Author Topic: Countdown to new smallsat launchers  (Read 84443 times)

Offline john smith 19

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Re: Countdown to new smallsat launchers
« Reply #360 on: 01/01/2018 06:49 AM »
For high mach operation, all airbreathers are limited by fuel energy density v.s. incoming air energy density. Even scramjets can't be much better than ramjets (gaining better mach range but loose lots of T/W ratio). Skylon is also limited to mach 5.
You seem to have a problem separating "Skylon," which is the vehicle concept, from SABRE, which is the engine.
SABRE In airbreathing mode is limited to M5,after which it closes the airflow path entirely and switches to full rocket mode.

An idea that some people also seem to have a great deal of trouble understanding.

Quote from: Katana
For low mach operation,  RBCC/TBCC/skylon are much more complex than either ramjets or pure rockets.
As always that depends where you draw the system boundaries. When you include "accelerate from zero speed" or "Don't burn through your entire propellant supply in 10 minutes" it turns out TBCC (which SABRE is a form of) as the SR71 and Concorde were ((in super cruise it's been estimated about 68% of Concorde thrust was generated by its inlets, much like the SR71, but without needing continuous after burner).
Quote from: Katana
If ramjets can't compete on R&D COST v.s. pure rockets (F9R style vtvl), nothing else can.
A low Mach ramjet can compete on R&D but you're comparing Apples with Oranges. One is a system that's basically a cruise engine and the other a semi-reusable launch system to full orbit. Like all air breathers (or systems with air breathing modes) it scores on the Isp front. In atmosphere the SSME got c380secs. A bad airbreather gets 2000secs.  That has huge implications for mass fraction of the vehicle.

Are you also confusing ramjets with SCramjets? Ramjets have been deployed in multiple operational systems since the mid 1950's. No SCramjet has (despite Northward of $4Bn in current year $) ever been fielded.
« Last Edit: 01/01/2018 06:53 AM by john smith 19 »
"Solids are a branch of fireworks, not rocketry. :-) :-) ", Henry Spencer 1/28/11  Averse to bold? You must be in marketing."It's all in the sequencing" K. Mattingly.  STS-Keeping most of the stakeholders happy most of the time.
So you're going to Mars to seek a better life. What does that mean to you? Always spot a fanbois by how they react to their idols failures.

Offline Katana

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Re: Countdown to new smallsat launchers
« Reply #361 on: 01/01/2018 06:58 AM »
Even ramjets of 1950s (Talos, Bomarc, Navaho) have much worse Thrust / R&D cost ratio compared to rockets of 1950s, either engine or vehicle.

No other airbreathers could be cheaper.
« Last Edit: 01/01/2018 07:03 AM by Katana »

Offline john smith 19

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Re: Countdown to new smallsat launchers
« Reply #362 on: 01/01/2018 08:04 AM »
Even ramjets of 1950s (Talos, Bomarc, Navaho) have much worse Thrust / R&D cost ratio compared to rockets of 1950s, either engine or vehicle.

No other airbreathers could be cheaper.
I see, you equate the engine with the vehicle.

That's a bad habit to have, given the engine builders were normally different companies. In fact I think most of them came from the Marquadt company.

Did you not know that air breathers have much worse T/W ratios than rockets but much better Isp's? The J58 used in the SR71 had a thrust to weight of about 5.5:1. The nacelle roughly doubled the weight. However wings and good aerodynamics meant despite that it could still cruise at M3+.

You also seem to ignore the fact that while some of them were vertically launched they spent most of the mission in horizontal flight, where thrust does not need to be > GTOW.

Is there some specific point you're trying to make? Perhaps you should make it more clearly.
"Solids are a branch of fireworks, not rocketry. :-) :-) ", Henry Spencer 1/28/11  Averse to bold? You must be in marketing."It's all in the sequencing" K. Mattingly.  STS-Keeping most of the stakeholders happy most of the time.
So you're going to Mars to seek a better life. What does that mean to you? Always spot a fanbois by how they react to their idols failures.

Offline john smith 19

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Re: Countdown to new smallsat launchers
« Reply #363 on: 01/01/2018 09:57 AM »
I reckon anyone who wants to get into the LV business should read this.

