Chinese Hypersonic Developments (HGVs/HCMs)

ficker22

ficker22

Senior Member
Registered Member
tonyget said:
We can use the bullet analogy. Kinetic energy depends on velocity&mass，light bullet with high muzzle speed decays much faster than heavy bullet with low muzzle speed in air
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Kinetic energy depends on m and v, here is the formula:

E kin = 1/2*m*v²

So a lighter warhead means faster velocity, more kinetic energy proportional to the V square.

Thus a higher Vmax always translates in more range than a higher m, if you throw 1 kg and 2 kg with same energy, the 1kg will fly faster and farther than 2 kg.
The work to get 2kg to the same distance as 1kg is therefore higher = larger rocket booster, more powerful propellant, yada yada.

The effect you describe is due to winds manipulating a light projectile's trajectory, but this is more of a fire arm catridge thing (under 1000 gram) than a ballistic missile warhead (~100kg or more kg) problem.

Also by miniturizing the warhead, we get a smaller warhead = lower cross-sectional area = less drag, lower RCS.
 
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tonyget

Senior Member
Registered Member
ficker22 said:
E kin = 1/2*m*v²

So a lighter warhead means faster velocity, more kinetic energy proportional to the V square.

A higher Vmax always translates in more range, if you throw 1 kg and 2 kg with same energy, the 1kg will fly faster and farther than 2 kg.
The work to get 2kg to the same distance as 1kg is therefore higher = larger rocket booster, more powerful propellant, yada yada

The effect you describe is due to winds manipulating a light projectile's trajectory, but this is more of a fire arm catridge thing than a ballistic missile warhead problem.

Also by miniturizing the warhead, we get a smaller warhead = lower cross-sectional area = less drag, lower RCS.
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We are talking about HGV here，not ballistic missile. HGV doesn't fly in ballistic trajectory. Also unlike ballistic missile which flys at outer atmosphere before landing. HGV flys much lower，within atmosphere，so aerodynamics applys here
 
ficker22

ficker22

Senior Member
Registered Member
tonyget said:
We are talking about HGV here，not ballistic missile. HGV doesn't fly in ballistic trajectory. Also unlike ballistic missile which flys at outer atmosphere before landing. HGV flys much lower，within atmosphere，so aerodynamics applys here
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The fundamental here is that you can not get proportional gains in kinetic energy by increasing mass instead of velocity.

Drag and head wind are not in the same way affecting range like a light bullet.


Less total mass on the other hand is affecting the amount of propellant needed to accelerate to a given speed and for that I refer back to the kinetic energy formula.
 
vincent

vincent

Grumpy Old Man
Staff member
Moderator - World Affairs
tonyget said:
We can use the bullet analogy. Kinetic energy depends on velocity&mass，light bullet with high muzzle speed decays much faster than heavy bullet with low muzzle speed in air
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High school physics: to move a mass for a certain distance requires certain amount of energy. The mass and distance is an inverse relationship if the amount of energy stay at constant.
 
ZeEa5KPul

ZeEa5KPul

Colonel
Registered Member
ficker22 said:
Less total mass on the other hand is affecting the amount of propellant needed to accelerate to a given speed and for that I refer back to the kinetic energy formula.
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There's a better way to explain it. Since I know he's not going to read a physics textbook, and other explanations are incorrect or beside the point, I'll present it in the vain hope that he'll read and learn something.

We begin with a simplified version of the rocket equation. Simplified in that we'll not consider the effects of gravity, air resistance, or rocket staging. It will be a single stage rocket in a vacuum away from any massive body. The change in velocity of the rocket is given by

Δv = v_e ln(m_i / m_f)

where v_e is the velocity of the rocket exhaust (given by I_sp * g, where I_sp is the specific impulse of the engine and g is the gravitational acceleration at sea level), m_i is the mass of the rocket loaded with fuel, and m_f is the rocket without fuel (including payload).

For the same mass and type of fuel, we see that the lighter we can make the rocket (including by lightening the payload), the larger we will make the ratio m_i / m_f, therefore the larger Δv will be.

The simplifications we've made do not change the fundamental point made above. It will hold true no matter how many complications and extra factors one adds to the model.
 
A

ACuriousPLAFan

Colonel
Registered Member
tphuang said:
The other thing is I would agree that you can increase range by just reducing warhead size. IIRC, ARRW warhead size is only 50 kg, which is nothing.
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50kg warhead on ARRW? That would be the same warhead weight as the Shahed 136 kamikaze drone. Even the old Harpoons has 220 kg of warhead.

tphuang said:
You can't do much with that. In general, anything America can launch from a ship will be limited by the VLS size. So, I think it's reasonable to just assumed that they are all conventional warhead. I would also assume that any PLAN VLS launched YJ-21 will also have smaller warhead size.
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I'm seeing a trend, starting with Zumwalt DDGs where larger VLS would replace the two ammo-less AGS mounts for launching hypersonic missiles. That way, the USN can have sea-based launch platforms for their hypersonic missiles with minimal reduction to warhead size and range compared to those fitted inside normal VLS. Similar proposals has been made for the upcoming DDG(X)s as well by offering the option to swap some of the onboard Mk 41 VLS with the larger VLS in the future.

Does PLAN have similar plans for their DDGs? Having navalized version of DF-17s (I'll just designate such missiles as DF-XX"N") would enable the PLAN to strike Guam from around 250 kilometers southeast of Taiwan. But for Oahu, Tindal and Diego Garcia, using the DF-17"N" would risk putting PLAN assets into areas that would not guarantee sufficient PLAAF and PLARF cover, therefore having DF-27"N" is very much necessary in those cases.

ChongqingHotPot92 said:
RMB or dollar?
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Dollar.

However, military experts in China estimated that once the production lines of DF-17 are expanded, then the price of each DF-17 can be further reduced to 7 million RMB (which is close to 1 million USD) at most.
 
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