,000 lb thrust for 6 sec. The total impulse of that is 480,000 lb-sec. If the specific impulse is in the vicinity of 245 sec (a realistic goal to be exceeded, if possible), then the propellant mass required is about 1959 lbm.
That is a big motor. The as-cast volume of the propellant would be about 31,100 cu.in, if the propellant density is 0.063 lbm/cu.in. That desity and Isp goes with an AP-HTPB-Aluminum propellant. .2 to .7 in/sec is an achievable burn rate at 1000-1500 psia with that material.
If I was to attempt a keyhole slot at L/D ~ 4, cross sectional loading could be 80%. The insulated inside volume of the case could be about 39,000 cu.in. That would be around a 23 inch dia case ID, and about 93 inches long inside. Web fraction might be as high as 75%, for a propellant web of 8.66 inch. That must burn in 6 seconds, for a burn rate of 1.44 in/sec. Very few propellants are practical with burn rates that high.
What that means is I need a longer L and a smaller ID with that keyhole. Try L/D = 6. Get ID = 20 inch. Web = 7.5 inch. Burn rate = 1.25 in/sec, still too high. Longer L/D is impractical with the keyhole, as it gets too progressive.
We could try a finocyl type design, with which I had less experience. To get around 0.5 in/sec burn rate, we'll need a web of about 3 inches. We'll need lower web fraction ~.67 and average cross sectional loading ~.65 for this type of design. We will need about a 9-inch ID motor that is somewhere around 940 inches long, which is not practical. Too much void space and too small a web needed.
I would have to think about this. The really long multi-motor they used for the rocket sled may not be so ridiculous. Perhaps I could go back to a high volume-packing L/D = 5 keyhole if I was to cluster multiple motors together. Dunno yet.
GW

Thanks for that analysis. It is notable that the SpaceX abort system also has a similar low ISP and requires also in the range of 1,000 kg of propellant. They solve the CG/CP positioning problem by having a long trunk. And on at least the SpaceX abort test they also put fins on the trunk. This may have been to help insure a straight flight but it would also help to bring the CP further rearward.
So the simplest answer may be install a trunk on the Blue Origin capsule to bring the CP rearward.

Bob Clark

GW Johnson · 2017-04-02 12:35:25

Bob:

I already have spreadsheets that do segment and keyhole-slot grains quickly for me. It's an inherently very iterative process. What I did above was just sitting, doing hand calculations.

I re-ran the keyhole spreadsheet, deliberately reducing web fraction so as to require only an achievable burn rate. To pack enough propellant in, I had to run longer motors, but it was not as progressive as I feared.

I got it done with one keyhole-slot grain design 18" grain OD = insulated case ID, with a 9 inch bore and a 1 inch slot width. Grain length face-to-face is 170 inches (both faces burn). Web fraction is 50%, cross sectional loading is 71% (these packaging factors suffered from what could be achieved, in order to limit the burn rate to easily-achieved values). Burn surface progressivity max/min is only 1.20. Perfectly-proportioned segment grains are usually 1.21 or greater.

The propellant is 80+% solids AP-HTPB-aluminum at 20% aluminum, density .063 lbm/cu.in, and sigma-P no more than 0.32%/F. With it the grain weight is 1941 lbm. For a 6.0 sec burn time, required average burn rate is 0.75 in/sec, quite achievable. With an exponent of 0.4, the 77 F rate at 1000 psia = .64 in/sec, right in the readily-achievable .2 to .7 in/sec range with these materials. Sigma-P usually falls closer to 0.2 %/F than 0.3 %/F.

The average motor pressure and thrust are 1500 psia and 79,245 lb, respectively, soaked to 77 F. Peak motor pressure and thrust are 1651 psia and 87,189 lb at 77 F. Soaked out hot to 165 F, peak motor pressure is 2197, which barely meets the 2200 psig MEOP I like to design with for steel cases. That's at sigma-P = 0.32 %/F; for smaller sigma-P, peak hot motor pressure is lower, giving safety margin in the overall design.

So, there's an easy-to-build solid motor that will give you about 80,000 lb thrust for 6 seconds. A D6ac case OD might be near 19 inches, and with gas collection spaces at the faces of the grain, and a nozzle, the motor assembly might be about 195-200 inches long.

Just goes to show that solids really are designed, not scaled. The last time a company just scaled a big solid, they had to take a billion-dollar write-off in one year, for destroying a USAF test stand facility.

Just scaling a design is also why the Titanic was vulnerable to that iceberg, and why its lifeboat count, while legal, was inadequate.