It's Georg Koopman's presentation about the AMROC rocket and how the company did business and designed it. I've often wondered if Elon Musk ever read it. I suspect not.

What's quite astonishing is that despite it being over 30 years old the numbers are still surprisingly current.

Amroc started before a major financial crash and nearly died, as did SpaceX.

What actually killed the company was Koopman's car driving off the road and hitting an obstacle a few months prior to their biggest engine test (250 000 lb). It failed due to LOX leakage freezing water vapor out of the air into some of the controls. Just like several other launch failures. His leadership and technical skills were the driving force. Without him it failed.

You have to wonder what would happen to SX if anything happened to Musk.
« Last Edit: 01/01/2018 09:59 AM by john smith 19 »
"Solids are a branch of fireworks, not rocketry. :-) :-) ", Henry Spencer 1/28/11  Averse to bold? You must be in marketing."It's all in the sequencing" K. Mattingly.  STS-Keeping most of the stakeholders happy most of the time.
So you're going to Mars to seek a better life. What does that mean to you? Always spot a fanbois by how they react to their idols failures.

Offline FutureSpaceTourist

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Re: Countdown to new smallsat launchers
« Reply #364 on: 01/07/2018 06:33 AM »
Quote
35 small launch vehicles (<1000 kg @ LEO) claim to be under development worldwide.  An additional 30 that I'm watching for further information. 8 have terminated since I started tracking. #SmallSat #Rocket #Crazy

https://twitter.com/RocketScient1st/status/949850176650346496

Online Kosmos2001

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Re: Countdown to new smallsat launchers
« Reply #365 on: 01/08/2018 09:05 AM »
Quote
35 small launch vehicles (<1000 kg @ LEO) claim to be under development worldwide.  An additional 30 that I'm watching for further information. 8 have terminated since I started tracking. #SmallSat #Rocket #Crazy

https://twitter.com/RocketScient1st/status/949850176650346496

The "defunct" bar grows faster than the "operational" one.

Online Svetoslav

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Re: Countdown to new smallsat launchers
« Reply #366 on: 01/08/2018 09:27 AM »

The "defunct" bar grows faster than the "operational" one.

Yah, I also noticed that.

I personally don't expect the situation to be different than the Suborbital Tourism hype 15-20 years ago. Only one company flew a spacecraft, most of them went bankrupt or eventually adopted other goals.

Right now the hype is about smallsats, but can we expect there will be more than several successful companies?
« Last Edit: 01/08/2018 09:28 AM by Svetoslav »

Offline ringsider

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Re: Countdown to new smallsat launchers
« Reply #367 on: 01/08/2018 11:07 AM »
The "defunct" bar grows faster than the "operational" one.

That is as you would expect. 80/20 - 80% of the gain from 20% of the work. At that rate you should expect there to be 10-15 companies actually building something that flies, and of those you would expect the same 80/20 principle to apply, and to end up with just 2-3 with surviving, thriving businesses. Anyone who gets to flight with a "me-too" approach is probably already doomed.

Offline ringsider

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Re: Countdown to new smallsat launchers
« Reply #368 on: 01/09/2018 02:42 PM »
Spanish PLD Space say they have a "big announcement coming tomorrow, the first of 2 big announcements in January":-

https://twitter.com/PLD_Space/status/949276449550295040

Offline imprezive

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Re: Countdown to new smallsat launchers
« Reply #369 on: 01/09/2018 03:26 PM »
The "defunct" bar grows faster than the "operational" one.

That is as you would expect. 80/20 - 80% of the gain from 20% of the work. At that rate you should expect there to be 10-15 companies actually building something that flies, and of those you would expect the same 80/20 principle to apply, and to end up with just 2-3 with surviving, thriving businesses. Anyone who gets to flight with a "me-too" approach is probably already doomed.

I think once two of them are in operation itís going to be tough for any new commercial companies to compete. At that point itís much easier for an existing company to simply build more rockets than for someone to design something from scratch. Youíd need to invest a ton of money into a step change of rocket technology to compete and I donít see many VCs being willing to so that. Youíll probably see some new government backed entries but going the pure commercial route will be brutal.

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