GW

Last edited by GW Johnson (2017-04-02 12:52:16)

RGClark · 2017-04-02 19:27:31

GW Johnson wrote:

...
So, there's an easy-to-build solid motor that will give you about 80,000 lb thrust for 6 seconds. A D6ac case OD might be near 19 inches, and with gas collection spaces at the faces of the grain, and a nozzle, the motor assembly might be about 195-200 inches long.
Just goes to show that solids really are designed, not scaled. The last time a company just scaled a big solid, they had to take a billion-dollar write-off in one year, for destroying a USAF test stand facility.
Just scaling a design is also why the Titanic was vulnerable to that iceberg, and why its lifeboat count, while legal, was inadequate.
GW

Thanks for that. The problem with scaling up a solid motor probably explains all the difficulty in getting the hybrid motor to work right on the Spaceship2.

I think the ca. 200 inch, over 16 feet, long solid would be too long for the capsule. Suppose you made the solid the width of the capsule about 12 feet with the same thrust and burn time? Or if you used four solids with the same total thrust and burn time, though with 4 solids you might have a problem getting them all to ignite at the same time and the same similar burn rates?

Bob Clark

GW Johnson · 2017-04-02 20:41:59

When I bust it into 4 motors, if I keep the keyhole slot grain design, I can meet achievable burn rate at higher web fraction (.71) and cross-sectional loading (.84). Insulated motor ID = 9.7 inch, face-to-face length 125 inches. Bore 2.8 inch dia, slot width 1 inch. It's more progressive at about 30% on surface area.

Same basic propellant as before, spec'd at .49 in/sec at 1000 psia and 77 F. Grain weight 491 lbm. I like the lower burn rate than the single-motor option. 0.4-something in/sec at 1000 psia 77 F might be achievable without having to resort to UFAP (sub-micron AP), which requires Freon-wet processing not to blow yourself up, if 83+% solids can be cast. Piece of cake at 86% solids, but you cannot gravity cast stuff that thixotropically-thick through a sleeve. You must pressure-extrude it.

Average pressure 1500 psia, avg thrust 20,054 lb, at 77 F. Max pressure 1726 psia and max thrust 23,081 lb at 77 F. Max pressure at 165 F and max surface is 2189 psia if sigma-P < 0.27 %/F. 77 F burn time still 6 sec.

It takes 4 of these to meet the 80,000 lbth for 6 sec spec. They're not very large size. If you only ever combine 4 motors from the very same mix, they will always have exactly the same burn time. Given a reliable, repeatable igniter, they will always burn out within millisec of each other.

There's no way to put this type of grain design into something 12 feet in diameter. It's some other grain design. I don't know what that might be.

GW

Last edited by GW Johnson (2017-04-02 20:47:53)

GW Johnson · 2017-04-02 21:20:43

By the way, my motor performance estimates for those grain designs were based on an assumed Isp = 245 sec. I did not do a nozzle design analysis for any of those grain designs. Chamber pressures are good, thrusts depend on CF, which in effect means thrust depends upon Isp assumed.

A quick look at my CF spreadsheet for specific heat ratio = 1.20, shows for those pressures, CF is probably closer to 1.57 than the effective 1.54 that correlates with the assumed Isp. All that means is the Isp is likely closer to 250 than 245 sec. That would be for a 15 degree half angle conical nozzle with smooth entrance and a short throat flat in its profile. That's sea level performance as expanded "ideally" to 10 psia.

So, the motor performance estimates that I gave you should be slightly conservative. If somebody was to actually build the things and test them, thrust should run just a tad higher.

GW

Last edited by GW Johnson (2017-04-02 21:22:33)

RGClark · 2017-04-03 05:16:19

GW Johnson wrote:

...
It takes 4 of these to meet the 80,000 lbth for 6 sec spec. They're not very large size. If you only ever combine 4 motors from the very same mix, they will always have exactly the same burn time. Given a reliable, repeatable igniter, they will always burn out within millisec of each other.
There's no way to put this type of grain design into something 12 feet in diameter. It's some other grain design. I don't know what that might be.
GW

Even breaking up the motor into 4 parts only reduces the length from 16 feet to 12 feet? That might still be too long.

Bob Clark

GW Johnson · 2017-04-03 09:21:04

Bob:

Actually, kibbitzing from the sidelines the way we are, we don't really know that 80,000 lb thrust for 6 seconds is even the right fundamental spec.

The kinds of L/D ratios I get are typical of internal-burning grain designs, as constrained by achievable propellant burn rates. I was using a keyhole slot because they can be very neutral, and they are easy to build (simple cast tooling).

For a burn rate in the vicinity of .4-something in/sec at 1000 psia, or near .5-something in/sec at average motor pressure ~1500 psia, the web of propellant you can burn through in 6 sec is rather close to 3 inches. There is just no way around that. If I slow the burn rate, the web to burn gets smaller still, and vice versa.

It would be rather difficult to increase the burn rate very much at all. It requires much higher solids (requiring pressure extrusion casting), a large UFAP percentage in your AP size distribution, and probably some class 1.1 explosives like RDX or HMX at the 5-10% level.

If you do this motor design instead as an end-burner, that 3 inches is the grain length, and for a single motor containing 1000 lbm propellant, the burning surface has to be not quite 5300 sq.in. If you assume the burning surface remains flat (and it does not, there is always bondline rate augmentation causing coning in end burners), the indicated motor diameter is near 82 inches. If you bust it into four 250 lbm motors, their diameters are near 41 inches. L/D ~ .07 to .035, which is ridiculously low.

41 or 82 in dia vs 3 inches long is one fat "pancake motor", which will have to have at least one flat or very near-flat head, that is extremely structurally inefficient. The case structure of pancake motor shapes like that is just inherently very heavy. More than half the motor weight will be inert structure, perhaps very much more than half.

If you cast that end burner into a rounded, structurally efficient case, most of your propellant will be down in the "rounded bowl" as under-performing "sliver". You either won't get the thrust-time impulse you need, or else you must put a lot more propellant into the motor, and accept an ugly, long tail-off burning out that sliver. No clean shutdown, either way.

What I suspect here is that I have been sizing motors to the wrong thrust-time spec.

GW

RGClark · 2017-04-03 10:30:09

GW Johnson wrote:

...
What I suspect here is that I have been sizing motors to the wrong thrust-time spec.
GW

Your suspicion is correct. I found this after a web search:

Blue Origin conducts in-flight abort test; booster lands successfully.
Curt Godwin
October 5th, 2016

As expected, the abort motor’s 70,000 pounds (310 kilonewtons) of thrust rocketed the capsule hundreds of feet from the booster and out of its path, allowing the craft to then descend to the desert floor under its three parachutes. Had occupants actually been on board New Shepard, they would have experienced a high load factor (g-force) for the duration of the abort motor’s firing – approximately two seconds – before entering a nominal descent profile.
Straight as an arrow.
The booster was able to power through the abort and make its way to space – without the capsule. While some of Blue Origin’s computer simulations showed this was possible, the likelihood of it actually happening was low.
However, as soon as the capsule’s abort motor had activated and cleared the module away from the booster, it became obvious that the rocket not only had survived the full brunt of the thrust from the escape pod, but also continued seemingly unperturbed by the fact that it had lost 8,000 pounds (3,600 kilograms) from its top.

http://www.spaceflightinsider.com/organ … cessfully/

So the thrust is 70,000 pounds at only 2 seconds. The capsule weight is 8,000 pounds which must include the solid motor weight. The dry weight of the capsule would be less perhaps 7,000 to 7,500 pounds. The size of the motor can be estimated from the diagram.

The acceleration is in the range of what I expected, about 9 to 10 g's. But I'm surprised the burn time is so short, only 2 seconds. I wouldn't think you would have enough time to clear a possible debris field from the rocket in that time.

Still, a burn time only 1/3rd as long suggests a motor 1/3rd as long, so perhaps 4 to 5 feet. This would certainly be containable in a trunk for the capsule.

Bob Clark

RGClark · 2017-04-04 03:29:40

RGClark wrote:

...
Thanks for that analysis. It is notable that the SpaceX abort system also has a similar low ISP and requires also in the range of 1,000 kg of propellant. They solve the CG/CP positioning problem by having a long trunk. And on at least the SpaceX abort test they also put fins on the trunk. This may have been to help insure a straight flight but it would also help to bring the CP further rearward.
So the simplest answer may be install a trunk on the Blue Origin capsule to bring the CP rearward.

Apparently, SpaceX does intend the fins to stay on the trunk for the crewed Dragon2:

crew-dragon-second-contract-1.jpg?auto=format%2Ccompress&ch=Width%2CDPR&fit=crop&h=347&q=60&rect=0%2C106%2C1620%2C912&w=616&s=b646a5af48ca1d18101a980b61758258

Bob Clark

RGClark · 2017-04-04 04:01:02

In a video animation of the tourism flight there are shown handholds on the solid rocket motor:

Be careful to mind your head!

Bob Clark

Oldfart1939 · 2017-04-04 08:07:38

The Blue Origin video is somewhat optimistic-insurers would probably demand the passengers all wear suitable head protection in the form of lightweight hard hats.

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Blue Origins capsule for New Shepard.

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